Skip to main content
NCBI home page
ACS Omega logoLink to ACS Omega
. 2023 Mar 6;8(11):10086–10099. doi: 10.1021/acsomega.2c07264

Chitosan-Based Architectures as an Effective Approach for the Removal of Some Toxic Species from Aqueous Media

Manar El-Sayed Abdel-Raouf 1,*, Reem Kamal Farag 1, Ahmed A Farag 1, Mohamed Keshawy 1, Alaa Abdel-Aziz 1, Abdulraheim Hasan 1
PMCID: PMC10035021  PMID: 36969416

Abstract

graphic file with name ao2c07264_0011.jpg

Modified uncrosslinked and crosslinked chitosan derivatives were investigated as green sorbents for the removal of copper (Cu2+) and lead (Pb2+) cations from simulated solutions. In this regard, N, O carboxymethyl chitosan (N, O CMC), chitosan beads (Cs-g-GA), chitosan crosslinked with glutaraldehyde/methylene bisacrylamide (Cs/GA/MBA), and chitosan crosslinked with GA/epichlorohydrin (Cs/GA/ECH) were prepared and characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy analyses. Atomic force microscopy investigation was carried out to compare the surface topography of the prepared samples before and after the metal uptake. The kinetics of the removal process were investigated by pseudo-first-order and -second-order models. Moreover, the adsorption isotherms were carefully studied by applying Langmuir and Freundlich models. The data reveal that upon adsorption of copper(II) metal ions, all chitosan-modified products followed the Langmuir isotherm except for Cs/GA/ECH which followed the Freundlich isotherms, and the highest adsorption capacity (qe) was obtained for Cs/GA/MBA due to the formation of stable chelate structures between the metal cation and the functional groups present on the modified chitosan product. The order of metal uptake at the optimum pH value is as follows: Cs/GA/MBA (Cu: 95.7 mg/g, Pb: 99.15 mg/g), Cs/GA/ECH (Cu: 80.4 mg/g, Pb: 93.14 mg/g), Cs-g-GA (Cu: 77 mg/g, Pb: 88.4 mg/g), and N, O CMCh (Cu: 30.2 mg/g, Pb: 44.8 mg/g). The AFM data confirmed the metal uptake process by comparing the roughness and height measurements of the free sorbents and the metal-loaded sorbents.

1. Introduction

There are different contaminants discharged into water resources such as hydrocarbons,1 oil spills and petroleum sludge,2 detergents,3 and heavy metals.4 Unlike organic pollutants which are mostly volatile or degradable, pollution caused by heavy metals is a major concern in modern civilization because of the considerable impact it has on both the health of individuals and the environment.5,6 Both lead (Pb) and copper (Cu) are examples of heavy metals that are frequently discharged into natural streams as a consequence of a wide range of industrial processes and activities such as burning of fuels, particularly coal and gasoline, industrial furnaces, waste motor oils, sewage, sewage sludge, and so on.7 Pb(II) exposure can result in several adverse health effects, including—but not limited to—poisoning, anemia, kidney diseases, mental disorders, malignant tumors, and even death.8,9 Cu(II) poisoning is associated with a variety of pathologic processes that are detrimental to the health of individuals.10 As a consequence of this, the development of a suitable technique for extracting lead and copper from wastewater is highly required.11 To date, diverse methods have been established to eliminate heavy metal ions from wastewater, including precipitation,12 coagulation/flocculation,13 photocatalytic degradation,14 ion exchange,15 and adsorption.16−18 Among them, the adsorption method is considered an operative wastewater handling process due to its simple and flexible design, low-cost, high effectiveness, and absolute readiness.19 Different materials have been studied for the adsorption of heavy metal ions from wastewater such as carbon-based materials, bio-char, nanoparticles, and organic frameworks.20 Nevertheless, there are limitations in most of these species, such as complex synthesis, longtime separation, low regeneration, and limited reuse.21 Thus, the application of such adsorbents for the disposal of heavy metal ions at the commercial level is relatively difficult. Natural polymers, particularly polysaccharides, are highly favored materials due to their considerable resources, bio-degradability, high functionality, and respectable economic and ecological benefits besides their sustainability.22−24 Chitosan (Cs) is an abundant naturalistic polysaccharide which has been widely investigated in the field of remediation of wastewater polluted with heavy metal ions and dyes.25,26 Chitosan involves numerous reactive amino groups and hydroxyl groups that can catch the heavy metal ions via electrostatic attraction, ion exchange, and chelation.27 Moreover, the high functionality of chitosan enables different chemical modifications through grafting or crosslinking with other reactive groups such as sulfate and phosphate.28 Chemical crosslinking of linear chains of Cs can be performed via crosslinking agents such as glutaraldehyde (GA) and epichlorohydrin (ECH) to form a triple network structure with enhanced mechanical properties and improved adsorption capacity. The Cs-based adsorbents are widely applied in wastewater treatment.29,30

In this regard, Wu et al.31 employed a double network hydrogel comprising chitosan cross-linked with ethylenediaminetetraacetic acid (EDTA) and a polyacrylamide network cross-linked with N,N-methylene bis(acrylamide) (MBA) for heavy metal ion adsorption. Özkahraman et al. synthesized a thermosensitive hydrogel using N-isopropylacrylamide as a thermosensitive monomer and chitosan as the parent chain to remove copper and lead ions from aqueous solution with adsorption capacities of 0.96 and 0.27 mmol/g, respectively.32 Zhang et al. produced a new grafted chitosan and biochar composite with polyacrylic acid (PAA/CTS/BC) for vastly effective and selective capture of heavy metals ions including Cu(II), Zn(II), Ni(II), Pb(II), Cd(II), Mn(II), Co(II), and Cr(III).33 In our previous work,34 green composites encompassed of guar gum (GG)/chitosan (CH) crosslinked with GA were prepared and then fabricated with different weight ratios (1, 2, and 3%) of talc powder as the inorganic core. The biosorbents were employed for the removal of methylene blue and toxic heavy metal cation (Hg2+) from aqueous solutions. Hg2+ and MB dye have attained the maximum removal performance of 277.4 and 57.992 mg/g, respectively. In another work,35 CH/erythritol/GO products were prepared by green protocols as sorbents for some toxic pollutants from simulated solutions. The synthesis plan was guided by the atomic force microscopy (AFM) outcomes to select the optimum sorbent at each step.

The novelty of this work relies on functionalization of the chitosan modified from chitin of shrimp shells via different protocols (carboxymethylation, grafting, and crosslinking) into cost-effective sorbents for the removal of copper(II) and lead(II) as model heavy metals from aqueous media. AFM is used to confirm the metal uptake process by comparing three AFM outcomes (topography, height, and roughness) in the dry and metal-loaded samples. The prepared derivatives were fully characterized by different techniques, and the kinetics of the removal process and the adsorption isotherms were carefully studied. Moreover, the experimental factors that affect the metal uptake process were thoroughly investigated.

2. Materials and Methods

The materials used throughout this work are illustrated in Table 1.

Table 1. Materials Used in This Work.

the material source description
chitosan obtained from chitin extracted from shrimp shells deacetylation degree of 88% and a Mw of 1.0–3.0 × 105 g mol–1
chloroacetic acid Sigma-Aldrich, Germany analytic reagent white crystals
glacial acetic acid El-Nasr chemicals, Egypt ultrapure colorless liquid
α-ketoglutaric acid local supplier (El-Nasr company for chemicals) analytic reagent fine white powder
sodium borohydride Local supplier (El-Nasr company for chemicals) white powder of 98% purity
GA Local supplier (El-Nasr company for chemicals) 50% wt in DW
ECH Local supplier (El-Nasr company for chemicals) colorless liquid
MBA Thermo-Fischer, USA pale white crystals
sodium hydroxide El-Nasr chemicals, Egypt white pellets
hydrochloric acid Local supplier (El-Nasr company for chemicals) colorless liquid
copper(II) nitrate trihydrate Thermo-Fischer, USA pure bright blue crystals
lead(II) nitrate Thremo-Fischer, USA white crystalline powder
Open in a new tab

2.1. Preparation of N, O Carboxymethyl Chitosan

A feasible procedure was followed. Briefly, 5 g of Cs was dissolved in 100 ml of 1% acetic acid solution and stirred until complete solubility. Then, 8 g of α-ketoglutaric acid was added, and the pH was adjusted to about 5.0 with sodium hydroxide solution with rapid stirring. After continuing the reaction for 4 h at room temperature, 1.2 g of sodium borohydride was added and the pH was adjusted to neutral with dilute hydrochloric acid solution. The reaction was continued for 12 h. Finally, the product was separated, filtered, and washed by ethanol and then transferred to a Soxhlet extractor and extracted continuously with ethanol for 6 h. The dried solid N, O- carboxymethyl chitosan (N, O-CMCs) was obtained after vacuum drying, Figure 1a. The degree substitution of N, O-CMCs was found to be 37.2% as calculated with the aid of the potentiometric titration method.

