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. 2020 Jul 2;5(27):16510–16520. doi: 10.1021/acsomega.0c00999

Sucrose-Triggered, Self-Sustained Combustive Synthesis of Magnetic Nickel Oxide Nanoparticles and Efficient Removal of Malachite Green from Water

Jhilirani Mohanta †, Banashree Dey ‡, Soumen Dey †,*
PMCID: PMC7364633  PMID: 32685815

Abstract

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Dye-containing industrial effluents create major concern nowadays. To address the problem, magnetic nickel oxide nanoparticles (NONPs) were synthesized using the autopropagator combustion technique assisted by sucrose as fuel and used for the removal of toxic malachite green (MG) from water. The material was characterized by scanning electron microscopy (SEM–EDS), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), vibrating sample magnetism (VSM), point of zero charge (pHZPC), and Brunauer–Emmet–Teller surface area analysis. SEM images show flowerlike texture with the presence of multiple pores. VSM reveals a well-defined hysteresis at room temperature, confirming a permanent magnetic nature of the material. pHZPC was found to be 6.63, which enables dye separation in the drinking water pH range. MG removal from water was carried out in the batch mode with optimized physicochemical parameters such as contact time, pH, temperature, and dose. Langmuir adsorption capacity was estimated to be 87.72 mg/g. Pseudo-second order kinetics (R2 = 0.999) and Langmuir isotherm model (R2 = 0.997) were found to best fit. The magnetic nature facilitates fast and quantitative separation of NONPs from solution using a hand-held magnet. Dye-loaded NONPs can be easily regenerated up to 89% and reused up to five cycles without significant loss of activity. The mechanism of adsorption is proposed to be a combination of electrostatic attraction and weak hydrogen bonding. Strategically designed straightforward synthetic protocol, low cost, high uptake capacity, and sustainable use render NONPs an ideal alternative for future dye treatment.

1. Introduction

Dyes are colored macromolecules which connect themselves to a matrix for developing a persistent color.1 Various industries such as food, pulp, textile, paper, paint, leather, silk, cotton, and wool use dyes. Waste dye discharge into water causes different environmental and health complications.2−6 Hence, the need emerges to address the problem. Because of mutagenicity, teratogenicity, and carcinogenicity, dyes are poisonous to aquatic life.7,8 Several methods such as chemical, biological, and physical methods have been developed to treat contaminated water. These methods include chemical reduction, oxidation, membrane separation, Fenton oxidation, photodegradation, coagulation–flocculation, and adsorption.9,10 Among all, adsorption stands as the best because it offers various advantages such as high degree of separation, easy operational technique, and low cost.11−14

Recently, metal oxides, related nanoparticles, and composites were reported for efficient removal of dyes. Metal oxides offer advantages such as small size and robustness along with high surface area, which make them the preferred choice for removal of dyes. Several metal oxides were synthesized by diverse methods such as chemical vapor deposition, sol–gel, coprecipitation, solvothermal, hydrothermal, mechanical alloying, microwave heating, and micelle synthesis.15−18 Among all, combustion-based protocol is free from byproducts, cost-effective, offers easy protocol, and rapid separation. Such reactions get initiated in an autopropagating manner and are generally exothermic. In addition, highly pure homogeneous powders are obtained having fine particle size.19

Flower-shaped iron oxide, magnetic nanoscale iron oxide, and magnetic MnO–Fe2O3 composites were employed as adsorbents for dye removal.20−22 Zinc oxide and stannous oxide nanoparticles were effectively used for the treatment of commercial dyes.23 Magnetic manganese oxide nanoparticles were synthesized and used for efficient removal of dyes.24,25 ZnCr2O4 nanoparticles were tested for the elimination of azo dye.26 Iron oxide nanoparticles obtained using the hydrolysis technique was found to be effective for the removal of Congo red (CR).27 Alumina-based mixed Al–Co oxide was effective for the removal of Color black G and CR.28,29 SrTiO3- and tungsten oxide-based nanoparticles were synthesized by the combustive protocol and used in dye removal.30−32 Fe3O4/Ag/C materials, layered perovskite La4Ni3O10, and Fe–Al oxide nanocomposite (IMANCs) were found to be promising adsorbents for azo dyes.33−35 Carbon nanocomposites and Fe2O3 (hematite nanoparticles) were used as economic adsorbents for water treatment.36−39 Recently, SiO2–Fe Oxide nanoparticles, nanosized Bi2WO6, and magnesium oxide were synthesized for water treatment.40−42 Nonstoichiometric NiFe1.98Re0.02O4 and ZnO·La2O3·CeO2 were also used.43,44 Recently, Fe3O4–trisodium citrate-based nanocomposite and copper ferrite (CuFe2O4) were investigated for dye removal.45,46 Fe/Mn-substituted polyoxometalates/hydrotalcites, graphene oxide nanosheets (GO@Fe3O4), and amino-functionalized nanotubes of titanates were exercised for the removal of multiple dyes.47−49

We have previously shown the synthesis of binary iron-zirconium-mixed metal oxide using the coprecipitation technique and related composites for the removal of dyes.50,51,58 Recently, we have shown sucrose-supported self-sustained combustive synthesis of nanoscale cobalt oxide and its dye detoxification property.59 Major processes that were followed to synthesize nickel oxide-based adsorbents are precipitation, sol–gel, hydrothermal, and microwave heating.64−68 Herein, we report the upscale synthesis of nickel oxide nanoparticles (NONPs) by sucrose-supported, self-propagating combustion of nickel nitrate hexahydrate and its high efficiency for malachite green (MG) removal in the batch process.

2. Results and Discussion

2.1. Synthesis and Characterization

NONPs were synthesized by 1:1 reaction of nickel salt and sucrose and isolated as a black powder. Detailed synthesis is given in the Experimental Section.

2.2. FTIR Analysis

Figure 1a represents the Fourier-transform infrared spectroscopy (FTIR) spectrum of NONPs before (green) and after (blue) adsorption. Broad bands around 3300–3600 cm–1 and at 1594 and 1366 cm–1 can be attributed to O–H stretching and bending vibrations of the lattice/surface water molecule. The sharp peak at 664 cm–1 is assigned to the Ni–O–H stretching and that at 564 cm–1 is for the Ni–O vibration mode.52 After adsorption, it was found that broadness of the peak around 3300–3600 cm–1 is reduced and the position is slightly changed. This could be attributed to the successful interaction of MG and NONPs. Additional peaks in the range of 1000–1380 cm–1 could be attributed to C–N, C–H, C–C, and C=C stretching, which supports the effective adsorption of MG dye. The Ni–O peak position was also seen to change to lower frequency with reduced sharpness.

Figure 1.

Figure 1

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(a) FTIR of NONPs. Green and blue lines represent FTIR before and after adsorption. (b) Powder XRD pattern of the as-synthesized NONPs.

