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. 2026 Sep 15;11(38):57548–57559. doi: 10.1021/acsomega.6c05400

Preparation, Pore Structure Development, and Properties of Bamboo Parenchyma Cell-Derived Activated Carbon by Phosphoric Acid Activation

Xinmeng Hu ‡, Tingting Feng †,‡, Danqi Feng †,‡, Jiaxin Weng †,‡, Rui Zhong †,‡, Lujie Zhang †,‡, Lin Wen ⊥, Minren Shi #, Yuxuan Yao ‡, Zhigao Liu †,‡,§,∥,*
PMCID: PMC13629360  PMID: 42825132

Abstract

Bamboo parenchyma is rich in lignocellulosic macromolecules, including cellulose, hemicellulose, and lignin, whose structural transformation plays a critical role during chemical activation processes. In this study, bamboo parenchyma cells were employed as a lignocellulosic precursor to prepare porous activated carbon via phosphoric acid activation, followed by silver loading to introduce antibacterial functionality. The activation process induced dehydration, depolymerization, and aromatization of cellulose, hemicellulose, and lignin, accompanied by crosslinking reactions that governed the formation of hierarchical pore structures. The obtained phosphoric-acid-activated carbon (PPAC) exhibited a predominantly microporous structure with a high specific surface area of 1534 m2 g–1 and a micropore volume of 0.260 cm3 g–1. TG–MS–FTIR analysis further revealed stepwise gas evolution and a phosphorus–oxygen reaction cycle associated with the transformation of lignocellulosic macromolecules during thermal activation. After silver loading, Ag nanoparticles were uniformly dispersed on the carbon surface with a maximum loading of 19.36 wt %. Although the specific surface area decreased to 525 m2 g–1, the composite material displayed excellent antibacterial activity. Antibacterial tests demonstrated that PPAC/Ag achieved nearly 100% inhibition against Escherichia coli and Staphylococcus aureus and maintained stable antibacterial performance after five reuse cycles. This work highlights the crucial role of lignocellulosic macromolecule transformation in pore structure formation during phosphoric acid activation and provides insights into the design of functional carbon materials derived from biomass for water purification and bio-protection applications.

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1. Introduction

With the continuous advancement of industrialization, efficient and green porous carbon materials are playing an increasingly important role in environmental governance, energy storage and catalysis. Among them, activated carbon, due to its well-developed pore structure, abundant surface functional groups and excellent chemical stability, has shown broad application prospects in adsorption separation and water treatment. Among them, activated carbon prepared from renewable biomass has attracted the attention of both the scientific research community and the industrial community under the dual background of fossil resource scarcity and sustainable development. Biomass materials such as wood, coconut shell and bamboo have their own pore structure. After activation, they are more likely to form activated carbon with a large specific surface area and reasonable pore size distribution, and activated carbon materials with controllable performance. Compared with traditional fossil energy, biomass raw materials have the advantages of being renewable, having a low carbon footprint, and good environmental compatibility. They have broad application prospects in the fields of food, medicine and environment. The synthesis of activated carbon includes two basic steps: carbonization and activation. Among the activation methods, in addition to the common KOH activation, , phosphoric acid activation has also attracted widespread attention due to its unique advantages. Phosphoric acid activation has a relatively low temperature and low energy consumption. In addition, phosphoric acid can act as a Lewis acid to promote the hydrolysis of cellulose and hemicellulose during the activation process, forming a rich mesoporous and macroporous structure, which is conducive to the diffusion and adsorption of macromolecular dyes in the material. In addition, the surface of activated carbon after phosphoric acid activation often contains a large number of phosphorus-containing and oxygen-containing functional groups, such as C–O–P, −COOH, etc. These groups not only enhance the affinity of the material for polar dyes but also provide a reaction platform for subsequent functional modification. The phosphoric acid activation method is mature and has controllable environmental risks. It shows good applicability and economy in the treatment of biomass raw materials. −

Traditional biomass activated carbon materials are mainly derived from agricultural and forestry by-products and natural organic materials, among which wood activated carbon has been studied earlier and has been widely used. However, the growth cycle of wood is long, and excessive logging can easily cause ecological problems. Bamboo is considered a strategic choice to alleviate the wood resource crisis and promote the transformation of green materials due to its rapid regeneration characteristics, high strength, and low carbon processing advantages. − As a typical lignocellulose biomass, bamboo cell walls are mainly composed of cellulose microfibers, hemicellulose and lignin. Its natural hierarchical structure and three-dimensional channels provide a good structural basis for the construction of porous carbon materials. During the activation process, cellulose and hemicellulose are conducive to the formation of abundant pores, while lignin, due to its highly cross-linked aromatic structure, is prone to form a dense carbon skeleton after carbonization, thus limiting the development of pore structure to a certain extent. By removing lignin, the hindering effect of lignin on pore formation can be effectively reduced, and the loose cytoskeleton structure can be preserved, providing more favorable conditions for the generation and expansion of pores in the subsequent activation process.

It is worth noting that most current research on bamboo-based activated carbon mainly uses whole bamboo or bamboo powder as raw materials, while the structural advantages of different cell tissues inside bamboo are relatively limited. Bamboo parenchyma cells (PCs), as the most abundant basic tissue in bamboo, have unique microstructures such as thin cell walls, large cell cavities, loose arrangement, and a large number of pits distributed in the cell walls. These natural structures are not only conducive to the penetration and mass transfer of activators, but also provide more active sites for the formation and expansion of pores. Therefore, they are considered to be ideal precursors for constructing activated carbon with high specific surface area and hierarchical pore structure. For example, Xia et al. made full use of their multilayer structure with abundant pits to prepare highly porous KOH activated carbon with a specific surface area of about 4000 m2 g–1 and a methylene blue adsorption value of 1750 mg g–1. This indicates that bamboo thin-walled cells have great application potential in the field of water treatment. At present, there is still a lack of systematic research on the evolution of pore structure and the mechanism of structural advantage of bamboo thin-walled cells during phosphoric acid activation. At the same time, the actual water environment is often complex and variable, and the single adsorption function can no longer meet the needs of efficient purification. In recent years, water pollution has become increasingly serious. In addition to organic pollutants and heavy metals, wastewater often carries pathogenic microorganisms, especially pathogenic bacteria such as Escherichia coli and Staphylococcus aureus. If not effectively treated, it will pose a serious threat to the ecological environment and human health. Therefore, developing adsorption materials with high efficiency antibacterial ability to achieve the simultaneous removal of pathogens in wastewater has important practical significance. , Silver nanoparticles are widely used in the construction of functional materials due to their excellent broad-spectrum antibacterial properties, but their easy aggregation and easy loss limit their practical application. Bamboo thin-walled fine activated carbon, due to its unique fiber structure and high porosity, is expected to achieve efficient adsorption and sterilization at the same time after loading silver particles, and has good application potential. Meanwhile, the abundant porous structure formed by phosphoric acid activation and the oxygen- and phosphorus-containing functional groups on the surface can provide stable loading sites for silver nanoparticles, which is expected to achieve uniform dispersion and stable fixation of silver nanoparticles, thereby endowing the material with dual functions of adsorption and antibacterial properties, and realizing the high-value utilization of bamboo thin-walled cell resources. Therefore, the construction of a composite material with both efficient adsorption and broad-spectrum antibacterial functions based on bamboo-derived activated carbon − has important scientific significance and application value for coping with complex water environment pollution and expanding the high-value utilization path of bamboo materials.