Figure 1.

Figure 1

Open in a new tab

Chitosan-modified products: (a) N, O CMC, (b) wet uncrosslinked CH beads, and (c) wet crosslinked chitosan beads (Cs/GA/MBA).

2.2. Preparation of Chitosan Beads (Cs-g-GA)

Cs solution was prepared by dissolving 2 g of chitosan in 60 mL of 5% (v/v) acetic acid solution. Then, the chitosan solution was dropped into a precipitation bath containing 500 mL of 0.50 M NaOH with continuous stirring. The desired amount of GA was added with constant stirring for an hour. The wet chitosan gel beads were extensively rinsed with distilled water to remove any NaOH, filtered, and finally air-dried to remove the water from the pore structure (hereafter called chitosan beads). The beads were ground and sieved to an average equal size (<250 μm) before use. The beads are relatively non-uniform due to relative sensitivity when adding NaOH, Figure 1b.

2.3. Preparation of Crosslinked Cs

A crosslinker solution containing 0.20 M of equimolar GA/ECH or GA/MBA mixture was prepared. The pH of this solution was adjusted to 10 by the addition of sodium hydroxide. Then, freshly prepared wet Cs beads were added to the mixed crosslinker solution to obtain a ratio of 1:1 with Cs (mol crosslinker/mol CH2OH). The solution containing Cs beads was heated to a temperature between 40 and 50 °C for 2 h and stirred continuously using a magnetic stirrer. Afterward, the crosslinked beads were filtered and washed intensively with distilled water to remove any unreacted crosslinkers and then filtered and air dried. The newly formed products (hereafter called Cs/GA/MBA and Cs/GA/ECH) were ground and sieved to a constant size (<250 μm) before use. Figure 1c displays Cs/GA/MBA.

2.4. Characterization of Prepared Derivatives

Fourier transform infrared (FTIR) spectra of chitosan derivatives were recorded by FTIR spectrometer Nicolet 6700 (Thermo Scientific). Each sample was mixed with KBr powder and then compressed under a hydraulic pressure of 400 kg cm–2 to make a pellet. The spectra were recorded at an ambient temperature at wavenumbers ranging from 4000 to 400 cm–1. The crystallographic properties of the prepared compounds were investigated via an X-ray diffractometer (Rigaku Ultima-IV). The powder of each sample was loaded on the sample holder and scanned in the reflection mode at a 2θ angle over a range from 5 to 90° at a speed of 8° min–1. The thermal properties were estimated by ELTRA’s thermogravimetric analysis (TGA) Thermostep ML in the temperature range 0–600 °C with rate of heating 10 °C/min. The surface area, average pore volume, and average pore size of the investigated sorbents were estimated by a BILSORB-Minix at 350 °C using the Brunauer–Emmett–Teller (BET) equations and Dubinin–Astakhov method. The surface of chitosan derivatives was photographed using a high-resolution field emission scanning electron microscope (JSM-7610F). The photographing took place at an accelerated voltage of 15 kV and a magnification of 2000×. An atomic force microscope, model Flex-Axiom Nanosurf, C3000 was used to study the topography and crystallinity of the prepared modified chitosan sorbent. The images were taken in the contact mode using an NCLR cantilever at a frequency of 9 KHz.

2.5. Adsorption Experiments

2.5.1. Preparation of Solutions

Stock solutions of Pb(II) and Cu(II) (0.01 mol/L) were prepared by dissolving Pb(NO3)2 and Cu(NO3)2·3H2O individually in distilled water. For the batch experiments, solutions containing metal ions were prepared by diluting the stock solution of the metal ions to the desired concentration. The pH value of the aqueous solutions was adjusted by adding small amounts of HCl or NaOH solutions.

2.5.2. Removal Performance Test

The metal ion adsorption experiment was carried out by adding 0.05 g of chitosan-modified product into 50 mL of (25, 50, 75, and 100 ppm) metal ion solution. The percentage of removal was monitored by withdrawing 1 ml of the solution at a predetermined time, and the remaining concentration of the metal after adsorption was measured using atomic adsorption spectroscopy (AAS). The percentage removal (R%) and the adsorption capacity (qe) of the metal ion can be computed as follows36

2.5.2. 1
2.5.2. 2

where C0 and Ce (mg/L) are the liquid-phase initial concentration of the metal cation and at equilibrium, respectively, V (L) is the volume of metal ion solution, and m (g) is the mass of adsorbent. The batch adsorption isotherm studies were conducted in a similar manner at pH 7 by varying the metal ions concentration 25–100 mg/L at 25 OC. The amount adsorbed at equilibrium (qe) was calculated by using eq 1. In order to verify the effect of application conditions on the efficiency of heavy metal removal, metal uptake experiments were conducted at pH range 4–9 and at temperature range 25–45 °C. Each experiment was repeated three times, and the mean value was considered.

2.6. Reusability Experiments

The metal-loaded sorbent was immersed in 20 mL of 1 N HCl for 60 °C at 250 rpm stirring speed under ambient temperature to ensure complete desorption. The sorbent was recovered from the solution by filtration and was carefully washed with double distilled water and reused in three successive cycles. The metal ion in the filtrate was measured by AAS. The reusability efficiency (%) was determined from eq 3.

2.6. 3

3. Results and Discussion

3.1. Preparation of Chitosan-Modified Products

The chemical modification protocols involved in this work include carboxymethylation, grafting, and crosslinking. All these reactions take place mainly on the hydroxyl and amine groups to increase the functionality of chitosan and to improve its overall properties. The carboxymethylation of chitosan is given in Scheme 1. Generally, the methylation was performed in two steps; the first step involved reductive substitution of the amine group with the aid of NaBH4, while the second step included carboxymethylation of the primary O–H group.

Scheme 1. Preparation of N, O CMC and Non-crosslinked Chitosan Beads (Cs-g-GA).

Scheme 1

Open in a new tab

On the other hand, GA can be connected with chitosan in two ways according to the chitosan/GA ratio. The first involves grafting onto the chitosan molecule via removal of water molecules from the carbonyl group of the aldehyde and the hydrogen of amine groups. According to Monteiro et al.,37 this reaction is best performed at pH 3–4 and the expected protonation of the amine groups of the chitosan does not affect the reaction (Scheme 1). However, the concentration of GA strongly affects the physical and chemical properties of the compounds formed. Thus, the increased chitosan/GA ratio may shift the reaction toward crosslinking rather than grafting to produce crosslinked chitosan. The addition of another crosslinker leads to formation of a double-crosslinked chitosan (Scheme 2a,b).38 In the present work, two double-crosslinked chitosans were prepared by using GA with MBA and ECH aiming to change the functionalities and the length of the spacer in order to enhance the adsorption process. Ritonga et al.39 prepared CH co-polyacrylamide-cl-GA with various degrees of swelling for agriculture purposes. They found that changing the ratio of chitosan/crosslinkers affects the swelling capacity of the hydrogel. In this work, we selected an optimized CH/crosslinker ratio for proper degree of crosslinking that fits maximum absorption. In addition, Gallan40 and his co-workers introduced an optimized formula comprising chitosan-CL-GA for the effective removal of Reactive Blue 4 anionic dye from the simulated solution. On the other hand, Farias et al.41 prepared chitosan beads crosslinked with GA or ECH for adsorption of diesel. In this article, we combined the two crosslinkers in one architecture in order to attain maximum adsorption performance by controlling the pore size and degree of crosslinking.

Scheme 2. Preparation of (a) Cs/GA/MBA and (b) Cs/GA/ECH.

