Preparation of Cu(II)‐chelated poly(vinyl alcohol) nanofibrous membranes for catalase immobilization

Poly(vinyl alcohol) (PVA) nanofibers were formed by electrospinning. Metal chelated nanofibrous membranes were prepared by reaction between Cu(II) solution and nanofibers, and which were used as the matrix for catalases immobilization. The constants of Cu(II) adsorption and properties of immobilized catalases were studied in this work. The Cu(II) concentration was determined by atomic absorption spectrophotometer (AAS), the immobilized enzymes were confirmed by the Fourier transform infrared spectroscopy (FTIR), and the amounts of immobilized enzymes were determined by the method of Bradford on an ultraviolet spectrophotometer (UV). Adsorption of Cu(II) onto PVA nanofibers was studied by the Langmuir isothermal adsorption model. The maximum amount of coordinated Cu(II) (q_m) was 2.1 mmol g⁻¹ (dry fiber), and the binding constant (K_l) was 0.1166 L mmol⁻¹. The immobilized catalases showed better resistance to pH and temperature inactivation than that of free form, and the thermal and storage stabilities of immobilized catalases were higher than that of free catalases. Kinetic parameters were analyzed for both immobilized and free catalases. The value of V_max (8425.8 μmol mg⁻¹) for the immobilized catalases was smaller than that of the free catalases (10153.6 μmol mg⁻¹), while the K_m for the immobilized catalases were larger. It was also found that the immobilized catalases had a high affinity with substrate, which demonstrated that the potential of PVA‐Cu(II) chelated nanofibrous membranes applied to enzyme immobilization and biosensors. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Simultaneous preconcentration of Cd(II), Cu(II) and Pb(II) on Nano-TiO2 modified with 2-mercaptobenzothiazole prior to flame atomic absorption spectrometric determination

Nano-TiO₂ modified with 2-mercaptobenzothiazole (MBT) was investigated as a new adsorbent for preconcentration of Cd(II), Cu(II) and Pb(II). The metal ions are adsorbed onto nano-TiO₂-MBT, eluted by nitric acid and determined by flame atomic absorption spectrometry. The parameters affecting the adsorption were investigated. Under optimized conditions, the calibration curves were linear in the range of 0.2–25.0, 0.2–20.0, and 3.0–70.0 ng mL⁻¹ for cadmium, copper and lead, respectively. The limits of detection for Cd(II), Cu(II) and Pb(II) were 0.12, 0.15 and 1.38 ng mL⁻¹, respectively. The method was applied to determination of Cd(II), Cu(II) and Pb(II) in water and ore samples.     

Synthesis of AgBiS2/gC3N4 and its application in the photocatalytic reduction of Pb(II) in the matrix of methyl orange,crystal violet,and methylene blue dyes

The removal of lead ions in contaminated water by the reduction of Pb(II) ions to the useful metallic Pb is challenging, especially in water polluted by other contaminants such as dye molecules. Most investigations focussed on the removal of Pb(II) in a single system. In reality, contaminated water contains a mixture of organic pollutants and heavy metals. Herein, we synthesized graphitic carbon nitride functionalized with ternary silver bismuth sulphide (AgBiS₂/gC₃N₄) for the photocatalytic removal of Pb(II) from dye-containing water. The as-synthesized gC₃N₄, AgBiS₂, and AgBiS₂/gC₃N₄ composite were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and transmission electron microscopy (TEM). The composite was used for the photocatalytic reduction of Pb(II) in the matrix of methyl orange, crystal violet, and methylene blue. The effect of the presence of easily-oxidizable organics and persulphate on the photocatalytic reduction of Pb(II) was also investigated. The results revealed that the presence of easily-oxidizable organics has synergistic effects on the photocatalytic reduction of Pb(II), while persulphate displayed inhibitive effect on Pb(II) reduction. The removal of Pb(II) in the dyes matrix was influenced by the type of dyes that were present in the water. The rate of Pb(II) reduction was reduced in the presence of methylene blue and methyl orange, but crystal violet displayed synergistic effects. Finally, the rate of degradation of dyes in the presence of Pb(II) was investigated. The rate of photocatalytic reduction of Pb(II) decreased from 0.0045 min^?1 to 0.0036 min^?1 and 0.0016 min^?1 in the matrix of methyl orange and methylene blue respectively. On the contrary, there was an increase in the rate of photocatalytic reduction of Pb(II) from 0.0045 to 0.0096 min^?1 in the matrix of crystal violet.     

