by V Hadadi — bon active. Accordingly, Sadegh et al. [11] studied a high adsorption capacity of magnetic carbon nanotube (CNT) composite for removing Hg(II). A new method
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193 (2020) 266Œ273JulySynthesizing fisulfonated styrene-divinylbenzene polymer/Fefl nanocomposite recycling factories kinetic, thermodynamic, and isotherm adsorption studiesVahid HadadiDepartment of Chemistry, Islamshahr Branch, Islamic Azad University, Islamshahr, Iran, Tel. +98 938659545; email: Hadadivahid57@gmail.com (V. Hadadi) Received 29 September 2019; Accepted 5 March 2020 Recycling of alkaline batteries releases toxic and life-threatening ions to the environment. Different methods were studied to eliminate these pollutants from wastewaters. In this study, for the first time, a novel and high porous iron nanocomposite with the sulfonated styrene-divinylbenzene polymer was synthesized and was applied to eliminate Mn and Zn ions from wastewater of bat – tery recycling factories. Fourier transform infrared and scanning electron microscope showed that a porous nanocomposite with an iron particle size of less than 100 nm was prepared. Subsequently, synthesized nanocomposite was used for adsorption of Mn and Zn ions. After optimizing adsorption parameters with standard solutions, the optimized parameters were applied for kinetic, thermo – dynamic, and isotherm adsorption study of real wastewater. The adsorption kinetics was modeled by first and second-order rate models and the results indicate that the second-order kinetics model was well-suited to model the kinetic adsorption of Zn and Mn ions. The thermodynamic study illustrated a spontaneous and endothermic adsorption process for both Mn and Zn ions. Isotherm studies indicated reasonable compatibility of the Freundlich model with adsorption of zinc ions. However, the Langmuir model was compatible with manganese adsorption. Consequently, synthe – sized nanocomposite showed reasonable characteristics for adsorption of zinc and manganese from wastewater. Keywords: Wastewater treatment; Alkaline battery recycling factory; Polymer nanocomposite; Sulfonated styrene-divinylbenzene; Adsorption isotherms; Thermodynamic study 1.Introduction Battery recycling factories release different heavymetal to wastewater s due to the battery washing or recy -cling process. Around 70% of al kaline batteries are valuable metals such as steel, zinc, and manganese. The black slag residue of the recycling process is rich in zinc and man-ganese that leaks to wastewaters [1]. Diffe rent methods were suggested for removing these toxic metals from the environment. Filtration, coagulation, adsorption, reverse osmosis, oxidation, ion exchange, and chemical precipita-tion were old fashion techniques for removing heavy metal ions from water and soil [2]. Most of these methods were costly and time consuming with low efficiency. However, the number of these techniques like coagulation and precipitation are still used in most factories. In recent years, adsorption methods are widely used because it is cost-ef- fective and simple. Numerous materials can be used as adsorbents to remove heavy metal ions from the water. Nanomaterials were presented as the best adsorbents because of their large specific surface area [3]. Metal nanopar-ticle adsorbents were suggested for removing organic and inorganic pollutants [4]. Iron nanoparticles because of quick reaction and high yield in removing metal ions were studied [5]. Also, the characterization of new adsorbent containing iron chloride hydroxide nanocrystal (akaganeite)
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267V. Hadadi / Desalination and Water Treatment 193 (2020) 266Œ273 for As(v) elimination was investigated by Deliyanni et al. [6]. Metal oxide nanoparticles like hydrous titanium diox-ide as potential sorbent was used for the removal of man -ganese from water [7]. The thermodynamic study showed that the adsorption of manganese on titanium dioxide was spontaneous and exothermic. Moreover, it was defined that adsorption of manganese followed Langmuir adsorption isotherm. Also, oxidized multiwalled carbon nanotubes (MWCNTs) were applied for the removal of manganese from aqueous solution [8]. This investigation revealed that adsorption of manganese onto this adsorbent was sponta -neous and endothermic. Second-order kinetics of reactions and following