Toxic metal ion removal by terpolymer ion-exchanger from aqueous environments: synthesis,thermal degradation,batch separation,kinetic and isotherm studies

A novel chelating resin was synthesized and characterized by elemental, physico-chemical, GPC, NMR, and SEM analyses. Batch separation was adopted to study the recovery of selected metal ions with respect to the pH, time, concentrations, and electrolytes. From the results, it was observed that the order of the rate of metal ion uptake by the resin was Fe³⁺ > Cu²⁺ > Zn²⁺ > Ni²⁺ > Co²⁺ > Pb²⁺ ions. The adsorption kinetics follows first order, and isotherm models were also found to fit each other. The resin showed three-step thermal degradation, and its kinetic and thermodynamic parameters were also evaluated.     

Competitive Separation of Lead,Cadmium, and Nickel from Aqueous Solutions Using Activated Carbon: Response Surface Modeling,Equilibrium, and Thermodynamic Studies

In this study, the competitive separation of lead, cadmium, and nickel ions from aqueous solutions using a commercial activated carbon (AC) has been investigated and optimized using response surface methodology (RSM). The optimal conditions to reach the highest adsorption capacity for these metals were found as follows: initial pH = 6.3, temperature = 56.8°C, and shaking speed = 308 rpm. Under these conditions, the sequence of adsorption capacity toward the metal ions was as follows: Pb (II): 9.44 mg g^?1 > Cd (II): 9.37 mg g^?1 > Ni (II): 4.52 mg g^?1. The effect of shaking speed on the adsorption capacity of AC was higher than the effects of the initial pH and temperature, indicating the more important role of physisorption than chemisorption in the adsorption of these metal ions. This was confirmed by the results of thermodynamic studies. The equilibrium adsorption data were fitted to the Freundlich, Langmuir adsorption isotherm models and the Dubinin–Radushkevich model parameters were evaluated. All the models were tested and all were shown to represent the experimental data satisfactorily. The thermodynamic parameters such as ΔH, ΔS, and ΔG were computed from the experimental data. These values show that the adsorption is endothermic and spontaneous. The positive value of ΔS° indicates increasing of randomness at the solid/liquid interface during the adsorption of metal ions on AC.     

Adsorption Characteristics of Congo Red from Aqueous Solution onto Tea Waste

The feasibility of using tea waste (TW) as a low-cost adsorbent for the adsorption of an anionic dye (Congo red) from aqueous solution has been investigated. Adsorption in a batch process was conducted to study the effect of adsorbent dosage, initial dye concentration, contact time, pH, and temperature. The experimental data were analyzed by the Langmuir, Freundlich, and Temkin models. The adsorption system was best described by the Langmuir isotherm (R ² > 0.99). Adsorption kinetics followed a pseudo-second-order model (R ² > 0.99). The effect of mechanical treatment (vibratory mill) was also studied. The experimental results showed that using this physical treatment leads to an increase in the adsorption capacity of TW from 32.26 to 43.48 mg/g. Thermodynamic analyses revealed that the adsorption of Congo red on TW was endothermic and spontaneous in nature. The results indicated that TW can be employed as a potential low-cost adsorbent for the removal of Congo red from aqueous solution.     

Removal of benzoic acid from industrial wastewater using metal organic frameworks: equilibrium,kinetic and thermodynamic study