Preparation of polyacryloamidoxime chelating cloth for the extraction of heavy metals from water

Woven polyacryloamidoxime cloth was prepared from the polyacrylonitrile precursor via reaction in methanolic hydroxylamine. Preparation was controllable and reproducible and the reaction conditions were optimized with respect to the time of conversion, the concentration of NH₂OH⋅HCl, and the temperature of conversion. The cloth produced had a large capacity for Cu(II) and Pb(II) of 71.2 and 450 mg g^7minus;1 (1.12 and 2.17 mmol g⁻¹) respectively, and adequate physical properties suitable for rigorous use. Sorption profiles of Pb(II) and Cu(II) were similar to those of chelate ion exchange resins and fibers containing the amidoxime group. The rate of uptake of metals by the cloth was found to be dependent on the percent surface area converted to amidoxime groups, the concentration and type of metal being tested for, and the time of exposure. Anomalous kinetics of sorption for Pb(II) and Cu(II) by cloth of increasing amidoxime group content were explained by a two-part sorption mechanism. Distribution coefficients of 3.5 × 10⁶ and 1.5 × 10⁶ for Cu(II) and Pb(II) were observed, and the average rates of uptake for Cu(II) and Pb(II) were 600 and 200 μg g⁷⁻¹ day⁻¹ (9.4 and 0.96 μmol g⁷⁻¹ day⁻¹), respectively, from dilute solution ([Cu] = 5.9 μg L⁻¹, [Pb] = 2.8 μg L⁻¹). Treatment of the cloth with aqueous NaOH did not improve the capacities for Pb(II) and Cu(II). © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1175–1192, 1997     

Preparation and characterization of magnetic polymethylmethacrylate microbeads carrying ethylene diamine for removal of Cu(II), Cd(II), Pb(II), and Hg(II) from aqueous solutions

Magnetic polymethylmethacrylate (mPMMA) microbeads carrying ethylene diamine (EDA) were prepared for the removal of heavy metal ions (i.e., copper, lead, cadmium, and mercury) from aqueous solutions containing different amount of these ions (5–700 mg/L) and at different pH values (2.0–8.0). Adsorption of heavy metal ions on the unmodified mPMMA microbeads was very low (3.6 μmol/g for Cu(II), 4.2 μmol/g for Pb(II), 4.6 μmol/g for Cd(II), and 2.9 μmol/g for Hg(II)). EDA‐incorporation significantly increased the heavy metal adsorption (201 μmol/g for Cu(II), 186 μmol/g for Pb(II), 162 μmol/g for Cd(II), and 150 μmol/g for Hg(II)). Competitive adsorption capacities (in the case of adsorption from mixture) were determined to be 79.8 μmol/g for Cu(II), 58.7 μmol/g for Pb(II), 52.4 μmol/g for Cd(II), and 45.3 μmol/g for Hg(II). The observed affinity order in adsorption was found to be Cu(II) > Pb(II) > Cd(II) > Hg(II) for both under noncompetitive and competitive conditions. The adsorption of heavy metal ions increased with increasing pH and reached a plateau value at around pH 5.0. The optimal pH range for heavy‐metal removal was shown to be from 5.0 to 8.0. Desorption of heavy‐metal ions was achieved using 0.1 M HNO₃. The maximum elution value was as high as 98%. These microbeads are suitable for repeated use for more than five adsorption‐desorption cycles without considerable loss of adsorption capacity. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 81–89, 2000     

Batch and fixed‐bed column adsorption of Cu(II), Pb(II) and Cd(II) from aqueous solution onto functionalised SBA‐15 mesoporous silica

