Syntheses and characterization of a chelating resin containing ONNO donor quadridentate Schiff base and its coordination complexes with copper(II), nickel(II), cobalt(II), iron(III), zinc(II), cadmium(II), molybdenum(VI) and uranium(VI),

A new mixed Schiff base N,N′-ethylenemono(3-carboxysalicylideneimine)mono(salicylideneimine) has been synthesized by the condensation of equimolar quantities of ethylenediamine, salicylaldehyde and 3-formylsalicylic acid. A polymer supported Schiff base (PS–CH₂–LH₂) has been synthesized by the reaction of chloromethylated polystyrene (containing 3.9 mmol of chlorine per g of resin and 2% cross-linked with divinylbenzene) and the Schiff base N,N′-ethylenemono(3-carboxysalicylideneimine)mono(salicylideneimine). The polymer-anchored Schiff base reacts with metal salt/metal complex and forms polymer-anchored complexes having the formulae PS–CH₂–LCu, PS–CH₂–LNi, PS–CH₂–LCo, PS–CH₂–LFeCl·DMF, PS–CH₂–LZn, PS–CH₂–LCd, PS–CH₂–LMoO₂ and PS–CH₂–LUO₂. The polymer-anchored complexes have been characterized on the basis of elemental analysis, infrared and electronic spectra and magnetic susceptibility measurements. The shifts of the ν(CN) (azomethine) stretch to lower energy and ν(CO) (carboxylic) to higher energy in the polymer-anchored complexes indicate the ONNO donor behaviour of the chelating resin. The metal ions in the metal bound polymers can be leached by hot dilute formic acid, acetic acid or hydrochloric acid. The coordinated dimethylformamide is completely lost on heating the complexes in air. The complexes PS–CH₂–LCu and PS–CH₂–LCo are paramagnetic with square planar structure, PS–CH₂–LNi is diamagnetic with square planar structure and PS–CH₂–LFeCl·DMF is paramagnetic and octahedral, PS–CH₂–LZn and PS–CH₂–LCd are diamagnetic and tetrahedral, PS–CH₂–LMoO₂ and PS–CH₂–LUO₂ are diamagnetic and have octahedral structure. The stoichiometry and the structure of the metal bound polymers are comparable with those of metal complexes of N,N′-ethylenebis(salicylideneimine). This is the first report of the syntheses of a mixed Schiff base and its coordination complexes.     

Separation of scandium(III) from lanthanides(III) with room temperature ionic liquid based extraction containing Cyanex 925

The separation of Sc(III) from Y(III), La(III) and Yb(III) in [C₈mim][PF₆] containing Cyanex 925 has been investigated, and is reported in this paper. A cation exchange mechanism of Sc(III) in [C₈mim][PF₆] and Cyanex 925 is proposed by study of the influence of anionic and cationic species on the extraction. The coefficient of the equilibrium equation of Sc(III) was confirmed by slope analysis of log D_Sc vs log [Cyanex 925], and the loading capacity also confirmed the stoichiometry of Cyanex 925 to Sc(III) was close to 3:1. Infrared data for Cyanex 925 saturated with Sc(III) in [C₈mim][PF₆] indicated strong interaction between P?O of Cyanex 925 and Sc(III). In addition, the relationship between log D_Sc and temperature showed that temperature had little influence on the extraction process, and the resulting thermodynamic parameters indicated that an exothermic process was involved. Copyright © 2007 Society of Chemical Industry     

Adsorption of cadmium (II) and copper (II) ions from aqueous solution using chitosan composite