This study prepared bamboo thin-walled cell-based activated carbon (PPAC) through phosphoric acid activation. The effects of different activation conditions on the material’s structure and physicochemical properties were systematically investigated, and its thermal decomposition and activation behavior were analyzed. Furthermore, a composite material was constructed by loading silver particles, aiming to achieve high-value utilization of the phosphoric acid-activated bamboo thin-walled cell-based activated carbon. This work provides a theoretical basis for optimizing the structural control and performance improvement of bamboo-derived activated carbon.

2. Materials and Methods

2.1. Materials and Drugs

Moso bamboo samples were collected from Hangzhou, Zhejiang Province, and were 4–6 years old. Phosphoric acid (AR) was purchased from Chengdu Jinshan Chemical Reagent Co., Ltd., sodium chlorite (AR) was purchased from Shanghai McLean Biochemical Technology Co., Ltd., silver nitrate (AR) was purchased from Sinopharm Chemical Co., Ltd., methylene blue (MB) was purchased from Tianjin Damao Chemical Reagent Factory, and methyl orange (MO), chrome black T (EBT), ciprofloxacin (AR), and ofloxacin (AR) were all purchased from Shanghai McLean Biochemical Technology Co., Ltd.

2.2. Preparation of Bamboo Parenchyma Cells

In 1% NaClO2 solution and adjust the solution pH to 4.5–4.6 with glacial acetic acid solution. Heat the water bath to 80 degrees, changing the solution every 6 h, and repeat the process until the bamboo strips turn completely white. The delignified bamboo strips were thoroughly washed with deionized water until neutral pH was reached and then freeze-dried. The dried bamboo parenchyma cells were subsequently separated by mechanical shaking to obtain the bamboo parenchyma cell powder.

2.3. Preparation of PC-Based Activated Carbon Activated by Phosphoric Acid

Five grams of bamboo parenchyma cell powder was mixed with 30 mL of phosphoric acid solutions at different concentrations (10 and 70 wt %) at room temperature, followed by impregnation for 1 h under magnetic stirring at 500 rpm. The phosphoric acid-impregnated bamboo parenchyma cells were then dried in an 80 °C drying oven. After drying to constant weight, the cells were transferred to a tube furnace and heated to the target temperatures. Based on previous studies of phosphoric acid activation of lignocellulosic biomass, activation temperatures of 400, 600, and 700 °C were selected to investigate the effect of activation severity on pore development and surface chemistry. Temperatures around 400 °C are generally sufficient to initiate dehydration and crosslinking reactions but often result in limited pore development, whereas temperatures above 700 °C may lead to excessive carbon burn-off, phosphorus loss, and partial pore collapse. Therefore, 400, 600, and 700 °C were chosen to represent low, intermediate, and high activation temperatures, respectively, under nitrogen flow (The heating rate was 8 °C min–1 and flow rate = 50 mL min–1). The temperature was then maintained for a specified time (0.5, 2, and 4 h). The process was terminated after the temperature was maintained, and the cells were allowed to cool naturally, rinsed, and dried, Phosphoric acid activated bamboo thin-walled activated carbon (PPAC) was obtained. The activated carbons were designated according to the investigated preparation parameter. They are PPAC-10%, PPAC-70%, PPAC-400, PPAC-600, PPAC-700, PPAC-0.5, PPAC-2 and PPAC-4, respectively.

1g of the PPAC-10% sample was immersed in 50 mL AgNO3 solutions with concentration of 0.05, 0.1, 0.2, and 0.4 mol L–1 for 24 h. The impregnated samples were then dried and subjected to a second heat treatment at 300 °C for 1 h under a nitrogen atmosphere using the same heating conditions described above. The resulting sample was labeled as PPAC/Ag-5, PPAC/Ag-10, PPAC/Ag-20, PPAC/Ag-40. The process parameters corresponding to the specific sample numbers can be found in Table S1.

2.4. Material Characterization

The pore structure of the materials was analyzed by nitrogen adsorption-desorption at −196 °C using an ASAP 2460 surface area and pore size analyzer (Micromeritics). The surface area and volume (SSA) of the micropores were calculated using the Brunauer-Emmett-Teller (BET) method. The micropore surface area (S micro) and volume (V micro) were obtained using the t-plot method. The mesopore surface area and volume (S meso, V meso) were determined using the Barrett-Joyner-Halenda (BJH) method. The total pore volume (V total) was calculated from the adsorption amount at P/P 0 = 0.995. The pore size distribution was calculated using the nonlocal density functional theory (NLDFT) model. Functional groups were characterized by Fourier transform infrared spectroscopy (FTIR, IRTracer-100, Shimadzu, Japan) in the 4000–400 cm–1 range. X-ray diffraction (XRD, D/MAX 2500 V, Rigaku, Japan) using Cu Kα radiation was performed at 40 kV, 30 mA, and a scan rate of 2 ° min–1 to measure diffraction patterns in the 5–65 ° (2θ) range. Crystal parameters were calculated using the Scherrer-Bragg equation. X-ray photoelectron spectroscopy (XPS, ESCALAB 250XI+, Thermo Fisher Scientific) was used to characterize the surface elemental composition and chemical bonding state. Scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) was used to observe the morphology and surface element distribution of bamboo cell raw materials, PPAC, and their silver-loaded precursors.

Thermogravimetric–infrared–mass spectrometry (TG–MS–FTIR, NETZSCH STA 449 F5/F3 Jupiter, Germany) was used to investigate the mass loss behavior, volatile evolution, and reaction pathways during precursor pyrolysis. The analysis was conducted from room temperature to 900 °C at a heating rate of 15 °C min–1 under argon flow, with the mass spectrometer scanning a mass-to-charge ratio (m/z) range of 2–71.

2.5. Antibacterial Experiments

The antimicrobial activity of the samples was evaluated according to GB/T 21510-2008. Before the experiment, phosphate buffer (pH 7.0–7.2), MH agar, nutrient broth, and test tubes were autoclaved at 121 °C and 0.1 MPa for 20 min. After cooling, 0.1 mL of bacterial suspension was inoculated onto a slant of nutrient agar and incubated at 37 °C for 2 days to prepare a bacterial suspension, which was then diluted with buffer to an appropriate concentration. For the antimicrobial assay, 0.02 g of sample, 9 mL of nutrient broth, and 1 mL of the diluted bacterial suspension were added to each tube and incubated at 37 °C in the dark with shaking for 1–8 h. Subsequently, 0.1 mL of the mixture was spread onto an agar plate and incubated at 37 °C for 24 h. Colony counts were calculated using the dilution plate method. The difference between the control and experimental groups was that the control group did not contain a sample. The antimicrobial rate (R) was calculated using the following formula

R=A−BA*100% 1

Where A is the average colony count per unit volume of the blank group after contact with bacteria (cfu mL–1), and B is the average colony count per unit volume of the experimental group under the same conditions (cfu mL–1).

3. Results and Discussion

3.1. Morphology

Figure a–c show SEM images of bamboo parenchyma and its phosphoric acid-activated carbon. After delignification, the separated bamboo parenchyma still has some flocculent fibers attached to the surface, and shows local damage or adhesion phenomena (Figure ). Figure d–f are SEM images of PPAC-10%, showing that after phosphoric acid activation and carbonization, the bamboo parenchyma activated carbon basically maintains its original morphology. During the carbonization process, the fiber tissue disappears, − making the surface more open, while the pit structure is retained (Figure f), which acts as a natural pore and active site to promote molecular diffusion and enhance adsorption capacity and selectivity.