Functionalised SBA‐15 mesoporous silica with polyamidoamine groups (PAMAM‐SBA‐15) was successfully prepared with the structure characterised by X‐ray diffraction, nitrogen adsorption–desorption, Fourier transform infrared spectra and thermogravimetric analysis. PAMAM‐SBA‐15 was applied as adsorbent for Cu(II), Pb(II) and Cd(II) ions removal from aqueous solution. The effects of the solution pH, adsorbent dosage and metal ion concentration were studied under the batch mode. The Langmuir model was fitted favourably to the experimental data. The maximum sorptive capacities were determined to be 1.74 mmol g^?1 for Cu(II), 1.16 mmol g^?1 for Pb(II) and 0.97 mmol g^?1 for Cd(II). The overall sorption process was fast and its kinetics was fitted well to a pseudo‐first‐order kinetic model. The mean free energy of sorption, calculated from the Dubinin–Radushkevich isotherm, indicated that the sorption of lead and copper, with E > 16 kJ mol^?1, followed the sorption mechanism by particle diffusion. The adsorbent could be regenerated three times without significant varying its sorption capacity. A series of column tests were performed to determine the breakthrough curves with varying bed heights and flow rates. The breakthrough data gave a good fit to the Thomas model. Maximum sorption capacity of 1.6, 1.3 and 1.0 mmol g^?1 were found for Cu(II), Pb(II) and Cd(II), respectively, at flow rate of 0.4 mL min^?1 and bed height of 8 cm, which corresponds to 83%, 75% and 73% of metallic ion removal, respectively, which very close to the value determined in the batch process. Bed depth service time model could describe the breakthrough data from the column experiments properly. © 2012 Canadian Society for Chemical Engineering     

Facile preparation of a silica‐sphere–poly(catechol hexamethylenediamine) composite for the competitive removal of cadmium(II), lead(II), and copper(II) ions

A silica‐sphere–poly(catechol hexamethylenediamine) (PCHA–SiO₂) composite was prepared via the one‐step facile polymerization of catechol and hexamethylenediamine; this method uses a silica sphere as a hard template. The chemical structures and morphologies of this composite were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and transmission electron microscopy. The adsorption experiments indicated that the PCHA–SiO₂ composite served as a very attractive adsorbent for Pb(II)‐, Cu(II)‐, and Cd(II)‐ion removal at lower concentrations and had very good selective adsorption abilities for Pb(II) and Cu(II) ions in a solution contaminated with these three ions at higher concentrations. These interesting results may have been due to the reversible H⁺ adsorption–desorption properties of the characteristic phenol amine structure of the PCHA–SiO₂ composite. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45839.     

PSSMA修饰磁性氧化石墨烯对Pb2+、Cu2+ 的吸附性能

以氧化石墨烯(GO)、FeCl_3·6H_2O及聚(4-苯乙烯磺酸-共聚-马来酸)钠盐(PSSMA)为主要原料,通过简便一步溶剂热法制备了阴离子聚电解质修饰磁性氧化石墨烯(MGO@PSSMA),并将其用于水溶液中重金属Pb~(2+)、Cu~(2+)的吸附去除。采用FTIR、SEM、TEM、VSM和DLS对制备的MGO@PSSMA进行了表征。考察了溶液pH、吸附时间、溶液初始质量浓度对Pb~(2+)、Cu~(2+)在MGO@PSSMA及未经PSSMA修饰磁性氧化石墨烯(MGO)上吸附的影响。探讨了吸附等温过程、吸附动力学及吸附作用机理。结果表明:MGO表面引入PSSMA可有效增加其对Pb~(2+)、Cu~(2+)的吸附量。在pH=5,溶液初始质量浓度为300 mg/L时,MGO@PSSMA对Pb~(2+)和Cu~(2+)的实际吸附量达141.1和104.8 mg/g。当溶液初始质量浓度为150 mg/L时,MGO@PSSMA对Pb~(2+)和Cu~(2+)的吸附平衡时间分别为2和1.5 min。MGO@PSSMA对Pb~(2+)、Cu~(2+)的吸附动力学及吸附等温数据分别符合准二级吸附动力学模型和Langmuir吸附等温模型。使用乙二胺四乙酸(EDTA)和HCl可实现MGO@PSSMA的有效再生;通过外加磁场作用可实现MGO@PSSMA的回收再利用。     