The binary chitosan/silk fibroin composite synthesized by reinforcement of silk fibroin fiber into the homogenous solution of chitosan in formic acid was used to investigate the adsorption of two metals of Cu(II) and Cd(II) ions in an aqueous solution. The binary composite was characterized by Fourier transform infrared and scanning electron microscopy. The optimum conditions for adsorption by using a batch method were evaluated by changing various parameters such as contact time, adsorbent dose, and pH of the solution. The experimental isotherm data were analyzed using the Freundlich and Langmuir equations, indicated to be well fitted to the Langmuir isotherm equation under the concentration range studied, by comparing the correlation co‐efficient. Adsorption kinetics data were tested using pseudo‐first‐order and pseudo‐second‐order models. Kinetics studies showed that the adsorption followed a pseudo‐second‐order reaction. Due to good performance and low cost, this binary chitosan/silk fibroin composite can be used as an adsorbent for removal of Cu(II) and Cd(II) from aqueous solutions. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Mono- and multi-component biosorption of lead(II), cadmium(II), copper(II) and nickel(II) ions onto coco-peat biomass

The potential of using coco-peat biomass (CPB) has been assessed for the removal of Pb(II), Cd(II), Cu(II) and Ni(II) ions from single and quaternary solutions. According to Langmuir isotherm, the maximum biosorption capacity of CPB was 0.484, 0.151, 0.383 and 0.181 mmol/g for Pb(II), Cd(II), Cu(II) and Ni(II) ions, respectively. Scanning electron microscopy along with energy-dispersive X-ray spectroscopy and Fourier-transform IR spectroscopy confirmed changes in the biosorbent functionality after metal sorption. Through quaternary isotherm experiments, 16.1%, 48.2%, 32.3% and 46.5% decrease in experimental uptakes were observed for Pb(II), Cd(II), Cu(II) and Ni(II), respectively, in the presence of other metal ions.     

Functionalized SBA-15 organosilicas as sorbents of mercury(II), cadmium(II) and copper(II)

Amino- and thiol-functionalized SBA-15 organosilicas have been synthesized by co-condensation of tetraethoxysilane (TEOS) with appropriate trifunctional silanes i. e. aminopropyltriethoxysilane (ATES) and mercaptopropyltriethoxysilane (MTES). The materials were characterized by nitrogen sorption measurements, XRD diffractometry, FTIR/PAS spectroscopy and SEM, TEM and AFM microscopy. The obtained materials exhibit high porosity, good ordering, and high content of functional groups (0.5–1.5 mmol/g). These materials have been tested as sorbents for three bivalent metal ions: Hg(II), Cd(II) and Cu(II) testifying to their usefulness in such sorption applications. The adsorption kinetics was were favour-able-all the metal ions were adsorbed just after several minute and the amounts of adsorbed metals were high and depended on the type and content of surface functionalities.     

Stability constants of adipate complexes of copper(II), nickel(II), zinc(II), cobalt(II), uranyl(II) and thorium(IV) determined by electrophoresis

Stability constants of Copper(II), Nickel(II), Cobalt(II), Zinc(II), Uranyl(II) and Thorium(IV) adipates have been determined by paper electrophoresis. Adipic acid (0.005 mol dm^?3) was added to the background electrolyte: 0.1 mol dm^?3 HClO₄. The proportions of (CH₂)₄COOH COO^? and (CH₂)₄C₂O⁼₂ were varied by changing the pH of the electrolyte. These anions yielded the complexes Zn(CH₂)₄COOH COO⁺, Co(CH₂)₄COOH COO⁺, Ni(CH₂)₄COOH COO⁺, Th(CH₂)₄COOH COO³⁺, Th[(CH₂)₄COOH COO]₄, Cu(CH₂)₄ C₂O₄ and UO₂[(CH₂)₄(C₂O₄)]^2?₂, whose stability constants are found to be 10^2.8, 10^2.8, 10^3.2, 10^5.2, 10^15.3, 10^2.7 and 10^11.8 respectively (μ = 0.1, temp. 40°C).     

