Chitin-halloysite nanoclay hydrogel composite adsorbent to aqueous heavy metal ions

Halloysite nanoclay (HNC) was mixed with Chitin hydrogel film by phase inversion in water vapor atmosphere at room temperature. In the preparation, Chitin was dissolved in N,N-dimethyl acetamine/lithium chloride (DMAc/LiCl) and different amounts of HCN was dispersed well for the gelation process. The resultant Chitin-Halloysite nanoclay (CTH) hydrogel films containing HCN at 0, 0.1, 0.5, 1, and 4 wt % were used for the adsorbents of heavy metal ions. As the results, the tensile strength of the hydrogel composite was enhanced from 0.34 to 0.71 N/mm² while the elongation decreased from 66.43% to 49.93% with the increment of HNC concentration from 0 to 4 wt %. A reduction in the water content and the increment in the modulus confirmed the formation of highly dispersed nano-composites with improved interfacial interactions between nano-fillers and matrix. In the adsorption experiments of the ternary ion of Pb²⁺, Cu²⁺, and Cd²⁺, the removal capacity of Pb(II) was highly retained by the CTH hydrogel film relative to Cd(II) and Cu(II), shown Langmuir model with the maximum binding amount on the hydrogel composites were followed as order Pb (8.2 mg/g), Cu (4.2 mg/g), and Cd (2.1 mg/g). © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47207.     

Dithiocarbamate functionalized Al(OH)3‐polyacrylamide adsorbent for rapid and efficient removal of Cu(II) and Pb(II)

Heavy metal ions such as Cu²⁺ and Pb²⁺ impose a significant risk to the environment and human health due to their high toxicity and non‐degradable characteristics. Herein, Al(OH)₃‐polyacrylamide chemically modified with dithiocarbamates (Al‐PAM‐DTCs) was synthesized using formaldehyde, diethylenetriamine, carbon disulfide, and sodium hydroxide for rapid and efficient removal of Cu²⁺ and Pb²⁺. The synthesized adsorbent was characterized by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis, scanning electron microscopy–energy dispersive X‐ray spectroscopy analysis, and transmission electron microscope measurements. Al‐PAM‐DTCs showed rapid removal of Cu²⁺ (<30 min) and Pb²⁺ (<15 min) with high adsorption capacities of 416.959 mg/g and 892.505 mg/g for Cu²⁺ and Pb²⁺ respectively. Al‐PAM‐DTCs also had high capacities in removing suspended solids and metal ions simultaneously in turbid bauxite suspensions. FTIR, thermodynamic study, and elemental mapping were used to determine the adsorption mechanism. The rapid, convenient, and effective adsorption of Cu²⁺ and Pb²⁺ indicated that Al‐PAM‐DTCs has great potential for practical applications in purification of other heavy metal ions from aquatic systems. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45431.     

Porous dye affinity beads for nickel adsorption from aqueous solutions: A kinetic study

We investigated a new adsorbent system, Reactive Red 120 attached poly(2‐hydroxyethyl methacrylate ethylene dimethacrylate) [poly(HEMA–EDMA)] beads, for the removal of Ni²⁺ ions from aqueous solutions. Poly(HEMA–EDMA) beads were prepared by the modified suspension copolymerization of 2‐hydroxyethyl methacrylate and ethylene dimethacrylate. Reactive Red 120 molecules were covalently attached to the beads. The beads (150–250 μm), having a swelling ratio of 55% and carrying 25.5 μmol of Reactive Red 120/g of polymer, were used in the removal of Ni²⁺ ions. The adsorption rate and capacity of the Reactive Red 120 attached poly(HEMA–EDMA) beads for Ni²⁺ ions was investigated in aqueous media containing different amounts of Ni²⁺ ions (5–35 mg/L) and having different pH values (2.0–7.0). Very high adsorption rates were observed at the beginning, and adsorption equilibria were then gradually achieved in about 60 min. The maximum adsorption of Ni²⁺ ions onto the Reactive Red 120 attached poly(HEMA–EDMA) beads was 2.83 mg/g at pH 6.0. The nonspecific adsorption of Ni²⁺ ions onto poly(HEMA–EDMA) beads was negligible (0.1 mg/g). The desorption of Ni²⁺ ions was studied with 0.1M HNO₃. High desorption ratios (>90%) were achieved. The intraparticle diffusion rate constants at various temperatures were calculated as k_20°C = 0.565 mg/g min^0.5, k_30°C = 0.560 mg/g min^0.5, and k_40°C = 0.385 mg/g min^0.5. Adsorption–desorption cycles showed the feasibility of repeated use of this novel adsorbent system. The equilibrium data fitted very well both Langmuir and Freundlich adsorption models. The pseudo‐first‐order kinetic model was used to describe the kinetic data. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100:5056–5065, 2006     

