Binding of several heavy metal ions by polyaspartyl polymers and their application to some Chinese herbal medicines

Water‐insoluble polyaspartyl polymers were synthesized by using water as medium instead of organic medium. Taking Ca²⁺ as a reference, the binding of several heavy‐metal ions, including Pb²⁺, Cd²⁺, Hg²⁺, Cr³⁺, Cu²⁺, and Mn²⁺, by polyaspartyl polymers was studied. The experimental results revealed that polyaspartate is an excellent binding agent for the investigated heavy‐metal ions. These cation ions were bound to polyaspartate polymer by the same mechanism as Pb²⁺, which can be explained by ion exchange model. Since polyaspartate has a protein‐resembling structure that is sensitive to trace heavy metal, it was used to remove some trace heavy‐metal elements in Chinese herbal medicines. It was found that polyaspartate material was an effective agent for the removal of Pb²⁺, Cd²⁺, and Hg²⁺ ions from glycyrrhizin, angelica, and gynostemma pentaphyllum. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Preparation of amidoximated bacterial cellulose and its adsorption mechanism for Cu2+ and Pb2+

Amidoximated bacterial cellulose (Am‐BC) was prepared through successive polymer analogous reactions of bacterial cellulose with acrylonitrile in an alkaline medium followed by reaction with aqueous hydroxylamine. It was used as an adsorbent to remove Cu²⁺ and Pb²⁺ from aqueous solutions. The adsorption behaviors of Cu²⁺ and Pb²⁺ onto Am‐BC were observed to be pH‐dependent. The maximum adsorption capacity of 84 and 67 mg g^–1 was observed, respectively, for Cu²⁺ and Pb²⁺ at pH 5. Scanning electronic microscopy (SEM) indicated that the microporous network structure of Am‐BC was maintained even after the modifacation. The adsorption mechanisms for Cu²⁺ and Pb²⁺ onto Am‐BC were investigated by fourier transform infrared spectroscopy (FTIR), ζ potential measurement and X‐ray photoelectron spectroscopy (XPS). The results revealed that the mechanism for the adsorption of Cu²⁺ onto Am‐BC could be mainly described as between metal ions and nitrogen atom in the amidoxime groups or oxygen atom in the hydroxyl groups. However, in the adsorption process for Pb²⁺, precipitation played the important role along with electrostatic interactions, although chelation action also existed in the process accounted for the adsorption process. The regeneration of Am‐BC was studied by treatment with a strong complexing agent, ethylenediaminetetracetic acid (EDTA). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Adsorption of Pb2+ and Pd2+ on polyethylene membrane with amino group modified by radiation‐induced graft copolymerization

Six chelating hollow fiber membranes were prepared by radiation‐induced grafting of glycidyl methacrylate onto a polyethylene hollow fiber membrane and its subsequent amination. The adsorption characteristics of Pb²⁺ and Pd²⁺ for the chelating hollow fiber membranes were presented when the solution of Pb²⁺ and Pd²⁺ permeates across the chelating membrane, respectively. The degree of grafting for glycidyl methacrylate increases with increasing monomer concentration, reaction temperature, and preirradiation dose. The adsorption of Pd²⁺ by chelating hollow fiber membranes modified with five kinds of amines was in the following order: diethylene triamine > hexamethyl diamine > ethylene diamine > dimethyl amine > trimethyl amine. The chelating hollow fiber membrane modified with iminodiacetic acid adsorbed Pb²⁺ ions much more than Pd²⁺. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 643–650, 1999     

Ligating behavior and metal uptake of N‐sulphonylpolyamine chelating resins anchored on polystyrene‐divinylbenzene beads

Amberlite XAD‐2 has been functionalized by coupling through –SO₂‐with ethylenediamine, propylenediamine, and diethylenetriamine to give the corresponding polyamine chelating resins I–III. The solid metallopolymer complexes of the synthesized chelating resins with Cu²⁺, Zn²⁺, Cd²⁺, and Pb²⁺ were synthesized. The polyamine derivatives and their metal complexes were characterized by elemental analysis, spectral (IR, UV/V, and ESR), and magnetic studies. The batch equilibrium method was utilized for using the chelating polyamines for the removal of Cu⁺², Zn⁺², Cd⁺², and Pb⁺² ions from aqueous solutions at different pH values and different shaking times at room temperature. The selective extraction of Cu⁺² from a mixture of the four metal ions and the metal capacities of the chelating resins were evaluated using atomic absorption spectroscopy. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1839–1846, 2005     