2.3. XRD

Powder X-ray diffraction (XRD) was performed to obtain the structural properties and nature of the material (Figure 1b). Distinct peaks at 2θ = 37.24, 43.33, 44.52, 51.95, 62.95, and 76.49 were observed. Peaks are identified as cubic crystallites of NONPs with diffraction planes (111), (200), (220), (311), (202), and (222), respectively, having the cubic NONPs (JCPDS Card no. 47-1049).53

2.4. SEM–EDS and TEM

Morphology and microstructural characteristics were determined by scanning electron microscopy/transmission electron microscopy (SEM/TEM) images, and energy-dispersive spectroscopy (EDS) was used to analyze elemental composition and their relative percentage. Figure 2a represents the SEM image of NONPs before adsorption. Flowerlike architecture was seen with lots of pores. Distinct pores and channels could be identified at regular spacing, which is responsible for facile adsorption. After MG adsorption, NONPs were seen highly agglomerated and condensed (Figure 2b). Blockage of pores was observed, which confirms successful dye adsorption. Furthermore, structural morphology was confirmed by TEM images (Figure 2c–d). The as-synthesized NONPs were found to be of irregular shape, and the average size lies in the range of 4–10 nm. Figure 2e represents the EDS profile of NONPs before adsorption. The presence of Ni and O was seen. Figure 2f represents EDS after adsorption. Appearance of C confirms dye adsorption.

Figure 2.

Figure 2

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SEM image of NONPs (a) before adsorption (b) after adsorption, (c) high-resolution TEM image before adsorption, (d) low-resolution TEM image before adsorption, and EDS (e) before and (f) after adsorption.

2.5. BET Surface Area

Uptake behavior and adsorption capacity of an adsorbent could be predicted from porosity and surface area. The specific surface area of NONPs was determined by the Brunauer–Emmet–Teller (BET) method, and the corresponding nitrogen adsorption desorption curve is presented in Figure 3a. The NONP adsorption isotherm could be classified as type II according to the IUPAC classification.21 The BET surface area of NONPs was found to be 11.617 m2/g. The Barrett–Joyner–Halenda (BJH) method revealed that the NONP is nanoporous with an average pore radius of 1.22 nm and a pore volume of 0.0183 cc/g. This leads to enhanced capacity of dye uptake. The corresponding pore size distribution curve is presented in Figure 3b. After MG adsorption, the surface area was found to get reduced. This confirms successful dye adsorption.

Figure 3.

Figure 3

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BET isotherm plot; (a) N2 adsorption desorption of NONPs and (b) BJH pore size distribution of NONPs. Particles have an average radius of 1.22−0.7 nm.

2.6. Magnetism

The as-synthesized NONPs were found to get attracted by a magnet. Such an observation prompted us to record hysteresis and assign magnetism. Magnetic nature was analyzed by room temperature hysteresis measurement and presented as an M versus H curve (Figure 4). The plot shows a weak hysteresis, which indicates that the NONP is a soft and robust magnetic material. Coercivity and remanence ratio suggest the measure of squareness of the curve. Values for saturation magnetization (Ms), remanent magnetization (Mr), and coercive field (Hc) are 20.02 emu/g, 5.0 emu/g, and 151 Oe, respectively.

Figure 4.

Figure 4

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M vs H hysteresis plot for NONPs.

2.7. Batch Studies

2.7.1. Dependence of pH on Adsorption

Solution pH plays an important role in the adsorption process. Keeping other parameters constant, pH dependence was tested in the range 3–9, and the relevant observation is presented in Figure 5a. It was found that adsorption is less than 10% at pH 3. Such a low adsorption rate in highly acidic solution is due to the presence of a large number of H+ ions which compete with cationic MG for adsorption sites. In addition, the adsorbent surface may get protonated, which hinders dye uptake. Because surface charge density decreases with the increase in solution pH, the electrostatic repulsion between the positively charged dye and the adsorbent surface is lowered, which favors increased uptake. pHzpc of NONPs was estimated and found to be 6.63 (Figure 5e). This indicates that at pH < pHzpc, the surface of the material is positively charged and at pH > pHzpc, the surface is negatively charged. Adsorption was found to steadily increase from 10 to 82% upon increasing the pH from 3 to 7. After pH 7, adsorption remains almost constant up to 9. Hence, for all other experiments, pH 7 was fixed. Because this is the desired pH for any water treatment, it can be concluded that the NONP has potential for practical application. It is known that pKa of MG is 10.3. Above pH 10.3, color starts changing, leading to a different species.60

Figure 5.

Figure 5

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Batch Studies: (a) effect of pH, (b) effect of contact time, (c) effect of concentration, (d) effect of dose, (e) pHzpc, and (f) effect of interference.

2.7.2. Equilibration Time

Adsorption experiments were carried out up to 160 min to ascertain the actual equilibration time (Figure 5b). It was observed that adsorption is very fast initially, and 82% adsorption is achieved within 40 min. An insignificant increase was found until 80 min, and thereafter, no more uptakes were seen. Hence, 40 min shaking was fixed for all other experiments. Such a low equilibration time provides the advantage of energy efficiency.

2.7.3. Effect of Concentration

Figure 5c presents the effect of input concentration on the adsorption process. As concentration increases from 10 to 50 mg/L, adsorption increases. After this, saturation takes place and no more uptakes were seen. This is due to the competitive inhibition of dye molecules via interelectronic repulsion, which hinders the adsorption process. An optimized concentration of 50 mg/L was fixed for all experiments. It was also noticed that with increasing adsorbent dose, adsorption increases (Figure 5d). This is consistent with the availability of a higher number of available pores.

2.7.4. Interference Test

Because any industrial effluent is a mixture of many ions, testing of interference is important. Few commonly present ions such as chloride, sulfate, nitrate, phosphate, sodium, calcium, and so forth were chosen for this study. As per WHO guidelines, maximum permissible concentration of the aforesaid ions was used with the dye solution and the interference was tested. Figure 5f shows the effect of interfering ions. It was observed that 25% decrease in adsorption percentage occurs with chloride ions and minimum decrease occurred with sodium ions. It can be concluded that efficiency remains good in the presence of coexistent ions.

2.7.5. Kinetic Study

The dye adsorption rate is dependent on time because the dye molecules have to first encounter the boundary effect, followed by adsorption from the bulk solution, and finally diffuse into the adsorbent core.

In order to assess the adsorption pathway, four kinetic models, namely, pseudo first order, pseudo second order, second order, and intraparticle diffusion, were investigated (eqs 1–4).54,55

2.7.5. 1

where qe & qt (mg/g) = the amount of dye adsorbed at equilibrium and time t (min), respectively. K1 is the rate constant.

2.7.5. 2
2.7.5. 3

where kt stands for the second-order rate constant (g·mg–1·min–1).

2.7.5. 4

where kid (mg·g–1·min1/2) stands for the intraparticle diffusion rate constant.