Enhancement of Palmarumycins C12 and C13 Production in Liquid Culture of Endophytic Fungus Berkleasmium sp. Dzf12 after Treatments with Metal Ions

The influences of eight metal ions (i.e., Na⁺, Ca²⁺, Ag⁺, Co²⁺, Cu²⁺, Al³⁺, Zn²⁺, and Mn⁴⁺) on mycelia growth and palmarumycins C₁₂ and C₁₃ production in liquid culture of the endophytic fungus Berkleasmium sp. Dzf12 were investigated. Three metal ions, Ca²⁺, Cu²⁺ and Al³⁺ were exhibited as the most effective to enhance mycelia growth and palmarumycin production. When calcium ion (Ca²⁺) was applied to the medium at 10.0 mmol/L on day 3, copper ion (Cu²⁺) to the medium at 1.0 mmol/L on day 3, aluminum ion (Al³⁺) to the medium at 2.0 mmol/L on day 6, the maximal yields of palmarumycins C₁₂ plus C₁₃ were obtained as 137.57 mg/L, 146.28 mg/L and 156.77 mg/L, which were 3.94-fold, 4.19-fold and 4.49-fold in comparison with that (34.91 mg/L) of the control, respectively. Al³⁺ favored palmarumycin C₁₂ production when its concentration was higher than 4 mmol/L. Ca²⁺ had an improving effect on mycelia growth of Berkleasmium sp. Dzf12. The combination effects of Ca²⁺, Cu²⁺ and Al³⁺ on palmarumycin C₁₃ production were further studied by employing a statistical method based on the central composite design (CCD) and response surface methodology (RSM). By solving the quadratic regression equation between palmarumycin C₁₃ and three metal ions, the optimal concentrations of Ca²⁺, Cu²⁺ and Al³⁺ in medium for palmarumycin C₁₃ production were determined as 7.58, 1.36 and 2.05 mmol/L, respectively. Under the optimum conditions, the predicted maximum palmarumycin C₁₃ yield reached 208.49 mg/L. By optimizing the combination of Ca²⁺, Cu²⁺ and Al³⁺ in medium, palmarumycin C₁₃ yield was increased to 203.85 mg/L, which was 6.00-fold in comparison with that (33.98 mg/L) in the original basal medium. The results indicate that appropriate metal ions (i.e., Ca²⁺, Cu²⁺ and Al³⁺) could enhance palmarumycin production. Application of the metal ions should be an effective strategy for palmarumycin production in liquid culture of the endophytic fungus Berkleasmium sp. Dzf12.     

Synthesis and characterization of salep sulfate and its utilization in preparation of heavy metal ion adsorbent