Langmuir isotherm were other results of this study. The application of isotherm, kinetics, and thermody -namic models for the adsorption of other ions like nitrate by graphene were considered [9]. Adsorption mechanisms and related isotherm of other heavy metals such as Zn ions onto carbon nano-tube multiwall were widely studied by Taghdir et al. [10]. They found that the capacity of metal ion adsorption for MWCNTs is 3 or 4 times higher than car -bon active. Accordingly, Sadegh et al. [11] studied a high adsorption capacity of magnetic carbon nanotube (CNT) composite for removing Hg(II). A new method consists of its thermodynamic, kinetic, and isotherm studies were suggested for the elimination of manganese from water by electrocoagulation method [12]. Simultaneous removal of Co, Cu, Cr, and arsenate were discussed by the electroco -agulation method as well [13,14]. By polymer development, the polymeric adsorbents emerged in terms of their vast surface area, adjustable surface chemistry, perfect mechan – ical rigidity, and pore size distribution [15]. CNT coated by poly-amidoamine dendrimer (PAMAM) was studied as an adsorbent for adsorption of As 3+, Co2+, and Zn2+ from aque-ous solution [16]. Recently, nanocomposite materials were developed to remove heavy metal ions from wastewater [17]. Nanocomposite materials displayed better adsorption capacities, granulometric properties, chemical and thermal stabilities, reproducibility, and better selectivity compared to nanoparticles and CNTs [18]. The polymer nanocom – posites (PNCs) because of easy preparation, cost-effective, environmental stability, large surface area, and pore volume were evaluated among nanocomposites [19Œ22]. Magnetite- carbon nanocomposites were studied for the removal of metal ions from aqueous solutions [23]. The magnetite-ben- tonite nanocomposite was used for the elimination of Ni 2+, Cu2+, Cd2+, and Zn2+ ions from an affluent [24]. In another study, magnetic Fe 3O4 nanoparticles were synthesized and its surface was modified with 3-aminopropyl trimethoxysi – lane for adsorption of Co2+, Cr3+, Zn2+, and Cd2+ [25]. Also, Magnetic carbon-coated Fe3O4 microspheres activated with 1-ethyl-3-(3-dimethyl aminopropyl)-carbodiimide hydro- chloride were discussed to adsorb bovine serum albumin [26]. A novel PNC adsorbent such as sulfonated styrene- divinylbenzene and iron was studied for adsorption of cadmium ions [27].In summary, it is clear that increases in surface area and porosity of PNC increases the contact area of adsorbent with metal. So, synthesizing higher porous nanocomposite leads to the evolution of adsorption capacity. Since the poly sulfonated styrene-divinylbenzene is a porous polymer, it was used as a base for synthesizing the iron PNC adsorbent in this study. On the other side, the elimination of toxic metal like Zn and Mn from wastewater of battery recycling facto – ries by PNCs wasn™t investigated yet. Then, the sulfonated styrene-divinylbenzene polymer/Fe nanocomposite was used for adsorption of Mn(II) and Zn(II) from the wastewater of the alkaline battery recycling factory. Adsorption param – eters like contact time, pH, PNC dosage, kinetic, thermody- namic behaviors, etc. were investigated. Finally, Langmuir, Freundlich, and Temkin adsorption isotherm models were applied to fit the experimental data. The novelty of this investigation was applying a novel and high porous iron nanocomposite for removal of Mn and Zn ions from the wastewater of recycling alkaline battery factories. 2. Materials and methods2.1. Materials, apparatuses, and equationsThe wastewater consists of Zn 2+ (34 ppm) and Mn2+ (28 ppm) were collected from Peyman Recycling factory. All chemical reagents were supplied by Fluka and Merck. A stock solution of Mn(II) and Zn(II) ion with an initial concentration of 30 ppm was prepared by using (Mn(NO3)2·4H2O and (Zn(NO3)2·4H2O) salts with purity above 97%. A Fourier transform infrared (FT-IR) spectrometer (Jasco, FT-IR 420) in transmission mode under dry nitrogen flow (10 cm3 per minute) was used. A scanning electron microscope (SEM, JEOL field emis – sion scanning electron microscope, JSM-6700F) was used for morphology investigation. Adsorbent and specimens were shaken in an ultrasonic bath Model S 80H, Elmasonic Co.The equilibrium concentrations of metal ions were deter -mined by atomic absorption spectrophotometer (Model AA220, Varian Co., USA). The