Crossflow filtration of iron(III), copper(II), and cadmium(II) aqueous solutions with alginic acid/cellulose composite membranes

The removal of Fe(III), Cu(II), and Cd(II) ions from aqueous solutions was investigated with a crossflow filtration technique. Alginic acid (AA)/cellulose composite membranes were used for retention. In the filtration of Fe(III) solutions, the effects of the crossflow velocity, applied pressure, AA content of the membranes, and pH on the retention percentage and the permeate flux were examined. The maximum retention percentage was found to be 89% for a 1 × 10^?4M Fe(III) solution at the flow velocity of 100 mL/min and the pressure of 60 kPa with 0.50% (w/v) AA/cellulose composite membranes at pH 3. Aqueous solutions of Cu(II) and Cd(II) were filtered at the flow velocity of 100 mL/min and pressure of 10 kPa. The effects of the AA content of the membranes and pH of the waste medium on the retention percentage and the permeate flux were determined. For 1 × 10^?4M Cu(II) and Cd(II) solutions, the maximum retention percentages were found to be 94 and 75%, respectively, at pH 7 with 0.50% (w/v) AA/cellulose composite membranes. When metal‐ion mixtures were used, the retention percentages of Fe(III), Cu(II), and Cd(II) were found to be 89, 48, and 10%, respectively, at pH 3 with 0.50% (w/v) AA/cellulose composite membranes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Adsorption of copper(II), cobalt(II), and iron(III) ions from aqueous solutions on poly(ethylene terephthalate) fibers

The adsorption behavior of poly(ethylene terephthalate) (PET) fibers towards copper(II), cobalt(II), and iron(III) ions in aqueous solutions was studied by a batch equilibriation technique. Influence of treatment time, temperature, pH of the solution, and metal ion concentration on the adsorption were investigated. Adsorption values for metal ion intake followed the following order: Co(II) > Cu(II) > Fe(III). One hour of adsorption time was found sufficient to reach adsorption equilibrium for all the ions. The rate of adsorption was found to decrease with the increase in the temperature. Langmuir adsorption isoterm curves were found to be significant for all the ions studied. The heat of adsorption values were calculated as −5, −2.8, and −3.6 kcal/mol for Cu(II), Co(II), and Fe(III) ions, respectively. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1935–1939, 1998     

Adsorption characterization of lead(II) and cadmium(II) on crosslinked carboxymethyl starch

The adsorption of Pb(II) and Cd(II) ions with crosslinked carboxymethyl starch (CCS) was investigated as function of the solution pH, contact time, initial metal‐ion concentration, and temperature. Isotherm studies revealed that the adsorption of metal ions onto CCS better followed the Langmuir isotherm and the Dubinin–Radushkevich isotherm with adsorption maximum capacities of about 80.0 and 47.0 mg/g for Pb(II) and Cd(II) ions, respectively. The mean free energies of adsorption were found to be between 8 and 16 kJ/mol for Pb(II) and Cd(II) ions; this suggested that the adsorption of Pb(II) and Cd(II) ions onto CCS occurred with an ion‐exchange process. For two‐target heavy‐metal ion adsorption, a pseudo‐second‐order model and intraparticle diffusion seem significant in the rate‐controlling step, but the pseudo‐second‐order chemical reaction kinetics provide the best correlation for the experimental data. The enthalpy change for the process was found to be exothermic, and the ΔS^θ values were calculated to be negative for the adsorption of Pb(II) and Cd(II) ions onto CCS. Negative free enthalpy change values indicated that the adsorption process was feasible. The studies of the kinetics, isotherm, and thermodynamics indicated that the adsorption of CCS was more effective for Pb(II) ions than for Cd(II) ions. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Adsorption of zinc(II) from water with purified carbon nanotubes

Commercial single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) were purified by sodium hypochlorite solutions and were employed as adsorbents to study the adsorption characteristics of zinc from water. The properties of CNTs such as purity, structure and nature of the surface were greatly improved after purification which made CNTs become more hydrophilic and suitable for adsorption of Zn²⁺. In general, the adsorption capacity of Zn²⁺ onto CNTs increased with the increase of pH in the pH range of 1-8, fluctuated very little and reached maximum in the pH range of 8-11 and decreased at a pH of 12. A comparative study on the adsorption of Zn²⁺ between CNTs and commercial powdered activated carbon (PAC) was also conducted. The maximum adsorption capacities of Zn²⁺ calculated by the Langmuir model are 43.66, 32.68, and with SWCNTs, MWCNTs and PAC, respectively, at an initial Zn²⁺ concentration range of 10-. The short contact time needed to reach equilibrium as well as the high adsorption capacity suggests that SWCNTs and MWCNTs possess highly potential applications for the removal of Zn²⁺ from water.     