Scheme 2

Open in a new tab

3.2. Characterization of the Prepared Derivatives

3.2.1. FTIR Spectra of Cs and N, O-CMCs

FTIR spectra for Cs extracted from crab shells and N, O-CMCs (Figure 2) were compared to confirm the carboxymethylation process and possible substitution sites of carboxymethylation in N, O-CMCs. For N, O-CMCs, the wide band in the range of 3200–3600 cm–1 corresponds to the axial stretching of the overlapped O–H and N–H beaks.42,43 This significant peak becomes broader which shows more hydrophilic character of N, O-CMCs compared to Cs. The peak at 2883 cm–1 corresponds to the axial stretching of the C–H bonds.44 The significant peak at 1625.50 cm–1 is assigned to NH3+, indicating that the carboxymethylation occurred mostly at the OH position, leaving some free amine groups. In the N, O-CMCs spectrum, the peak at 3307 cm–1 assigned for the secondary amine is broader than the corresponding peak at chitosan, indicating that the carboxymethylation had also occurred at NH position in N, O-CMCs. The stretching vibration of C–O in the CH2COOH group gives rise to the peak at 1405.53 cm–1, which was not observed in chitosan. The peaks at 1154.79 and 1072.41 cm–1 are the results of vibrations of C–O and C–O–C of the polysaccharide chain also observed in chitosan. From the FTIR spectra, it is confirmed that the carboxymethylation takes place at both amino groups and hydroxyl groups. On the other hand, the most significant peak of chitosan is observed at 1635.47 cm–1, which is assigned to the bending vibration of the −NH2 group. The definite peak observed at the wavenumber of 3437.64 cm–1 is the stretching vibration of overlapped peaks of −NH2 and −OH groups.45−47

Figure 2.

Figure 2

Open in a new tab

IR spectra of Cs extracted from crab shells, N, O-CMCs, Cs-g-GA, Cs/GA/MBA, and Cs/GA/ECH.

3.2.2. FTIR Spectra of Other Chitosan-Modified Products

T FTIR spectra of Cs-g-GA, Cs/GA/MBA, and Cs/GA/ECH are also displayed in Figure 2. The FTIR spectrum of Cs-g-GA reveals that the main peaks are shifted upfield or downfield from their original position due to the grafting process due to the interaction between the reacting groups which may include protonation, electron delocalization, and polarization.41,48 For instance, the N–H and O–H stretching vibration peaks shifted to 3417 cm–1, the CH3 symmetric stretch shifted to 2993 cm–1, the C=O stretching vibration shifted to 1640 cm–1, and the C–N stretching vibration shifted to 1470.7 cm–1.49,50 The appearance of the peak at 1513 cm–1 can be attributed to the grafting of GA onto the chitosan backbone. Also, the new sharp peak that emerged at 1640 cm–1 represents stretching vibrations of C=N in Schiff’s base formed by the reaction of GA and CH. In addition, Monteiro et al.37 revealed that the increase of GA in the sequence of these modified CH products caused a successive increase in the intensity of the ethylenic bond frequency at 1562 cm–1 (appears at 1513 cm–1 in this work). On the other hand, the IR spectrum of Cs/MBA/GA displays a wide peak at 3512.31 cm–1 for the overlapped NH2 and OH groups. The peak at 2911.1 cm–1 is attributed to the symmetric vibration of aliphatic C–H. The peaks at 1560 and 1510 cm–1 are assigned to the secondary amine groups of MBA which confirm the reaction with MBA. The peak at 1130.3 cm–1 is common for the ether bond of the saccharide ring.51 The IR spectrum of Cs/GA/ECH shows the following peaks: a broad band at 3588 cm–1 attributed to N–H stretching overlapped with the O–H stretching vibration and the bands at 2912 cm–1 correspond to the characteristic C–H stretching, while the absorption bands at 1750 and 1270 cm–1 are related to amide I. The ECH modification does not introduce new absorbance bands. In particular, the characteristic peaks of the epoxy group are absent in the modified product. ECH can react with hydroxyl, amino, and carboxyl groups of modified chitosan so as to crosslink chitosan chains via the formation of the −CH2–CH(OH)–CH2– linkage which does not produce any new significant peaks.

3.3. Scanning Electron Microscopy Characterization

Scanning electron microscopy (SEM) was used to characterize the surface and morphology of selected samples of the prepared modified products and to confirm the chemical modification process.52 In this regard, the SEM images of N, O CMC, Cs-g-GA, and Cs/GA/MBA are given in Figure 3a–c. All the provided images clearly indicated that there is a difference in the surface microscopic morphology between all the investigated derivatives. Indeed, compared to the crystalline nature of chitosan, the SEM images revealed that N, O CMC had a clustered appearance with a rough and porous surface, which is consistent with the result of previous studies.53 The rough surface morphology of Cs-g-GA may be due to fact that GA groups were partly grafted onto chitosan, indicating that the reaction has taken place on the surface.54

Figure 3.

Figure 3

Open in a new tab

SEM images of (a) N, O CMCs, (b) Cs-g-GA, and (c) Cs/GA/MBA.

3.4. X-ray Diffraction Characterization

X-ray diffraction (XRD) was conducted to verify the microstructure and crystallinity of the sample. Figure 4a displays the diffraction patterns of N, O CMCs, Cs-g-GA, Cs/GA/MBA, and Cs/GA/ECH. The peak at 13° exists only in the XRD pattern of N, O CMC and absent in all the other patterns. Other peaks appear in the diffractograms of N, O CMC at 32, 35, and 39° reveal more amorphous nature than chitosan. On the other hand, the XRD pattern of Cs-g-GA showed only one broad peak at about 20°. The lower crystallinity of Cs-g-GA is ascribed to the presence of grafted GA residue, which hindered the formation of inter- and extra-molecular hydrogen bonds.55 On the other hand, the diffractograms of Cs/GA/ECH show multiple peaks at different 2θ values, indicating a highly crystalline structure due to the crosslinking process. Our data are consistent with the findings of other workers.56

Figure 4.

Figure 4

Open in a new tab

Charts of (a) XRD patterns of crosslinked CH derivatives, (b) TGA thermograms of chitosan-based sorbents, and (c) DTG curves of chitosan-based sorbents.

3.5. Thermal Properties of Chitosan-Modified Products

The TGA and DTG thermograms of the chitosan-based sorbents are illustrated in Figure 4b,c, respectively. It can be seen that the thermal stability of the crosslinked compound(s) is higher than that of the grafted and non-crosslinked modified products. The degradation patterns imply that the degradation stages of the crosslinked Cs/GA/MBA appear at higher temperatures than the other compounds. Moreover, the amount of the material left is greater than other non-crosslinked compounds which proves the higher thermal stability of the crosslinked derivative and designate its possible use at high temperature applications. Therefore, the order of thermal stability is as follows: crosslinked Cs/GA/MBA, Cs/GA/ECH> grafted Cs-gGA> modified N, O CMC. Our data are consistent with Yan et al.57 in their investigation on CMC hydrogels.

3.6. Total Surface Area and Average Pore Volume

The interior features of the modified products were studied using BET measurements via the N2 adsorption–desorption isotherm method. The BET surface area and Dubinin–Astakhov average pore volume and average pore diameter are tabulated in Table 2. It can be seen that the crosslinked products displayed higher total surface area and average pore volume than the grafted and the functionalized products. The data showed that the measurements assigned for Cs/GA/MBA are the highest, which indicates that this crosslinked derivative possesses a more developed pore structure and more active adsorption sites, thus reducing the mass transfer resistance in the adsorption process and smoothing the adsorption. This finding may assist the data of the removal performance mentioned in the next sections. It is stated that the porosity can be controlled by adjusting the degree of crosslinking.58

Table 2. Data for Interior Features of the Investigated Sorbents.

sorbent total surface area (m2/g) average pore volume (cc/g) average pore diameter (nm)
N, O CMCs 22.4 0.013 4.02
Cs-g-GA 31.6 0.038 4.13
Cs/GA/MBA 68.9 0.092 5.56
Cs/GA/ECH 51.6 0.051 4.91
Open in a new tab

3.7. Adsorption Experiments

3.7.1. Effect of Contact Time

The data in Figure 5a,b illustrate the effect of contact time and metal ion concentrations on the uptake of each pollutant by the chitosan-modified products for copper ions and lead cations, respectively. Regarding the contact time, the adsorption rates were found to be fast, conquering 35–75% of adsorption equilibrium uptake within the first 15 min, approaching an equilibrium after 170–250 min. Thus, an excessive contact time of 360 min was chosen for conducting the subsequent adsorption experiments.59,60 This may be attributed to the occupation of the active sites available for metal uptake leading to a decrease in the rate of metal removal by time.

Figure 5.

