Search

Two optimized methods, based on epoxy-amino reactivity of the Cellulose fibres (Cell) modified with diethylenetriamine (Cell‒DETA), (3-Glycidyloxypropyl)trimethoxysilane (Cell-Glymo), Lignin modified with epichlorohydrine (EL) and Tannic acid (TA), as an additional crosslinker, were developed for the production of the bio-renewable Cell-EL and Cell-EL-TA membranes. The influences of pH, contact time, adsorbent dose, and temperature on adsorption performances were studied by batch adsorption tests. The calculated capacities: 53.9, 99.9, 97.8 and 63.5, 115.8, 127.5 mg g−1 for Ni2+, Pb2+, Cr(VI) using Cell-EL and Cell-EL-TA, respectively, were obtained from Langmuir model fitting at 25 °C. The thermodynamic parameters indicated spontaneous and low endothermic processes. The results of the kinetic study, i.e. pseudo-second-order (PSO) and Weber-Morris (W-M), suggest an intra-particle diffusion as a rate-limiting step. The semi-empirical quantum chemical calculations aided the analysis of the non-specific and specific adsorbent/adsorbate interactions and their contribution to the overall bonding mechanism. Membrane utility was confirmed by performing a bed column study. In general, three main environmental issues of the present study, biodegradability of the used membrane, desorption efficiency, and development of the technology for the effective effluent water treatment and safe disposal of by-products highly conform to the demand of integrated environmental management system applicability in practice.

The presented study describes macroporous crosslinked poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) [PGME] functionalized with diethylenetriamine [PGME-deta] as a potential recovery agent for Mo(VI) oxyanions from aqueous solutions. Sorption studies were carried out by varying experimental conditions (pH, time, concentration, temperature). Kinetics of Mo(VI) sorption was investigated in batch (static) experiments, in the temperature range 298-343K. Sorption dynamics data were fitted to seven chemical-reaction and particle-diffusion models. The kinetics studies showed that Mo(VI) sorption adhered to the pseudo-second-order model under all investigated operating conditions. The sorption kinetics was determined to be governed by both the intraparticle diffusion and the external film diffusion to a lesser extent. The temperature rise promotes the molybdate species removal, with the maximum experimental uptake capacity of 4.02mmolg- 1 at 298K, at the selected pH which is consistent with the predominance range of hydrolized polynuclear Mo(VI) forms and optimum electrostatic attraction.

As soil cadmium (Cd) contamination becomes a serious concern and one of the significant environmental pollution issues all over the world, knowledge of the basic chemistry, origin, inputs, sources, quantity, chemical forms, reactions, as well as the fate and transport of Cd in different types of soil is crucial for better understanding Cd bioavailability, health risks and remedial options. This study aimed to increase the current knowledge on the complex interdependence between the factors affecting behavior, transport and fate of Cd in the soil and to test and compare the performance of the stabilization agents in different soil types. Soils demonstrated various sorption affinity and capacity for Cd accumulation, which proved to be positively correlated with soil pH and the cation exchange capacity (CEC). With increasing levels of contamination, sequential extraction analysis showed the highest increase of relative Cd amounts in the exchangeable fraction regardless of the soil properties, suggesting that added Cd is principally associated with the easily accessible and mobile fraction. For different initial Cd concentrations and soil types, Cd sorption reached the quasi-equilibrium within 24 h of contact. Prolonged aging (two months) influenced the natural stabilization of Cd in all types of soil, but only at low contamination level. The application of both, conventional (slaked lime Ca(OH) 2 ) and alternative phosphate-rich (annealed bovine bones B 400 ) amendments, resulted in Cd relocation and reduction of exchangeable Cd content. Although the effect was smaller when apatite amendment was utilized, observed re-distribution of Cd to more stable soil fractions is preferable for achieving long-term stabilization. Cd concentrations extracted in exchangeable and acid soluble fractions after the treatments of contaminated soil samples suggest that the practical applicability of in situ immobilization depends on the soil properties and the level of contamination, as we

Magnetic macroporous crosslinked copolymer glycidyl methacrylate (GMA) and ethylene glycol dimethacrylate (EGDMA) samples with different magnetite content were prepared by suspension copolymerization and functionalized with diethylene triamine. Samples were characterized by elemental analysis, mercury porosimetry, Fourier transform infrared spectroscopy (FTIR) analysis, scanning electron microscopy with energy-dispersive X-ray spectroscopy, transmission electron microscopy, SQUID magnetometry and X-ray photoelectron spectroscopy (XPS). The selected amino-functionalized sample was tested as a potential sorbent for the Mo(VI) and Re(VII) oxyanions from aqueous solutions. The influence of pH, ionic strength and possible interfering of cations and anions was investigated. Equilibrium data were analyzed with Langmuir, Freundlich and Tempkin adsorption isotherm models. Sorption studies were carried out in a batch competitive experiments, in the pH range 1-8, at 298 K. Obtained results indicate that 92% of Re(VII) and 98% of Mo(VI) were sorbed at pH 2.