Adsorption of copper(II) and EDTA‐chelated copper(II) onto granular activated carbons

Waste streams generated by electroless copper plating in the printed circuit boards manufacturing industry often contain copper complexed by strong chelating agents such as EDTA. The consequence of metal complexation by chelating agents is that alternative treatment to chemical precipitation is often necessary to achieve the low metal concentrations required by increasingly stringent environmental regulations. This paper examines the feasibility of using activated carbon to remove EDTA‐chelated copper(II) species as well as free copper(II) ions from aqueous solution. The adsorption characteristics of copper(II) and EDTA‐chelated copper(II) on two granular activated carbons prepared from coal and coconut shell were evaluated. Adsorption equilibrium data of copper(II) on the two carbons corresponded well to the Langmuir model. The coconut shell‐based carbon exhibited a greater adsorption capacity for copper(II) than the coal‐based carbon under similar experimental conditions. Solution pH had a considerable influence on copper(II) adsorption by the two carbons. Low adsorption levels of copper(II) at pH 3 and high adsorption levels in the pH range of 4–6 were observed. However, a reverse adsorption trend was observed when the chelating agent EDTA was added to the copper(II) solution. Adsorption of EDTA‐chelated copper(II) by the two carbons was higher at pH 3 than at pH 6. The contrasting adsorption behaviour of copper(II) ions and EDTA‐chelated copper(II) species can be readily explained in terms of electrostatic interaction in that solution pH influences the surface charge of the carbons as well as the charge property of copper(II) ions and EDTA‐chelated copper(II) species. © 2000 Society of Chemical Industry     

Adsorption of Zn(II) by crosslinked acrylic copolymers with amine functional groups

Adsorption of Zn(II) ions from diluted aqueous solutions by the acrylic copolymer based on ethylacrylate : acrylonitrile : divinylbenzene matrix with different crosslinking degrees and ethylenediamine and triethylenetetramine functional groups was investigated. Adsorption experiments were carried out by batch method. The effects of the pH, initial concentration of zinc, time of contact, and the crosslinking degree of the copolymers were studied. On the basis of Langmuir and Freundlich isotherms, the parameters that characterize the adsorption were determined. The maximum Zn(II) retention capacity value (500 mg g^?1) was obtained for the acrylic copolymer with 2% crosslinking degree and ethylenediamine, as functional groups. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 803–808, 2004     

Adsorption of Cr(III), Ni(II), Zn(II), Co(II) ions onto phenolated wood resin

In this study, phenolated wood resin was used an adsorbent for the removal of Cr(III), Ni(II), Zn(II), Co(II) ions by adsorption from aqueous solution. The adsorption of metal ions from solution was carried at different contact times, concentrations and pHs at room temperature (25°C). For individual metal ion, the amount of metal ions adsorbed per unit weight of phenolated wood resin at equilibrium time increased with increasing concentration and pH. Also, when the amounts of metal ions adsorbed are compared to each other, it was seen that this increase was order of Cr(III) > Ni(II) > Zn(II) > Co(II). This increase was order of Cr(III) > Ni(II) > Co(II) > Zn(II) for commercial phenol–formaldehyde resin. Kinetic studies showed that the adsorption process obeyed the intraparticle diffusion model. It was also determined that adsorption isotherm followed Langmuir and Freundlich models. Adsorption isotherm obtained for commercial phenol–formaldehyde resin was consistent with Freundlich model well. Adsorption capacities from Langmuir isotherm for commercial phenol–formaldehyde resin were higher than those of phenolated wood resin, in the case of individual metal ions. Original adsorption isotherm demonstrated the monolayer coverage of the surface of phenolated wood resin. Adsorption kinetic followed the intraparticle diffusion model. The positive values of ΔG° determined using the equilibrium constants showed that the adsorption was not of spontaneous nature. It was seen that values of distribution coefficient (K_D) decreasing with metal ion concentration in solution at equilibrium (C_e) indicated that the occupation of active surface sites of adsorbent increased with metal ions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2838–2846, 2006     