Preparation of Chelating Resins Containing a Pair of Neighboring Carboxylic Acid Groups and the Adsorption Characteristics for Heavy Metal Ions

Abstract

For the functional enhancement of chelating resins containing carboxylic acids, copolymer beads were prepared by suspension polymerization of styrene (St), methyl methacrylate (MMA), and divinylbenzene (DVB) in the presence of toluene as diluent. The phenyl rings of the beads were directly chloromethylated, and the carboxylic ester groups of the beads were converted into hydroxymethyl groups by reduction followed by chlorination to give chloromethyl groups, respectively. The chelating resins containing a pair of neighboring carboxylic acid groups (NCAGs) were obtained by the alkylation of chloromethyl groups in copolymer beads with diethyl malonate in the presence of sodium hydride followed by hydrolysis using aqueous alkali solution. Accordingly, the structural effects of the resins on the adsorption of heavy metal ions were investigated. Poly(St‐co‐DVB)‐based chelating resin containing NCAGs showed adsorption abilities toward heavy metal ions like Pb²⁺, Cd²⁺, and Cu²⁺, whereas poly(MMA‐co‐DVB)‐based chelating resin containing NCAGs showed adsorption abilities toward heavy metal ions like Cu²⁺, Cd²⁺, and Co²⁺. On the other hand, poly(St‐co‐MMA‐co‐DVB)‐based chelating resin containing NCAGs showed adsorption abilities toward heavy metal ions like Pb²⁺, Cd²⁺, Hg²⁺, Co²⁺, and Cu²⁺: a synergistic effect on the adsorption of heavy metal ions like Pb²⁺, Cd²⁺, Hg²⁺, and Co²⁺ was observed. The adsorption ability of poly(St‐co‐MMA‐co‐DVB)‐based chelating resin among three kinds of chelating resins was relatively good.     

Superabsorbent hydrogel based on modified polysaccharide for removal of Pb2+ and Cu2+ from water with excellent performance

This contribution describes the absorption percentage of Pb²⁺ and Cu²⁺ from water by a superabsorbent hydrogel matrix (SH) made from an anionic polysaccharide copolymerized with acrylic acid (AAc) and acrylamide (AAm). Metal‐absorption tests, upon sequential pH variation, indicated that the SH has pH‐sensitivity for the absorption of both metals from solution, attributed to the functional ionic groups (? COOH) present in the AAc and arabic gum (AG) segments. At the pH 5.0, the SH exhibited good absorption capacity: 73.10% for Pb²⁺, 81.99% for Cu²⁺ in water and 63.64% for Pb²⁺, and 76.67% for Cu²⁺ in saline water with 0.1 mol kg^?1 ionic strength. A replicated 2² full factorial design with a central point was built to evaluate the maximum absorption capacity of the metals into the SH. It was found that both the interaction and main effects of the pH and the initial concentration of metal solution on absorption percentage of the metals were statistically significant. Surface response plots indicated that the absorption capacity of both metals into the SH may be appreciably improved by using the solutions with lower initial concentration of metal and with higher pH values. Metal‐absorption results demonstrated that the SH is a convenient material for absorption of Pb²⁺ and Cu²⁺ from pure aqueous and saline aqueous environments. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Removal of heavy‐metal ions from aqueous solution with nanochelating resins based on poly(styrene‐alt‐maleic anhydride)

Chelating resins have been considered to be suitable materials for the recovery of heavy metals in water treatments. A chelating resin based on modified poly(styrene‐alt‐maleic anhydride) with 2‐aminopyridine was synthesized. This modified resin was further reacted with 1,2‐diaminoethan or 1,3‐diaminopropane in the presence of ultrasonic irradiation for the preparation of a tridimensional chelating resin on the nanoscale for the recovery of heavy metals from aqueous solutions. The adsorption behavior of Fe²⁺, Cu²⁺, Zn²⁺, and Pb²⁺ ions were investigated by the synthesis of chelating resins at various pH's. The prepared resins showed a good tendency for removing the selected metal ions from aqueous solution, even at acidic pH. Also, the prepared resins were examined for the removal of metal ions from industrial wastewater and were shown to be very efficient at adsorption in the cases of Cu²⁺, Fe²⁺, and Pb²⁺. However; the adsorption of Zn²⁺ was lower than those of the others. The resin was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction analysis, and differential scanning calorimetry analysis. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Adsorption properties of novel chelating resins containing 2‐amino‐5‐methylthio‐1,3,4‐thiadizole and hydrophilic spacer arms for Hg2+ and Ag+