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SEM images of the surface morphology of PPAC and their raw materials; (a–c) bamboo parenchyma cells; (d–f) PPAC-10%

3.2. Porosity and Structural Characterization

As shown in Table , the carbon yield of PPAC was significantly influenced by activation temperature, holding time, and phosphoric acid concentration. With increasing activation temperature from 400 to 700 °C, the carbon yield decreased from 58.80 to 36.18%, indicating enhanced decomposition of biomass and greater release of volatile components at elevated temperatures. The carbon yield increased from 39.32 to 67.82% as the holding time was prolonged from 0.5 to 4 h, suggesting that phosphoric acid promoted the stabilization of the carbon framework during carbonization, thereby reducing excessive carbon loss. For samples prepared with different phosphoric acid concentrations, PPAC-10% and PPAC-70% exhibited relatively low carbon yields of 22.91 and 23.75%, respectively, implying that phosphoric acid activation facilitated the removal of noncarbon elements and the development of pore structures during pyrolysis.

1. Activated Carbon Yield.

sample code PPAC-400 PPAC-600 PPAC-700 PPAC-0.5 PPAC-2 PPAC-4 PPAC-10% PPAC-70%
carbon yield (%) 58.80 46.55 36.18% 39.32% 58.35% 67.82 22.91 23.75
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Figure a shows the N2 adsorption–desorption isotherms of PPAC prepared under different activation temperatures (400, 600, and 700 °C), activation times (0.5, 2, and 4 h), and phosphoric acid impregnation concentrations. All samples exhibit a sharp nitrogen uptake in the low-pressure region (P/P 0 < 0.05), suggesting the presence of micropores. This observation is further supported by micropore volume data (Table S3), which confirm the contribution of micropores to the overall pore structure. However, significant differences are observed in the medium- and high-pressure regions, reflecting variations in mesopore development and hierarchical pore structures. According to the IUPAC classification, PPAC-10% exhibits an isotherm close to Type I, suggesting that its pore structure is predominantly microporous. Correspondingly, the pore structural parameters in Table S2 show that PPAC-10% possesses a high specific surface area (1534 m2 g–1) and a micropore volume of 0.260 cm3 g–1, indicating that micropores contribute substantially to the total porosity. At low impregnation ratios, phosphoric acid generates P2O5 under high-temperature and anhydrous conditions, which reacts with the carbon matrix to form C–O–P structures and promotes micropore formation.

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(a) Nitrogen adsorption and release isotherms of PPAC samples synthesized under different conditions, (b) pore size distribution of PPAC samples synthesized under different conditions, (c) IR spectra of PPAC samples prepared at various heat treatment temperatures, (d) XRD patterns of PPAC prepared at different activation temperatures, (e) IR spectra of PPAC samples prepared at various heat treatment temperatures, (f) IR spectra of PPAC samples prepared under various phosphoric acid pretreatment concentrations.

With increasing activation severity, including higher activation temperature, longer activation time, or higher phosphoric acid concentration, the isotherms gradually evolve from Type I toward Type IV. Meanwhile, pronounced H4–H3 hysteresis loops appear, indicating the progressive development of mesopores and hierarchical pore structures. This trend is further confirmed by the pore size distribution curves (Figure b) and pore volume data (Table S3), which show an increase in mesopore contribution accompanied by pore widening. For example, PPAC-70% exhibits a mesopore volume of 2.044 cm3 g–1, far exceeding its micropore volume, demonstrating that the pore system becomes predominantly mesoporous at high impregnation ratios. This transition is mainly attributed to the extraction of phosphoric acid-derived species during hydrolysis and washing, resulting in pore enlargement and mesopore generation. The effects of activation temperature, activation time, and phosphoric acid concentration on pore evolution can be further analyzed using the structural parameters summarized in Table S3. For activation temperature, PPAC-400 contains mainly underdeveloped micropores because pore formation is insufficient at relatively low temperatures. Increasing the temperature to 600 °C promotes pore development and mesopore generation, resulting in a more hierarchical pore structure. However, further increasing the temperature to 700 °C may cause partial collapse or shrinkage of mesopores, leading to a reduction in pore development efficiency. Activation time also influences pore structure evolution. PPAC-0.5 exhibits the highest adsorption capacity and a distinct H4 hysteresis loop, indicating the presence of slit-shaped pores. , Consistent with the BET and pore volume data, both the specific surface area and micropore volume reach their maximum values at 0.5 h. Prolonged activation causes excessive etching of the carbon framework, resulting in micropore widening and a gradual shift toward larger pores. Similarly, increasing the phosphoric acid impregnation ratio continuously promotes pore expansion. At low impregnation ratios, micropores dominate the pore system and contribute most of the specific surface area. As the impregnation ratio increases, micropores gradually develop into mesopores, and the pore structure evolves toward a hierarchical mesoporous network.

Overall, the combined results of N2 adsorption–desorption isotherms, pore size distribution curves, and pore structural parameters demonstrate that PPAC undergoes a gradual transition from a predominantly microporous structure to a hierarchical micro/mesoporous structure and finally to a mesopore-dominated structure with increasing activation severity. Among the investigated conditions, an activation temperature of approximately 600 °C, an activation time of 0.5 h, and an appropriate phosphoric acid impregnation ratio provide the most balanced combination of specific surface area and pore size distribution, which is favorable for the design and application of bamboo-based activated carbons.

Figure c shows the infrared spectra of PPAC prepared under different activation temperatures, activation times, and phosphoric acid impregnation concentrations. Overall, the samples exhibit typical absorption peaks at 3400 cm–1 (−OH, N–H), 2923/2860 cm–1 (−CH3, −CH2), 1633 cm–1 (CC, CO), and 1050 cm–1 (C–O–P), indicating the introduction and regulation of surface oxygen-containing functional groups and phosphate structures during activation. The peak intensities at 3400 and 1633 cm–1 initially decrease and then increase at different phosphoric acid concentrations, reflecting that phosphoric acid promoted biomass dehydration and aromatization while also increasing the content of surface carboxyl and carbonyl groups at high concentrations. The presence of the C–O–P absorption peak (1050 cm–1) further demonstrates the interaction of H3PO4 with the carbon skeleton. At different activation times, the C–O–P related peaks increased with time, indicating that the structure was relatively stable; while the C–O–C absorption peak gradually weakened, indicating that some oxygen-containing functional groups would be destroyed during long-term activation, resulting in an overall reduction in surface functional groups. At different activation temperatures, the peak intensity at 3400 and 1633 cm–1 of the 700 °C sample was significantly enhanced, which may be due to the decomposition of phosphate at high temperature to produce new hydroxyl and carboxyl structures; while above 600 °C, the C–O–P structure gradually weakened, indicating that too high a temperature is not conducive to the stabilization of phosphoric acid, and may even have caused the carbon structure to gasify and escape, transforming into other structures. In summary, phosphoric acid activation not only gives PPAC oxygen-containing functional groups such as carboxyl, carbonyl, and C–O–C, but also introduces a stable C–O–P structure; its type and content are synergistically regulated by the impregnation concentration, activation time, and temperature, thereby affecting the chemical properties and structural stability of the activated carbon surface.