A multicomponent polysaccharide obtained from dried tubers of certain natural terrestrial orchids was chemically modified by sulfonation using chlorosulfonic acid–dimethylformamide (HClSO_3–DMF) complex as a reagent. For a structural characterization of salep sulfate ¹H nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectra, and Thermogravimetric analysis (TGA) curves were recorded. The sulfate content of modified salep was determined using elemental analysis. This modified biopolymer was used to prepare a new environment‐friendly heavy metal ion adsorbent, salep sulfate‐graft‐polyacrylic acid hydrogel (SS‐g‐PAA). Swelling rate and equilibrium water absorbency in various pH and saline solutions were investigated to study the effect of salep sulfate on swelling behavior of the hydrogel. In addition, the effect of sulfate content on heavy metal ion adsorption from aqueous solution was investigated. The results show that SS‐g‐PAA can effectively remove heavy metal ions (Co²⁺, Zn²⁺, Cu²⁺) from aqueous solution and swelling behavior of the hydrogels highly dependent on the amount of sulfate group on corresponding modified polysaccharide. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3001–3008, 2013     

Bimetallic ions synergistic cross‐linking high‐strength rapid self‐healing antibacterial hydrogel

In this work, a novel PAA‐Fe³⁺‐Al³⁺ hydrogel with triple network structure (TN) was synthesized via bimetallic ions synergistic cross‐linking strategy. As‐synthesized samples were characterized by scanning electron microscope, Fourier transform infrared analysis, and X‐ray diffractometer. The relevant experiment results demonstrated that the hydrogel can rapidly self‐heal in ambient temperature without any external stimulus with 95% healing efficiency in 60 s. Simultaneously, the relatively rapid self‐healing of PAA‐Fe³⁺‐Al³⁺ polymer can be obtained through the coordination of metal ions with the ? COO^? in PAA and the oxygen of agar in the TN hydrogel system. And the prepared hydrogels demonstrate excellent mechanical properties—high tensile strength (the tensile strain ≈ 1.011 mm/mm, tensile stress ≈ 0.34 MPa) and large elasticity (the elongation at break ≈ 74%). Especially, the antimicrobial activity of the novel hydrogel against Staphylococcus aureus and Escherichia coli bacteria was investigated using the inhibition zone method, showing remarkable antibacterial activity. POLYM. ENG. SCI., 59:919–927, 2019. © 2018 Society of Plastics Engineers     

Silica nanoparticles modified with a Schiff base ligand: An efficient adsorbent for Th(IV), U(VI) and Eu(III) ions

Modification of SiO₂ nanoparticles by salicylaldiminepropyl results in efficient adsorbents for removal of Th⁴⁺, UO ₂ ²⁺ and Eu³⁺ ions from aqueous solutions. The effect of parameters influencing the adsorption efficiency such as aqueous phase pH, contact time, initial metal ions concentration, adsorbent dosage and temperature dependency of the process was verified and discussed. Under optimal conditions (pH 5.5, adsorbent dosage 0.05 g, contact time 30 min. and 25 °C), thorium and uranyl ions (initial concentration 20 mg/l) were quantitatively removed from 20 ml of sample solution. Under such conditions 85% of europium ions was removed. Comparison of the adsorption efficiency of the studied modified nano-particles with those unmodified ones shows a shift for uptake of the metal ions vs. pH curves towards lower pH values by applying the modified adsorbents. In addition, a significant improvement of europium ions adsorption was observed by using the modified nanoparticles. Kinetics of the process was studied by considering a pseudo second-order model. This model predicts chemisorption for the adsorption mechanism. Freundlich, Langmuir and Temkin models were suitable for describing the equilibrium data of Th⁴⁺, UO₂ ²⁺ and Eu³⁺ adsorption process, respectively. Thermodynamic investigation reveals the adsorption process of the studied ions is entropy driven.     

Synthesis and adsorption performance of fly ash/steel slag-based geopolymer for removal of Cu (II) and methylene blue