adsorbed metal ions concentration was obtained using Eq. (1):˜˚˚˛˝˙˙˜˚˛˝0 (1)where qe is the equilibrium uptake (mg gŒ1) of adsor-bate, C0 is the initial ion concentration (mg LŒ1), Ce is the equilibrium ion concentration (mg LŒ1), V and m are the volume of the solution (L), and the adsorbent mass (g), respectively. The adsorption percentages were calculated by the following equation: ˜˚˛˝˙˙ˆˇ˘˘˜˜˜˚ (2)2.2. Polymer nanocomposite preparation PNC was prepared by mixing 1 g of poly sulfonated styrene-divinylbenzene and benzol peroxide (as a cross- linked agent) to 300 mL of ethanol and FeCl 2·4H2O (0.4 M) solution. Then, NaBH4 solution (1 M) was added and was stirred for 20 min. The synthesized PNC was collected from
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V. Hadadi / Desalination and Water Treatment 193 (2020) 266Œ273 268the solution and was washed thrice with isopropanol to prevent oxidation of nanoparticles in PNC (Fig. 1). 2.3. Determination of adsorption percentages The required dosages of PNCs were added to Mn and Zn ions solutions and were mixed in an ultrasonic bath under the adjusted time and temperature. The PNC was separated from the solution by centrifuging and filtration. Finally, the concentrations of unadsorbed metal ions and their percentages were determined by atomic absorption and Eq. (2).3. Results and discussion3.1. PNC characteristicsThe morphology of synthesized PNC was investigated with SEM and is presented in Fig. 2. The morphology study showed that the spherical nanoparticles were distrib – uted in uniform size (less than 100 nm) in PNC. According to the SEM picture, too many holes were created by this polymer that made a high porous PNC with a high surface.Also, FT-IR was used to consider the physicochemi -cal interactions between the polymer and iron nanopar -ticles. In order to see the stretching vibration of iron, the iron particles in PNC were converted to the iron oxide by contacting PNC with water and oxygen for 48 h. Only the polysulfonated styrene-divinylbenzene (PSD) was con – tacted with water and oxygen in the same condition as reference. The FT-IR spectrum of iron oxide particles, PSD, and PNC are presented in Figs. 3aŒc, respectively. Fig. 3a showed a stretching vibration peak of iron oxide in about 600 cmŒ1. On the other side, a comparison between the PSD spectrum (Fig. 3b) and the PNC (Fig. 3c) showed a peak related to Iron oxide particles in the range of 600Œ500 cmŒ1 for PNC. This wide and strong peak proved that iron nano – composite was prepared in PSD. Obtained data from SEM and FT-IR of PNC showed that porous iron nanocomposite with a size of less than 100 nm were synthesized. Subsequently, in the next step, the synthesized PNC was used for consideration of effective adsorption parame – ters of Zn and Mn ions.3.2. Effect of contact timeSince contact time is one of the most important factors in adsorption value, contact time between the adsorbate and adsorbent were studied. The optimum contact time was calculated by mixing 25 mg of PNCs with 10 mL of Mn(II) and 10 mL of Zn(II) solutions with an initial concentration of 30 mg LŒ1 in separate beakers. The mixing process con-tinued for 5Œ60 min and the adsorption percentage of Mn and Zn ions were determined from time to time according to section 2.3 (determination of adsorption percentages). Extracted results are plotted in Fig. 4. Evidence showed that the best contact time for Mn and Zn ions was about 5 and 10 min, respectively. 3.3. Effect of pHTo estimating optimum pH, 25 mg of PNCs were mixed with 10 mL of Mn(II) and 10 mL of Zn(II) solutions with an initial concentration of 30 mg LŒ1. Then in different pHs from 3 to 11 and at optimum contact time (5 min for Mn(II) and 10 min for Zn(II)) adsorptions were determined (Fig. 5). Optimum pHs for Mn(II) and Zn(II) adsorption were calcu – lated in pH = 7 and 9, respectively. 3.4. Effect of adsorbent dosageThe different values of adsorbent were added to 10 mL of Mn(II) and 10 mL of Zn(II) solutions with a concentration of 30 mg LŒ1 to optimize dosages of adsorbent (Fig. 6). 20 min. stirring Filtration and collecting nanocomposite Washing thrice Prepared PNC Step 1 Step 2 Step 3 Polymer FeCl2.4H2O NaBH4 With iso-propanol Ethanol Fig. 1. PNC preparation flowchart. Fig. 3. FT-IR spectrums of (a) iron oxide, (b) only polysulfonated styrene-divinylbenzene, and (c) PNC. Fig. 2. SEM of synthesized PNC.