The pseudo first-order model assumes that the rate of adsorption depends on the number of vacant sites on the adsorption surface. Pseudo second order considers solid-phase sorption, that is the assumption that the adsorption rate relates to the squared product of the difference between the number of vacant sites on the adsorbent surface to that of the occupied sites on the adsorbent surface. Intraparticle diffusion suggests that the mass transfer of the adsorbate to the adsorbent happens through the diffusion process. Diffusive transfer of dye molecules occurs from the liquid phase to the adsorbent surface across the external liquid layer. This facilitates attachment of the dye molecules at the vacant active sites on the adsorbent surface.

Fitting curves are presented in Figure 6a–d. It was found that the pseudo second-order model (Figure 6b) is the best fit (R2 = 0.999), suggesting that chemisorption is the dominating rate-limiting step. Selected kinetic parameters are shown in the table below (Table 1). A close introspection to the intraparticle diffusion model deliberates an impression that the actual uptake process is a combination of three steps. It could be seen that adsorption is rapid in initial 20 min, manifested by a steep positive slope. During 20–40 min, the rate of uptake became slow, the steepness of the slope is reduced. After 40 min, a straight line almost parallel to the X-axis suggests that saturation is reached. The relevant linear fitting plot is presented in Figure S1 (Supporting Information).

Figure 6.

Figure 6

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Kinetics plots of (a) pseudo first order, (b) pseudo second order, (c) intraparticle diffusion, and (d) second order.

Table 1. Selected Kinetic Constants.
order qe (mg/g)a Kb R2c
pseudo 1st 0.51 0.034 min–1 0.882
pseudo 2nd 16.66 0.351 g mg–1 min–1 0.999
2nd order 1.94 0.704 g mg–1 min–1 0.919
intra-particle diffusion 0.641 0.0351 mg g–1 min0.5 0.805
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a

Equilibrium uptake of MG on the adsorbent.

b

Kinetic constants.

c

Correlation coefficient.

2.7.6. Isotherm Study

The isotherm data were fitted to the Langmuir and Freundlich isotherms.56,57 Langmuir isotherm is represented by the following linear eq 5.

2.7.6. 5

where Ce (mg/L) is the equilibrium concentration, qe (mg/g) is the amount of adsorbate adsorbed per unit mass of the adsorbate, and Q0 and b are the Langmuir constants related to adsorption capacity and rate of adsorption, respectively. When Ce/qe is plotted against Ce, a straight line with slope 1/Q0 was obtained. Constants Q0 and b were calculated from the slope and the intercept, respectively, and their values are tabulated (Table 2).

Table 2. Isotherm Parameters for the Removal of MG by NONPs.
    temperature (K)
isotherm parameter 293 298 303 308
Langmuir Q0 (mg/g) 87.72 83.33 76.92 71.42
  b (L/mg) 0.832 0.859 0.866 0.893
  R2 0.997 0.997 0.995 0.994
Freundlich Kf (mg/g) 37.25 33.15 30.84 29.36
  1/n (L/mg) 0.647 0.594 0.572 0.588
  R2 0.990 0.983 0.994 0.986
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The linear form of the Freundlich equation is given below in eq 6

2.7.6. 6

where qe = the amount adsorbed at equilibrium (mg/g). Ce = equilibrium concentration of MG. Kf and n are Freundlich constants.

The plot of ln qe versus ln Ce gives a straight line with slope 1/n. Accordingly, Freundlich constants (Kf & n) were calculated and given in the table below. From Table 2, it can be concluded that adsorption follows the Langmuir model (R2 = 0.997), indicating a homogeneous and monolayer adsorption. At 293 K, removal capacity was found to be maximum (Q0 = 87.72 mg/g), higher than that at 308 K (Q0 = 71.42 mg/g). This suggests that lower temperature is conducive to adsorption. An increase in the initial concentration at the beginning could provide a driving force for the diffusion of the adsorbate to the adsorbent surface, which contributes to a significant increase in adsorption capacity. The linear plot of both isotherms is presented in Figure 7.

Figure 7.

Figure 7

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Isotherm plots: (a) Langmuir isotherm model for MG onto NONPs at different temperatures and (b) Freundlich isotherm model at different temperatures.

2.7.7. Thermodynamic Studies

Thermodynamic parameters are indispensable to further explore the adsorption process. Feasibility of adsorption is directly related to Gibbs free energy (ΔG), change in entropy (ΔS), and change in enthalpy (ΔH). Relevant equations are given (eqs 7–9).

2.7.7. 7
2.7.7. 8
2.7.7. 9

The linear van’t Hoff plot of log(qe/ce) versus 1/T is shown in Figure 8a, and the corresponding thermodynamic parameters are summarized in Table 3. Negative ΔG values indicate that the adsorption process is spontaneous. ΔG became slightly less negative upon increasing temperature, indicating that lower temperature is more favorable for adsorption. This is consistent with higher capacity at lower temperatures. Negative ΔH values indicate that the adsorption process is exothermic in nature, which was consistent with the result that adsorption capacities decrease with increasing temperature. Upon increasing the concentration from 20 to 60 mg/L, ΔG becomes less negative (−10.265 to −7.125 KJ/mol). This suggests that adsorption is less favorable at higher concentrations. Entropy changes are negative, which indicates that the randomness at the adsorption site is reduced upon dye uptake.

Figure 8.

Figure 8

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(a) Van‘t Hoff plot for adsorption of MG by NONPs and (b) Arrhenius plot for adsorption of MG by NONPs.

Table 3. Selected Thermodynamic Parameters.
concentration (mg/L)a T (K)b ΔG (KJ/mol)c ΔH (KJ/mol)d ΔS (J/mol/K)e
20 293 –10.265 –15.246 –0.017
  298 –10.18    
  303 –10.095    
  308 –10.00    
40 293 –8.935 –12.451 –0.012
  298 –8.875    
  303 –8.815    
  308 –8.755    
60 293 –7.451 –14.209 –0.023
  298 –7.355    
  303 –7.24    
  308 –7.125    
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a

Concentration of MG (mg/L).

b

Temperature.

c

Change in Gibbs free energy.

d

Change in enthalpy.

e

Change in entropy.

2.8. Activation Energy

With increasing concentration, it was found that free energy gets reduced. Such an observation indicates that at higher concentration, the percentage of adsorption decreases. To understand the ease of adsorption, the activation energy of a process is informative.

Activation energy Ea of adsorption was estimated by utilizing a modified Arrhenius equation (eqs 10 and 11) related to surface coverage (θ)

2.8. 10
2.8. 11

where θ and S* are adsorbate/adsorbent function related to sticking probability and surface coverage fraction, respectively. S* should lie in the range 0 < S* <1.

C0 and Ce are initial dye concentration and equilibrium concentration of the MG dye, respectively.

Substituting θ (eq 11) in eq 10, we get eq 12.

2.8. 12

Activation energy (Ea) of the adsorption process is estimated from the slope and the intercept of the plot of ln(1 – θ) versus 1/T (Figure 8b). It is worth mentioning that the Ea value indicates the nature of adsorption, physisorption or chemisorption. Values in the range 5–20 kJ/mol signify physisorption, and values in the range 20–800 KJ/mol signify chemisorption. The activation energy value was found to be 11.584,14.752, and 22.507 KJ/mol for 20, 40, and 60 mg/L MG solution, respectively, indicating that the process is predominately physisorption.