In order to realize the value-added resource utilization of solid waste, geopolymer particle adsorbents were prepared at low temperatures using silica-aluminum-rich fly ash and steel slag powders as raw materials. In order to investigate the mechanism of their adsorption of dyes and heavy metal ions from wastewater, the effects of steel slag/fly ash ratio, adsorbent dosage, initial concentration of methylene blue (MB) and Cu²⁺ solution, adsorption time and temperature on the adsorption performance of the fly ash/steel slag-based geopolymer adsorbents were investigated, systematically. Results presented that the adsorption capacities of MB and Cu²⁺ were 33.30 and 24.15 mg/g, and the removal efficiencies were 99.90% and 96.59% with the dosages of 3 and 4 g/L geopolymer adsorbents (steel slag/fly ash ratio of 20 wt.%), respectively. The adsorption processes of MB and Cu²⁺ on the adsorbents were in accordance with the proposed pseudo-second-order and Langmuir isotherm models, which mainly included physical and chemical adsorption mechanisms. The adsorption was a spontaneous endothermic process. The fly ash/steel slag-based geopolymer had good removal ability for dyes and heavy metal ions, and it could maintain good adsorption performance after three cycles of regeneration. It had potential application in wastewater treatment.     

Optimization of parameters for competitive adsorption of heavy metal ions (Pb+2, Ni+2, Cd+2) onto activated carbon

This study investigates optimization of various competitive adsorption parameters for removal of Cd(II), Ni(II) and Pb(II) from aqueous solutions by commercial activated carbon (AC) using the Taguchi method. Adsorption parameters such as initial metal concentration of each metal ion (C_0,i ), initial pH (pH₀), adsorbent dosage (m) and contact time (t) in batch technique were studied to observe their effects on the total adsorption capacity of metals onto activated carbon (q _tot ). The adsorbent dosage has been found to be the most significant parameter. Interactions between C_0,Cd ×C_0,Ni , C_0,Cd ×C_0,Pb and C_0,Ni ×C_0,Pb have been considered for simultaneous metal ions adsorption. The optimum condition for adsorption of metal ions were obtained with C_0,i =100 mg L^?1, pH₀=7, m=2 g L^?1 and t=80 min. Finally, experimental results showed that a multi-staged adsorptive treatment would be necessary to reach the minimal discharge standards of metal ions in the effluent.     

Removal of heavy metal ions from aqueous solutions by radiation‐induced chitosan/(acrylamidoglycolic acid‐co‐acrylic acid) magnetic nanopolymer

An effective method was developed to isolate toxic heavy metal ions from the aqueous solution by the magnetic nanopolymers. The magnetic sorbent was prepared with radiation‐induced crosslinking polymerization of chitosan (CS), 2‐acrylamido‐glycolic acid (AMGA), and acrylic acid (AAc), which stabilized by magnetite (Fe₃O₄) as nanoparticles. The formation of magnetic nanoparticles (MNPs) into the hydrogel networks was confirmed by Fourier transform infrared spectroscopy, X‐ray diffraction, transmission electron microscopy, and Scanning electron microscopy, which revealed the formation of MNPs throughout the hydrogel networks. The swelling behavior of the hydrogels and magnetic ones was evaluated at different pH values. The adsorption activity for heavy metals such as Cu²⁺ and Co²⁺ by nonmagnetic and magnetic hydrogels, Fe₃O₄/CS/(AMGA‐co‐AAc), in terms of adsorption amount was studied. It was revealed that hydrogel networks with magnetic properties can effectively be used in the removal of heavy metal ions pollutants and provide advantageous over conventional ones. POLYM. ENG. SCI., 55:1441–1449, 2015. © 2015 Society of Plastics Engineers     

Evaluating Cu(II) Removal From Aqueous Solutions with Response Surface Methodology by Using Novel Synthesized CaCO3 Nanoparticles Prepared in a Colloidal Gas Aphron System

Removal of heavy metals from water and wastewaters has recently gained a great deal of attention due to their serious environmental problems. In this study, novel synthesized calcium carbonate nanoparticles, prepared in a colloidal gas aphron (CGA) system, were used as adsorbents for the removal of Cu²⁺ ions from aqueous solutions under different conditions. A developed pseudo-second-order (PSO) model well described the adsorption kinetics of the process. Langmuir and Freundlich adsorption isotherms have been examined and the maximum adsorption capacity from the Langmuir isotherm equation was found to be 666.67?mg Cu/g adsorbent. The effects of temperature, Cu²⁺ initial concentration, and CaCO₃ dosage on the removal capacity were also investigated using the three-level Box–Behnken experimental design method. The response surface modeling results demonstrated that under certain experimental conditions (i.e., T?=?26°C, [Cu²⁺]?=?200?mg/L, and [CaCO₃]?=?0.5?g/L), maximum removal capacity value (393.52?mg/g) was achieved.     