In this work, the adsorption of benzoic acid (BA) over metal organic framework of chromium-benzenedicarboxylates (MIL-101) is reported for the first time. The influences of pH, contact time, initial concentration, and temperature of BA solution on the adsorption behavior were investigated. The Langmuir adsorption isotherm was adequate to represent the experimental data (R² > 0.99) and the adsorption kinetics was well-represented by a pseudo-second order kinetic model (R² > 0.96). The zeta potential of MIL-101 decreased with increasing pH confirming the importance of electrostatic interactions between MIL-101 and BA as well as the importance of the large pore volume (1.32 m³/g) and large surface area (2390 m²/g) of MIL-101 for adsorption interaction. The thermodynamics analysis indicated negative free energy, enthalpy, and entropy changes suggesting that the adsorption of BA on MIL-101 is spontaneous and exothermic. The adsorption capacity of BA adsorption over MIL-101 was compared with those for other conventional adsorbents. The maximum capacities of BA uptake on MIL-101, activate carbon, and multiwall carbon nanotubes were 769.2, 406.5, and 341.2 mg/g, respectively, suggesting the superiority of MIL-101 as an adsorbent. Adsorption of real wastewaters containing other organic compounds in addition to BA confirmed the versatility of MIL-101 as a suitable adsorbent in wastewater treatment compared with conventional adsorbents.     

Reuse of a waste adsorbent poly(AAc/AM/SH)‐Cu superabsorbent hydrogel,for the potential phosphate ion removal from waste water: Matrix effects,adsorption kinetics,and thermodynamic studies

The most commonly applied methods for the treatment of used adsorbents is to recover them in acid/alkaline medium or direct enflame them. This work dealt with a new potential and economic method to utilize a waste adsorbent. Poly(AAc/AM/SH) superabsorbent hydrogels have proved to be a good adsorbent for Cu²⁺ ions and after adsorption the hydrogels were recovered in acid medium. In this report, the Cu²⁺ ion adsorbed hydrogel has not undergone any regeneration process and applied directly to phosphate ion adsorption. The Cu²⁺ ions‐loaded poly(AAc/AM/SH) hydrogels, were stable within a wide pH range and suitable for phosphate ion adsorption. The factors affecting the phosphate adsorption, such as pH, ionic strength, contact time, temperature, initial concentration of the phosphate ion, and coexisting ions were systematically investigated. The phosphate adsorption was highly pH dependent; and the maximum adsorption of 87.62 mg/g was achieved at pH 6.1. The adsorption data fitted the Langmuir adsorption isotherm better than the Freundlich isotherm. The concomitant anions show profounder adverse influence on phosphate ion adsorption of poly(AAc/AM/SH)‐Cu hydrogel and the effect follows the order citrate > sulfate > bicarbonate > chloride > nitrate. The thermodynamic parameters including ΔH°, ΔG°, and ΔS° for the adsorption processes of phosphate ions on the gel were also evaluated, and the negative ΔG° and ΔH° confirmed that the adsorption process was spontaneous and exothermic. The adsorption kinetic results suggest that the adsorption process was well described by the pseudo second‐order kinetic model. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Heavy Metal Adsorption by Magnetic Hybrid-Sorbent: An Experimental and Theoretical Approach

This study examined the sorption and desorption behaviors of Cu²⁺ and Pb²⁺ ions, which were adsorbed on the vinyl benzene chloride divinylbenzene (VBC-DVB-OH) polymer and magnetic hybrid adsorbent (VBC-DVB-OH-Fe) at pH 5. Batch and fixed bed column experiments were performed to study practical applicability and the breakthrough curves were obtained. The experimental equilibrium data, suitably fitted by the Langmuir and Freundlich isotherms, have shown that ferric oxide loaded magnetic hybrid sorbent (VBC-DVB-OH-Fe) exhibits higher adsorption capacity than vinyl benzene chloride divinylbenzene (VBC-DVB-OH) polymer. The results indicate the following order to fit the isotherms for both metal ions: Langmuir > Freundlich for polymeric sorbent and Freundlich > Langmuir for VBC-DVB-OH-Fe. The maximum adsorption capacity of VBC-DVB-OH adsorbent is 26.39 mg/g for Pb²⁺ and 7.93 mg/g for Cu²⁺ whereas it is increased to 45.81 mg/g for Pb²⁺and 25.64 mg/g for Cu²⁺ by using VBC-DVB-OH-Fe adsorbent. A series of column experiments were carried out to determine the breakthrough curves. The regeneration efficiency of the column runs was determined using HCl (10% v/v). The elution efficiency was 90% for each adsorbent.     