2.9. Regeneration and Reuse

Regeneration helps identify the type of adsorption and the scope of recovery of the adsorbate from the adsorbent. Successful regeneration renders adsorption an economically advantageous process. In our case, 89% regeneration was achieved by 1 M HCl, 15% with 1 M NaCl, and 3% with 1 M NaOH. After regeneration, cycle-wise reusability was tested and found that up to four consecutive batches, performance is almost retained. Figure S2a,b represents regeneration and reusability (Supporting Information). In an acidic medium, proton could replace dye molecules from the surface of NONP in the form of a cation exchanger. So, higher regeneration was seen. With sodium chloride, the process is not so feasible, and with alkaline solution, no ion exchange could take place.

2.10. Probable Mechanism of Dye Binding

The binding interaction of the adsorbent with the adsorbate depends on different properties such as molecular structure of the dye, functional groups present, and adsorbent surface properties. The mechanism of interaction between MG and NONPs is depicted below (Figure 9). It is proposed to be a combination of electrostatic force and weak interactions. The negatively charged surface of NONPs attracts the cationic MG dye electrostatically over zero-point charge.

Figure 9.

Figure 9

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Possible mechanism of adsorption of MG with NONPs.

2.11. Comparisons of NONPs with Other Materials for Adsorption

In order to establish advantage and potential of an adsorbent, it becomes necessary to compare efficiency with the reported ones. Table 4 comprehensively represents the maximum adsorption capacity of various nickel oxides synthesized through various routes. It was seen that NONPs are superior over many others.

Table 4. Comparison of Adsorption Capacity Of NONPs with Other Nickel Oxide Adsorbents.

dye adsorbent Qmax (mg/g) synthesis procedure refs.
basic red 46 (BR46) NONPs 105.61 coprecipitaion (69)
CR porous NiO 124.35 additive-free solvothermal (70)
basic blue 41 (BB41) NiO–MnO2 nanocomposite 58.99 coprecipitaion (71)
brilliant red X-3B        
CR        
fuchsin acid NiO(111) 30.4    
35.15        
22.0 combustion processes 5    
CR NiO nanosheets 39.7 chemical precipitation (72)
MG NiO 158 hydrothermal (63)
bromophenol blue dye (BB) NONPs 58.48 microwave-assisted (73)
rhodamine B NiO nanoparticles 111 hydrothermal (74)
MG NONP 87.72 self-sustained combustion present work
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3. Conclusions

NONPs were strategically synthesized by the sucrose-assisted self-sustained combustion method and thoroughly characterized by XRD, FTIR, vibrating sample magnetism (VSM), SEM–EDS, TEM, pHzpc, and BET surface area. Removal of MG was tested with optimized physicochemical parameters. VSM confirms the magnetic nature of the material. Adsorption was found to be pH-dependent and achieved best in the pH range of drinking water (6–8). Maximum uptake was found to be 87.72 mg/g at room temperature. Adsorption followed the Langmuir isotherm and pseudo second-order kinetic model. Thermodynamic data suggest that the process is spontaneous and exothermic in nature. The material can be regenerated and can be reused. The adsorbent could be easily separated from the solution mixture with a hand-held magnet. This is highly advantageous and energy-efficient. Effective removal of the dye by NONPs could be explained by electrostatic interaction and weaker forces. Thus, NONPs could be used as an efficient scavenger for cationic dyes and be regarded as a cost-effective adsorbent in future water treatment.

4. Experimental Section

4.1. Materials (Reagents and Chemicals)

A. R.-grade samples of nickel nitrate hexahydrate [Ni(NO3)2·6H2O], sucrose (D(±)C12H22O11), MG, hydrochloric acid, sodium hydroxide, and sodium chloride were purchased from Merck. The chemicals were used as received. Deionized water was used for making all solutions.

4.2. Synthesis of NONPs

The synthesis of NONPs was achieved by the modified solution combustion method. An aqueous solution of nickel nitrate hexahydrate ([Ni(NO3)2·6H2O], 5 gm, 0.0172 mol) and sucrose (5.896 gm, 0.0172 mol) was dissolved in 60 mL of water. Sucrose was used as fuel. The solution mixture was magnetically stirred for 1 h and gradually heated to 350 °C in the presence of air. Water evaporation triggers an autoignition with the release of a large amount of gases. After completion of the reaction, a fine black product was collected, washed with water, dried, and calcined at 600 °C for 6 h. The final product was received as a magnetic nanopowder (NONP). Scheme 1 outlines the synthesis and relevant reaction. We have tested the autoignition reaction with three different sucrose:Ni salt ratios of 1:1, 1:2, and 2:1. The best product was obtained in the 1:1 case. Therefore, it was considered as the optimized one. With the 1:2 sucrose-to-Ni-salt ratio, it was observed that some mixture of compounds appear, out of which the major part is magnetic with some nonmagnetic components. In order to avoid separation and identification, we discarded it. With 2:1 ratio, the product yield was found to be almost same but larger volume of gas evolution was noticed. In order to not contaminate the air to a greater extent, we decided to discard this. Therefore, 1:1 ratio was taken as optimum.

Scheme 1. Synthesis Route of NONPs.

Scheme 1

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Combustion temperature plays important role in the autoignition experiment. We have tested three different temperatures, 250, 350, and 450 °C. At 250 °C, combustion remains incomplete, leading to less yield. At 450 °C and above, possibilities are there that nickel nitrate decomposes to form higher valent and nonstoichiometric nickel oxides.62 Hence, 350 °C was fixed as the optimum temperature for combustion.

The effect of solvent volume was also tested. Three different sets were designed with 30, 60, and 90 mL of water. It was found that 60 mL was sufficient to propagate the reaction easily and in a controlled manner. Excess addition of the solvent in a reaction is against the principle of green engineering and has no practical justification. With less than 30 mL of water, the solution becomes concentrated and rapid augmentation to ignition takes place. Hence, 60 mL was optimized.

4.3. Material Characterization

NONPs were characterized by FTIR, PXRD, SEM-EDS, BET surface area, and pHZPC. FTIR spectra were recorded using a spectrophotometer (Shimadzu Corpn., Japan; IR-Prestige 21 model). SEM images were obtained on a Jeol JSM-6390LV instrument equipped with EDS. Powder XRD was performed using an AXRD proto benchtop X-ray diffractometer. Solution dye concentrations were measured using a Hitachi double beam UV–vis spectrophotometer (model U-2900) at 618 nm. VSM was recorded at room temperature on an EV-7 VSM ADE–DMS instrument with a step size of 500 Oe/min. A rotary orbital shaker (Sohag) was used for all batch experiments. The pH of solutions was measured with the help of a pH meter (Systronics). A Remi benchtop centrifuge (R-8 M) was used for centrifugation.