Preparation of composites of liquid‐crystalline matrix of poly(p‐phenylene‐sulfoterephthalamide) and CaCO3 by In situ mineralization

Liquid‐crystalline (LC) hydrogels were obtained from an aqueous solution of poly(p‐phenylene‐sulfoterephthalamide) (PPST) by the addition of calcium ions (Ca²⁺). The critical hydrogel formation ratio of Ca²⁺ to the sulfonic acid group in PPST (^crtR_Ca = [Ca²⁺]/[ ]) depended on the concentration of PPST, and was independent of the molecular weight of PPST. When the LC hydrogel was prepared at a concentration of 0.5 wt % and ^crtR_Ca = 0.6, and was exposed to ammonium carbonate vapor for 96 h, all Ca²⁺ in the LC hydrogel were converted into calcite crystals. The alternate soaking process for the LC hydrogel induced the formation of two mesocrystal morphologies on and in the Ca²⁺ cross‐linked LC hydrogel. Plate‐like calcite mesocrystals grew at the hydrogel/solution interface and cubic mesocrystals were present in the inner space of the hydrogel, thus composites with some ordered structures of LC matrix and CaCO₃ have been prepared through in situ mineralization. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41455.     

Preparation of aminoalkyl celluloses and their adsorption and desorption of heavy metal ions

Aminoalkyl celluloses (AmACs) were prepared from 6-chlorodeoxycellulose and aliphatic diamines H₂N(CH₂)_mNH₂ (m = 2, 4, 6, 8). Their adsorption and desorption of divalent heavy metal ions such as Cu²⁺, Mn²⁺, Co²⁺, Ni²⁺ and their mixtures were also investigated in detail. Adsorption of metal ions on AmACs was remarkably affected by the pH of the solution, the metal ion and its initial concentration, and also the number of methylene units in the diamines. No adsorption of metal ions occurred on AmACs in strongly acidic solutions. However, metal ions were adsorbed rapidly on AmACs from weakly acidic solutions and the amount of adsorption increased with increasing pH. The effectiveness of AmACs as adsorbents decreased with increasing length of the methylene moiety, and AmACs from ethylenediamine (m = 2) was most effective. The adsorption of metal ions on AmACs was in the order Cu²⁺ > Ni²⁺ > Co²⁺ > Mn²⁺. Accordingly, their behavior followed the Irving-Williams series and Cu²⁺ ions were preferentially adsorbed from solutions containing metal ion mixtures. The adsorbed ions were easily desorbed from the AmACs by stirring in 0.1 M HCl.     

Preparation of gel resins and removal of copper and lead from water

A series of gel resins were prepared by polymerizing glycidyl methacrylate (GMA) and 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS) and functionalizing with ammonia (NH₃) and tetraethylenepentamine (TEPA). The aminated gel resins were then used as an adsorbent for the removal of heavy metal ions (Cu²⁺ and Pb²⁺). These gel resins containing amino groups and chelating amino groups had excellent adsorptive properties for Cu²⁺ and Pb²⁺. The adsorption process reached equilibrium in 40 min, and the adsorption capacities of Cu²⁺ and Pb²⁺ were 75.0 mg g^?1 and 266.6 mg g^?1 for the NH₃‐aminated gel resins and 57.5 mg g^?1 and 330.6 mg g^?1 for the TEPA‐aminated gel resins, respectively. After five adsorption–desorption processes, the adsorption capacities only decreased slightly. Thus, these aminated gel resins can be used as effective adsorbents for aqueous heavy metal ions (Cu²⁺ and Pb²⁺). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44466.     