Figure 5

Open in a new tab

(a) Variation of adsorption capability vs time and the initial concentration of Cu2+ ions. pH = 7, sorbent dose = 0.05 gm, 25 °C. (b) Variation of adsorption capability vs time and initial concentration of Pb2+ ions. pH = 7, sorbent dose = 0.05 gm, 25 °C.

3.7.2. Effect of Metal Ion Concentration

Recalling Figure 5, it can be observed that the rate of metal removal (R %) decreases with the increase of initial concentration of copper metal ions from 25 to 100 ppm for N, O CMCs, while the opposite trend is observed for the crosslinked products. This observation was also recorded by Vieira et al. in a similar work.61 Moreover, the data reveal that the maximum metal removal was achieved by Cs/GA/MBA with R% values of 91.8 and 93.4% for copper and lead cations at 100 ppm, respectively, which indicates the presence of numerous active sites on Cs/GA/MBA crosslinked chitosan available for heavy metal uptake at high concentrations.

3.7.3. Effect of pH on the Metal Uptake Process

The pH of the medium is a very important factor that controls the process of metal uptake since it influences the protonation of the functional groups existing in the sorbent material and it controls its degree of ionization. The effect of pH was verified by the batch mode experiments in a range 4–9 keeping the other conditions constant (0.05 adsorbent, 100 ppm of the metal cation, ambient temperature, and 300 min of contact time). The maximum uptake values were attained at pH 5.0 for Cu(II) and pH 8 for Pb(II) according to the data presented in Figure 6a,b for copper and lead cations, respectively. Some investigators claimed that the largest adsorption values in the case of Cu(II) and Pb(II) ions are in the pH range 6–8.62

Figure 6.

Figure 6

Open in a new tab

(a) Effect of pH on adsorption of copper(II), (b) effect of pH on adsorption of lead(II), and (c) effect of temperature on removal capacity of chitosan-modified sorbents vs copper(II) and lead(II).

Lower removal efficiencies in the strong acidic medium were attributed to a competition between metal ions and protons for adsorption sites. Thus, the adsorption of both metal ions increased when the pH was shifted toward higher values (from 4 to 5 for copper and from 4 to 8 for lead) due to that the amino groups become deprotonated for enhanced adsorption capacity in the chelation mechanism of heavy metal ions. However, further increase in the pH of the medium in copper removal experiment leads to precipitation of copper cations which causes a reduction of Qmax. This finding was observed by other workers.63 Wan Ngah et al.64 found that the maximum uptake of Cu(II) onto chitosan beads, chitosan/GLA beads, chitosan/ECH beads, and chitosan/EGDE beads was attained at pH = 6 with remarkable decrease in the metal uptake over this value. When comparing the removal capacities of the as-prepared sorbents toward both metal cations, it is clear that the crosslinked species achieved more metal uptake than the functionalized products. This finding may be due to several factors including the effectiveness in charge compensation and ionic binding, length of interconnections between chains,65,66 and the degree of crosslinking.67 Therefore, the order of metal uptake at the optimum pH value is as follows: Cs/GA/MBA (Cu: 95.7 mg g, Pb: 99.15 mg g), Cs/GA/ECH (Cu: 80.4 mg g, Pb: 93.14 mg g), Cs-g-GA (Cu: 77 mg g, Pb: 88.4 mg g), and N, O CMCh (Cu: 30.2 mg g, Pb: 44.8 mg g).

3.7.4. Effect of Temperature on Removal Performance

The impact of temperature on metal uptake in the temperature range of 25–45 °C is illustrated in Figure 6c,d for copper and lead, respectively. The data display that the maximum amount of metal adsorbed onto the sorbent material slightly decreases upon rising temperature from 25 to 45 °C. It can be observed that this decrement is governed by several factors as follows:

  • The types and distribution of the functional groups.

  • The nature of material: chemically modified, grafted, or crosslinked.

  • The nature of crosslinking.

The effect of increasing temperature on the metal uptake of the uncrosslinked sorbents is less pronounced than the same effect on the crosslinked derivatives due to that the higher temperature causes shrinkage and disorder in the network structure which finally leads to desorption of metals and escaping of the desorbed metal from the pores.68,69 Chitosan crosslinked products possess a high surface area than grafted counterparts and thus they can capture the dissolved species which interact with the functionalities of the polymer matrix either by electrostatic attraction or by complexation. This interaction is disturbed at higher temperatures, and the adsorbed species are liberated into the solution.

3.8. Adsorption Kinetics

3.8.1. Adsorption Kinetics of the Chitosan-Modified Products toward Copper and Lead Ions

The kinetics of the metal uptake process was thoroughly studied in order to evaluate the typical mechanism and the efficiency of the process. Although there are numerous models that can be applied, the classical pseudo-first order and pseudo-second order were used for characterizing the kinetics data. They can be expressed in eqs 4 and 5, respectively.

3.8.1. 4
3.8.1. 5

where t is the time (min), qe, qt, and qe2 are the amounts of metal adsorbed onto adsorbent at equilibrium, at time t, and the maximum adsorption capacity (mg/g), respectively. The terms k1 and k2 are the adsorption rate constant of pseudo-first-order (1/min) and pseudo-second-order (g/mg/min). The first-order model implies that the reaction only depends on concentration of one reactant, while the pseudo-second-order model points that the chemisorption depends on two reactants. The adsorption kinetics are presented in Figure S1a,b for Cu(II) and Pb(II) adsorption for N, O CMC, chitosan beads (Cs-g-GA), Cs/GA/MBA, and Cs/GA/ECH, respectively, while the obtained kinetic parameters of Cu(II) and lead(II) adsorption are summarized in Table 3a.

Table 3. (a) Adsorption Kinetic Parameters for Metal Ion Removal; (b) Adsorption Isotherms for the Copper and Lead Cations Sorbed onto Chitosan Modified Products.
(a)
  pseudo-first order
 pseudo second order
  
  k1 ads (1/min) R2 qe (mg/g) K2 ads (1/min) R2 qe (mg/g) Qexp
Kinetics Parameter/Compound/Cu2+ Cations
N, O CMC 0.0131 0.9907 18.5 0.00136 0.9758 21.8 20.1
Cs-g-GA 0.0138 0.9640 32.622 0.00131 0.9961 68.17 66.75
Cs/GA/MBA 0.0347 0.937 211.75 4.89 × 10–4 0.99 98.713 91.75
Cs/GA/ECH 0.022 0.893 125.2 3 × 10–4 0.961 83.73 76.37
Kinetics Parameter/Compound/Pb2+ Cations
N, O CMC 0.0131 0.9907 14.8 0.00291 0.9977 36.70 36.09
Cs-g-GA 0.0138 0.9647 26.1 0.0018 0.9983 74.38 73.4
Cs/GA/MBA 0.0347 0.9410 169.4 0.00073 0.9951 98.04 93.4
Cs/GA/ECH 0.0210 0.8911 100.2 0.0006 0.9821 85.39 81.096
(b)
  Langmuir kinetics
   Freundlich kinetics
  Qmax (mg g) RL R2 N kF (mg g) R2
Isotherm Parameters CH Derivatives Cu2+
N, O CMC 1.805 0.746 0.992 6.197 0.020 0.978
Cs-g-GA 32.72 0.411 0.997 0.722 0.053 0.995
Cs/GA/MBA 45.41 0.192 0.9854 0.3196 0.103 0.954
Cs/GA/ECH 27.52 0.407 0.9704 0.73 0.055 0.974
Pb2+
N, O CMC 9.771 0.65 0.9985 2.179 0.004 0.9973
Cs-g-GA 43.44 0.308 0.999 0.503 0.075 0.997
Cs/GA/MBA 55.72 0.13 0.992 0.234 0.114 0.962
Cs/GA/ECH 39.78 0.3 0.987 0.49 0.0783 0.982
Open in a new tab

3.8.2. Adsorption Isotherms of Chitosan modified Products

Adsorption isotherm is an important factor for understanding the adsorption efficiency and exploring the adsorption mechanism. The adsorption isotherm explores the relationship between the adsorption capacity and concentration at equilibrium. The linear Langmuir adsorption isotherm and linear Freundlich adsorption isotherm are given in eqs 6 and 7, respectively