XRD analysis (Figure d) reveals that all PPAC samples exhibit typical characteristics of amorphous/turbostratic carbon, with two broad diffraction bands located at approximately 2θ = 23 and 43°, corresponding to the (002) and (100) planes, respectively. As the activation temperature increases, the intensity of the (002) diffraction peak gradually increases, indicating enhanced stacking of carbon layers and the development of short-range ordered carbon domains. Meanwhile, the slightly increased intensity of the (100) diffraction band suggests a gradual improvement in in-plane structural ordering. However, the broad nature of these diffraction peaks indicates that the carbon framework remains largely disordered, and the degree of graphitization is limited. The calculated interlayer spacing (d002) remains larger than that of ideal graphite, confirming the turbostratic carbon structure of PPAC. Such a disordered carbon framework is beneficial for maintaining abundant active sites and facilitating adsorption applications.

The XPS analysis results show (Figure e) that C, O, and P elements were detected in PPAC prepared under different activation temperatures, times, and phosphoric acid impregnation concentrations. The presence of P indicates that phosphorus-containing structures such as phosphates were successfully introduced during the H3PO4 activation process. This may be because phosphoric acid formed a large number of phosphate bonds during the activation of bamboo parenchyma cells, thereby achieving high cross-linking with the bamboo parenchyma. In the temperature variable (Figure a), the carbon content first increases and then decreases with temperature, while the oxygen content and O/C ratio show opposite trends. In the 400 °C range, phosphoric acid promoted the dehydration of lignocellulose, reducing the surface oxygen content; but after exceeding 600 °C, the phosphate bonds are partially thermally decomposed, resulting in a decrease in the P content and the ratio of O–CO functional groups. Taking PPAC-400 as an example, the C 1s spectrum (Figure. f) can be deconvoluted into four components located at approximately 284.8 eV (C–C/CC), 286.1 eV (C–O), 287.5 eV (CO), and 289.0 eV (O–CO). These functional groups reflect the evolution of surface chemical properties under different activation conditions. The C 1s peak shows (Figure f) that the C–C ratio gradually decreases with increasing temperature, while the O–CO ratio increases at medium temperatures and decreases at high temperatures due to the fact that carboxyl groups and esters decomposed. Regarding activation time (Figure S2b), the C content first increased and then decreased, while the O and O/C ratios gradually increased, indicating the continuous enrichment of oxygen functional groups and the formation of structures such as C–O–P. However, after activation for more than 2 h, some CO and C–O groups were reduced due to thermal decomposition, and the proportion of O–CO functional groups also continued to decrease with time, reflecting poor thermal stability (Figure S2g,i). Regarding phosphoric acid concentration (Figure c), all samples contained P, but the elemental distribution showed that the C ratio first decreased and then increased, while the O and P ratios and the O/C ratio first increased and then decreased. C 1s peak analysis results (Figure S2j,k) showed that the proportion of graphitic carbon increased with increasing concentration, while the O–CO functional groups decreased significantly at high concentrations, indicating that excessively high phosphoric acid concentrations destroyed structures such as carboxyl groups and esters, resulting in a more graphitized and hydrophobic surface. In summary, phosphoric acid activation not only introduces stable C–O–P bonds and a variety of oxygen-containing functional groups but also affects the degree of graphitization and surface polarity of PPAC by regulating temperature, time, and concentration, providing a controllable means to optimize its structure and properties.

3.3. Activation Process of Phosphoric Acid-Activated PPAC

Figure a shows the TG–DTG curves of phosphoric-acid-impregnated bamboo parenchyma during heating to 900 °C. The total mass loss reached 74.55%, and the thermal decomposition process can be divided into four main stages based on the weight-loss rate. At temperatures below 120 °C, the weight loss mainly results from the evaporation of free and bound water in the lignocellulosic matrix. In the range of 120–250 °C, a significant mass loss is observed, accompanied by the release of gaseous products such as H2O, CO2, CO and CH4, as identified by the subsequent FTIR–MS analysis. Upon further heating to 250–800 °C, the mass loss becomes more gradual, whereas above 800 °C a slight increase in the weight-loss rate is detected. These experimental observations provide the basis for the following mechanistic interpretation.

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(a) TG-DTG curve of bamboo thin wall impregnated with phosphoric acid, (b) 3D infrared spectrum of pyrolysis gas products of bamboo thin wall impregnated with phosphoric acid, and gas phase FTIR spectra of bamboo thin wall impregnated with phosphoric acid at 120 °C (c), 190 °C (d), 600 °C (e), and 850 °C (f).

From 120 to 250 °C, the thermal decomposition of hemicellulose and the initial depolymerization of cellulose occur. The FTIR spectra (Figure b–d) show that the main gas-release region lies within this temperature range, with characteristic absorption bands assigned to H2O (3910–3436 and 1500–1300 cm–1), CO2 (2338 and 2359 cm–1), CO (2120 and 2173 cm–1), CO (1829–1680 cm–1), aromatic CC (1600–1450 cm–1), and C–O–C (1178 and 1117 cm–1). At 120 °C, the CO absorption corresponds to the mass signal m/z = 30, suggesting the presence of a mixture of carbonyl-containing intermediates rather than pure formaldehyde. , At approximately 190 °C, the appearance of absorption bands at 3189–3018 cm–1 indicates the release of CH4 (Figure d), which is consistent with the m/z = 16 signal reaching a maximum at about 194 °C in the MS spectra (Figure b), although the intensity remains relatively weak. According to previous studies, such CH4 evolution may be associated with radical reactions and early aromatization processes during the depolymerization of cellulose and hemicellulose.

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MS responses of bamboo parenchyma cells impregnated with phosphoric acid in thermogravimetric-mass spectrometry analysis: (a) hydrogen (m/z 2), (b) CH4 (m/z 16), (c) hydroxyl cation OH+ (m/z 17), (d) H2O (m/z 18), (e) carbon monoxide (m/z 28), (f) formaldehyde (m/z 30), and (g) phosphorus vapor (m/z 31). (h) argon (m/z 40), and (i) carbon dioxide (m/z 44).

Based on these experimental observations and previous literature reports, several mechanisms may contribute to the thermal conversion process. Phosphoric acid may act as a Brønsted acid catalyst, promoting the hydrolysis and dehydration of polysaccharide chains while facilitating condensation and aromatization reactions of carbon precursors. The formation of phosphate ester linkages between phosphoric acid and hydroxyl groups in cellulose and hemicellulose has been reported to inhibit excessive structural shrinkage and may facilitate the development of initial pore frameworks. The relatively weak CH4 release may be related to the dehydration-promoting effect of phosphoric acid and the suppression of tar formation. The increased evolution of CO2 and the appearance of CO are likely associated with decarboxylation and decarbonylation reactions of lignocellulosic components, including cleavage of hemicellulose side chains and partial fragmentation of lignin-derived aromatic structures. The absorption bands within 1200–1000 cm–1 indicate the presence of oxygen-containing volatile compounds such as alcohols, phenols, and ethers, whereas the band at 1600–1450 cm–1 suggests the formation of aromatic and phenolic species. Accordingly, the major gaseous products in this stage are H2O, CO2, CO, CH4, carbonyl compounds, alcohols, phenols, and ethers.

Within the temperature range of 250–800 °C, the mass-loss rate gradually stabilizes, and the release intensities of alcohols, phenols, carbonyl compounds, and CO2 decrease significantly (Figure e). FTIR spectra collected at 600 °C indicate that the major gaseous products are H2O, CO2, CO, and minor amounts of oxygenated organic compounds. These observations suggest that the primary decomposition reactions of lignocellulosic constituents are largely completed. According to previous studies, phosphate ester crosslinking initiated at approximately 150–200 °C may contribute to stabilization of the carbon framework and may remain effective up to around 450 °C. Above this temperature, the gradual thermal decomposition of phosphate ester structures is expected to occur. The decomposition and transformation of phosphorus-containing species, including phosphorus oxides such as P2O5, may participate in carbon structural rearrangement and could contribute to the evolution of pore structures during activation.