4.4. Batch Studies

To understand the adsorption behavior of MG onto NONPs, batch studies were executed with optimized parameters such as contact time (0–120 min), input concentrations of MG (10–60 mg/L), working pH (3–9), adsorbent dose (0.05–0.2 g), and temperature (293–308 K). In a typical experiment, 50 mL of dye solution (50 mg/L) was mixed with 0.05 g of NONPs and agitated at 120 ± 5 rpm at 25 ± 0.5 °C. After completion of the reaction, particles were separated using a hand-held magnet, solutions were centrifuged at 5000 ± 10 rpm for 2 min, and residual concentrations were measured. Adsorption percentage and capacities were calculated using eqs 13 and 14, respectively.

4.4. 13
4.4. 14

where C0 is the initial concentration in dye solution (mg/L) and Ce is the equilibrium dye concentration (mg/L). V is the volume (mL) of the solution taken and m (g) is the mass of adsorbent used. R % and qe represent adsorption percentage and capacity, respectively.

For kinetics study, solutions were withdrawn at 5, 10, 15, 20, 30, 40, 60, and 80 min and instantaneous concentrations were measured.

For isotherm study, four different temperatures of 293, 298, 303, and 308 K were chosen keeping other parameters fixed. To check thermal stability of MG in the experimental solution, control experiments were performed in parallel. MG solutions of set concentrations were agitated at the above mentioned temperatures without the adsorbent, parallel to the actual experiment. Initial and final concentrations were measured and found to be identical in control sets. This confirms the stability of the dye over the entire temperature range. It is noteworthy to mention that isotherms for MG were reported up to the temperature 333 K (60 °C).61

Desorption study was carried out with NaOH (1 M), HCl (1 M), and 1 M NaCl solutions. Dye-loaded materials were washed, dried, and treated with each of these solutions and shaken for 12 h. Adsorbents were magnetically separated, solutions were centrifuged, and reusability efficiency was measured using following equation:

efficiency (%) = (dye uptake in the second run/dye uptake in the first run) × 100%

Reusability was also tested to check sustainability of the material.

4.5. Point of Zero Charge (pHzpc) Estimation

Point of zero charge of NONPs was determined by the pH drift method. Sodium chloride solution (0.01 M) was taken and initial pH was adjusted from 2 to 12 by adding hydrochloric acid (0.01 M) and sodium hydroxide (0.01 M). A quantity of 0.05 gm of the material was added to each bottle. The resultant mixture was kept for stirring at 120 rpm for 24 h at 25 °C. The final pH was measured. The initial and final pH was plotted, and pHzpc was calculated from the graph.

Acknowledgments

J.M. thanks the Central University of Jharkhand for fellowship.

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsomega.0c00999.

  • Multistep intraparticle diffusion plot, regeneration of NONPs, and cycle efficiency (PDF)

The authors declare no competing financial interest.

Supplementary Material

ao0c00999_si_001.pdf (160.2KB, pdf)