3.8.2. 6
3.8.2. 7

where Ce (mg/L) is the equilibrium concentration, qe (mg/g) is the equilibrium adsorption capacity, and qm (mg/L) is the highest adsorption capacity. KL (L mg–1) is the Langmuir adsorption constant linked to the adsorption energy, whereas KF (L/g) is the Freundlich adsorption constant relevant to the adsorption capacity and n is the Freundlich constant related to the degree of surface inhomogeneity. RL is known as the separation factor defined by Webber and Chakkravorti was used to calculate the shape of the Langmuir isotherm in eq 8

3.8.2. 8

where Ci is the initial metal ion concentration and KL is the Langmuir constant. The value of RL indicates the type of isotherm. The findings are illustrated in Table 3b. The data reveal that N, O CMC, Cs-g-GA, and Cs/GA/MBA obey Langmuir isotherm with 0 < RL < 1 for copper absorption which indicates that the reaction is favorable, while Cs/GA/ECH best fits Freundlich isotherm with an R2 value of 0.974 and a N value of 0.73 and a KF of 0.055 which may be due to the change in the length of the side chains of the network and the nature of combination with copper. Our finding is consistent with Sahin et al.69 in their study concerning the adsorption properties of two chitosan-based ligands toward Cu(II), Pb(II), Zn(II), and Ni(II) ions in an aqueous solution. On the other hand, N, O CMCs, Cs-g-GA, Cs/GA/MBA, and Cs/GA/ECH, all chitosan-modified products are all following Langmuir isotherm for lead uptake with correlation coefficients (R2) of 0.9985, 0.999, 0.9923, and 0.987 with RL of 0.65, 0.308, 0.13, and 0.3, respectively. From Table 4, Cs/GA/MBA showed the highest adsorption capacity with Qmax values 45.4 mg/g and 55.7 mg/g for copper and lead adsorption, respectively. Following the Langmuir isotherm model indicated the homogeneous distribution of adsorption sites on the adsorption’s surface and this means a single layer of the metal copper ions was formed on the surface of chitosan-modified products. The Langmuir and Freundlich isotherm models are displayed in Figure S2a,b.

Table 4. AFM Data of the Unloaded and Metal-Loaded CH Derivatives.
  height
 Ra (nm) (average area roughness)
sample before Cu loaded Pb loaded before Cu loaded Pb loaded
N, O CMC 561 pm 1.02 nm 8.9 nm 23.23 11.17 9.28
Cs-g-GA 64.1 nm 87.3 nm 92.11 nm 27.41 20.09 18.92
Cs/GA/MBA 8.31 nm 158 nm 177.1 nm 34.54 20.78 19.31
Cs/GA/ECH 3.21 nm 87.3 nm 110.4 nm 40.22 25.66 22.14
Open in a new tab

3.8.3. Surface Mapping and AFM Characterization

AFM is a very effective tool for surface and mapping characteristics.36,47 Herein, a deep AFM investigation was conducted to monitor the surface and topography changes of the modified chitosan before and after metal uptake. The main AFM outcomes are the height and roughness. Moreover, the images are analyzed with advanced software (Gwyddion) in order to give the complete details of surface features and the changes occurred due to the chemical modification. Different images with variable outputs are given for all the modified products as illustrated in Figures S3 and S4. The data obtained from these images are tabulated in Table 4. Interpretation of the data that are given in Table 4:

  • The non-crosslinked derivative depicts the lowest height and roughness.

  • The height range of the grafted chitosan, that is, chitosan/GA is lower than the double-crosslinked chitosan derivative. This may be due to increased crosslinking points and greater pore volume.

  • The values of height and roughness changed remarkably after metal uptake. The height increased proportionally to the metal uptake process, while the roughness measurements decreased due to wetting of the surface with the metal cation solution.

  • Upon comparing the images of the investigated compounds before and after adsorption, the adsorbed metal appeared as a bright layer on the surface. The intensity of this layer increased with increasing removal capacity.

In our previous works,34,35 we could apply the AFM for confirming the adsorption process by comparing the AFM outcomes before and after metal uptake. We found that the adsorbed species appear as a bright layer covering the surface causing the increase in the height measurement and the change in roughness values.

3.8.4. Monitoring the Removal Process by an Optical Camera

The photos of the dry compounds and the copper loaded ones are given in Figure S5. The blue color is due to the uptake of Cu2+ cations. The intensity of the color is dependent on the removal performance. It is worth mentioning that lead nitrate is colorless and no change in color can be noticed between dry and lead-loaded samples. Moreover, the adsorption performance of the prepared sorbents was compared to other chitosan adsorbents (Table 5).

Table 5. Adsorption Performance of Some Chitosan-Based Sorbents in the Removal of Heavy Metal Ions.
adsorbent adsorbate pH ads. cap. (mg g) kinetic model isotherm model ref
CS/CNT/CoFe2O4 Pb(II) 6 140 PSO Langmuir (5)
MCS/CNT Pb (II) 5 101 PSO Sips (18)
CS/CNT/PDA Cu(II) 7 112 PSO Langmuir (7)
CS/CMSt Cu(II) 5 96 PSO Freundlich (49)
N, O CMCs Cu(II) 5 30.2 PFO Freundlich this work
  Pb(II) 8 44.8 PSO Langmuir this work
Cs-g-GA Cu(II) 5 77 PSO Langmuir this work
  Pb(II) 8 88.4 PSO Langmuir this work
Cs/GA/MBA Cu(II) 5 95.7 PSO Langmuir this work
  Pb(II) 8 99.15 PSO Langmuir this work
Cs/GA/ECH Cu(II) 5 80.4 PFO Freundlich this work
  Pb(II) 8 93.14 PSO Freundlich this work
Open in a new tab

3.9. Regeneration Study

As displayed in Figure 7, the adsorption capacity and recovery ratio toward copper and lead are slightly reduced after three repeated adsorption–desorption cycles. However, the prepared materials show relatively similar selectivity toward the two metals which confirms that the metal uptake process is probably a chemical rather than a physical mechanism.

Figure 7.

Figure 7

Open in a new tab

Reusability investigation for three metal uptake cycles.

4. Conclusions

Four chitosan-modified products were prepared and applied as sorbents for copper and lead from simulated solutions. They were characterized by different analytical techniques such as IR, XRD, TGA, SEM, and AFM.

The obtained results can be summarized in the following points:

  • The removal performance slightly decreased with the increase of the temperature from 25 to 45 °C.

  • The optimum pH value was 5 for copper and 8 for lead.

  • The order of metal uptake at the optimum pH value is as follows: Cs/GA/MBA (Cu: 95.7 mg/g, Pb: 99.15 mg/g), Cs/GA/ECH (Cu: 80.4 mg/g, Pb: 93.14 mg/g), Cs-g-GA (Cu: 77 mg/g, Pb: 88.4 mg/g), and N, O CMCs (Cu: 30.2 mg/g, Pb: 44.8 mg/g). These values are comparable to those mentioned in literature.

  • The adsorption kinetics and isotherms show that Cs/GA/MBA follows the pseudo-second-order reaction and Langmuir isotherm with the highest adsorption capacity compared to Cs/GA/ECH, Cs-gGA, and N, O CMC, with qe = 98.7 and 98.04 mg/g upon copper and lead adsorption, respectively, which means a chemisorption reaction and homogeneous distribution of metal ions on the Cs/GA/MBA surface.

  • AFM was used as a perfect tool for characterizing and confirming the metal uptake process by comparing three AFM outcomes between the metal-free and metal-loaded samples: topography, height, and roughness.

  • The claimed products can be applied as effective green sorbents for copper and lead cations with relatively equal tendencies toward lead and copper due to the similar nature of combination between the sorbent material and the metal cation.

Acknowledgments

The authors acknowledge the STDF for funding this work under the call BARG 7, project no 37056.

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsomega.2c07264.

  • Pseudo-first-order and pseudo-second order kinetics of adsorption of copper metal ion onto chitosan-modified products at 100 ppm and of lead metal ions onto chitosan-modified products at 100 ppm, Langmuir and Freundlich isotherms of copper metal ions adsorbed on chitosan-modified products at 100 ppm and of lead metal ions adsorbed on chitosan-modified products at 100 ppm, dry and copper-loaded chitosan derivatives, lead-loaded chitosan-modified products, and dry and copper-loaded chitosan-modified products (PDF)

Author Contributions

Prof. M.E.-S.A.-R. is the PI of the project, conceptualization, methodology, investigation, AFM data, and writing—review and editing. R.K.F.: data presentation and validation. A.A.F.: conceptualization, methodology, review, and editing. M.K.: synthesis, experimental, and data presentation. A.A.-A.: experimental, AFM imaging, and adsorption kinetics study. A.H.: writing and editing and supervision.