EQUILIBRIUM,KINETICS, AND BREAKTHROUGH STUDIES FOR ADSORPTION OF Cr(VI) ON CHITOSAN

Wastewater containing low levels of pollutants can be effectively treated by the adsorption technique. In the present work, an adsorption study was carried out using chitosan as adsorbent in a fixed-bed column for the removal of Cr(VI) from wastewater solutions. The column performance of Cr(VI) adsorption onto chitosan was studied at different bed heights (3–9 cm), flow rates (50–200 mL/min), initial metal concentrations (2–10 mg/L), pH values (2–7), and temperatures (30°–60°C). The equilibrium data for the batch adsorption of Cr(VI) on chitosan were tested using the Langmuir, Freundlich, and BET isotherm models. The Langmuir model was found to be the most suitable, with a maximum adsorption capacity of 35.7 mg/g and a correlation coefficient (R ²) = 0.952. The experimental data were found to fit well with the pseudo-second-order kinetic model, with R ² = 0.999. The dynamics of the adsorption process was modeled using the Adams-Bohart, Thomas, and mass transfer models. The models were used to predict the breakthrough curves of adsorption systems and to determine the characteristic design parameters of the column. The adsorption data were observed to fit well with all three models. The model parameters were derived using MATLAB software. In order to compare quantitatively the applicability of adsorption dynamic models in fitting to experimental data, the percentage relative deviation (P) was calculated and found to be less than 5, confirming that the fit is good for all three models.     

Adsorption of different dyes from aqueous solution using Si-MCM-41 having very high surface area

Adsorption characteristics of four different dyes Safranin O (cationic), Neutral Red (neutral), Congo Red (anionic) and Reactive Red 2 (anionic) on Si-MCM-41 material having very high surface area are reported. The surface morphology of Si-MCM-41 material before and after adsorbing dye molecules are characterised by FTIR, HRXRD, nitrogen adsorption–desorption isotherms, FESEM, and HRTEM. The adsorption capacities of Si-MCM-41 for the dyes followed a decreasing order of NR > SF > CR > RR2. The adsorption kinetics, isotherm and thermodynamic parameters are investigated in detail for these dyes using calcined Si-MCM-41. The kinetics and isotherm data showed that both SF and NR adsorb more rapidly than CR and RR2, in accordance with pseudo-second-order kinetics model as well as intraparticle diffusion kinetics model and Langmuir adsorption isotherm model respectively. The thermodynamic data suggest that the dye uptake process is spontaneous. The high adsorption capacities of dyes on Si-MCM-41 (q_m = 275.5 mg g^?1 for SF, q_m = 288.2 mg g^?1 for NR) is explained on the basis of electrostatic interactions as well as H-bonding interactions between adsorbent and adsorbate molecules. Good regeneration capacity is another important aspect of the material that makes it potent for the uptake of dyes from aqueous solution.     

Characterization of Adsorptive Capacity and Investigation of Mechanism of Cu2+, Ni2+ and Zn2+ Adsorption on Mango Peel Waste from Constituted Metal Solution and Genuine Electroplating Effluent

Abstract

The present study reports the potential of mango peel waste (MPW) as an adsorbent material to remove Cu²⁺, Ni²⁺, and Zn²⁺ from constituted metal solutions and genuine electroplating industry wastewater. Heavy metal ions were noted to be efficiently removed from the constituted solution with the selectivity order of Cu²⁺ > Ni²⁺ > Zn²⁺. The adsorption process was pH-dependent, while the maximum adsorption was observed to occur at pH 5 to 6. Adsorption was fast as the equilibrium was established within 60 min. Maximum adsorption of the heavy metal ions at equilibrium was 46.09, 39.75, and 28.21 mg g for Cu²⁺, Ni²⁺, and Zn²⁺, respectively. Adsorption data of all the three metals fit well the Langmuir adsorption isotherm model with 0.99 regression coefficient. Release of alkali and alkaline earth metal cations (Na⁺, K⁺, Ca²⁺, Mg²⁺) and protons H⁺ from MPW, during the uptake of Cu²⁺, Ni²⁺, and Zn²⁺, and EDX analysis of MPW, before and after the metal sorption process, revealed that ion exchange was the main mechanism of sorption. FTIR analysis showed that carboxyl and hydroxyl functional groups were involved in the sorption of Cu²⁺, Ni²⁺, and Zn²⁺. MPW was also shown to be highly effective in removing metal ions from the genuine electroplating industry effluent samples as it removed all the three metal ions to the permissible levels of discharge legislated by environment protection agencies. This study indicates that MPW has the potential to effectively remove metal ions from industrial effluents.     