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269V. Hadadi / Desalination and Water Treatment 193 (2020) 266Œ273 Normally, an increase in adsorbent concentration should lead to rising in adsorption percentage. However, Fig. 6 shows a decreasing in adsorption value in more than 15 mass/mg of PNC for both Mn(II) and Zn(II) ions. Diminish in adsorption in the high concentration of absorbent was due to an aggregation of absorbent particles. Thus, 15 mg of PNC was selected as an optimum adsorbent dosage for both ions. 3.5. Kinetic studyIn order to consider the kinetics of Mn and Zn adsorp-tion over the PNC, the adsorption kinetics was investi -gated by first-order and second-order kinetic models. Two pseudo-first-order and pseudo-second-order models were tested to obtain the rate constants and adsorption mechanism.3.5.1. First-order modelThe first-order model generally explains as Eq. (3):˜˚˛˜˚˛˝˜˜˜˚˛˝˛˝˜˚˛˝˚˛˜˙ˆˇ˘˙ˆˇ˘ˇ (3)where qe is adsorption capacities at equilibrium and qt is adsorption capacities at time t (min), k1 (minŒ1) is the rate constant of the first-order adsorption. The plot of log(qeqt) vs. t gives the linear relationship in which k1 and qe can be determined by the slope and intercept, respectively. The results of kinetic adsorption of Mn and Zn according to the first-order equation are plotted in Fig. 7. The k1 for Mn and Zn was estimated at 0.201 and 0.219, respectively. The poor correlation coefficient (less than 0.987) proved that the kinetic of ions was not fitted with the first-order model. 3.5.2. Second-order modelSecond-order kinetic model is expressed as Eq. (4):˜˚˛˚˜˚˜˝˝˜˚˜˚˚ (4)where k2 is the rate constant of second-order adsorption that is calculated from the slope of the straight line. Fig. 8 presents the t/qt variation vs. t for both Mn and Zn adsorp-tion onto PNC. The rate constants (k2) for Mn and Zn were calculated 0.008 and 0.09, respectively. The kinetic data such as a good correlation coefficient (more than 0.997) for both ions indicated that the adsorption process was controlled by the pseudo-second-order equation.3.6. Thermodynamic behavior and the effect of temperature on real sample To understand the effect of temperature on the adsorp -tion process, thermodynamic parameters were determined at various temperatures. So, a real sample in optimized conditions (pH, contact time, and adsorbent dosage) was used for the thermodynamic study. But in additional pro – cesses, some interference substances were precipitated by controlling pH between 7 and 9. The sediments were separated from the solution by centrifuging and filtra- tion. In the next step, the residue solution was separated into two parts. In one part, 15 mg of PSD (polysulfonated styrene-divinylbenzene alone) was added as a reference and in the next part, 15 mg of PNC was added. Then, the adsorption of Zn and Mn ions was studied in opti – mized conditions at different temperatures (25°C, 40°C, 50°C, 55°C, and 65°C). The adsorption results onto PNC and PSD are presented in Fig. 9 and Table 1, respectively. The data in Table 1 showed that adsorption of Mn and Zn ions onto polymer alone was negligible and it was ignored. Note that the adsorption process in wastewater was performed in two beakers, once in pH = 7 for adsorption of Mn and once in pH = 9 for adsorption of Zn. According to Fig. 9, the adsorption increased at higher temperatures Fig. 4. Effect of contact time on adsorption of Mn and Zn ions onto the PNC. Fig. 5. Effect of pH on the adsorption of Mn(II) and Zn(II) onto the PNCs.Fig. 6. Effect of the dosage of PNCs on the adsorption percentage of Mn(II) and Zn(II) from aqueous solution.