Electron paramagnetic resonance evidence for direct co-ordination of copper(II) ions by acrylic resins containing amine groups

Summary E. p. r. and absorption spectra were used to indicate the formation of the complexes between copper (II) ions and acrylic resins containing oligoamines bound via amide bonds to acrylate units. The number of bound nitrogen atoms depends on the length of the amine chain attached to acrylamide unit.     

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.     

Extraction kinetics of cerium(IV) from sulfuric acid medium by the primary amine N1923 using a constant interfacial area cell with laminar flow

BACKGROUND: Thermodynamic studies on Ce(IV) extraction with primary amine N1923 demonstrate that primary amine N1923 is an excellent extractant for separation of Ce(IV) from Re(III). In order to clarify the mechanism of extraction and to optimize the parameters in practical extraction systems used in the rare earth industry, the extraction kinetics was investigated using a constant interfacial area cell with laminar flow in the present work. RESULTS: The data indicate that the rate constant (k_ao) becomes constant when stirring speed exceeds 250 rpm. The apparent forward extraction rate is calculated to be 10^?1.70. The activation energy (E_a) was calculated to be 20.5 kJ/mol from the slope of log k_ao against 1000/T. The minimum bulk concentration of the extractant necessary to saturate the interface (C_min) is lower than 10^?5 mol L^?1. CONCLUSION: Studies of interfacial tension and the effects of stirring rate and specific interfacial area on the extraction rate show that the extraction rate is kinetically controlled, and a mass transfer model has been proposed. The rate equation has been obtained as: ? d[Ce(IV)]/dt = 10^?1.70[Ce(IV)] [(RNH₃)₂SO₄]^1.376. The rate‐controlling step has been evaluated from analysis of the experimental results. Copyright © 2007 Society of Chemical Industry     

Adsorption Thermodynamics and Kinetics of Mercury (II), Cadmium (II) and Lead (II) on Lignite

This study examines the adsorption thermodynamics and kinetics of heavy metal ions [(Hg (II), Cd (II), Pb (II)] on a demineralized lignite coal. The study also investigates the effects of process parameters like contact time, pH, concentration of metal ion, temperature and adsorbent mass on the extent of metal-ion adsorption from solution.The results of the kinetic studies show that the adsorption reaction is first order with respect to the metal cation solution concentration, with activation energies of 4.9, 8.2 and 9.1 kJ mol^–1 for Hg (II), Cd (II) and Pb (II), respectively. These low activation energy values indicate that the adsorption reaction is diffusion-controlled. The results of the thermodynamic investigations indicate that the adsorption reactions are spontaneous (ΔG°< 0), slightly exothermic (ΔH°< 0) and irreversible (ΔS°> 0).The results of the study further show that the adsorption process is pH, adsorbent mass and metal-ion concentration dependent. Adsorption increases with increase in these variables. Temperature has only a marginal effect on adsorption. The reasons for these observations have been suggested.     

Construction and photoluminescence properties of two novel zinc(II) and cadmium(II) benzyl-tetrazole coordination polymers

Two new d¹⁰ coordination polymers, Zn(Beta)₂ (1) and Cd₂(Beta)₃Cl(H₂O) (2) (Hbeta = 5-benzyl-tetrazole) have been synthesized by the in situ [3 + 2] cycloaddition reaction of 5-benzylacetonitrile, sodium azide and MCl₂ [M = Zn (1); M = Cd (2)] under hydrothermal condition. Complex 1 is a coordination polymer comprised of numerous mildly undulated two-dimensional (2D) layers with a (4, 4) topological network; while complex 2 is a 3D coordination framework constructed from the interconnection of various helical chains through cadmium–chlorine bridges. Furthermore, the luminescence properties of two complexes have been investigated.