The adsorption properties, including the adsorption kinetics, adsorption isotherms, and adsorption selectivity, of newly formed chelating resins that contained a heterocyclic functional group and a hydrophilic spacer arm of poly(ethylene glycol) [polystyrene–diethylene glycol–2‐amino‐5‐methylthio‐1,3,4‐thiadizole (PS–DEG–AMTZ) and polystyrene–triethylene glycol–2‐amino‐5‐methylthio‐1,3,4‐thiadizole (PS–TEG–AMTZ)] were studied in detail. The results show that the adsorption kinetics of PS–DEG–AMTZ and PS–TEG–AMTZ for Hg²⁺ and Ag⁺ could be described by a pseudo‐second‐order rate equation. The introduction of a spacer arm between the polymeric matrix and functional group was beneficial for increasing the adsorption rates. The apparent activation energies of the resins for Hg²⁺ and Ag⁺ were within 20.89–32.32 kJ/mol. The Langmuir model could describe the isothermal process of Hg²⁺ and Ag⁺. The competitive adsorption of the resins for Hg²⁺ and Ag⁺ in binary mixture systems was also investigated. The results show that Hg²⁺ and Ag⁺ were adsorbed before the other metal ions, such as Cu²⁺, Zn²⁺, Fe³⁺, Cd²⁺, and Pb²⁺, under competitive conditions. Five adsorption–desorption cycles were conducted for the reuse of the resins. The results indicate that these two resins were suitable for reuse without considerable changes in the adsorption capacity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effects on the removal of Pb2+ from aqueous solution by crab shell

The effects of temperature, pH, chitin and chitosan on Pb²⁺ removal by crab shell were investigated. Pb²⁺ removal by crab shell was greater than that of chitin and chitosan, indicating that chitin did not contribute to Pb²⁺ removal by crab shell. The quantity and rate of Pb²⁺ removal increased as the pH value increased. The rate of Pb²⁺ removal increased with increased temperature, but the maximum amount of Pb²⁺ removal was constant irrespective of temperature. Metal ions (K⁺, Na⁺, Mg²⁺, Ca²⁺) were released from crab shell concomitant with Pb²⁺ removal by ion exchange. The amount of Ca²⁺ released was greater than any for other metal ions in both Pb²⁺ and Pb²⁺‐free solutions. The amount of Ca²⁺ released in Pb²⁺ solution was greater than that in Pb²⁺‐free solution, whereas CO₃^2? release in Pb²⁺ solution was less than in Pb²⁺‐free solution. Pb²⁺ removal was mainly a consequence of dissolution of CaCO_3(s) with consequence precipitation of Pb₃(CO₃)₂(OH)_2(s) and PbCO_3(s). Pb²⁺ accelerated the dissolution of CaCO_3(s) by ion exchange and the precipitation occurred both at the surface and in the inner part of the crab shell. © 2001 Society of Chemical Industry     

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.     

Radiation synthesis and application of a hydrogel based on acrylic acid and 2‐mercaptobenzimidazole