Immobilization of laccase on itaconic acid grafted and Cu(II) ion chelated chitosan membrane for bioremediation of hazardous materials

BACKGROUND: Chitosan membranes were formed through a phase inversion technique and then cross‐linked with epichlorohydrin (CHX). Heterogeneous graft copolymerization of itaconic acid (IA) onto membrane was carried out with different monomer concentrations (CHX‐g‐p(IA)). The membrane properties such as equilibrium swelling ratio, porosity, and contact angle were measured, together with analysis by scanning electron microscopy (SEM), energy dispersive analysis of X‐rays (EDAX), atomic force microscopy (AFM), and Fourier transform infrared (FTIR) spectroscopy. RESULTS: The Cu(II) ion incorporated membranes (i.e. CHX‐g‐p(IA)‐Cu(II)) were used for reversible immobilization of laccase using CHX‐g‐p(IA) membrane as a control system. Maximum laccase adsorption capacities of the CHX‐g‐p(IA) and CHX‐g‐p(IA)‐Cu(II) membranes (with 9.7% grafting yield) were found to be 6.3 and 17.6 mg mL^?1 membrane at pH 4.0 and 6.0, respectively. The K_m value for immobilized laccase on CHX‐g‐p(IA)‐Cu(II) (4.16 × 10^?2 mmol L^?1) was 2.11‐fold higher than that of free enzyme (1.97 × 10^?2 mmol L^?1). Finally, the immobilized laccase was used in a batch system for degradation of three different dyes (Reactive Black 5, RB5; Cibacron Blue F3GA, CB; and Methyl Orange, MO). The immobilized laccase on CHX‐g‐p(IA)‐Cu(II) membrane was more effective for removal of MO dye than removal of CB and RB5 dyes. CONCLUSION: Flexibility of the enzyme immobilized grafted polymer chains is expected to provide easy reaction conditions without diffusion limitation for substrate dye molecules and their products. The support described, prepared from green chemicals, can be used for the immobilization of industrially important enzymes. Copyright © 2012 Society of Chemical Industry     

High surface area-activated carbon from Glycyrrhiza glabra residue by ZnCl2 activation for removal of Pb(II) and Ni(II) from water samples

A high-surface-area activated carbon was prepared by chemical activation of Glycyrrhiza glabra residue with ZnCl₂ as active agent. Then, the adsorption behavior of Pb(II) and Ni(II) ion onto produced activated carbon has been studied. The experimental data were fitted to various isotherm models. According to Langmuir model, the maximum adsorption capacity of Pb(II) and Ni(II) ions were found to be 200 and 166.7 mg g⁻¹, respectively, at room temperature. Kinetic studies showed the adsorption process followed pseudo second-order rate model. High values of intra-particle rate constants calculated shows the high tendency of activated carbon for removal of Pb(II) and Ni(II) ions.     

Nanocomposite Bead (NCB) Based on Bio-polymer Alginate Caged Magnetic Graphene Oxide Synthesized for Adsorption and Preconcentration of Lead(II) and Copper(II) Ions from Urine,Saliva and Water Samples