The authors declare no competing financial interest.

Notes

The raw data supporting the conclusions of this article will be made available by the authors upon reasonable request.

Supplementary Material

ao2c07264_si_001.pdf (967.6KB, pdf)

References

  1. Abdel-Raouf M. E.; Maysour N. E.; Abdul-Raheim A. M.; El-Saeed S. M.; Farag R. K. Synthesis and Study of the Surface Properties of Alkylnaphthalene and Alkylphenanthrene Sulfonates. J. Surfactants Deterg. 2011, 14, 23–30. 10.1007/s11743-010-1197-4. [DOI] [Google Scholar]
  2. Atta A. M.; Abdel-Raouf M. E.; Abdul-Raheim A. M.; Abdel-azim A. A. Water Based Surfactants from Recycled Poly (ethylene terephthalate) Waste: their use as beach cleaners and in Petroleum Sludge Recovery. Prog. Rubber, Plast. Recycl. Technol. 2004, 20, 311. [Google Scholar]
  3. Abdel-Raouf M. E. Biodegradable polyoxyethylenated pentaerythritol quadric esters as oil spill dispersants. Tenside, Surfactants, Deterg. 2012, 49, 114–123. 10.3139/113.110172. [DOI] [Google Scholar]
  4. Keshawy M. A.-R.; Mahmoud M. E.; Abdel-Raouf M. E.-S. Polystyrene-based magnetic hydrogels for elimination of some toxic metal cations from aqueous solutions. Environ. Sci. Pollut. Res. 2020, 27, 26982–26997. 10.1007/s11356-020-08340-z. [DOI] [PubMed] [Google Scholar]
  5. Poudel M. B.; Awasthi G. P.; Kim H. J. Novel Insight into the Adsorption of Cr(VI) and Pb(II) Ions by MOF Derived Co-Al Layered Double Hydroxide @hematite Nanorods on 3D Porous Carbon Nanofiber Network. Chem. Eng. J. 2021, 417, 129312. 10.1016/j.cej.2021.129312. [DOI] [Google Scholar]
  6. Hong H.-J.; Ban G.; Kim H. S.; Jeong H. S.; Park M. S. Fabrication of Cylindrical 3D Cellulose Nanofibril (CNF) Aerogel for Continuous Removal of Copper(Cu2+) from Wastewater. Chemosphere 2021, 278, 130288. 10.1016/j.chemosphere.2021.130288. [DOI] [PubMed] [Google Scholar]
  7. Zhang L.; Zeng Y.; Cheng Z. Removal of Heavy Metal Ions Using Chitosan and Modified Chitosan: A Review. J. Mol. Liq. 2016, 214, 175–191. 10.1016/j.molliq.2015.12.013. [DOI] [Google Scholar]
  8. Teng Y.; Zhu J.; Xiao S.; Ma Z.; Huang T.; Liu Z.; Xu Y. Exploring Chitosan-Loaded Activated Carbon Fiber for the Enhanced Adsorption of Pb(II)-EDTA Complex from Electroplating Wastewater in Batch and Continuous Processes. Sep. Purif. Technol. 2022, 299, 121659. 10.1016/j.seppur.2022.121659. [DOI] [Google Scholar]
  9. Farag A. A.; Gafar Afif A.; Salih S. A.; Altalhi A. A.; Mohamed E. A.; Mohamed G. G. Highly Efficient Elimination of Pb+2and Al+3Metal Ions from Wastewater Using Graphene Oxide/3,5-Diaminobenzoic Acid Composites: Selective Removal of Pb2+from Real Industrial Wastewater. ACS Omega 2022, 7, 38347. 10.1021/acsomega.2c03150. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Mallik A. K.; Kabir S. M. F.; Bin Abdur Rahman F.; Sakib M. N.; Efty S. S.; Rahman M. M. Cu(II) Removal from Wastewater Using Chitosan-Based Adsorbents: A Review. J. Environ. Chem. Eng. 2022, 10, 108048. 10.1016/j.jece.2022.108048. [DOI] [Google Scholar]
  11. Verma M.; Kumar A.; Lee I.; Kumar V.; Park J.-H.; Kim H. Simultaneous Capturing of Mixed Contaminants from Wastewater Using Novel One-Pot Chitosan Functionalized with EDTA and Graphene Oxide Adsorbent. Environ. Pollut. 2022, 304, 119130. 10.1016/j.envpol.2022.119130. [DOI] [PubMed] [Google Scholar]
  12. Kazadi Mbamba C.; Tait S.; Flores-Alsina X.; Batstone D. J. A Systematic Study of Multiple Minerals Precipitation Modelling in Wastewater Treatment. Water Res. 2015, 85, 359–370. 10.1016/j.watres.2015.08.041. [DOI] [PubMed] [Google Scholar]
  13. Teh C. Y.; Budiman P. M.; Shak K. P. Y.; Wu T. Y. Recent Advancement of Coagulation–Flocculation and Its Application in Wastewater Treatment. Ind. Eng. Chem. Res. 2016, 55, 4363–4389. 10.1021/acs.iecr.5b04703. [DOI] [Google Scholar]
  14. Sinar Mashuri S. I.; Ibrahim M. L.; Kasim M. F.; Mastuli M. S.; Rashid U.; Abdullah A. H.; Islam A.; Asikin Mijan N.; Tan Y. H.; Mansir N.; Mohd Kaus N. H.; Yun Hin T.-Y. Photocatalysis for Organic Wastewater Treatment: From the Basis to Current Challenges for Society. Catalysts 2020, 10, 1260. 10.3390/catal10111260. [DOI] [Google Scholar]
  15. Obotey Ezugbe E.; Rathilal S. Membrane Technologies in Wastewater Treatment: A Review. Membranes 2020, 10, 89. 10.3390/membranes10050089. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Sukmana H.; Bellahsen N.; Pantoja F.; Hodur C. Adsorption and Coagulation in Wastewater Treatment - Review. Prog. Agric. Eng. Sci. 2021, 17, 49–68. 10.1556/446.2021.00029. [DOI] [Google Scholar]
  17. Pillai S. B.. Adsorption in Water and Used Water Purification BT - Handbook of Water and Used Water Purification; Lahnsteiner J., Ed.; Springer International Publishing: Cham, 2020; pp 1–22. [Google Scholar]
  18. Younas F.; Mustafa A.; Farooqi Z. U.; Wang X.; Younas S.; Mohy-Ud-Din W.; Ashir Hameed M.; Mohsin Abrar M.; Maitlo A. A.; Noreen S.; Hussain M. M. Current and Emerging Adsorbent Technologies for Wastewater Treatment: Trends, Limitations, and Environmental Implications. Water 2021, 13, 219. 10.3390/w13020215. [DOI] [Google Scholar]
  19. Sayed A.; Hany F.; Abdel-Raouf M. E.; Mahmoud G. A. Gamma Irradiation Synthesis of Pectin- Based Biohydrogels for Removal of Lead Cations from Simulated Solutions. J. Polym. Res. 2022, 29, 372. 10.1007/s10965-022-03219-8. [DOI] [Google Scholar]
  20. Hu S.; Huang T.; Zhang N.; Lei Y.; Wang Y. Chitosan-Assisted MOFs Dispersion via Covalent Bonding Interaction toward Highly Efficient Removal of Heavy Metal Ions from Wastewater. Carbohydr. Polym. 2022, 277, 118809. 10.1016/j.carbpol.2021.118809. [DOI] [PubMed] [Google Scholar]
  21. Zhang F.; Wang B.; Jie P.; Zhu J.; Cheng F. Preparation of Chitosan/Lignosulfonate for Effectively Removing Pb(II) in Water. Polymer 2021, 228, 123878. 10.1016/j.polymer.2021.123878. [DOI] [Google Scholar]
  22. Xu K.; Li L.; Huang Z.; Tian Z.; Li H. Efficient Adsorption of Heavy Metals from Wastewater on Nanocomposite Beads Prepared by Chitosan and Paper Sludge. Sci. Total Environ. 2022, 846, 157399. 10.1016/j.scitotenv.2022.157399. [DOI] [PubMed] [Google Scholar]