A hydrogel based on gamma‐radiation polymerization of acrylic acid (AAc) in the presence of 2‐mercaptobenzimidazole (MBI) and a crosslinking agent was prepared. The properties of this AAc/MBI hydrogel were characterized in terms of gel content, swelling in different solvents, structure morphology, and IR spectroscopy. Moreover, the thermal decomposition behavior of the prepared hydrogel was investigated by thermogravimetric analysis (TGA). The TGA thermograms were also used to determine the different kinetic parameters such as order of reaction and activation energy. The sorption of some divalent metal ions such as Cu²⁺, Pb²⁺, Cd²⁺, and Hg²⁺ by the AAc/MBI hydrogel also was studied. The results showed that the AAc/MBI hydrogel has a higher tendency to swell in water and polar solvents than in nonpolar solvents. The highest metal uptake by the hydrogel was found for Hg²⁺ and Cd²⁺, whereas the lowest was for Cu²⁺ and Pb²⁺ ions. The ratios between the distribution coefficients of the different metals [separation factors (SF)] indicate that the hydrogel has a high selectivity for Hg²⁺ over Cu²⁺ (SF = 10.923) and Pb²⁺ (SF = 19.110). However, the hydrogel prefers Hg²⁺ over Cd²⁺ (SF = 1.356) and showed a high selectivity for Cd²⁺ over Cu²⁺ (SF = 7.822) and Pb²⁺ (SF = 7.240). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1607–1614, 2002     

Pb2+ as a Substrate and a Cofactor of a Porphyrin Metalation DNAzyme

We herein report a DNAzyme named T30695 (sequence: (G₃T)₄) that can catalyze Zn²⁺ insertion into three different porphyrins in the presence of Pb²⁺ as a cofactor. Meanwhile, T30695 with Pb²⁺ alone was found to cause a shift in both the fluorescence and UV-vis spectra of protoporphyrin IX (PPIX), thus suggesting that metalation of Pb²⁺ was also achieved at room temperature. From kinetic measurements, the reaction required two Pb²⁺ ions; this is consistent with one being a cofactor and the other being a substrate. No previous reports inserted Pb²⁺ into porphyrins by using DNAzymes or protein-based enzymes. This reaction was most significantly inhibited in the presence of K⁺ followed by Na⁺ and Li⁺, suggesting the importance of the Pb²⁺-stabilized G-quadruplex. When Pb²⁺ is inserted into PPIX, its emission blue shifts from 635 to 590 nm, thus allowing simple ratiometric fluorescent sensing with a detection limit of 1.2 nM Pb²⁺.     

Investigation of luminescence properties of Pb2+‐doped Sr2B2O5 phosphor

A near‐UV emitting phosphor, Pb²⁺‐doped Sr₂B₂O₅ was synthesized by the solid‐state reaction method at 900°C for 3 hours in air. The structure of the phosphor was verified by X‐ray diffraction study which shows monoclinic phase. Fourier transform infrared (FTIR) analysis confirmed the formation of Sr₂B₂O₅. The excitation and emission spectra of the synthesized phosphors were investigated at room temperature with photoluminescence spectrophotometer. The emission and excitation bands of Pb²⁺‐doped Sr₂B₂O₅ were observed at 370 and 289 nm, respectively. The dependence of the PL intensities on the Pb²⁺ concentration for the Sr_2?xPb_xB₂O₅ (0.01 ≤ x ≤ 0.03) phosphors was studied and it was observed that the concentration quenching of Pb²⁺ in Sr₂B₂O₅ is 0.025 mol.     

REMOVAL OF TOXIC Pb2+ IONS BY SYNTHETIC HYDROXYAPATITES

The removal behavior of toxic Pb²⁺ ions from aqueous and nonaqueous solutions by two synthetic hydroxyapatites (S-1 and S-2) has been investigated by using both batch and column methods.

It was found that Pb²⁺ ions in the both solutions were easily removed to the apatite samples mainly by cation-exchange reactions between the Pb²⁺ ions in the solutions and Ca²⁺ ions of the samples at room temperature. Further, in the system of aqueous PbF₂ solutions, anion-exchange reactions between F^? ions in the solutions and OH ^? ions of the samples occurred simultaneously and the liberated OH ^? and Ca²⁺ ions influenced removal behavior of Pb²⁺ and F^? ions. The maximum removal amount of Pb²⁺ ions from the aqueous solutions was 400?mg per g of S-1. Pb^? ions in the waste water from lead plating factories were completely removed to the apatite samples. In this manner, it was found that the apatites, especially S-1 can be employed as a new removal agent for the treatment of poisonous Pb²⁺ ions in waste water.     