The objective of this study was to investigate the modification of materials used in wastewater treatment for possible antimicrobial application(s). Granulated activated carbon (GAC) and natural clinoptilolite (CLI) were activated using Cu2+-and Zn2+-ions and the disinfection ability of the resulting materials was tested. Studies of the sorption and desorption kinetics were performed in order to determine and clarify the antimicrobial activity of the metal-activated sorbents. The exact sorption capacities of the selected sorbents, GAC and CLI, activated through use of Cu2+-ions, were 15.90 and 3.60 mg/g, respectively, while for the materials activated by Zn2+-ions, the corresponding capacities were 14.00 and 4.72 mg/g,. The desorption rates were 2 and 3 orders of magnitude lower than their sorption efficacy for the Cu2+-, and Zn2+-activated sorbents, respectively. The intermediate sorption capacity and low desorption rate indicated that the overall antimicrobial activity of the metal-modified sorbents was a result of metal ions immobilized onto surface sites. The effect of antimicrobial activity of free ions desorbed from the metal-activated surface may thus be disregarded. The antimicrobial activities of Cu/GAC, Zn/GAC, Cu/CLI and Zn/ CLI were also tested against Escherichia coli, Staphylococcus aureus, and Candida albicans. After 15 min exposure, the highest levels of cell inactivation were obtained through the Cu/CLI and the Cu/GAC against E. coli, 100.0 and 98.24%, respectively. However, for S. aureus and yeast cell inactivation, all Cu2+-and Zn2+-activated sorbents proved to be unsatisfactory. A characterization of the sorbents was performed by Xray diffraction (XRD), X-ray photo electron spectroscopy (XPS), and field emission scanning electron microscopy (FE-SEM). A concentration of the adsorbed and released ions was determined by inductively coupled plasma-optical emission spectroscopy (ICP-OES) and mass spectrometry (ICP-MS). The results showed that the anti

The mechanism of Cu(II), Cd(II) and Pb(II) ions sorption from aqueous solutions by macroporous poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) (PGME) functionalized by reaction of the pendant epoxy groups with diethylene triamine (PGME-deta) was studied using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) analysis. Atomic force microscopy (AFM) and scanning energy-dispersive X-ray spectroscopy (SEM-EDX) were used for the determination of surface morphology of the copolymer particles. The sorption behavior of heavy metals Cu(II), Cd(II) and Pb(II) ions sorption was investigated in batch static experiments under non-competitive conditions at room temperature (298 K). The obtained results were fitted to pseudo-first order, pseudo-second order and intraparticle diffusion kinetic model. The kinetics studies showed that Cu(II), Cd(II) and Pb(II) sorption obeys the pseudo-second-order model under all investigated operating conditions with evident influence of pore diffusion.

The distribution of elements in soil fractions affects their mobility and availability and thus their potential beneficial or harmful impact on ecosystems, biota and humans. Different mineralogical and chemical characteristics of soil influence elemental distribution. In the present study, chemical speciation of macro and micro elements (Al, Fe, Mn, K, Cd, Cr, Cu, Li, Ba, Ni, Pb and Zn) in unpolluted soils of different types, collected from the territory of the Republic of Serbia, were analysed by sequential extraction procedure. The impact of the physicochemical soil properties on the content, distribution, mobility and availability of elements was investigated. Principal component analysis was employed for the evaluation and characterization of the experimental data, understanding of the relationships between soil properties and the distribution, affiliation and connection of the elements. Finally, an artificial neural network (ANN) model was developed to explore the applicability of this approach for the prediction of the elemental distribution based on soil properties. Good agreement between the model and the experimental results implied that the ANN could be considered as a useful tool for control and prediction purposes. (C) 2016 Elsevier B.V. All rights reserved.