Above 800 °C, a slight increase in the weight-loss rate is observed (Figure f). FTIR spectra collected at 850 °C show enhanced absorption peaks corresponding to H2O, CO2, alcohols, phenols, CO, and CH4. The MS results also reveal a weak CO2 peak between 800 and 950 °C and a distinct CO peak near 870 °C. These findings suggest that additional high-temperature reactions continue during this stage. The enhanced CO signal may be associated with the Boudouard reaction (C + CO2 → 2CO) and the water–gas reaction (C + H2O → CO + H2), the latter typically occurring above 750 °C. The increased CH4 and sustained H2 signals further indicate the occurrence of secondary cracking and dehydrogenation reactions. Therefore, the transformation of phosphorus-containing species at elevated temperatures may contribute to carbon framework activation and further pore development.

Figure a–i shows the mass spectrometry curves of bamboo thin wall impregnated with phosphoric acid during the heating process. The main gas products include H2 (m/z = 2), H2O (m/z = 18), CH4 (m/z = 16), OH+ (m/z = 17), CO (m/z = 28), formaldehyde (m/z = 30), phosphorus vapor (m/z = 31), Ar (m/z = 40) and CO2 (m/z = 44). Hydrogen (m/z = 2) has a significant peak at about 200 °C and forms a shoulder peak near 700 °C, which comes from the thermal cracking of tar during pyrolysis. , The introduction of phosphoric acid promoted further cracking of tar and catalytic carbonization, which promoted the formation of aromatic rings and dehydrogenation condensation, allowing the bamboo thin wall to form a network carbon structure at a lower temperature and release more H2. The hydrogen signal maintains a certain intensity throughout the entire heating stage, indicating that the dehydrogenation reaction continues. The main mechanisms include: hydrogen radical combination at low temperature (eq ); aromatic group dehydrogenation and water gas shift reaction at high temperature (eq ).

H+H→H2 2
CO+H2O→CO2+H2 3

At 194 °C, signal peaks at m/z = 16 and 17 were detected (Figure b, c). The intensity of m/z = 17 (OH+) was highest, while that of m/z = 16 decreased, following a consistent trend. Since FTIR spectra did not reveal the corresponding N–H stretching vibration absorption peaks (3280 and 920–870 cm–1), these signals are more likely derived from H2O fragment ions rather than ammonia or other nitrogen-containing compounds. Water vapor at low temperatures (60–140 °C) primarily originates from the evaporation of free and bound water, while the strong peak at 194 °C is attributed to chemical dehydration catalyzed by phosphoric acid, which allows the formation of aromatic carbon skeletons from the starting materials at low temperatures. Reactions at higher temperatures may include hydroxyl group cracking reactions and dehydration condensation of phosphoric acid. CO2 is mainly released in large quantities at 150–400 °C, originating from the decarboxylation and branch cleavage of cellulose and hemicellulose; the weak peak at 800–950 °C is related to the secondary cracking of the phosphoric acid cross-linked structure. CO peaks at 194 and 870 °C, corresponding to C–O–C bond cleavage and Boudouard reaction/water gas reaction. , Methane gradually weakens after reaching a peak at 194 °C, while the methanol signal indicates that the methoxyl group cleavage and aromatization process occur. The phosphorus element signal is generally weak, indicating that it mainly exists in a stable binding state, and the weak signal at m/z = 40 is mainly due to the interference of carrier gas Ar (Figure h).

The results of TG-DTG, FTIR, elemental analysis and TG-MS-FTIR indicate that the activation process of phosphoric acid-activated bamboo thin walls at 900 °C can be divided into five stages: first, during the impregnation and drying process, phosphoric acid gradually penetrated the cell wall, catalyzing the hydrolysis of cellulose and hemicellulose and changing the lignin structure, causing the cell wall to plasticize; then, at temperatures <120 °C, the evaporation of free water and bound water mainly occurs; in the range of 120–250 °C, cellulose and hemicellulose are further hydrolyzed to produce oligosaccharides or monosaccharides, phosphoric acid promoted aromatization and dehydrogenation condensation, and inhibits structural shrinkage through phosphate cross-linking to form initial pores; in the 250–800 °C stage, phosphate cross-linking continues and decomposes at high temperatures, and the generated P2O5/P2O3 reacts with carbon to continuously reshape the carbon structure; at temperatures >800 °C, residual phosphate further decomposes, and P2O5 reacts with carbon to produce P and CO, promoting pore expansion. Overall, phosphoric acid acts as a catalyst to promote hydrolysis, aromatization, and cross-linking throughout the activation process, and regulates pore development through high-temperature decomposition and cyclic reactions, ultimately forming high-performance porous activated carbon while maintaining the original microstructure of the cells.

3.4. Antibacterial Properties

Figure shows that silver is distributed on the surface of bamboo parenchyma cells in the form of particles or aggregates. Although increasing AgNO3 concentration promotes the growth of silver particles and the formation of flaky aggregates, the overall distribution remains relatively uniform. EDS analysis of PPAC/Ag-40 shows an Ag content of 27.95% in the analyzed region. Because EDS provides semi-quantitative information on the local surface elemental composition, ICP-OES analysis was further used to determine the bulk Ag content, which was 19.36 wt % for PPAC/Ag-40 (Table S7).

5.

5

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(a–c) SEM images of PPAC/Ag-40; (d) EDS spectrum of silver-loaded phosphoric acid-activated bamboo parenchyma cell-derived activated carbon.

After silver loading, white particles of different sizes appear on the surface of the bamboo parenchyma cells, which are Ag particles. The formation mechanism is as follows: anions are adsorbed and reduced on the surface of the material, the crystals grow due to the migration of nuclei, and new active sites are generated, continuously capturing silver ions. However, when the concentration of silver nitrate is high, the increased migration frequency results in more adsorption sites not yet covered by silver, allowing more silver particles to form on the surface. The EDS results further confirm the presence and relatively uniform distribution of Ag on the carbon surface (Figure ).

The XRD results indicate that metallic silver was formed after silver loading, suggesting that part of the adsorbed Ag+ was reduced during the heat-treatment process. For instance, in the PPAC/Ag-40 sample, diffraction peaks of metallic silver appear at 2θ values of 38.1, 44.3, and 64.5 °, which agree well with the standard Ag-PDS#97-018-0878 pattern. The metallic silver (Ag0) crystal structure is obtained (Figure a)., which corresponds to the characteristic peak of AgNO3 (AgNO3–PDF-#97-002-6506), suggesting that a small amount of residual silver precursor may remain after heat treatment. BET and pore size distribution results indicate that the silver-loaded material remains predominantly microporous, but the introduction of silver significantly reduces the specific surface area and pore volume (from 1534 to 525 m2 g–1), and the mesopores almost disappear (Figure b,c), primarily due to pore clogging or compression by silver particles. XPS results show that silver loading not only alters the surface functional group distribution of the carbon skeleton but also greatly increases the ratio of carbonyl (CO) to carboxyl (O–CO) groups, demonstrating that surface oxidation occurs during silver loading (Figure d,e). To further understand the chemical form of silver in the PPAC/Ag-40 composite, XPS of the Ag 3d region is conducted (Figure f). The Ag 3d spectrum can be deconvoluted into four main peaks: peak (I) is located at about 368.47 eV, corresponding to the 3d5/2 orbital of Ag+; peak (II) is located at about 368.50 eV, attributed to the 3d5/2 orbital of metallic silver (Ag0); peak (III) is located at about 374.50 eV, corresponding to the 3d3/2 orbital of Ag0. Silver coexists in two valence states, Ag0 and Ag+, with proportions of approximately 72.21 and 27.80%, respectively. The coexistence of Ag0 and Ag+ may contribute to both immediate and sustained antibacterial activity.