Removal of Pb2+ and Cd2+ from drinking water using polysaccharide extract isolated from cactus pads (Opuntia ficus indica)

The use of a polysaccharide extract isolated from cactus pads (Opuntia ficus indica) as a low‐cost adsorbent for the removal of Pb²⁺ and Cd²⁺ from water was investigated. The Brunauer?Emmett?Teller study showed that the surface area of the extract powder was approximately 2.373 m²/g. Inductively coupled plasma optical emission spectrometry was used to monitor changes in ion concentrations during the adsorption. The adsorption mechanism was studied as a function of physicochemical variables such as initial metal ion concentration, adsorbent dosage, contact time, and pH of the solution. The results indicated that the adsorption percentage of the two cations increased with contact time, attaining equilibrium at 150 and 120 min for Cd²⁺ and Pb²⁺, respectively. At these optimal times, the adsorption capacity of Pb²⁺ and Cd²⁺ increased with increasing pH. Langmuir, Freundlich, Toth, Dubinin–Radushkevich, Sips, and Redlich–Peterson isotherm models were thereafter applied to understand the adsorption mechanism. The qe plot against C_e for the Toth isotherm model had the best fit with low error values and the highest correlation coefficient (R²) values of 0.9973 and 0.9953 for Pb²⁺ and Cd²⁺, respectively. Therefore, the isotherm study reveals that the adsorption mechanism involved is complex because of the presence of different interactions (such as ionic exchange and coagulation), yielding maximum adsorption capacities of 256 and 151 gm/L for Pb²⁺ and Cd²⁺, respectively. Generally, the polysaccharide extract exhibited higher adsorption capacity of Pb²⁺ than of Cd²⁺ under similar conditions. Besides the removal capacities reported in this study, the adsorbent regeneration and its reusability was also investigated. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43913.     

Preparation and adsorption mechanism of polyvinyl alcohol/graphene oxide-sodium alginate nanocomposite hydrogel with high Pb(II) adsorption capacity

A series of polyvinyl alcohol (PVA)/graphene oxide (GO)-sodium alginate (SA) nanocomposite hydrogel beads were prepared through in situ crosslinking for Pb²⁺ removal. It was found that PVA and SA molecules were intercalated into GO layers through hydrogen bonding interactions, leading to the destruction of orderly structure of GO, while GO uniformly distributed in PVA matrix. With increasing PVA solution concentration, the hydrogel beads became more regular, a large number of polygonal pores with thin walls and open pores formed, the average pore size decreased, and the dense network structure formed. Meanwhile, the permeability of the composite hydrogel decreased, leading to the decline of Pb²⁺ adsorption capacity of the composite hydrogel. With increasing GO content, the ballability of the hydrogel beads was weakened, the pore size increased, and relatively loose network structure formed, resulting in an increase in permeability and Pb²⁺ adsorption capacity of the hydrogel, reaching up to 279.43 mg g⁻¹. Moreover, the composite hydrogel presented relatively good reusability for Pb²⁺ removal. The adsorption mechanism was explored and showed that the adsorption system of the composite hydrogel belonged to the second-order kinetic model and fitted Langmuir adsorption isotherm model for Pb²⁺ removal, which might be mono-layer chemical adsorption. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47318.     

Synthesis of Copper and Lead Ion Imprinted Polymer Submicron Spheres to Remove Cu2+ and Pb2+

In this paper, Methacrylic acid (MAA) and 4-vinyl pyridine (4-VP) as functional monomers, Ethylene glycol two methyl acrylate (EGDMA) as crosslinking agent, isopropyl alcohol as the solvent, prepared the Cu(II)- and Pb(II)- imprinted polymers (IIPs) submicron spheres by precipitation polymerization. The presence/absence of the template ion in the preparation of the imprinted polymer was confirmed by EDX spectroscopy, and the structure of the particles was investigated using IR, SEM and BET analysis. From different components of crosslinker/monomer (C/M) ratio analysis, C/M at 1:3 was the optimal ratio for preparing IIPs. Atomic absorption spectroscopy (AAS) was characterized the imprinted polymers absorption behavior. The results show that the maximum adsorption capacity of Cu²⁺ and Pb²⁺ -imprinted polymer were 26.9 mg g^?1 and 25.3 mg g^?1, respectively. They also have good adsorption capacity and superior selectivity property for Cu²⁺ and Pb²⁺ in water, respectively. The selectivity factors (α) for Ni²⁺, Zn²⁺, Co²⁺ and Fe²⁺ were 16.5 (Cu²⁺) and 12.1 (Pb²⁺), 13.8 (Cu²⁺) and 16.2 (Pb²⁺), 10.8 (Cu²⁺) and 10.1 (Pb²⁺), 20.4 (Cu²⁺) and 20.7 (Pb²⁺), respectively. The regeneration experiment result demonstrates an excellent re-utilization property of these two type IIPs, after ten uses, the adsorption capacity can maintain above 60%.