Pollution control and water purification are the main concerns associated with hazardous component eliminations from wastewaters which have inspired the research, among the others, on various clay minerals as useful adsorbents. The aim of this study was to examine morphological, structural, adsorption, and electrochemical characteristics of serpentinite in order to check its potential for removal of cadmium and textile dyes from synthetic waters. SEM technique has provided a detailed insight into the surface morphology of serpentinite indicating irregularly shaped particles and lamellar aggregates which are characteristic of lizardite mineral. Crystal phases detected in composition of serpentinite by using XRD technique are lizardite and tiny amount of periclase. Serpentinite adsorption characteristics were investigated towards Cd2+ and anionic textile dyes (Procion red MX-5B, Procion orange and Ramazol black) in aqueous solutions. The main goal of the study was the reliable removal of hazardous Cd2+ at low initial concentrations (up to 200 mu g/dm(3)). Textile dyes were taken as the models of anionic organic pollutants in water. All the adsorption experiments were carried out in batch conditions by varying initial parameters such as concentration of pollutant, contact time, mass of adsorbent and pH. Based on the obtained results, serpentinite has proven to be efficient adsorbent with removal efficiency over 98% for the selected pollutants. Native serpentinite was further modified in order to obtain forsterite. Electrochemical characteristics of serpentinite and forsterite were examined by using cyclic voltammetry of solution of 0.1 M H2SO4 as acidic supporting electrolyte and K-4[Fe(CN)(6)] which was chosen as a redox model compound. Due to its specific structure, surface groups, morphology, and non-stoichiometric composition, serpentinite and forsterite exhibited prominent electrocatalytic activity. (C) 2016 Elsevier B.V. All rights reserved.

Films of chitosan and poly(itaconic acid) in various different ratios have been prepared by membrane casting. The enhancement in the proton conductivity and uptake of water was observed as the content of poly(itaconic acid) in film increased. The proton conductivity of chitosan/poly(itaconic) films was comparative with commercially used synthetic sensor Nafion 117. Films showed thermal stability up to 185 degrees C. The proposed experiment might open up a new possibility for use of chitosan/poly(itaconic acid) films as a biosensors due to their advantages: low cost, simple preparation and good conductive sensitivity. (C) 2015 Elsevier B.V. All rights reserved.

This article described the synthesis and characterization of new copolymer hydrogels containing two hydrophilic units-methacrylic acid (MAA) and 2-Acrylamido-2-methylpropane sulfonic acid (AMPS). The resulting hydrogels were characterized by various techniques: FTIR, Elemental analysis, SEM, Dynamic Molecular simulation, Dynamic-Mechanical analysis and DSC in order to confirm the structure of hydrogels and to predict the best ratio composition with enhanced physical chemical properties. The swelling behavior in water was studied as a function of ratio of monomers and their concentration in medium. An increase in AMPS content led to expansion of network and increase in swelling degree capacity in water. An increase in AMPS content did not significantly influence the glass transition temperature of copolymers, indicated that the physical properties of initial components were preserved. The equal amount of monomers contributed to the highest strength of hydrogels. Meanwhile, the introduction of AMPS to the system was an effective method for improving the performances of the poly(methacrylic acid)- based hydrogels. (C) 2016 Elsevier B.V. All rights reserved.

Polyethersulfone membranes with integrated negatively-charged hydrogel of crosslinked poly(acrylamido-2-methylpropane sulfonic acid) were prepared by a combination of a liquid phase inversion process with photopolymerization and crosslinking of functional monomers included in the casting solution. A designed experiment was conducted to select the optimal composition for preparing membranes with a sufficient degree of swelling and ion exchange capacity. Scanning electron microscopy images revealed an ultrafine hybrid structure with an interconnected network of submicron particles embedded within the microporous polyethersulfone support. An intramembrane diffusion model was used to describe kinetics of heavy metal sorption by these hydrogels and the calculated apparent diffusion coefficients were 2–3 times larger than in commercial ion-exchange resins. Equilibrium sorption of heavy metals was described using a semi-empirical Langmuir model.

Series of novel hydrogels based on 2-hydroxyethyl acrylate (HEA) and itaconic acid (IA), P(HEA/IA) copolymers, were prepared by free radical cross-linking copolymerization and investigated as potential adsorbents for Cd2+ removal from aqueous solution. The hydrogels before and after Cd2+ adsorption were characterized using FTIR, temperature sensitive. In order to evaluate adsorption behavior of samples various factors affecting the Cd2+ uptake behavior, such as: contact time, temperature, pH, ionic strength, adsorbent weight, competitive ions and initial concentration of the metal ions were investigated. Five adsorption isotherms and two kinetic models were studied. The adsorption behavior can be very well described by the pseudo-second order kinetic model and Langmuir isotherm. Multicomponent adsorption studies revealed that adsorption of cadmium depends on the type of metal ions present in the system. Desorption studies showed that hydrogel can be reused three times with only 15% loss of adsorption capacity. All results indicate that the sample with the highest IA content is the most promising adsorbent for Cd2+ removal.

Asymmetric polyethersulfone membranes with submicron particles comprising crosslinked glycidyl methacrylate copolymer were prepared by a combination of a traditional immersion precipitation process for making membranes with photopolymerization and crosslinking of functional monomers included in the casting solution. As the concentration of polymerizable monomers increased the original macrovoid structure was replaced by a hybrid morphology with microglobules typical of macroporous methacrylate adsorbers embedded within microporous structure with no significant effects on water permeability. The epoxide groups present in glycidyl methacrylate copolymer were transformed into amine functionalities by ring opening under alkaline conditions. Permeation of Orange G solution at low transmembrane pressures was used to demonstrate suitability of these novel membranes for membrane adsorption.