6.

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(a) XRD patterns of PPAC-10% and its samples with different silver loading concentrations, (b) N2 adsorption/desorption isotherms of PPAC-10% and PPAC/Ag-40, (c) pore size distributions of PPAC-10% and PPAC/Ag-40, (d) XPS spectra of PPAC-10% and PPAC/Ag-40, (e) C 1s spectra of PPAC-10% and PPAC/Ag-40, (f) Ag 3d spectrum of PPAC/Ag-40, (g) Representative antibacterial plate images of PPAC and PPAC/Ag samples against Escherichia coli and Staphylococcus aureus.

Antibacterial testing results show that PPAC possessed some antibacterial activity, but its efficacy decreased significantly with increasing bacterial concentration. In contrast, the PPAC/Ag series exhibited enhanced antibacterial activity against both the Gram-negative bacterium Escherichia coli and the Gram-positive bacterium Staphylococcus aureus. Representative antibacterial culture plate images (Figure g) demonstrate that PPAC-10% exhibited only limited antibacterial activity against both Escherichia coli and Staphylococcus aureus. Compared with PPAC-10%, the silver-loaded samples showed a pronounced reduction in bacterial colony growth, confirming the enhanced antibacterial performance after silver incorporation. Among the tested samples, PPAC/Ag-40 exhibited the highest antibacterial performance and maintained high inhibition rates over the investigated bacterial concentration range (Table S9). The results also suggested that antibacterial activity increased with increasing silver loading. The contact-time experiments further showed that samples with higher silver contents achieved bacterial inactivation more rapidly than those with lower silver contents (Table S10). In the cyclic antibacterial tests, PPAC/Ag-10, PPAC/Ag-20, and PPAC/Ag-40 retained strong antibacterial activity after five consecutive cycles, whereas PPAC/Ag-5 exhibited a noticeable decline in performance (Table S11). These observations suggest that silver loading contributes to the persistence of antibacterial activity during repeated use. Overall, the results demonstrate that PPAC can serve as an effective support for Ag loading, enabling the formation of silver-loaded porous carbon materials with antibacterial functionality. Although silver loading partially reduced the pore characteristics of the carbon matrix, it enhanced the antibacterial performance of the materials against both Gram-negative and Gram-positive bacteria. These findings indicate the potential of silver-loaded PPAC materials for applications requiring both adsorption and antibacterial functions. Further optimization of the preparation process, particularly with respect to heat-treatment conditions and silver dispersion, may improve the balance between pore structure and antibacterial performance.

4. Conclusion

In this study, phosphoric acid-activated porous carbon (PPAC) was successfully prepared from bamboo parenchyma cells. The results demonstrated that phosphoric acid promoted the hydrolysis, dehydration, aromatization, and crosslinking of lignocellulosic components, leading to the formation of a hierarchical pore structure composed of micropores and mesopores. Activation conditions significantly influenced pore development, and the optimal PPAC was obtained at 600 °C, 0.5 h, and a low phosphoric acid impregnation ratio, achieving a specific surface area of 1534 m2 g–1 and abundant oxygen- and phosphorus-containing functional groups.

As a preliminary exploration of value-added utilization, silver-loaded PPAC exhibited effective antibacterial activity against both Escherichia coli and Staphylococcus aureus. Future work should focus on optimizing silver loading, evaluating Ag leaching and residual precursor removal, and validating the material performance under realistic water-treatment conditions. These findings provide guidance for the structural design and functional application of bamboo-based activated carbons.

Supplementary Material

ao6c05400_si_001.pdf (543.7KB, pdf)

Acknowledgments

This research was supported by the National Natural Science Foundation of China (No. 32560408). We would like to thank the Guangxi University Multidisciplinary Integration Innovation Experimental Teaching Center for Resources, Environment, and Materials for their equipment support.

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsomega.6c05400.

  • Additional nitrogen adsorption–desorption isotherms, pore size distributions, FTIR spectra, XPS spectra and C 1s peak-fitting results, and the proposed phosphoric acid-catalyzed dehydration reaction; sample preparation conditions, activated carbon yields, pore structure parameters, surface chemical compositions, XPS peak-fitting results, assignments of gaseous products identified by FTIR, silver contents determined by ICP-OES, and antibacterial performance of PPAC/Ag composites at different bacterial concentrations and contact times and during cyclic antibacterial tests (PDF)

The authors declare no competing financial interest.