     

Copolymer resin. VII. 8‐hydroxyquinoline‐5‐sulfonic acid–thiourea–formaldehyde copolymer resins and their ion‐exchange properties

8‐Hydroxyquinoline‐5‐sulfonic acid–thiourea–formaldehyde copolymer resins were synthesized through the condensation of 8‐hydroxyquinoline‐5‐sulfonic acid and thiourea with formaldehyde in the presence of hydrochloric acid as a catalyst and with various molar ratios of the reacting monomers. The resulting copolymers were characterized with UV‐visible, IR and 1H‐NMR spectral data, employed to determine the reactivity of monomers. The average molecular weights of these resins were determined with vapor pressure osmometry and conductometric titration in a nonaqueous medium. The chelation ion‐exchange properties were also studied with the batch equilibrium method. The resins were proved to be selective chelating ion‐exchange copolymers for certain metals. The chelation ion‐exchange properties of these copolymers were studied for Cu²⁺, Ni²⁺, Co²⁺, Pb²⁺, and Fe³⁺ ions. The study was carried out over a wide pH range and in media of various ionic strengths. The copolymers showed a higher selectivity for Fe³⁺ ions than for Cu²⁺, Ni²⁺, Co²⁺, and Pb²⁺ ions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation of thiourea functionalized polyvinyl alcohol‐coated magnetic nanoparticles and their application in Pb2+ ions adsorption

We have prepared a novel kind of magnetic nanoparticle with high adsorption capacity and good selectivity for Pb²⁺ ions by modifying the magnetic nanoparticles with polyvinyl alcohol (PVA) and thiourea. The resultant magnetic nanoparticles were used to adsorb Pb²⁺ ions from aqueous solution. The influence of the solution pH, the adsorption time, the adsorption temperature, coexisting ions, and the initial concentration of Pb²⁺ ions on the adsorption of Pb²⁺ ions were investigated. The results indicated that Pb²⁺ ions adsorption was an endothermic reaction, and adsorption equilibrium was achieved within 30 min. The optimal pH for the adsorption of Pb²⁺ ions was pH 5.5, and the maximum adsorption capacity of Pb²⁺ ions was found to be 220 mg/g. Moreover, the coexisting cations such as Ca²⁺, Co²⁺, and Ni²⁺ had little effect on adsorption of Pb²⁺ ions. The regeneration studies showed that thiourea functionalized PVA‐coated magnetic nanoparticles could be reused for the adsorption of Pb²⁺ ions from aqueous solutions over five cycles without remarkable change in the adsorption capacity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40777.     

Process Design of Groundnut Husk Waste for Pb2+ and Cd2+ Ions Mitigation in Drinking Water Purification

This present work has explored a novel application of modified Arachis hypogaea (groundnut) husk on mitigation of toxic Pb²⁺ and Cd²⁺ ions in aqueous phase. Ecotoxicological assessment of exhausted adsorbent was investigated as per standard OECD guidelines. Standard deviation, correlation coefficient, and the reduced chi square test were evaluated and compared statistically on experimental data. The results showed good sorption capacities—31.62 and 29.78 mg g^?l for Pb²⁺ and Cd²⁺ ions, respectively. Pseudo first-order rate kinetics was well correlated for Pb²⁺ and Cd²⁺ ions sorption over all kinetic models. The sorption data was in good agreement with the Freundlich isotherm for Pb²⁺ and the Sips model for Cd²⁺ ions sorption. The sorption capacity was endothermic in nature. Pb²⁺ ions desorption was three times faster than Cd²⁺ ions. The sorption mechanism was plausibly explained by spectroscopic techniques. Herein, the tailored abundant agro-waste material is a competitive sorbent and may be exploited in decontamination of metal ions in a wide range of concentrations. Supplemental materials are available for this article. Go to the publisher's online edition of Separation Science and Technology to view the free supplemental file.