Mechanistic insights into simultaneous removal of copper, cadmium and arsenic from water by iron oxide-functionalized magnetic imogolite nanocomposites

Imogolite and magnetic imogolite-Fe oxide nanocomposites (Imo-Fe50 and Imo-Fe25, at 50 and 25 % Fe loading (w/w), respectively) were synthesized and tested for the removal of aqueous copper (Cu), cadmium (Cd), and arsenic (As) pollutants. The materials were characterized by transmission electron microscopy, and specific surface area and isoelectric point measurements. The Fe-containing samples were additionally characterized by Mössbauer spectroscopy and vibrating-sample magnetometry. Significant differences were found in the morphological, electrophoretic, and magnetic characteristics between imogolite and the nanocomposites. The in-situ Fe-oxide precipitation process modified the active surface sites of the imogolite. The Fe–oxide, mainly magnetite, favored the contaminants’ adsorption over the pristine imogolite. The adsorption kinetics of these pollutants were adequately described by the pseudo-second order and intraparticle diffusion models. The kinetic models showed that surface adsorption was more important than intraparticle diffusion in the removal of the pollutants by all the adsorbents. The Langmuir-Freundlich model described the experimental adsorption data, and both nanocomposites showed greater adsorption capacity than the imogolite. The adsorption of Cu and Cd was sensitive to cationic competition, showing a decrease of the adsorption capacity when the two cations coexisted, while their adsorption increased in the presence of arsenate

Efficient and selective removal of SeVI and AsV mixed contaminants from aqueous media by montmorillonite-nanoscale zero valent iron nanocomposite

Nanoscale zero-valent iron (NZVI) and NZVI supported onto montmorillonite (NZVI-Mt) were synthetized and used in this study to remove SeVI and AsV from water in mono- and binary-adsorbate systems. The adsorption kinetics and isotherm data for SeVI and AsV were adequately described by the pseudo-second-order (PSO) (r2>0.94) and Freundlich (r2>0.93) equations. Results from scanning electron microscopy showed that the dimension of the NZVI immobilized on the Mt was smaller than pure NZVI. Using 0.05 g of adsorbent and an initial 200 mg L−1 AsV and SeVI concentration, the maximum adsorption capacity (qmax) and partition coefficient (PC) for AsV on NZVI-Mt in monocomponent system were 54.75 mg g-1 and 0.065 mg g-1·μM-1, which dropped respectively to 49.91 mg g-1 and 0.055 mg g-1·μM-1 under competitive system. For SeVI adsorption on NZVI-Mt in monocomponent system, qmax and PC were 28.63 mg g-1 and 0.024 mg g-1·μM-1, respectively. Values of qmax and PC were higher for NZVI-Mt than NZVI and montmorillonite, indicating that the nanocomposite contained greater adsorption sites for removing both oxyanions, but with a marked preference for AsV. Future research should evaluate the effect of different operational variables on the removal efficiency of both oxyanions by NZVI-Mt

Enhanced removal of mercury and lead by a novel and efficient surface-functionalized imogolite with nanoscale zero-valent iron material

A novel hybrid nanomaterial, nanoscale zero-valent iron (nZVI)-grafted imogolite nanotubes (Imo), was synthesized via a fast and straightforward chemical procedure. The as-obtained nanomaterial (Imo-nZVI) was characterized using transmission electron microscopy (TEM), electrophoretic mobility (EM), and vibrating sample magnetometry (VSM). The prepared Imo-nZVI was superparamagnetic at room temperature and could be easily separated by an external magnetic field. Sorption batch experiments were performed for single- and multicomponent systems and demonstrated that Hg2+ and Pb2+ could be quantitatively adsorbed at pH 3.0. For multicomponent systems, maximum adsorption capacities of 61.6 mg·g−1 and 76.9 mg·g−1 were obtained for Hg2+ and Pb2+ respectively. It was observed that the functional groups in Imo-nZVI interact preferentially with analytes according to the Misono softness parameter. The higher performance of Imo-nZVI compared with Imo and nZVI is related to the increased number of adsorption sites in the functionalized nanomaterial. The sorption equilibrium data obeyed the Langmuir model, while kinetic studies demonstrated that the sorption processes of Hg2+ and Pb2+ followed the pseudo-second-order model. This study suggests that the Imo-nZVI composite can be used as a promising sorbent to provide a simple and fast separation method to remove Hg and Pb ions from contaminated water.Fil: Martinis, Estefanía Mabel. Universidad Nacional de Cuyo. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; ArgentinaFil: Denardin, Juliano Casagrande. Universidad de Santiago de Chile; ChileFil: Calderón, Raul. Universidad Bernardo O’Higgins; ChileFil: Flores, Cristóbal. Universidad de Santiago de Chile; ChileFil: Manquián Cerda, Karen. Universidad de Santiago de Chile; ChileFil: Maldonado, Tamara. Universidad de Santiago de Chile; ChileFil: Arancibia Miranda, Nicolás. Universidad de Santiago de Chile; Chil

Synthesis and characterization of zeolite-based composites functionalized with nanoscale zero-valent iron for removing arsenic in the presence of selenium from water

We studied the sorption of As(V) in single and multi-component (As(V)-Se(VI)) aqueous systems using nanoscale zero-valent iron (nZVI) and nZVI-functionalized zeolite (Z-nZVI) adsorbents. Morphological and physico-chemical characterization of the adsorbents was conducted using X-ray diffraction (XRD), scanning electron microscopy (SEM), surface area and electrophoretic mobility measurements. SEM and XRD analyses showed that Fe-nanoparticle size and crystallinity were better preserved in Z-nZVI than nZVI after As(V) sorption. Highly efficient As(V) removal was achieved for all tested adsorbents with a minimal competition effect of Se(VI). In the single-component system, the equilibrium As(V) sorption time on nZVI and Z-nZVI was 40 and 60 min, respectively, while in the multi-component system, this time was 90 min for both the adsorbents. The Freundlich and pseudo-second-order models provided good fittings for the experimental sorption data (r2>0.96). The As(V) removal capacity was higher using Z-nZVI than nZVI both in the single and multi-component systems, suffering minimal differences in removal in both cases. The results suggested that Z-nZVI had more specific surface sites for As(V) than nZVI and zeolite, which makes Z-nZVI a more effective adsorbent than nZVI for the removal of As(V) from aqueous solutions in the presence of other oxyanions