References

  1. Yagub M. T.; Sen T. K.; Afroze S.; Ang H. M. Dye and its removal from aqueous solution by adsorption: A review. Adv. Colloid Interface Sci. 2014, 209, 172–184. 10.1016/j.cis.2014.04.002. [DOI] [PubMed] [Google Scholar]
  2. Chan S. H. S.; Wu T. Y.; Ching J.; Chee J.; Teh Y. Recent developments of metal oxide semiconductors as photocatalysts in advanced oxidation processes (AOPs) for treatment of dye waste-water. J. Chem. Technol. Biotechnol. 2011, 86, 1130–1158. 10.1002/jctb.2636. [DOI] [Google Scholar]
  3. Hajnajafi M.; Khorshidi A.; Gilani A. G.; Heidari B. Catalytic degradation of malachite green in aqueous solution by porous manganese oxide octahedral molecular sieve (OMS-2) nanorods. Res. Chem. Intermed. 2018, 44, 3313–3323. 10.1007/s11164-018-3308-1. [DOI] [Google Scholar]
  4. Altintig E.; Onaran M.; Sarı A.; Altundag H.; Tuzen M. Preparation, characterization and evaluation of bio-based magnetic activated carbon for effective adsorption of malachite green from aqueous solution. Mater. Chem. Phys. 2018, 220, 313–321. 10.1016/j.matchemphys.2018.05.077. [DOI] [Google Scholar]
  5. Song Z.; Chen L.; Hu J.; Richards R. NiO (111) nanosheets as efficient and recyclable adsorbents for dye pollutant removal from wastewater. Nanotechnology 2009, 20, 275707–275716. 10.1088/0957-4484/20/27/275707. [DOI] [PubMed] [Google Scholar]
  6. Ramalingam S.; Jonnalagadda R. R. Tailoring Nanostructured Dyes for Auxiliary Free Sustainable Leather Dyeing Application. ACS Sustainable Chem. Eng. 2017, 5, 5537–5549. 10.1021/acssuschemeng.7b00896. [DOI] [Google Scholar]
  7. Srivastava S.; Sinha R.; Roy D. Toxicological effects of malachite green. Aquat. Toxicol. 2004, 66, 319–329. 10.1016/j.aquatox.2003.09.008. [DOI] [PubMed] [Google Scholar]
  8. Ahmad R.; Kumar R. Adsorption studies of hazardous MG onto treated ginger waste. J. Environ. Manage. 2010, 91, 1032–1038. 10.1016/j.jenvman.2009.12.016. [DOI] [PubMed] [Google Scholar]
  9. Islam M. A.; Ali I.; Karim S. M. A.; Hossain Firoz M. S.; Chowdhury A.-N.; Morton D. W.; Angove M. J. Removal of dye from polluted water using novel nano manganese oxide based materials. J. Water Process Eng. 2019, 32, 100911–100932. 10.1016/j.jwpe.2019.100911. [DOI] [Google Scholar]
  10. Idris M. N.; Ahmad Z. A.; Ahmad M. A. Adsorption equilibrium of malachite green dye onto rubber seed coat based activated carbon. Int. J. Sci. Basic Appl. Res. 2011, 11, 38–43. [Google Scholar]
  11. Sharma Y. C.; Singh B.; Uma Fast Removal of MG by Adsorption on Rice Husk Activated Carbon. Open Environ. Pollut. Toxicol. J. 2009, 1, 74–78. [Google Scholar]
  12. Afroze S.; Sen T. K. A Review on Heavy Metal Ions and Dye Adsorption from Water by Agricultural Solid Waste Adsorbents. Water, Air, Soil Pollut. 2018, 229, 225. 10.1007/s11270-018-3869-z. [DOI] [Google Scholar]
  13. Manippady S. R.; Singh A.; Basavaraja B. M.; Samal A. K.; Srivastava S.; Saxena M. Iron-Carbon hybrid magnetic nanosheets for adsorption-removal of organic dyes and 4-Nitrophenol from Aqueous Solution. ACS Appl. Nano Mater. 2020, 3, 1571. 10.1021/acsanm.9b02348. [DOI] [Google Scholar]
  14. Ali I. New Generation Adsorbents for Water Treatment. Chem. Rev. 2012, 112, 5073–5091. 10.1021/cr300133d. [DOI] [PubMed] [Google Scholar]
  15. Guo T.; Yao M.-S.; Lin Y.-H.; Nan C.-W. A comprehensive review on synthesis methods for transition-metal oxide nanostructures. CrystEngComm 2015, 17, 3551–3585. 10.1039/c5ce00034c. [DOI] [Google Scholar]
  16. Zhang L.; Lu H.; Yu J.; McSporran E.; Khan A.; Fan Y.; Yang Y.; Wang Z.; Ni Y. Preparation of High-Strength Sustainable Lignocellulose Gels and Their Applications for Anti ultraviolet Weathering and Dye Removal. ACS Sustainable Chem. Eng. 2019, 7, 2998–3009. 10.1021/acssuschemeng.8b04413. [DOI] [Google Scholar]
  17. Li F.-t.; Ran J.; Jaroniec M.; Qiao S. Z. Solution combustion synthesis of metal oxide nano materials for energy storage and conversion. Nanoscale 2015, 7, 17590–17610. 10.1039/c5nr05299h. [DOI] [PubMed] [Google Scholar]
  18. Deng H.; Mao Z.; Xu H.; Zhang L.; Zhong Y.; Sui X. Synthesis of fibrous LaFeO3 perovskite oxide for adsorption of Rhodamine B. Ecotoxicol. Environ. Saf. 2019, 168, 35–44. 10.1016/j.ecoenv.2018.09.056. [DOI] [PubMed] [Google Scholar]
  19. Wen W.; Wu J.-M. Eruption Combustion Synthesis of NiO/Ni Nanocomposites with Enhanced Properties for Dye-Absorption and Lithium Storage. ACS Appl. Mater. Interfaces 2011, 3, 4112–4119. 10.1021/am2010064. [DOI] [PubMed] [Google Scholar]
  20. Zhong L.-S.; Hu J.-S.; Liang H.-P.; Cao A.-M.; Song W.-G.; Wan L.-J. Self-Assembled 3D Flowerlike Iron Oxide Nanostructures and Their Application in Water Treatment. Adv. Mater. 2006, 18, 2426–2431. 10.1002/adma.200600504. [DOI] [Google Scholar]
  21. Păcurariu O.; Ianos P. R.; Muntean S. G. Effective removal of methylene blue from aqueous solution using a new magnetic iron oxide nanosorbent prepared by combustion synthesis. Clean Technol. Environ. Policy 2016, 18, 705–715. 10.1007/s10098-015-1041-7. [DOI] [Google Scholar]
  22. Wu R.; Qu J.; Chen Y. Magnetic powder MnO–Fe2O3 composite—a novel material for the removal of azo-dye from water. Water Res. 2005, 39, 630–638. 10.1016/j.watres.2004.11.005. [DOI] [PubMed] [Google Scholar]
  23. Kumar K. Y.; Muralidhara H. B.; Nayaka Y. A.; Balasubramanyam J.; Hanumanthappa H. Low-cost synthesis of metal oxide nanoparticles and their application in adsorption of commercial dye and heavy metal ion in aqueous solution. Powder Technol. 2013, 246, 125–136. 10.1016/j.powtec.2013.05.017. [DOI] [Google Scholar]
  24. Chen H.; He J. Facile Synthesis of Monodisperse Manganese Oxide Nanostructures and Their Application in Water Treatment. J. Phys. Chem. C 2008, 112, 17540–17545. 10.1021/jp806160g. [DOI] [Google Scholar]
  25. Chen H.; Chu P. K.; He J.; Hu T.; Yang M. Porous magnetic manganese oxide nanostructures: Synthesis and their application in water treatment. J. Colloid Interface Sci. 2011, 359, 68–74. 10.1016/j.jcis.2011.03.089. [DOI] [PubMed] [Google Scholar]
  26. Yazdanbakhsh M.; Khosravi I.; Goharshadi E. K.; Youssefi A. Fabrication of nanospinel ZnCr2O4 using sol–gel method and its application on removal of azo dye from aqueous solution. J. Hazard. Mater. 2010, 184, 684–689. 10.1016/j.jhazmat.2010.08.092. [DOI] [PubMed] [Google Scholar]