Two porous and one non-porous crosslinked poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) [abbreviated PGME] were prepared by suspension copolymerization and functionalized with diethylene triamine [abbreviated PGME-deta]. Samples were characterized by elemental analysis, mercury porosimetry, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and transmission electron microscopy. Kinetics of Cr(VI) sorption by PGME-deta were investigated in batch static experiments, in the temperature range 25-70 degrees C. Sorption was rapid, with the uptake capacity higher than 80% after 30 min. Sorption behavior and rate-controlling mechanisms were analyzed using five kinetic models (pseudo-first order, pseudo-second order, Elovich, intraparticle diffusion and Bangham model). Kinetic studies showed that Cr(VI) adsorption adhered to the pseudo-second-order model, with definite influence of pore diffusion. Equilibrium data was tested with Langmuir, Freundlich and Tempkin adsorption isotherm models. Langmuir model was the most suitable indicating homogeneous distribution of active sites on PGME-deta and monolayer sorption. The maximum adsorption capacity from the Langmuir model, Q(max),at pH 1.8 and 25 degrees C was 143 mg g(-1) for PGME2-deta (sample with the highest amino group concentration) while at 70 degrees C Q(max) reached the high value of 198 mg g(-1). Thermodynamic parameters revealed spontaneous and endothermic nature of Cr(VI) adsorption onto PGME-deta.

Two samples of macroporous crosslinked poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate), poly(GMA-co-EGDMA), with different porosity parameters were synthesized by suspension copolymerization and functionalized with ethylene diamine and diethylene triamine. The kinetics of Cr(VI) sorption by amino-functionalized poly(GMA-co-EGDMA) was investigated under non-competitive conditions. Competitive kinetics was studied from following multicomponent solutions: Cu(II) and Cr(VI); Cu(II), Co(II), Cd(II) and Ni(II); Cr(VI), Cu(II), Co(II) and Cd(II) solutions. Two kinetic models (the pseudo-first and pseudo-second-order) were used to determine the best-fit equation for the metals sorption by poly(GMA-co-EGDMA)-en and poly(GMA-co-EGDMA)-deta.

Inverse gas chromatography (IGC) is an attractive technique for polymer characterization due to possible simultaneous determination of various physicochemical properties of polymer systems merely from retention times of selected sorbates. The technique is especially advantageous to polymers that cannot be characterized by conventional methods. In this review, the utilization of the method for glass transition determination of homopolymers, copolymers and polymer blends is described. Advantages and drawbacks of the IGC method over traditionally used methods for glass transition temperature determination is discussed, along with the most important parameters that influence the precision and accuracy of the glass transition temperature (Tg) measurements.

Two samples of macroporous crosslinked poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate), poly(GMA-co-EGDMA), with different porosity parameters were synthesized by suspension copolymerization and modified by ring-opening reaction of the pendant epoxy groups with ethylene diamine (EDA). The samples were characterized by mercury porosimetry, FT-IR spectroscopy and elemental analysis. The sorption rate of the modified copolymer, poly(GMA-co-EGDMA)-en for Cu(II) ions determined under non-competitive conditions was relatively rapid, i.e. the maximum capacity was reached within 30 min. Batch sorption capacities for Cu(II), Fe(II), Mn(II), Cd(II), Zn(II), Pb(II), Cr(III) and Pt(IV) ions were determined under non-competitive conditions in the pH range 1.25– 5.5 at room temperature. The maximum sorption capacities of poly(GMA-co-EGDMA)-en under non-competitive conditions were 1.30 mmol/g for Pt(IV) at pH 5.5, 1.10 mmol/g for Cu(II) at pH 5.5, 1.06 mmol/g for Pb(II) at pH 1.25 and 0.67 mmol/g for Cd(II) ions at pH 5.5. The selectivity of poly(GMA-co-EGDMA)-en towards Cu(II), Co(II), Ni(II), Pb(II) and Pt(IV) ions was investigated under competitive conditions. Poly(GMA-co-EGDMA)-en showed high selectivity for Pt(IV) over Cu(II), Co(II), Ni(II) and Pb(II) ions at pH 2.1. At pH 5.5, the metal sorption capacities of poly(GMA-co-EGDMA)-en decreased in the order: Cu(II)>Co(II)>Pt(IV)_Ni(II)>Pb(II). Regeneration of the Cu(II), Ni(II) and Pb(II) loaded poly(GMA-co-EGDMA)-en with 2 M H2SO4 showed that the polymer can be reused in several sorption/desorption cycles.