  23. Verma M.; Ahmad W.; Park J.-H.; Kumar V.; Vlaskin M. S.; Vaya D.; Kim H. One-Step Functionalization of Chitosan Using EDTA: Kinetics and Isotherms Modeling for Multiple Heavy Metals Adsorption and Their Mechanism. J. Water Proc. Eng. 2022, 49, 102989. 10.1016/j.jwpe.2022.102989. [DOI] [Google Scholar]
  24. Jeyaseelan C.; Chaudhary N.; Jugade R. Sulphate-Crosslinked Chitosan as an Adsorbent for the Removal of Congo Red Dye From Aqueous Solution. Air, Soil Water Res. 2018, 11, 117862211881168. 10.1177/1178622118811680. [DOI] [Google Scholar]
  25. Zhang Y.; Zhao M.; Cheng Q.; Wang C.; Li H.; Han X.; Fan Z.; Su G.; Pan D.; Li Z. Research Progress of Adsorption and Removal of Heavy Metals by Chitosan and Its Derivatives: A Review. Chemosphere 2021, 279, 130927. 10.1016/j.chemosphere.2021.130927. [DOI] [PubMed] [Google Scholar]
  26. Mahmoud G. A.; Sayed A.; Thabit M.; Safwat G. Chitosan Biopolymer Based Nanocomposite Hydrogels for Removal of Methylene Blue Dye. SN Appl. Sci. 2020, 2, 968. 10.1007/s42452-020-2753-9. [DOI] [Google Scholar]
  27. Jiang Q.; Han Z.; Li W.; Ji T.; Yuan Y.; Zhang J.; Zhao C.; Cheng Z.; Wang S. Adsorption Properties of Heavy Metals and Antibiotics by Chitosan from Larvae and Adult Trypoxylus Dichotomus. Carbohydr. Polym. 2022, 276, 118735. 10.1016/j.carbpol.2021.118735. [DOI] [PubMed] [Google Scholar]
  28. Mohammed M. A.; Syeda J. T. M.; Wasan K. M.; Wasan E. K. An Overview of Chitosan Nanoparticles and Its Application in Non-Parenteral Drug Delivery. Pharmaceutics 2017, 9, 53. 10.3390/pharmaceutics9040053. [DOI] [PMC free article] [PubMed] [Google Scholar]
  29. Wang Q.; Li L.; Kong L.; Cai G.; Wang P.; Zhang J.; Zuo W.; Tian Y. Compressible Amino-Modified Carboxymethyl Chitosan Aerogel for Efficient Cu(II) Adsorption from Wastewater. Sep. Purif. Technol. 2022, 293, 121146. 10.1016/j.seppur.2022.121146. [DOI] [Google Scholar]
  30. Zhu X.; Tong J.; Zhu L.; Pan D. In Situ Growth of ZIF-8 on Carboxymethyl Chitosan Beads for Improved Adsorption of Lead Ion from Aqueous Solutions. Int. J. Biol. Macromol. 2022, 205, 473–482. 10.1016/j.ijbiomac.2022.02.120. [DOI] [PubMed] [Google Scholar]
  31. Wu M.; Bai Y.; Wang K.; Li W.; Xu D.; Ma H. Facile synthesis of ethylenediamine-modified magnetic chitosan composite and its adsorption property. Desalin. Water Treat. 2018, 127, 231–242. 10.5004/dwt.2018.22646. [DOI] [Google Scholar]
  32. Özkahraman B.; Acar I.; Emik S. Removal of Cu2+ and Pb2+ Ions Using CMC Based Thermoresponsive Nanocomposite Hydrogel. Clean: Soil, Air, Water 2011, 39, 658–664. 10.1002/clen.201000553. [DOI] [Google Scholar]
  33. Zhang L.; Tang S.; He F.; Liu Y.; Mao W.; Guan Y. Highly Efficient and Selective Capture of Heavy Metals by Poly(Acrylic Acid) Grafted Chitosan and Biochar Composite for Wastewater Treatment. Chem. Eng. J. 2019, 378, 122215. 10.1016/j.cej.2019.122215. [DOI] [Google Scholar]
  34. Keshawy M. S.; Kamal R. S.; Abdel-Raouf M. Synthesis and Investigation of Green Hydrogels for Simultaneous Removal of Mercuric Cations and Methylene Blue from Aqueous Solutions. Egypt. J. Chem. 2022, 65, 325. 10.21608/ejchem.2021.100722.4678. [DOI] [Google Scholar]
  35. Sayed A.; Mazrouaa A. M.; Mohamed M. G.; et al. Green synthesis of chitosan/erythritol/graphene oxide composites for simultaneous removal of some toxic species from simulated solution. Environ. Sci. Pollut. Res. 2022, 1. 10.1007/s11356-022-23951-4. [DOI] [PMC free article] [PubMed] [Google Scholar]
  36. Abdel Wahab M. M.; Sayed G. H.; Ramadan R. M.; Mady A. H.; Rabie A. M.; Farag A. A.; Negm N. A.; Mohamed E. A. Synergistic Effects of Graphene Oxide Grafted with Barbituric Acid Nanocomposite for Removal of Heavy Metals from Aqueous Solution. Nanotechnol. Environ. Eng. 2022, 10.1007/s41204-022-00274-w. [DOI] [Google Scholar]
  37. Monteiro O. A. C.; Airoldi C. Some Studies of Crosslinking Chitosan–Glutaraldehyde Interaction in a Homogeneous System. Int. J. Biol. Macromol. 1999, 26, 119–128. 10.1016/s0141-8130(99)00068-9. [DOI] [PubMed] [Google Scholar]
  38. Yang Y.; Li L.; Wang W.; Wu W.; Zhen Z.; Xiong X.; Sun S. Double Cross-Linked Chitosan Composite Films Developed with Oxidized Tannic Acid and Ferric Ions Exhibit High Strength and Excellent Water Resistance. Biomacromolecules 2019, 20, 801–812. 10.1021/acs.biomac.8b01420. [DOI] [PubMed] [Google Scholar]
  39. Ritonga H.; Basri M. I.; Rembon F. S.; Ramadhan L. A.; Nurdin M. High performance of chitosan-co-polyacrylamide-TiO2 crosslinked glutaraldehyde hydrogel as soil conditioner for soybean plant (Glycine max). Soil Sci. Annu. 2020, 71, 194–204. 10.37501/soilsa/125847. [DOI] [Google Scholar]
  40. Galan J.; Trilleras J.; Zapata P. A.; Arana V. A.; Grande-Tovar C. D. Optimization of Chitosan Glutaraldehyde-Crosslinked Beads for Reactive Blue 4 Anionic Dye Removal Using a Surface Response Methodology. Life 2021, 11, 85. 10.3390/life11020085. [DOI] [PMC free article] [PubMed] [Google Scholar]
  41. Farias P. V. S.; Aragão D. C.; Farias M. V.; Correial L. M.; Carvalho T. V.; Aguiar J. E.; Vieira R. S. Natural and Cross-Linked Chitosan Spheres as Adsorbents for Diesel Oil Removal. Adsorpt. Sci. Technol. 2015, 33, 783. 10.1260/0263-6174.33.9.783. [DOI] [Google Scholar]
  42. Yan H.; Dai J.; Yang Z.; Yang H.; Cheng R. Enhanced and Selective Adsorption of Copper(II) Ions on Surface Carboxymethylated Chitosan Hydrogel Beads. Chem. Eng. J. 2011, 174, 586–594. 10.1016/j.cej.2011.09.064. [DOI] [Google Scholar]
  43. Dai J.; Yan H.; Yang H.; Cheng R. Simple Method for Preparation of Chitosan/Poly(Acrylic Acid) Blending Hydrogel Beads and Adsorption of Copper(II) from Aqueous Solutions. Chem. Eng. J. 2010, 165, 240–249. 10.1016/j.cej.2010.09.024. [DOI] [Google Scholar]
  44. Hasan A. M. A.; Keshawy M.; Abdel-Raouf M. E.-S. Atomic Force Microscopy Investigation of Smart Superabsorbent Hydrogels Based on Carboxymethyl Guar Gum: Surface Topography and Swelling Properties. Mater. Chem. Phys. 2022, 278, 125521. 10.1016/j.matchemphys.2021.125521. [DOI] [Google Scholar]
  45. Mohamed H. A.; Farag A. A.; Badran B. M. Corrosion inhibitiob of mild steel using emulsified thiazole adduct in Different binder systems. Eurasian Chem.-Technol. J. 2008, 10, 67. [Google Scholar]