Synthesis of polyamine-grafted chitosan and its adsorption behavior

The development of new environment-friendly and efficient adsorbents has attracted a great interest in recent years. In this study, ethylene diamine-grafted chitosan copolymer (CS–MAA–EN) and triethylene tetramine-grafted chitosan copolymer (CS–MAA–TN) were synthesized to remove heavy metal ions from water. The influence of pH, adsorbents dosage and initial metal concentration were investigated to study the adsorbing effect of CS–MAA–EN and CS–MAA–TN for the removal of Cu²⁺ from aqueous solutions. The equilibrium adsorption capacities of CS–MAA–EN and CS–MAA–TN were 85.91 and 102.67 mg/g, respectively. The adsorption process was fitted better by the Langmuir isotherm model (R ² = 0.9993, 0.9991) than the Freundlich isotherm model (R ² = 0.8781, 0.8775). The adsorption kinetics confirmed that the adsorption mechanism could be better described by the pseudo-second-order equation. Two adsorbents showed excellent desorption efficiency (D _e) and reuse ratio (R _u). D _e and R _u of CS–MAA–EN were evaluated as 95.2 and 89.35 %, respectively, and those values of CS–MAA–TN were 92.73 and 83.25 %. The competitive adsorption results of the two adsorbents indicated that the rate sequence was Fe³⁺ > Cu²⁺ > Cr⁶⁺ > Ni²⁺ > Zn²⁺.     

Removal of Heavy Metal Ions using New Chelating Material Containing N,O, and S Donor Sites

Abstract

A new chelating material (AT‐PHE‐HCHO) was synthesized by reacting 2‐aminothiazole‐phenol (AT‐PHE) azodye and formaldehyde (HCHO) in an alkaline medium. The materials were characterized by elemental analysis, FT‐IR and ¹H‐NMR spectroscopic studies. The chelating material was used for the adsorption of Cu(II), Zn(II), Mn(II), and Cr(III) from dilute aqueous solutions with variation of adsorption parameters. The adsorption was described quantitatively by fitting the equilibrium data to the Freundlich isotherm. The thermodynamic parameters ΔS and ΔH were calculated to be 86.02 J mol^?1 K^?1 and ?126.9 KJ mol^?1, respectively. The metal adsorption followed the sequence Cu(II)>Zn(II)～Cr(III)>Mn(II). The material was used for the removal of metal ions from synthetic as well as real samples.     

Adsorption of Lignosulfonate Compound from Aqueous Solution onto Chitosan-Silica Beads

The main objective of this study is to investigate the possibility of crosslinked chitosan-tetraethoxy orthosilane (TEOS) (chitosan-silica) beads to be used as an adsorbent material to adsorb the lignosulfonate compound in solution. Different parameters affecting the adsorption capacity such as contact time, adsorbent dosage, initial concentration, pH, ionic strength, and temperature have been investigated. Adsorption isotherms of lignosulfonates onto chitosan-silica beads were also studied. Batch adsorption experiments were carried out and the optimum lignosulfonate adsorption onto chitosan-silica beads occurred at contact time of 30 minutes, the adsorbent dosage of 40 g/L, initial concentration of 50 mg/L, pH 5, and a temperature of 45°C. Adsorption isotherms studied through the use of graphical methods revealed that the adsorption of lignosulfonates onto chitosan-silica beads follows the Langmuir model, with the maximum adsorption capacity being 238.3 mg/g at pH 7. Adsorption is dependent on the ionic strength. The adsorption of lignosulfonate on chitosan-silica beads was best described with the pseudo-second-order kinetic model with a rate constant of 0.32 g · mg^?1 · min^?1, while intra-particle-diffusion was the main rate-determining step in the lignosulfonate adsorption process. The chitosan-silica beads investigated in this study were thus exhibited as a high potential adsorbent for the removal of lignosulfonate from solution.     