The present study describes the successful fabrication of bio-polymeric nanocomposite bead (NCB) of alginate caged magnetic graphene oxide (Alg-MGO). NCB was obtained by crosslinking of sodium alginate and calcium ions in the presence of MGO. Analytical techniques Fourier transform infra-red (FT-IR), field emission scanning electron microscope (SEM), and energy-dispersive X-ray spectroscopy (EDX) were used to characterize the Alg-MGO. Analytical application is conducted with magnetic solid phase extraction (MSPE) method for determination of Cu(II) and Pb(II) in urine, saliva and river water sample. The linear concentration range obtained were 0.33–25.00 µg L^??1 with appropriate coefficient of determination (R²?=?0.99) and low limit of detection (LOD?=?0.21–0.71 µg L^??1, n?=?3). The newly developed MSPE-NCB was successfully validated with standard reference material (SRM 2670a, NIST). Metal ions removal process was studied at high concentration level (1–200 mg L^??1) and isotherm models were applied. Langmuir isotherm is well fitted to experiments due to high value of coefficient of determination (R²) and proper adsorption capacity 96.13 and 103.09 mg g^??1 obtained for Cu(II) and Pb(II), respectively. Thermodynamic model is suggested spontaneous process, endothermic nature and physical sorption mechanism for uptake of selected metal ions from aqueous solution.     

Mechanistic study of active transport of copper (II) using LIX 54 across a liquid membrane

The present work describes the mechanism of active transport of copper(II) through an immobilized liquid membrane (ILM) containing LIX 54 (β‐diketone) dissolved in Iberfluid as mobile carrier. An uphill transport model has been described and equations have been derived taking into account aqueous boundary layer diffusion and liquid membrane diffusion as simultaneous controlling factors. In the present model, various cases were discussed using the carrier LIX 54 and different chemical species; the diffusional membrane resistance for lower and higher concentrations of extractant was evaluated. The diffusion coefficients were observed to decrease with increase in ­the extractant concentration, ranging from 4.1 × 10⁻³ to 1.65 × 10⁻² mol dm⁻³ Plotting [Cu]₀−[Cu]_t vs time resulted in a slope of [HR]₀A/2Δ_orgV taking into account the complex species, CuR₂, in the membrane. The mass transfer coefficient (Δ_org ⁻¹), the diffusion coefficient of the metal carrier species (D_org) and the thickness of the aqueous boundary layer were calculated from the proposed model for LIX 54. More than 90% of the Cu(II) could be separated using LIX 54 in the presence of various metals such as Ni, Co(II) and Zn. © 2000 Society of Chemical Industry     

Modern hybrid sorbents – New ways of heavy metal removal from waters

The possibility of hybrid ion exchanger (HIX) application in the simultaneous removal of heavy metal ions such as Cr(VI), Cu(II) and Zn(II) as well as Cd(II) and Pb(II) was presented. The ion exchanger in question combines the unique properties of hydrated metal oxides with the mechanical and thermal stability of synthetic ion exchangers. The kinetics of the sorption process of Cr(VI), Cu(II) and Zn(II) as well as Cd(II) and Pb(II) in the presence of Cl⁻, NO₃⁻ and SO₄²⁻ as well as EDDS (ethylenediaminedisuccinic acid) was also analyzed. Additionally, the effect of initial concentration, phase contact time and pH was also studied. Taking into account the possibility of its application on a large scale, the parameters of the adsorption process were estimated based on the linear form of the Langmuir and Freundlich isotherms.     

Chitosan modified with Reactive Blue 2 dye on adsorption equilibrium of Cu(II) and Ni(II) ions

This study aimed at immobilizing Reactive Blue 2 (RB 2) dye in chitosan microspheres through nucleophilic substitution reaction. The adsorbent chemical modification was confirmed by Raman spectroscopy and thermogravimetric analysis. This adsorption study was carried out with Cu(II) and Ni(II) ions and indicated a pH dependence, while the maximum adsorption occurred around pH 7.0 and 8.5, respectively. The pseudo second-order kinetic model resulted in the best fit with experimental data obtained from Cu(II) (R = 0.997) and Ni(II) (R = 0.995), also providing a rate constant, k₂, of 4.85 × 10⁻⁴ and 3.81 × 10⁻⁴ g (mg min)⁻¹, respectively, thus suggesting that adsorption rate of metal ions by chitosan-RB 2 depends on the concentration of ions on adsorbent surface, as well as on their concentration at equilibrium. The Langmuir and Freundlich isotherm models were employed in the analysis of the experimental data for the adsorption, in the form of linearized equations. Langmuir model resulted in the best fit for both metals and maximum adsorption was 57.0 mg g⁻¹ (0.90 mmol g⁻¹) for Cu(II) and 11.2 mg g⁻¹ (0.19 mmol g⁻¹) for Ni(II). The Cu(II) and Ni(II) ions were desorbed from chitosan-RB 2 with aqueous solutions of EDTA and H₂SO₄, respectively.     