Poly(acrylic acid)/poly(acrylamide) hydrogel adsorbent for removing methylene blue

Cationic dye can cause severe damage to the environment due to their refractory degradation, complex composition and strong stability. Hydrogels as adsorbents have been widely used to treatment the wastewater with dyestuff for their low prices, simple operations, and high efficiency. This work uses poly(acrylic acid) (PAA)/poly(acrylamide)(PAM)/calcium hydroxide nanoparticles (CHN) polymeric hydrogel absorbent to eliminate methylene blue (MB) dye. First, PAM/PAA/CHN hydrogel is produced through copolymerization of acrylic acid monomer and acrylamide monomer using inorganic CHN as cross-linker. And then, the adsorption performance of such PAM/PAA/CHN hydrogel adsorbent for adsorbing MB dye is explored at different conditions including pH, contacting time, adsorbent dosage, initial concentration of MB, and temperature. A maximum adsorption capability for adsorbing MB reaches 1,056 mg/g. Furthermore, the pseudo-first-order mode and Langmuir isotherm model can well describe adsorption behavior of MB dye onto such PAA/PAM/CHN hydrogel adsorbent. Thereby, as-prepared PAA/PAM/CHN hydrogel could be a potential adsorbent for eliminating organic dyes from wastewater.     

Thiourea modified hyper‐crosslinked polystyrene resin for heavy metal ions removal from aqueous solutions

A hyper‐crosslinked resin chemically modified with thiourea (TM‐HPS) was synthesized, characterized, and evaluated for the removal of heavy metal ions (Pb²⁺, Cd²⁺, and Cu²⁺) from aqueous solutions. The structural characterization results showed that a few thiourea groups were grafted on the surface of the resin with a big BET surface area and a large number of narrow micropores. Various experimental conditions such as pH, contact time, temperature, and initial metal concentration of the three heavy metal ions onto TM‐HPS were investigated systematically. The results indicated that the prepared resin was effective for the removal of the heavy metal ions from aqueous solutions. The isotherm data could be better fitted by Langmuir model, yielding maximum adsorption capacities of 689.65, 432.90, and 290.69 mg/g for Pd²⁺, Cd²⁺, and Cu²⁺, respectively. And the adsorption kinetics of the three metal ions followed the pseudo‐second‐order equation. FTIR and XPS analysis of TM‐HPS before and after adsorption further revealed that the adsorption mechanism could be a synergistic effect between functional groups and metal ions and electrostatic attraction, which may provide a new insight into the design of highly effective adsorbents and their potential technological applications for the removal of heavy metal ions from aqueous solutions. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45568.     

Poly (Acrylate -Acrylic acid-co-Maleic acid) hydrogel: A Cost Effective and Efficient Method for Removal of Metal Ions from Water

Noncompetitive adsorption of Zn (II) and Cd(II) from aqueous solution was carried out using Poly(Acrylate-Acrylic acid)(PAA) and Poly(Acrylate -Acrylic acid-co-Maleic acid)(PAAAM) hydrogels as adsorbents. Adsorption capacity was affected by the adsorbate concentration, temperature, and time and was investigated in detail. Results showed a decrease in adsorption with increase in the temperature whereas a steady increase followed by an equilibrium state (within 60 min.) was observed with time. The maximum adsorption capacity obtained for Zn²⁺ and Cd²⁺ were 227.89 and 369.51 mg/g, respectively. Even though the isotherms could be explained both with Langmuir and Freundlich, the present result was better explained by the Freundlich isotherm. This points to the fact that the hydrogel surface is heterogeneous and the adsorption occurred is a multilayered one. Adsorption was well modeled by the pseudo-second-order kinetic model. All metal ions used in the studies were successfully desorbed using 0.1 N HCl and the regeneration of hydrogel took place even after four cycles without any loss in its adsorption capacity.     