BIOSORPTION STUDIES ON NACL-MODIFIED CERATOPHYLLUM DEMERSUM: REMOVAL OF TOXIC CHROMIUM FROM AQUEOUS SOLUTION

The present research provides information on the Cr(VI) removal potential of NaCl-modified Ceratophyllum demersum, an aquatic plant biomass. The effects of various parameters including pH, biomass dosage, contact time, and initial concentration on Cr(VI) biosorption were investigated. The best conditions for Cr(VI) biosorption in the present study were: pH of 2, biosorbent dose of 8 g/L, and contact time of 60 min. Under these conditions, maximum adsorption capacity of modified C. demersum for Cr(VI) was 10.20 mg/g. The experimental biosorption data were modeled by Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherms. The biosorption process followed the Langmuir isotherm model with a high coefficient of determination (R² > 0.99). The biosorption process followed pseudo-second-order kinetics. Further, the biosorbent was characterized by Fourier transform-infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). The results showed that biosorption of Cr(VI) on NaCl-modified C. demersum occurred through chemical sorption.     

Anthracene Bioadsorption from Simulated Wastewater by Chemically-Treated Unripe Plantain Peel Bioadsorbent: Batch Kinetics and Isothermal Modeling Studies

The main purpose of this study was to investigate and evaluate the bioadsorption potential of a chemically-treated unripe plantain peel in the removal of a polycyclic aromatic hydrocarbon (PAH) from its wastewater using anthracene as a model contaminant. The effects of physical factors such as initial anthracene concentration, agitation time, and pH and bioadsorbent dosage on the anthracene removal process were investigated. Results showed that the bioadsorption process was physical factors dependent. The pseudo-second-order kinetic model gave the best correlation of the bioadsorption kinetic data (R² > 0.998), whereas the bioadsorption mechanism was diffusion controlled. Both the Freundlich and Dubinin–Radushkevich isotherm models gave the best fit to the batch experimental equilibrium bioadsorption data. The maximum monolayer bioadsorption capacity (Q_max?) was found to be 27.70 mg/g. The bioadsorption process suggests to be of dual nature, physisorption and chemisorption; however, the chemisorption process is more dominant. Conclusively, chemically-treated unripe plantain peels have the adsorptive potential for application as an effective bioadsorbent for anthracene PAHs removal from wastewaters.     

L-cystein modified bentonite-cellulose nanocomposite (cellu/cys-bent) for adsorption of Cu2+, Pb2+, and Cd2+ ions from aqueous solution

In this study, L-cystein modified bentonite-cellulose (cellu/cys-bent) nanocomposite was synthesized and characterized by XRD, FTIR, SEM with EDS, TGA, and TEM techniques. In order to optimize the process the effect of various operational parameters such as pH, adsorbent dosage, contact time, and temperature were also investigated. The adsorption experiments were carried out in initial concentrations range of 20-100 mg L^?1and the adsorbent affinity for metal ions was found to be in order of Cu²⁺ > Pb²⁺ > Cd²⁺. The optimum pH for adsorption of Cu²⁺ and Cd²⁺ was observed at 5 while for Pb²⁺ it was pH 6. Based on the Langmuir model, the maximum adsorption capacity of Cu²⁺, Pb²⁺, and Cd²⁺ at 50^?C was found to be 32.36, 18.52, and 16.12 mg g^?1, respectively. The Langmuir isotherm and pseudo-second order model were found to be better fitted than the other isotherms and kinetic models. The results of thermodynamic parameters confirmed the process to be endothermic and spontaneous in nature.     