References

  1. Shen C., Gu L., Chen S.. et al. Sewage sludge-derived FeCl3-activated biochars as efficient adsorbents for the treatment of toxic As (III) and Cr (VI) wastewater. J. Environ. Chem. Eng. 2022;10(6):108575. doi: 10.1016/j.jece.2022.108575. [DOI] [Google Scholar]
  2. Yu L., Liang L., Bajaj I.. et al. Tailored mesoporous structures of lignin-derived nano-carbons for multiple applications. Carbon. 2023;213:118285. doi: 10.1016/j.carbon.2023.118285. [DOI] [Google Scholar]
  3. Deng Z., Zhang Q., Deng Q.. et al. Modification of coconut shell activated carbon and purification of volatile organic waste gas acetone. Adv. Compos. Hybrid Mater. 2022;5(1):491–503. doi: 10.1007/s42114-021-00345-7. [DOI] [Google Scholar]
  4. Zuo H., Li Z., Shi Q.. et al. Industrial scale utilization of bamboo-based columnar activated carbon for efficient treatment of Rhodamine B: Process optimization and performance analysis. Sep. Purif. Technol. 2025;379:134877. doi: 10.1016/j.seppur.2025.134877. [DOI] [Google Scholar]
  5. Cao H., Ding X., Ao S.. et al. Cellulose-based biomass foams for food packaging: current trends and future challenges. Trends Food Sci. Technol. 2025;163:105185. doi: 10.1016/j.tifs.2025.105185. [DOI] [Google Scholar]
  6. Bisht M., Thayallath S. K., Bharadwaj P.. et al. Biomass-derived functional materials as carriers for enzymes: towards sustainable and robust biocatalysts. Green Chem. 2023;25(12):4591–4624. doi: 10.1039/D2GC04792F. [DOI] [Google Scholar]
  7. Xue X., Hu J., Guo P.. et al. Cellulose-Based Composite Hydrogels for Heavy Metal Ion Removal: Recent Advances and Engineering Perspectives. Gels. 2026;12(5):380. doi: 10.3390/gels12050380. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Wang S., Nam H., Nam H.. Preparation of activated carbon from peanut shell with KOH activation and its application for H2S adsorption in confined space. J. Environ. Chem. Eng. 2020;8(2):103683. doi: 10.1016/j.jece.2020.103683. [DOI] [Google Scholar]
  9. Williams N. E., Oba O. A., Aydinlik N. P.. Modification, production, and methods of KOH-activated carbon. ChemBioEng. Rev. 2022;9(2):164–189. doi: 10.1002/cben.202100030. [DOI] [Google Scholar]
  10. Ozpinar P., Dogan C., Demiral H.. et al. Activated carbons prepared from hazelnut shell waste by phosphoric acid activation for supercapacitor electrode applications and comprehensive electrochemical analysis. Renewable Energy. 2022;189:535–548. doi: 10.1016/j.renene.2022.02.126. [DOI] [Google Scholar]
  11. Hu S. C., Cheng J., Wang W. P.. et al. Structural changes and electrochemical properties of lacquer wood activated carbon prepared by phosphoric acid-chemical activation for supercapacitor applications. Renewable Energy. 2021;177:82–94. doi: 10.1016/j.renene.2021.05.113. [DOI] [Google Scholar]
  12. Cheng T., Li J., Ma X.. et al. Behavior of VOCs competitive adsorption with water vapor in a slit-shaped phosphoric acid mesoporous activated carbon model. Sep. Purif. Technol. 2023;326:124776. doi: 10.1016/j.seppur.2023.124776. [DOI] [Google Scholar]
  13. Mishra R. K., Singh B., Acharya B.. A comprehensive review on activated carbon from pyrolysis of lignocellulosic biomass: An application for energy and the environment. Carbon Resour. Convers. 2024;7(4):100228. doi: 10.1016/j.crcon.2024.100228. [DOI] [Google Scholar]
  14. Li X., Zhang W., Lei W.. et al. Physical and mechanical properties of novel multilayer bamboo laminated composites derived from bamboo veneer. Polymers. 2022;14(22):4820. doi: 10.3390/polym14224820. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Li C., Li Z., Wang L.. et al. High-Performance Phenolic Resin Reinforced by Tannic Acid-Polyethyleneimine Functionalized Multi-Walled Carbon Nanotubes for Wood-Based Panels. Macromol. Rapid Commun. 2026;47(2):e00814. doi: 10.1002/marc.202500814. [DOI] [PubMed] [Google Scholar]
  16. Wang Y., Fang Z.. Progress in the preparation of bamboo-derived hard carbon for sodium-ion batteries: Microstructure, mechanisms, and performance optimization. J. Energy Storage. 2025;128:117244. doi: 10.1016/j.est.2025.117244. [DOI] [Google Scholar]
  17. Fu J., Bai L., Chi M.. et al. Study on the evolution pattern of the chemical structure of Fenton pretreated lignin during hydrothermal carbonization. J. Environ. Chem. Eng. 2022;10(2):107184. doi: 10.1016/j.jece.2022.107184. [DOI] [Google Scholar]
  18. Wei S., Qin Q., Liu Z.. Thermal behavior analysis and reaction mechanism in the preparation of activated carbon by ZnCl2 activation of bamboo fibers. J. Anal. Appl. Pyrolysis. 2024;179:106500. doi: 10.1016/j.jaap.2024.106500. [DOI] [Google Scholar]
  19. Zhang X., Guo F., Yu Z.. et al. Why do bamboo parenchyma cells show higher nanofibrillation efficiency than fibers: an investigation on their hierarchical cell wall structure. Biomacromolecules. 2022;23(10):4053–4062. doi: 10.1021/acs.biomac.2c00224. [DOI] [PubMed] [Google Scholar]
  20. Xia Y., Zuo H., Lv J.. et al. Preparation of multi-layered microcapsule-shaped activated biomass carbon with ultrahigh surface area from bamboo parenchyma cells for energy storage and cationic dyes removal. J. Cleaner Prod. 2023;396:136517. doi: 10.1016/j.jclepro.2023.136517. [DOI] [Google Scholar]
  21. Yameen M. Z., Naqvi S. R., Juchelková D.. et al. Harnessing the power of functionalized biochar: progress, challenges, and future perspectives in energy, water treatment, and environmental sustainability. Biochar. 2024;6(1):25. doi: 10.1007/s42773-024-00316-3. [DOI] [Google Scholar]
  22. Zhao X., Yang M., Shi Y.. et al. Multifunctional bacterial cellulose-bentonite@ polyethylenimine composite membranes for enhanced water treatment: Sustainable dyes and metal ions adsorption and antibacterial properties. J. Hazard. Mater. 2024;477:135267. doi: 10.1016/j.jhazmat.2024.135267. [DOI] [PubMed] [Google Scholar]
  23. Li J., Yeszhan Y., Bexeitova K.. et al. Recent Progress in Bio-Based SiO2–Metal Oxide Composites for Water Treatment Applications: A Review. Res. Eng. 2026;29:109416. doi: 10.1016/j.rineng.2026.109416. [DOI] [Google Scholar]
  24. Li W., Li Y., Sun P.. et al. Correction: Antimicrobial peptide-modified silver nanoparticles for enhancing the antibacterial efficacy. RSC Adv. 2024;14(20):13944. doi: 10.1039/D4RA90040E. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Liu H., Dai K., Deng J.. et al. Synthesis of antibacterial polyaluminium silicate sulfate/sepiolitenano composite coagulant for oilfield sewage treatment. J. Cleaner Prod. 2022;379:134385. doi: 10.1016/j.jclepro.2022.134385. [DOI] [Google Scholar]
  26. Kong F., Ge J., Zhu Z.. et al. A Conjugated Microporous Polymer/Wood Aerogel with Physical Adsorption, Chemical Degradation and Antibacterial Self-Cleaning Triple Sewage Treatment Functions. Polymers. 2023;15(19):3929. doi: 10.3390/polym15193929. [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. Chen W., Zhang P., Ding Y.. et al. Bioactives from biomass: Treasure for future potent antimicrobial applications. Chem. Eng. J. 2024;499:155669. doi: 10.1016/j.cej.2024.155669. [DOI] [Google Scholar]
  28. Chen Y., Zhou C., Xing X.. et al. Interconnected pyrolysis and activation with in-situ H3PO4 activation of biochar from pear wood chips in a pilot-scale dual fluidized bed. Chem. Eng. J. 2024;495:153579. doi: 10.1016/j.cej.2024.153579. [DOI] [Google Scholar]