Metal ion retention properties of water‐insoluble polymers containing carboxylic acid groups

Crosslinked poly(acrylic acid), PAA, and poly(2‐acrylamidoglycolic acid), PAAG, were synthesized by radical polymerization. Both resins contain carboxylic acid groups. PAA at basic pH exists basically as an acrylate anion and PAAG shows three atoms or groups, carboxylic acid, hydroxyl, and amide groups, that can act as ion exchanger or chelating groups. Both resins are studied as adsorbents to trace metal ions from saline aqueous solutions and natural sea water and their properties by Batch equilibrium procedure are compared. The metal ions studied under competitive and noncompetitive conditions were Cu(II), Pb(II), Cd(II), and Ni(II). The effects of pH, time of contact, amount of resin, temperature, and salinity were studied. Resin PAA shows a high affinity (>80%) for Cu(II) and Cd(II) and resin PAAG shows also a high affinity for Ni(II), Pb(II), and Cd(II). By treatment of the metal ion‐loaded resin with 4M HNO₃ it is possible to recover completely the Cu(II) ions from resin PAA and Ni(II) and Pb(II) from resin PAAG. The metal ion retention properties were studied with natural sea water. For those natural sea waters containing Cu(II) and Cd(II), the resins showed a high affinity for Cd(II) ions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 697–705, 2006     

Optimization of parameters for adsorption of metal ions onto rice husk ash using Taguchi's experimental design methodology

The present paper deals with optimization of various batch parameters for the simultaneous removal of cadmium (Cd(II)), nickel (Ni(II)) and zinc (Zn(II)) metal ions from aqueous solutions by rice husk ash (RHA) using Taguchi's optimization methodology. Various adsorption parameters such as initial metal concentration of each metal ion (C_0,i), temperature (T), initial pH (pH₀), adsorbent dosage (m) and contact time (t) were varied at three levels to see their effects on the total adsorption of metals onto RHA (q_tot). L₂₇ orthogonal array (OA) has been used for experimental design, and the results have been analyzed using signal-to-noise (S/N) ratio and Pareto analysis of variance (ANOVA). The parameter m has been found to be the most significant parameter with 47.38 and 37.78% contribution to the q_tot and S/N ratio data. It is also observed that the interactions between C_0,i's (i.e. C_0,Cd × C_0,Ni, C_0,Cd × C_0,Zn and C_0,Ni × C_0,Zn) contribute significantly to both raw and S/N ratio data for simultaneous metal ions removal by RHA. All the parameters and their interactions considered are found to be statistically significant at 95% confidence level for the desired response characteristic, q_tot. The study shows that the Taguchi's method is suitable to optimize the experiments for total metal ions removal. The total optimum adsorptive removal of metal ions were obtained with C_0,i = 0–100 mg/l, T = 40 °C, pH₀ = 6, m = 10 g/l and t = 60 min. The results showed that a multi-staged adsorptive treatment is necessary to meet the minimal discharge standards of metal ions in the effluent.     

Synthesis and characterization of a new guar gum 4‐hydroxybenzoic acid resin and its use for the separation of heavy metal ions in industrial effluents

Hydroxybenzoic acid group has been incorporated onto guar gum by modified Porath's method of functionalization of polysaccharides. The newly synthesized guar gum 4‐hydroxybenzoic acid (GHBA) resin was characterized by Fourier‐transform infrared spectroscopy, elemental analysis, ion‐exchange capacity, column reusability, and physicochemical properties. The distribution coefficient (K_d) values and effect of pH on chelation of these metal ions using batch method were studied. The separations of mixture of Fe²⁺, Zn²⁺, Cu²⁺, Cd²⁺, and Pb²⁺ metal ions on GHBA resin on the basis of their distribution coefficient at various pH were also achieved using column chromatography. The effect of experimental parameters such as pH, treatment time, agitation speed, temperature, adsorbent dose, initial metal ion concentration, and flow rate on the removal of metal ions has been also studied. GHBA resin is effective adsorbents for the removal of different toxic metal ions from aqueous solutions and follows the order: Fe²⁺ > Zn²⁺ > Cu²⁺ > Cd²⁺ > Pb²⁺. POLYM. ENG. SCI. 2013. © 2012 Society of Plastics Engineers