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V. Hadadi / Desalination and Water Treatment 193 (2020) 266Œ273 270for both Mn and Zn ions. Comparison between Fig. 6 (adsorption of Zn and Mn lonely at 25°C) and Fig. 9 (adsorp- tion of Zn and Mn ions together in a real sample at 25°C) showed that adsorption of Zn ions decreased in the presence of Mn. However, adsorption of Mn(II) was independent of Zn ions in solution.In the aim of explaining the thermodynamic behavior of the real sample, thermodynamic parameters like enthalpy, entropy, and Gibbs free energies are extracted from Fig. 9. H°) and entropy changes S°) were calculated by the Van™t Hoff equation: ˜˚˜˚˛˝˛˙ˆ˜˚˛˚˝˝˛ (5)where KL was given from the division of qe on Ce and R was the ideal gas constant (8.314 J molŒ1KŒ1). The Van™t Hoff equation for Zn(II) and Mn(II) adsorption are shown in Figs. 10 and 11, respectively. H°) and standard S°) were extracted from the slope and intercept of the line, respectively. The results are given in Tables 2 and 3. G°s were calculated by Eq. (6) and are presented in Tables 2 and 3. ˜˜˜˜˚˛˝˚˛˚˝˚ (6) H° in Tables 2 and 3 explained endother -mic adsorption processes for both ions. In addition, positive S° showed that the entropy of reactions for Mn and Zn ions was expanded in the adsorption process. Positive val -ues of entropy change showed increase randomness of the solution interface during the adsorption of manganese and zinc ions. The evolution in adsorption capacity at higher temperatures was related to high porosity due to PNC G° in whole temperatures discussed a spontaneous reaction between PNC and adsorption of ions. The same results were obtained by other researchers about Mn and Zn removal by different adsorbent [7,8,12]. 3.7. Effect of initial ion concentrations and adsorption isotherms in the real sample In this study, different sorption isotherms, namely, Langmuir, Freundlich, and Temkin isotherms were exam -ined [13]. The Langmuir isotherm, which is valid for monolayer sorption onto a surface, is given by Eq. (7): ˜˜˚˛˚˛˝˙˝˝˜˚˛˝1 (7)Generally, the Langmuir model presents in several linear forms. In this study, the linear model Eq. (8) was used. 1111˜˜˚˜˛˝˙˙˝˜˚˛˝˙˙ˆˇ˘˘ (8)where qe (mg gŒ1) was the adsorbate value that adsorbed by 1 g of adsorbent, Ce (mg LŒ1) was the equilibrium concentra -tion of adsorbate in the solution, qm (mg gŒ1) was the value of Fig. 7. Adsorption kinetics of Mn and Zn ions by PNC for pseudo-first-order model. Fig. 8. Adsorption kinetics of Mn and Zn ions by PNC for pseudo-second-order model. Fig. 9. Effect of the temperature on the adsorption of Mn(II) and Zn(II) onto PNC.Table 1 Effect of the temperature on the adsorption of Zn and Mn ions onto the PSDMn adsorption (%) Zn adsorption (%)Temperature (°C) 0.91281.041.02421.11.1521.11.13581.181.265
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271V. Hadadi / Desalination and Water Treatment 193 (2020) 266Œ273 monolayer capacity of the adsorbate that adsorbed in 1 g of adsorbent, and K is the Langmuir constants.The 1/qe vs. 1/Ce diagrams for Zn(II) and Mn(II) ions are plotted in Figs. 12 and 13, respectively. The results should be in a straight line that its intercept represents 1/ qm and slope shows 1/Kqm. Hence, the Langmuir isotherm parame-ters for adsorption of Mn(II) and Zn(II) ions are presented in Table 4. Good correlation coefficients for manganese adsorp-tion indicated the applicability of the Langmuir model. The value of qm calculated by the Langmuir isotherm was close to the experimental value at given experimental con -ditions. Consequently, the manganese is adsorbed in the form of monolayer coverage on the surface of the adsor -bent. This result was compatible with the results of other researchers [9,13].The Freundlich adsorption isotherm model which is applicable for heterogeneous surfaces was analyzed as well. This model is generally valid for reversible adsorption that is not limited to monolayer adsorption. The equation is as follows:˜˚˛˝˙˝ˆ˜˚ (9)or in the logarithmic form:˜˚˛˜˚˛˜˚˛˜˚˛˝˙ˆ˙˜˚˝ (10)where kF and n are the Freundlich model constants. The numerical value of 1/ n indicates the adsorption capacity. Fig. 10. Van™t Hoff equation for Zn(II). Fig. 12. Langmuir adsorption isotherm for Zn(II).Fig. 13. Langmuir adsorption isotherm for Mn(II). Fig. 11. Van™t Hoff equation for Mn(II). Table 2 GHS° for Zn ionS° (kJ/mol)H° (kJ/mol)G° (kJ/mol)Temperature (K) Œ400.4301Œ768.631526.37,515.9Œ1,031.6325Œ1,189.4331Œ1,373.5338Table 3 GHS° for Mn ionS° (kJ/mol)H° (kJ/mol)G° (kJ/mol)Temperature (K) 73.223,686.6Œ453.9301Œ768.9315Œ993.9325Œ1,128.9331Œ1,286.4338Table 4 Langmuir isotherm parameters for adsorption of Mn(II) and Zn(II) ions onto the PNCR2K (L mgŒ1)qm (mg gŒ1)Ion0.984Œ3.180.913Zn0.999Œ3.10.907Mn
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273V. Hadadi / Desalination and Water Treatment 193 (2020) 266Œ273 less than 100 nm was prepared. In the next experiment, PNC was used for the elimination of Mn and Zn ions from wastewater of battery recycling factories. Experimental data showed that optimum contact times for adsorption of zinc and manganese ions onto PNC were 10 and 5 min, respectively. These results proved that reasonable adsorp – tion efficiency achieved in a short time (maximum 10 min.). Also, the optimum pHs calculated for adsorption of Zn(II) (pH = 9) and Mn(II) (pH = 7). The maximum PNC dos- age for both considered ions was obtained about 15 mg. A comparison between PNC absorbents and MWCNT absorbent [10] showed that PNC absorbents were more effective for the elimination of these ions. Study on the real sample (wastewater of battery recycling factories) consid – ered although adsorption of Zn ions decreased in presence of Mn and other ions, adsorption of Mn ions was indepen – dent of other substances in the real sample. The adsorption kinetics was modeled by first- and second-order rate models and the results indicate that the second-order kinetics model was well-suited to model the kinetic adsorption of Zn and Mn ions. The thermodynamic studies on the real sample proved a spontaneous and endothermic adsorption process for both Mn and Zn ions onto PNC. Furthermore, positive S° showed that the entropy of reactions increased in the adsorption process. Isotherm™s study represented that the adsorption of Zn ions onto PNC followed the Temkin model. So, the adsorption process for Zn ions was monolayer with different energy in absorbent sites. The results also showed that adsorption of Mn(II) ions onto PNC had better agree- ment with the Langmuir isotherm. The results of this study exhibited that synthesized nanocomposite showed good efficiency for adsorption of Zinc and Manganese from the recycling battery wastewaters. Acknowledgments Special thanks from Elham Taghdir for help. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. References[1] ABRI, Australian Battery Recycling Initiative, 2019. Available at: http://www.batteryrecycling.org.au/home [2] D.W. Connell, C. Birkinshaw, T.F. Dwyer, Heavy metal adsorbents prepared from the modification of cellulose: a review, Bioresour. Technol., 99 (2008) 6709Œ6724. [3] S.S. Banerjee, D.H. Chen, Fast removal of copper ions by gum arabic modified magnetic nano-adsorbent, J. Hazard. Mater., 147 (2007) 792Œ799.[4] X. Chen, J.V. Wright, J.L. Conca, L.M. Peurrung, Effects of pH on heavy metal sorption on mineral apatite, Environ. Sci. Technol., 31 (1997) 624Œ631.[5] J. Gao, H. Gu, B. 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