  29. Wang L. G., Yan G. B.. Adsorptive removal of direct yellow 161dye from aqueous solution using bamboo charcoals activated with different chemicals. Desalination. 2011;274(1-3):81–90. doi: 10.1016/j.desal.2011.01.082. [DOI] [Google Scholar]
  30. Ren W., Li C., Fan M.. et al. Production of poplar branch-derived activated carbon with acidic deep eutectic solvent pretreatment coupled with chemical activation. Fuel. 2025;381:133417. doi: 10.1016/j.fuel.2024.133417. [DOI] [Google Scholar]
  31. Ouachtak H., El Haouti R., El Guerdaoui A., Haounati R., Amaterz E., Addi A. A., Akbal F., Taha M. L.. Experimental and molecular dynamics simulation study on the adsorption of Rhodamine B dye on magnetic montmorillonite composite gamma-Fe2O3@Mt. J. Mol. Liq. 2020;309(1):113142. doi: 10.1016/j.molliq.2020.113142. [DOI] [Google Scholar]
  32. Nwodika C. G., Mihalinec G., Grošev V. M.. et al. Surface-constrained catalytic graphitization and phase evolution in phosphorus-activated porous carbon. Appl. Surf. Sci. 2026;745:167445. doi: 10.1016/j.apsusc.2026.167445. [DOI] [Google Scholar]
  33. Cheng X., Li H., Jiang D.. et al. Insights into simultaneous efficient removal of cationic and anionic dyes by nitrogen-rich seaweed carbon adsorbent. Process Saf. Environ. Prot. 2024;184:38–49. doi: 10.1016/j.psep.2024.01.067. [DOI] [Google Scholar]
  34. El Hadrami A., Ojala S., Brahmi R.. Production of activated carbon with tunable porosity and surface chemistry via chemical activation of hydrochar with phosphoric acid under oxidizing atmosphere. Surf. Interfaces. 2022;30:101849. doi: 10.1016/j.surfin.2022.101849. [DOI] [Google Scholar]
  35. Baldovino-Medrano V. G., Nio-Celis V., Giraldo R. I.. Systematic Analysis of the Nitrogen Adsorption–Desorption Isotherms Recorded for a Series of Materials Based on Microporous–Mesoporous Amorphous Aluminosilicates Using Classical Methods. J. Chem. Eng. Data. 2023;68(9):2512–2528. doi: 10.1021/acs.jced.3c00257. [DOI] [Google Scholar]
  36. Zhu G. Z., Deng X. L., Hou M.. et al. Comparative study on characterization and adsorption properties of activated carbons by phosphoric acid activation from corncob and its acid and alkaline hydrolysis residues. Fuel Process. Technol. 2016;144:255–261. doi: 10.1016/j.fuproc.2016.01.007. [DOI] [Google Scholar]
  37. Wang Y., Zuo S., Yang J.. et al. Evolution of phosphorus-containing groups on activated carbons during heat treatment. Langmuir. 2017;33(12):3112–3122. doi: 10.1021/acs.langmuir.7b00095. [DOI] [PubMed] [Google Scholar]
  38. Fu R., Liu L., Huang W.. et al. Studies on the structure of activated carbon fibers activated by phosphoric acid. J. Appl. Polym. Sci. 2003;87(14):2253–2261. doi: 10.1002/app.11607. [DOI] [Google Scholar]
  39. Wan X., Yao F., Tian D.. et al. Pretreatment of wheat straw with phosphoric acid and hydrogen peroxide to simultaneously facilitate cellulose digestibility and modify lignin as adsorbents. Biomolecules. 2019;9(12):844. doi: 10.3390/biom9120844. [DOI] [PMC free article] [PubMed] [Google Scholar]
  40. Chen J., Mu L., Jiang B.. et al. TG/DSC-FTIR and Py-GC investigation on pyrolysis characteristics of petrochemical wastewater sludge. Bioresour. Technol. 2015;192:1–10. doi: 10.1016/j.biortech.2015.05.031. [DOI] [PubMed] [Google Scholar]
  41. Wei X., Ma X., Peng X.. et al. Comparative investigation between co-pyrolysis characteristics of protein and carbohydrate by TG-FTIR and Py-GC/MS. J. Anal. Appl. Pyrolysis. 2018;135:209–218. doi: 10.1016/j.jaap.2018.08.031. [DOI] [Google Scholar]
  42. Zhang J., Liu J., Evrendilek F.. et al. TG-FTIR and Py-GC/MS analyses of pyrolysis behaviors and products of cattle manure in CO2 and N2 atmospheres: Kinetic, thermodynamic, and machine-learning models. Energy Convers. Manage. 2019;195:346–359. doi: 10.1016/j.enconman.2019.05.019. [DOI] [Google Scholar]
  43. Chen D., Xu C., Ye H.. et al. New Poplar-Derived Biocomposites via Single-Step Thermoforming Assisted by Phosphoric Acid Pretreatment. Polymers. 2022;14(17):3636. doi: 10.3390/polym14173636. [DOI] [PMC free article] [PubMed] [Google Scholar]
  44. Zuo S., Xiao Z., Yang J.. Evolution of gaseous products from biomass pyrolysis in the presence of phosphoric acid. J. Anal. Appl. Pyrolysis. 2012;95:236–240. doi: 10.1016/j.jaap.2012.02.011. [DOI] [Google Scholar]
  45. Huang H., Liu J., Liu H.. et al. Pyrolysis of water hyacinth biomass parts: Bioenergy, gas emissions, and by-products using TG-FTIR and Py-GC/MS analyses. Energy Convers. Manage. 2020;207:112552. doi: 10.1016/j.enconman.2020.112552. [DOI] [Google Scholar]
  46. Shen D. K., Gu S., Luo K. H.. et al. The pyrolytic degradation of wood-derived lignin from the pulping process. Bioresour. Technol. 2010;101(15):6136–6146. doi: 10.1016/j.biortech.2010.02.078. [DOI] [PubMed] [Google Scholar]
  47. Widyawati M., Church T. L., Florin N. H.. et al. Hydrogen synthesis from biomass pyrolysis with in situ carbon dioxide capture using calcium oxide. Int. J. Hydrogen Energy. 2011;36(8):4800–4813. doi: 10.1016/j.ijhydene.2010.11.103. [DOI] [Google Scholar]
  48. Liu C., Huang J., Huang X.. et al. Theoretical studies on formation mechanisms of CO and CO2 in cellulose pyrolysis. Comput. Theor. Chem. 2011;964(1-3):207–212. doi: 10.1016/j.comptc.2010.12.027. [DOI] [Google Scholar]
  49. Yagmur E., Inal I. I. G., Gokce Y.. et al. Examination of gas and solid products during the preparation of activated carbon using phosphoric acid. J. Environ. Manage. 2018;228:328–335. doi: 10.1016/j.jenvman.2018.09.046. [DOI] [PubMed] [Google Scholar]
  50. Li J., Lian C., Wu J.. et al. Morphology, chemical composition, and thermal stability of bamboo parenchyma cells and fibers isolated by different methods. Cellulose. 2023;30(4):2007–2021. doi: 10.1007/s10570-022-05030-6. [DOI] [Google Scholar]
  51. Liang F., Wang R., Hongzhong X.. et al. Investigating pyrolysis characteristics of moso bamboo through TG-FTIR and Py-GC/MS. Bioresour. Technol. 2018;256:53–60. doi: 10.1016/j.biortech.2018.01.140. [DOI] [PubMed] [Google Scholar]
  52. Zhu Y., Huo G., Yang W.. et al. Catalytic pyrolysis of duckweed with phosphoric acid: Pyrolysis behavior and kinetics analysis. J. Anal. Appl. Pyrolysis. 2024;177:106384. doi: 10.1016/j.jaap.2024.106384. [DOI] [Google Scholar]
  53. Shadangi K. P., Mohanty K.. Kinetic study and thermal analysis of the pyrolysis of non-edible oilseed powders by thermogravimetric and differential scanning calorimetric analysis. Renewable Energy. 2014;63:337–344. doi: 10.1016/j.renene.2013.09.039. [DOI] [Google Scholar]
  54. Fan Q. G., Lewis D. M., Tapley K. N.. Characterization of cellulose aldehyde using Fourier transform infrared spectroscopy. J. Appl. Polym. Sci. 2001;82(5):1195–1202. doi: 10.1002/app.1953. [DOI] [Google Scholar]
  55. Chen S., Liu J., Zeng H.. Structure and antibacterial activity of silver-supporting activated carbon fibers. J. Mater. Sci. 2005;40(23):6223–6231. doi: 10.1007/s10853-005-3149-3. [DOI] [Google Scholar]
  56. Yue Z. R., Jiang W., Wang L.. et al. Adsorption of precious metal ions onto electrochemically oxidized carbon fibers. Carbon. 1999;37(10):1607–1618. doi: 10.1016/S0008-6223(99)00041-X. [DOI] [Google Scholar]

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