Surface Modification of Synthesized Nanozeolite NaX with TEAOH for Removal of Bisphenol A

In the present study, the surface modification of a freshly synthesized nanozeolite NaX was done with tetraethylammonium hydroxide (TEAOH) and applied as an adsorbent for the removal of bisphenol A (BPA) from its aqueous solutions. The adsorbent was characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results indicated that the synthesized adsorbent can remove BPA rapidly and effectively because of its high surface area (572 m²/g) and small particle size (35 nm). Uptake of BPA was greatly influenced by pH, stirring rate, temperature, contact time, and adsorbent dose. The optimum values of these parameters were 10.5 pH, 250 rpm, 25°C, 2 h, and 0.6 g/L. The adsorption was found to be spontaneous and exothermic. The Freundlich isotherm model and pseudo-first-order kinetic model fitted the experimental results well. The monolayer and multilayer adsorption capacities were found to be 42.8 and 122.6 mg/g, respectively.     

Treatment of Polyvinyl Alcohol from Aqueous Solution via Electrocoagulation

This study investigates the feasibility of removing the chemical oxygen demand (COD) from a solution containing polyvinyl alcohol (PVA) by electrocoagulation. Several parameters—including the current density, supporting electrolyte, and temperature—were evaluated in terms of COD removal efficiency. The effects of these parameters on the electrical energy consumption were also investigated. The optimum current density, supporting electrolyte concentration, and temperature were found to be 5 mA/cm², 0.012 N NaCl, and 298 K, respectively. The experimental data were also tested against different adsorption isotherm models to describe the electrocoagulation process; the COD adsorption studied here best fit the Freundlich adsorption isotherm model. Thermodynamic parameters, including the Gibbs free energy, enthalpy, and entropy, indicated that the adsorption of COD on metal hydroxides was feasible, spontaneous, and endothermic in the temperature range of 288 K to 318 K.     

Competitive Adsorption of Ag+, Pb2+, Ni2+, and Cd2+ Ions on Vermiculite

Competitive adsorption of Ag⁺, Pb²⁺, Ni²⁺, and Cd² ions on vermiuculite in a binary, ternary, and quaternary mixture was investigated in batch experiments. The effects of the presence of Ag⁺, Ni²⁺, and Cd²⁺ ions on the adsorption of Pb²⁺ ions were investigated in terms of the equilibrium isotherm. Experimental results indicated that Pb²⁺ ions always favorably adsorbed on vermiculite over Ag⁺, Ni²⁺, and Cd²⁺ ions. The adsorption equilibrium data of Pb²⁺ ions better fitted the Langmuir model than the Freundlich model. The results showed that the pseudo-second-order kinetics model was in good agreement with the experimental results for all metal ions, and the adsorption rate among the metal ions followed Ag⁺ > Pb²⁺ > Ni²⁺ > Cd²⁺. The desorption and regenration study indicated that vermiculite can be used repeatedly and be suitable for the design of a continuous process.     

Synthesis of a novel inorganic cation exchanger based on molybdate: Applications for removal of Pb2+, Fe3+ and Mn2+ ions from polluted water

A novel manganese phosphomolybdate exchanger was synthesized, dried at different temperatures, and evaluated for the elimination of lead, iron, and manganese ions from aqueous solutions. The chemical structure of the cation exchanger was established using Fourier-transform infrared, scanning electron microscopy, Thermo gravimetric analysis/ Differential thermal analysis, and X-ray diffraction. The adsorption performance of the heavy metals Pb²⁺, Fe³⁺, and Mn²⁺ toward the synthesized material has been studied. The obtained outcomes show that the selectivity of the cationic exchanger was descending in this order, Pb²⁺ > Fe³⁺ > Mn²⁺. The highest adsorption capacity was shown to be decreased as drying temperature of the exchanger increases from 50°C to 800°C.