  27. Hao T.; Yang C.; Rao X.; Wang J.; Niu C.; Su X. Facile additive-free synthesis of iron oxide nanoparticles for efficient adsorptive removal of Congo red and Cr(VI). Appl. Surf. Sci. 2014, 292, 174–180. 10.1016/j.apsusc.2013.11.108. [DOI] [Google Scholar]
  28. Shukla R.; Madras G. Facile synthesis of aluminium cobalt oxide for dye adsorption. Int. J. Chem. Environ. Eng. 2014, 2, 2259–2268. 10.1016/j.jece.2014.10.007. [DOI] [Google Scholar]
  29. Bhargavi R. J.; Maheshwari U.; Gupta S. Synthesis and use of alumina nanoparticles as an adsorbent for the removal of Zn(II) and CBG dye from wastewater. Int. J. Ind. Chem. 2015, 6, 31–41. 10.1007/s40090-014-0029-1. [DOI] [Google Scholar]
  30. Bhagya N. P.; Prashanth P. A.; Raveendra R. S.; Sathyanarayani S.; Ananda S.; Nagabhushana B. M.; Nagabhushana H. Adsorption of hazardous cationic dye onto the combustion derived SrTiO3 nanoparticles: Kinetic and isotherm studies. J. Asian Ceram. Soc. 2016, 4, 68–74. 10.1016/j.jascer.2015.11.005. [DOI] [Google Scholar]
  31. Aliasghari H.; Arabi A. M.; Haratizadeh H. A novel approach for solution combustion synthesis of tungsten oxide nanoparticles for photocatalytic and electrochromic applications. Ceram. Int. 2020, 46, 403–414. 10.1016/j.ceramint.2019.08.275. [DOI] [Google Scholar]
  32. Kaplan S. S.; Sonmez M. S. Single step solution combustion synthesis of hexagonal WO3 powders as visible light photocatalysts. Mater. Chem. Phys. 2020, 240, 122–152. 10.1016/j.matchemphys.2019.122152. [DOI] [Google Scholar]
  33. Muntean S. G.; Nistor M. A.; Ianoş R.; Păcurariu C.; Căpraru A.; Surdu V.-A. Combustion synthesis of Fe3O4/Ag/C nanocomposite and application for dyes removal from multicomponent systems. Appl. Surf. Sci. 2019, 481, 825–837. 10.1016/j.apsusc.2019.03.161. [DOI] [Google Scholar]
  34. Wu J.-M.; Wen W. Catalyzed Degradation of Azo Dyes under Ambient Conditions. Environ. Sci. Technol. 2010, 44, 9123–9127. 10.1021/es1027234. [DOI] [PubMed] [Google Scholar]
  35. Pehlivan M.; Simsek S.; Ozbek S.; Ozbek B. An extensive study on the synthesis of iron based magnetic aluminium oxide nanocomposites by solution combustion method. J. Mater. Res. Technol. 2019, 8, 1746–1760. 10.1016/j.jmrt.2018.12.005. [DOI] [Google Scholar]
  36. Ianoş R.; Pacurariu C.; Mihoc G. Magnetite/carbon nanocomposites prepared by aninnovative combustion synthesis technique—Excellent adsorbent materials. Ceram. Int. 2014, 40, 13649–13657. 10.1016/j.ceramint.2014.05.092. [DOI] [Google Scholar]
  37. Abdelrahman E. A.; Hegazey R. M.; Kotp Y. H.; Alharbi A. Facile synthesis of Fe2O3 nanoparticles from Egyptian insecticide cans for efficient photocatalytic degradation of methylene blue and crystal violet dyes. Spectrochim. Acta Mol. Biomol. Spectrosc. 2019, 222, 117195–117206. 10.1016/j.saa.2019.117195. [DOI] [PubMed] [Google Scholar]
  38. Ianoş R.; Pacurariu C.; Muntean S. G.; Muntean E.; Nistor M. A.; Niznansky D. Combustion synthesis of iron oxide/carbon nanocomposites, efficient adsorbents for anionic and cationic dyes removal from wastewaters. J. Alloys Compd. 2018, 741, 1235–1246. 10.1016/j.jallcom.2018.01.240. [DOI] [Google Scholar]
  39. Dafare S.; Deshpande P. S.; Bhavsar R. S. Photocatalytic degredation of Congo red on combustion synthesized Fe2O3. Indian J. Chem. Technol. 2013, 20, 406–410. [Google Scholar]
  40. Hong Y.; Cha B. J.; Kim Y. D.; Seo H. O. Mesoporous SiO2 Particles Combined with Fe Oxide Nanoparticles as a Regenerative Methylene Blue Adsorbent. ACS Omega 2019, 4, 9745–9755. 10.1021/acsomega.9b00726. [DOI] [PMC free article] [PubMed] [Google Scholar]
  41. Nassar M. Y.; Mohamed T. Y.; Ahmed I. S.; Samir I. MgO nanostructure via a sol-gel combustion synthesis method using different fuels: An efficient nano-adsorbent for the removal of some anionic textile dyes. J. Mol. Liq. 2017, 225, 730–740. 10.1016/j.molliq.2016.10.135. [DOI] [Google Scholar]
  42. Zhang Z.; Wang W.; Shang M.; Yin W. Low-temperature combustion synthesis of Bi2WO6 nanoparticles as a visible-light-driven photocatalyst. J. Hazard. Mater. 2010, 177, 1013–1018. 10.1016/j.jhazmat.2010.01.020. [DOI] [PubMed] [Google Scholar]
  43. Samoila P.; Cojocaru C.; Sacarescu L.; Dorneanu P. P.; Domocos A.-A.; Rotaru A. Remarkable catalytic properties of rare-earth doped nickel ferrites synthesized by sol-gel auto-combustion with maleic acid as fuel for CWPO of dyes Petrisor. Appl. Catal. B Environ. 2017, 202, 21–32. 10.1016/j.apcatb.2016.09.012. [DOI] [Google Scholar]
  44. Kumari V.; Kumar N.; Yadav S.; Mittal A.; Sharma S. Novel mixed metal oxide (ZnO.La2O3.CeO2) synthesized via hydrothermal and solution combustion process – A comparative study and their photocatalytic properties. Mater. Today: Proc. 2019, 19, 650–657. 10.1016/j.matpr.2019.07.748. [DOI] [Google Scholar]
  45. Alqadami A. A.; Naushad M.; Abdalla M. A.; Khan M. R.; Alothman Z. A. Adsorptive Removal of Toxic Dye Using Fe3O4–TSC Nanocomposite: Equilibrium, Kinetic, and Thermodynamic Studies. J. Chem. Eng. Data 2016, 61, 3806–3813. 10.1021/acs.jced.6b00446. [DOI] [Google Scholar]
  46. Vergis B. R.; Hari Krishna R.; Kottam N.; Nagabhushana B. M.; Sharath R.; Darukaprasad B. Removal of MG from aqueous solution by magnetic CuFe2O4 nano-adsorbent synthesized by one pot solution combustion method. J. Nanostruct. Chem. 2018, 8, 1–12. 10.1007/s40097-017-0249-y. [DOI] [Google Scholar]
  47. Wu X.; Luo B. B.; Chen M.; Chen F. Tunable surface charge of Fe, Mn substituted polyoxometalates/hydrotalcites for efficient removal of multiple dyes. Appl. Surf. Sci. 2020, 509, 145344. 10.1016/j.apsusc.2020.145344. [DOI] [Google Scholar]
  48. El-Shafai N. M.; Abdelfatah M. M.; El-Khouly M. E.; El-Mehasseb I. M.; El-Shaer A.; Ramadan M. S.; Masoud M. S.; El-Kemary M. A. Magnetite Nano-spherical quantum dots decorated graphene oxide Nano sheet (GO@Fe3O4): Electrochemical properties and applications for Removal heavy metals, pesticide and solar cell. Appl. Surf. Sci. 2020, 506, 144896. 10.1016/j.apsusc.2019.144896. [DOI] [Google Scholar]