  46. Gupta K. C.; Jabrail F. H. Glutaraldehyde and Glyoxal Cross-Linked Chitosan Microspheres for Controlled Delivery of Centchroman. Carbohydr. Res. 2006, 341, 744–756. 10.1016/j.carres.2006.02.003. [DOI] [PubMed] [Google Scholar]
  47. Knaul J. Z.; Hudson S. M.; Creber K. A. M. Crosslinking of Chitosan Fibers with Dialdehydes: Proposal of a New Reaction Mechanism. J. Polym. Sci., Part B: Polym. Phys. 1999, 37, 1079–1094. 10.1002/(sici)1099-0488(19990601)37:11<1079::aid-polb4>3.0.co;2-o. [DOI] [Google Scholar]
  48. H S H. S.; A a A. A.; M a M. A.; S H S. H. The effect of synthesized chitosan grafted poly (N-L-lactide) on human genetic material. Innovaciencia Facultad de Ciencias Exactas Físicas y Naturales 2018, 6, 1–10. 10.15649/2346075X.462. [DOI] [Google Scholar]
  49. Konno Y.; Farag A. A.; Tsuji E.; Aoki Y.; Habazaki H. Formation of Porous Anodic Films on Carbon Steels and Their Application to Corrosion Protection Composite Coatings Formed with Polypyrrole. J. Electrochem. Soc. 2016, 163, C386. 10.1149/2.1451607jes. [DOI] [Google Scholar]
  50. Tripathi S.; Mehrotra G. K.; Dutta P. K. Physicochemical and Bioactivity of Cross-Linked Chitosan–PVA Film for Food Packaging Applications. Int. J. Biol. Macromol. 2009, 45, 372–376. 10.1016/j.ijbiomac.2009.07.006. [DOI] [PubMed] [Google Scholar]
  51. Kluczka J.; Gnus M.; Dudek G.; Turczyn R. Removal of Boron from Aqueous Solution by Composite Chitosan Beads. Sep. Sci. Technol. 2017, 52, 1559–1571. 10.1080/01496395.2017.1290659. [DOI] [Google Scholar]
  52. Li X.; Li Y.; Ye Z. Preparation of Macroporous Bead Adsorbents Based on Poly(Vinyl Alcohol)/Chitosan and Their Adsorption Properties for Heavy Metals from Aqueous Solution. Chem. Eng. J. 2011, 178, 60–68. 10.1016/j.cej.2011.10.012. [DOI] [Google Scholar]
  53. Farag R. K.; Mohamed R. R. Synthesis and Characterization of Carboxymethyl Chitosan Nanogels for Swelling Studies and Antimicrobial Activity. Molecules 2013, 18, 190. 10.3390/molecules18010190. [DOI] [PMC free article] [PubMed] [Google Scholar] [Retracted]
  54. Kim H.-R.; Jang J.-W.; Park J.-W. Carboxymethyl Chitosan-Modified Magnetic-Cored Dendrimer as an Amphoteric Adsorbent. J. Hazard. Mater. 2016, 317, 608–616. 10.1016/j.jhazmat.2016.06.025. [DOI] [PubMed] [Google Scholar]
  55. Chen C.; Hossain H. M.; Duan D.; Lu L.; Tsang F. T.; Islam M. S.; Zhou Y. Isotherm models for adsorption of heavy metals from water - A review. Chemosphere 2022, 307, 135545. 10.1016/j.chemosphere.2022.135545. [DOI] [PubMed] [Google Scholar]
  56. Maskawat Marjub M.; Rahman N.; Dafader N. C.; Sultana Tuhen F.; Sultana S.; Tasneem Ahmed F. Acrylic Acid-Chitosan Blend Hydrogel: A Novel Polymer Adsorbent for Adsorption of Lead(II) and Copper(II) Ions from Wastewater. J. Polym. Eng. 2019, 39, 883–891. 10.1515/polyeng-2019-0139. [DOI] [Google Scholar]
  57. Yan E. Y.; Hao X. Y.; Cao M. L.; Fan Y. M.; Zhang D. Q.; Xie W.; Sun J. P.; Hou S. Q. Preparation and Characterization of Carboxymethyl Chitosan Hydrogel. Pigm. Resin Technol. 2016, 45, 246–251. 10.1108/prt-10-2014-0093. [DOI] [Google Scholar]
  58. Wessely D.; Matt Y.; An Q.; Bräse S.; Tsotsalas M. Dynamic porous organic polymers with tuneable crosslinking degree and porosity. RSC Adv. 2021, 11, 27714. 10.1039/d1ra05265a. [DOI] [PMC free article] [PubMed] [Google Scholar]
  59. Sayed A.; Yasser M.; Abdel-raouf M. E.; Mohsen R. Green Starch/Graphene Oxide Hydrogel Nanocomposites for Sustained Release Applications. Chem. Pap. 2022, 76, 5119–5132. 10.1007/s11696-022-02236-7. [DOI] [Google Scholar]
  60. Wan Ngah W. S.; Endud C. S.; Mayanar R. Removal of Copper(II) Ions from Aqueous Solution onto Chitosan and Cross-Linked Chitosan Beads. React. Funct. Polym. 2002, 50, 181–190. 10.1016/s1381-5148(01)00113-4. [DOI] [Google Scholar]
  61. Vieira M. L. G.; Pinheiro C. P.; Silva K. A.; Lutke S. F.; Cadaval T. R. S. A.; Dotto G.; Pinto L. A. d. A. Chitosan and Cyanoguanidine-Crosslinked Chitosan Coated Glass Beads and Its Application in Fixed Bed Adsorption. Chem. Eng. Commun. 2019, 206, 1474–1486. 10.1080/00986445.2019.1581618. [DOI] [Google Scholar]
  62. Chen L.; Hao H.; Zhang W.; Shao Z. Adsorption Mechanism of Copper Ions in Aqueous Solution by Chitosan–Carboxymethyl Starch Composites. J. Appl. Polym. Sci. 2020, 137, 48636. 10.1002/app.48636. [DOI] [Google Scholar]
  63. Dragan E. S.; Dinu M. V. Removal of copper ions from aqueous solution by adsorption on ionic hybrids based on chitosan and clinoptilolite. Ion Exch. Lett. 2009, 2, 15–18. [Google Scholar]
  64. Wan Ngah W. S.; Endud C. S.; Mayanar R. Removal of copper(II) ions from aqueous solution onto chitosan and cross-linked chitosan beads. React. Funct. Polym. 2002, 50, 181–190. 10.1016/s1381-5148(01)00113-4. [DOI] [Google Scholar]
  65. Amer A.; Sayed G. H.; Ramadan R. M.; Rabie A. M.; Negm N. A.; Farag A. A.; Mohammed E. A. Assessment of 3-Amino-1H-1,2,4-Triazole Modified Layered Double Hydroxide in Effective Remediation of Heavy Metal Ions from Aqueous Environment. J. Mol. Liq. 2021, 341, 116935. 10.1016/j.molliq.2021.116935. [DOI] [Google Scholar]
  66. Chen H.; Zhou Y.; Wang J.; Lu J.; Zhou Y. Polydopamine modified cyclodextrin polymer as efficient adsorbent for removing cationic dyes and Cu2+. J. Hazard. Mater. 2020, 389, 121897. 10.1016/j.jhazmat.2019.121897. [DOI] [PubMed] [Google Scholar]
  67. Lee Z. L.; Zaini A.; Tang Z.; Shu H. T.. Porous Nanomaterials for Heavy Metal Removal. In Handbook of Ecomaterials; Martínez L. M. T., et al. , Eds; Springer Nature Switzerland AG, 2019. [Google Scholar]
  68. Nagireddi S.; Katiyar V.; Uppaluri R. Pd(II) adsorption characteristics of glutaraldehyde cross-linked chitosan copolymer resin. Int. J. Biol. Macromol. 2017, 94, 72–84. 10.1016/j.ijbiomac.2016.09.088. [DOI] [PubMed] [Google Scholar]
  69. Sahin S.; Kocak K.; Arslan A.; Ucan I. U. Synthesis of Crosslinked Chitosan with Epichlorohydrin Possessing Two Novel Polymeric Ligands and Its Use in Metal Removal. J. Inorg. Organomet. Polym. 2011, 21, 69–80. 10.1007/s10904-010-9421-2. [DOI] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

ao2c07264_si_001.pdf (967.6KB, pdf)

Articles from ACS Omega are provided here courtesy of American Chemical Society

RESOURCES