Studies on Ambient Cured Biobased Mn(II), Co(II) and Cu(II) Containing Metallopolyesteramides

In this paper linseed oil based metallopolyesteramides (Mn(II)-/Co(II)-/Cu(II)-LPEA) containing metals [with half filled (d ⁵) and partially filled (d ⁷ and d ⁹) d orbitals] were synthesized via green route for the application of eco-friendly protective green material. This paper also described the role of occupancy of d orbitals on the performance of such polymers. The synthesis reaction was carried out in situ through condensation polymerization among linseed fatty amide diol (HELA), phthalic anhydride and respective metal acetates [M (OCOCH₃)₂; M = Mn(II), Co(II), Cu(II); different mole ratios] in absence of any harmful organic solvent. The structural determination (FTIR, ¹H-NMR and ¹³C-NMR), curing, thermal, physico-chemical, physico-mechanical, anticorrosive/chemical resistance, antibacterial properties of Mn(II)-/Co(II)-/Cu(II)-LPEA were carried out. The curing mechanism of the resin was confirmed by the comparison of FTIR spectra of uncured and cured resin. The curing mechanism of Mn(II)-/Co(II)-/Cu(II)-LPEA is found to be contrary to that of reported oil based polymer that involves the lipid autoxidation (slow process) in which driers are required to speed up the room temperature curing process. The incorporation of metals in Mn(II)-/Co(II)-/Cu(II)-LPEA improved the thermal stability as compared to virgin linseed oil based polyesteramide (LPEA). Mn(II)-/Co(II)-/Cu(II)-LPEA also show excellent antibacterial performance against Staphylococcus aureus and Escherichia coli. The observed diversity in material properties suggests that Mn-LPEA may be useful as an eco-friendly protective green material with thermal stability up to 320–330 °C.     

Synthesis,characterization, and application of a new chelating resin functionalized with dithiooxamide

Chloromethylated polystyrene‐divinylbenzene has been functionalized with dithiooxamide. The resulting chelating resin (DTOA) has been characterized by elemental analyses, infrared spectroscopy, thermogravimetric analysis, and metal ion sorption capacities. It has been used for the preconcentration and separation of Cu(II), Zn(II), Cd(II), and Pb(II) prior to their determination by FAAS. Parameters such as the amount of the resin, effect of pH, equilibration rate, sorption and desorption of metal ions, and effect of diverse ions have been studied. The maximum sorption capacities found are 0.97, 0.12, 0.08, and 0.12 mmol g^?1 for Cu(II), Zn(II), Cd(II), and Pb(II) at pH 6.0, 5.5, 1.0, and 5.5, respectively. The preconcentration factors are 100, 100, 50, and 50 for Cu(II), Zn(II), Cd(II), and Pb(II), respectively. Recoveries of the metal ions were 96 ± 5, 97 ± 6, 96 ± 5, and 96 ± 5 at 95% confidence level, whereas the limits of detection are 2.0, 1.3, 2.5, and 25.0 μg L^?1 for Cu(II), Zn(II), Cd(II), and Pb(II), respectively. The calibration curves were linear up to 12 μg mL^?1 (R² = 1.000), 2 μg mL^?1 (R² = 0.998), 2 μg ml^?1 (R² = 1.000), and 5 μg mL^?1 (R² = 0.979) for Cu(II), Zn(II), Cd(II), and Pb(II), respectively. The reliability of the method has been tested by analyzing certified samples. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2281–2285, 2007     

Fast removal of Pb(II) and Cu(II) from contaminated water by groundwater treatment waste: impact of sorbent composition