  49. Marques T. M. F.; Sales D. A.; Silva L. S.; Bezerra R. D. S.; Silva M. S.; Osajima J. A.; Ferreira O. P.; Ghosh A.; Silva Filho E. C.; Viana B. C.; Matos J. M. E. Amino-functionalized titanate nanotubes for highly efficient removal of anionic dye from aqueous solution. Appl. Surf. Sci. 2020, 512, 145659. 10.1016/j.apsusc.2020.145659. [DOI] [Google Scholar]
  50. Mohanta J.; Dey B.; Dey S. Highly Porous Iron-Zirconium Binary Oxide for Efficient Removal of Congo Red from Water. Desalin. Water Treat. 2020, 189, 227–242. 10.5004/dwt.2020.25570. [DOI] [Google Scholar]
  51. Kumari R.; Dey S. Synthesis of porous iron- zirconium mixed oxide fabricated ethylene diamine composite for removal of cationic dye. Desalin. Water Treat. 2019, 158, 319–329. 10.5004/dwt.2019.24223. [DOI] [Google Scholar]
  52. Rahdar A.; Aliahmad M.; Azizi Y. NiO Nanoparticles: Synthesis and Characterization. J. Nanostruct. 2015, 5, 145–151. [Google Scholar]
  53. Srivastava N.; Srivastava P. C. Realizing NiO nanocrystals from a simple chemical method. Bull. Mater. Sci. 2010, 33, 653–656. 10.1007/s12034-011-0142-0. [DOI] [Google Scholar]
  54. Lagergren S. K. About the theory of so-called adsorption of soluble substances. Sven. Vetenskapsakad. Handingarl. 1898, 24, 1–39. [Google Scholar]
  55. Ho Y. S.; McKay G. Pseudo-second order model for sorption processes. Process Biochem. 1999, 34, 451–465. 10.1016/s0032-9592(98)00112-5. [DOI] [Google Scholar]
  56. Langmuir I. The adsorption of gases on plane surfaces of glass, mica and platinum. J. Am. Chem. Soc. 1918, 40, 1361–1403. 10.1021/ja02242a004. [DOI] [Google Scholar]
  57. Freundlich H. Über die adsorption in lösungen. Z. Phys. Chem. 1907, 57U, 385–470. 10.1515/zpch-1907-5723. [DOI] [Google Scholar]
  58. Mohanta J.; Xalxo R.; Dey B.; Dey S.. Efficient Removal of Malachite Green from Contaminated Water using Pyrolusite. In Green and Sustainable Technologies, Alternative Fuels, Renewable Energies and Energy Materials and Application; Bhattachryya A. S., Kumar S., Eds.; Lap Lambert Academic Publishing: Mauritius, 2020; pp 15–22. [Google Scholar]
  59. Mohanta J.; Dey B.; Dey S. Magnetic Cobalt Oxide Nanoparticles: Sucrose Assisted Self Sustained Combustion Synthesis, Characterization and Efficient Removal of Malachite Green from Water. J. Chem. Eng. Data 2020, 65, 2819–2829. 10.1021/acs.jced.0c00131. [DOI] [Google Scholar]
  60. Sartape A. S.; Mandhare A. M.; Jadhav V. V.; Raut P. D.; Anuse M. A.; Kolekar S. S. Removal of malachite green dye from aqueous solution with adsorption technique using Limonia acidissimia (wood apple) shell as low cost adsorbent. Arabian J. Chem. 2017, 10, S3229–S3238. 10.1016/j.arabjc.2013.12.019. [DOI] [Google Scholar]
  61. Bhatti H. N.; Jabeen A.; Iqbal M.; Noreen S.; Naseem Z. Adsorptive behavior of rice bran-based composites for malachite green dye: Isotherm, kinetic and thermodynamic studies. J. Mol. Liq. 2017, 237, 322–333. 10.1016/j.molliq.2017.04.033. [DOI] [Google Scholar]
  62. Brockner W.; Ehrhardt C.; Gjikaj M. Thermal decomposition of nickel nitrate hexahydrate, Ni(NO3)2·6H2O, in comparison to Co(NO3)2·6H2O and Ca(NO3)2·4H2O. Thermochim. Acta 2007, 456, 64–68. 10.1016/j.tca.2007.01.031. [DOI] [Google Scholar]
  63. Kumar K. Y.; Archana S.; Vinuth Raj T. N.; Prasana B. P.; Raghu M. S.; Muralidhara H. B. Superb Adsorption Capacity of Hydrothermally Synthesized Copper oxide and Nickel oxide nanoflakes towards Anionic and Cationic dyes. J. Sci.: Adv. Mater. Devices. 2017, 2, 183–191. 10.1016/j.jsamd.2017.05.006. [DOI] [Google Scholar]
  64. Jahromi S. P.; Huang N. M.; Muhamad M. R.; Lim H. N. Green gelatine-assisted sol–gel synthesis of ultra-small nickel oxide nanoparticles. Ceram. Int. 2013, 39, 3909–3914. 10.1016/j.ceramint.2012.10.237. [DOI] [Google Scholar]
  65. Alagiri M.; Ponnusamy S.; Muthamizhchelvan C. Synthesis and characterization of NiO nanoparticles by sol–gel method. J. Mater. Sci.: Mater. Electron. 2012, 23, 728–732. 10.1007/s10854-011-0479-6. [DOI] [Google Scholar]
  66. Al-Aoh H. A. Adsorption performances of nickel oxide nanoparticles (NiO NPs) towards bromophenol blue dye (BB). Desalin. Water Treat. 2018, 110, 229–238. 10.5004/dwt.2018.22223. [DOI] [Google Scholar]
  67. Jayakumar G.; Albert Irudayaraj A.; Dhayal Raj A. Photocatalytic Degradation of Methylene Blue by Nickel Oxide Nanoparticles. Mater. Today Proc 2017, 4, 11690–11695. 10.1016/j.matpr.2017.09.083. [DOI] [Google Scholar]
  68. Khansari A.; Enhessari M.; Salavati-Niasari M. Synthesis and Characterization of Nickel Oxide Nanoparticles from Ni(salen) as Precursor. J. Cluster Sci. 2013, 24, 289–297. 10.1007/s10876-012-0521-8. [DOI] [Google Scholar]
  69. Sheshdeh R. K.; Nikou M. R. K.; Badii K.; Limaee N. Y.; Golkarnarenji G. Equilibrium and Kinetics Studies for the Adsorption of Basic Red 46 on Nickel Oxide Nanoparticles-Modified Diatomite in Aqueous Solutions. J. Taiwan Inst. Chem. Eng. 2014, 45, 1792–1802. 10.1016/j.jtice.2014.02.020. [DOI] [Google Scholar]
  70. Ai L.; Zeng Y. Hierarchical Porous NiO Architectures as Highly Recyclable Adsorbents for Effective Removal of Organic Dye from Aqueous Solution. Chem. Eng. J. 2013, 215–216, 269–278. 10.1016/j.cej.2012.10.059. [DOI] [Google Scholar]
  71. Mahmoodi N. M.; Hosseinabadi-farahani Z.; Chamani H. Dye Adsorption from Single and Binary Systems Using NiO-MnO 2 Nanocomposite and Artificial Neural Network Modeling. Environ. Prog. Sustainable Energy 2017, 36, 111–119. 10.1002/ep.12452. [DOI] [Google Scholar]
  72. Cheng B.; Le Y.; Cai W.; Yu J. Synthesis of Hierarchical Ni(OH)2 and NiO Nanosheets and Their Adsorption Kinetics and Isotherms to Congo Red in Water. J. Hazard. Mater. 2011, 185, 889–897. 10.1016/j.jhazmat.2010.09.104. [DOI] [PubMed] [Google Scholar]
  73. Al-Aoh H. A. Adsorption Performances of Nickel Oxide Nanoparticles (NiO NPs) towards Bromophenol Blue Dye (BB). Desalin. Water Treat. 2018, 110, 229–238. 10.5004/dwt.2018.22223. [DOI] [Google Scholar]
  74. Motahari F.; Mozdianfard M. R.; Salavati-Niasari M. Synthesis and Adsorption Studies of NiO Nanoparticles in the Presence of H2acacen Ligand for Removing Rhodamine B in Wastewater Treatment. Process Safety Environ. Prot. 2015, 93, 282–292. 10.1016/j.psep.2014.06.006. [DOI] [Google Scholar]

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