ABSTRACT

A non-hazardous groundwater treatment waste (GWTW) was examined as a low-cost sorbent for Pb(II) and Cu(II) ions. The content of the dominant elements in GWTW was as follows: 78% Fe₂O₃, 7.4% P₂O₅, 7.4% CaO and 5.2% SiO₂. The removal of Pb(II) and Cu(II) was fast, and more than 67–95% of ions were accumulated by GWTW during the first 3 min. The sorption capacity of GWTW depends on solution pH, concentration and temperature. Equilibrium data fitted well with Langmuir–Freundlich and Langmuir-partition models. The inherently formed nano-adsorbent could be utilized for the treatment of water contaminated with Pb(II) and Cu(II) ions.     

Biosorption of Cu(II) onto agricultural materials from tropical regions

BACKGROUND: In Ghana, the discharge of untreated gold mine wastewater contaminates the aquatic systems with heavy metals such as copper (Cu), threatening ecosystem and human health. The undesirable effects of these pollutants can be avoided by treatment of the mining wastewater prior to discharge. In this work, the sorption properties of agricultural materials, namely coconut shell, coconut husk, sawdust and Moringa oleifera seeds for Cu(II) were investigated. RESULTS: The Freundlich isotherm model described the Cu(II) removal by coconut husk (R² = 0.999) and sawdust (R² = 0.993) very well and the Cu(II) removal by Moringa oleifera seeds (R² = 0.960) well. The model only reasonably described the Cu(II) removal by coconut shell (R² = 0.932). A maximum Cu(II) uptake of 53.9 mg g^?1 was achieved using the coconut shell. The sorption of Cu(II) onto coconut shell followed pseudo‐second‐order kinetics (R² = 0.997). FTIR spectroscopy indicated the presence of functional groups in the biosorbents, some of which were involved in the sorption process. SEM‐EDX analysis confirmed an exchange of Mg(II) and K(I) for Cu(II) on Moringa oleifera seeds and K(I) for Cu(II) on coconut shell. CONCLUSION: This study shows that coconut shell can be an important low‐cost biosorbent for Cu(II) removal. The results indicate that ion exchange, precipitation and electrostatic forces were involved in the Cu(II) removal by the biosorbents investigated. Copyright © 2011 Society of Chemical Industry     

Synthesis of superabsorbent hydrogel and manganese dioxide nanowires composite for adsorption of Pb(II) from aqueous solution

The superabsorbent composite was prepared by aqueous solution polymerization, using manganese dioxide, acrylic acid, acrylic amide, 2‐acrylamide‐2‐methyl‐1‐propanesulfonic acid as raw materials, N,N′‐methylene bisacrylamide as cross‐linker, and K₂S₂O₈ as initiator. The composite was characterized by Fourier transform infrared spectrophotometer, thermogravimetric analysis and scanning electron microscopy analysis. This article also described the adsorption behavior of the superabsorbent composite with respect to Pb(II) removal from aqueous solution. The kinetic studies for Pb(II) adsorption showed that the pseudo‐second‐order adsorption mechanism was predominant. Moreover, adsorption isotherm data were reliably described by the Freundlich model. Regeneration of the adsorbent was attained by 0.1 mol L⁻¹ HCl. POLYM. COMPOS., 36:775–784, 2015. © 2014 Society of Plastics Engineers     

Photoinduced electron ejection from trihydroxoplumbate(II) in alkaline aqueous solution

In alkaline solution (1 M NaOH) irradiation (λ_ir=266 nm) of Pb(OH)₃⁻ leads to the formation of hydrated electron and oxidized complex in the primary photochemical step. The nascent hydrated electrons react with the ground-state trihydroxoplumbate(II) complexes to form the corresponding reduced Pb(I) compound. The main reaction of this latter species is recombination (synproportionation) with the oxidized (Pb(III)) complex, significantly diminishing the efficiency of the overall light-induced oxidation of Pb(OH)₃⁻ in air-saturated solution.