Preparation, characterization, and adsorption kinetics of graphene oxide/chitosan/carboxymethyl cellulose composites for the removal of environmentally relevant toxic metals.

This study attempted to develop a low-cost and eco-friendly bio-based composite adsorbent that is highly efficient in capturing potential toxic metals. The bio-composite adsorbent was prepared using graphene oxide (GO), carboxymethyl cellulose (CMC) and chitosan (CS); and characterized using FTIR, SEM-EDX and WAXD techniques. Metal-ion concentration in an aqueous solution was measured by ICP-OES. This article reveals that the adsorption of heavy metal ions varied according to the adsorbent quantity, initial metal concentration, pH, and interaction time. The metal ions' adsorption capacity (mg/g) was observed to increase when the interaction time and metal concentration increased. Conversely, metal ions adsorption was decreased with an increase in adsorbent dosages. The effect of pH on metal ions' adsorption was ion-specific. The substantial adsorption by GO/CMC/CS composite for Co2+, CrO42-, Mn2+ and Cd2+, had the respective values of 43.55, 77.70, 57.78, and 91.38 mg/g under acidic conditions. The metal ions experimental data were best fitted with pseudo-second-order (PSO) kinetics, and Freundlich isotherm model (except Co2+). The separation factors (RL) value in the present investigation were found between 0 and 1, meaning that the metal ions adsorption onto GO/CS/CMC composite is favorable. The RL and sorption intensity (1/n) values fitted well to the adsorption isotherm.

Hydrothermal synthesis of cobalt substitute zinc-ferrite (Co1-xZnxFe2O4) nanodot, functionalised by polyaniline with enhanced photocatalytic activity under visible light irradiation.

Fabrication and development of effective visible-light-responsive photocatalysts are required to tackle critical environmental issues. The aim of this study was to develop a nanocomposite material with improved photocatalytic activity for the degradation of industrial dyes such as Reactive Orange-16 (RO-16), Reactive Blue (RB-222), Reactive Yellow-145 (RY-145), and Disperse Red-1 (DR-1) without the need for a post-separation process after use. Here we report the hydrothermal synthesis of nanodots of Co1-xZnxFe2O4 (x = 0.3, 0.5 and 0.7), coated with polyaniline, by in situ polymerization. The Co1-xZnxFe2O4 nanodots, coated with polyaniline (PANI) nanograins, facilitated optical properties by easily capturing visible light. X-ray Diffraction (XRD) patterns and Scanning Electron Microscopy (SEM) images have confirmed the single-phase spinel structure of Co1-xZnxFe2O4 nanodot and nano-pore size of the Co1-xZnxFe2O4/PANI nanophotocatalyst. The specific surface area of the Brunauer-Emmett-Teller (BET) of the Co1-xZnxFe2O4/PANI photocatalyst was determined to be 24.50 m2/g by multipoint analysis. The final Co1-xZnxFe2O4/PANI (x = 0.5) nanophotocatalyst showed high efficiency in the catalytic degradation of toxic dyes (∼98% within 5 min), with good mechanical stability and recyclability under visible light irradiation. The nanophotocatalyst was re-used and its efficiency was largely maintained, even after seven cycles (∼82%) of degradation. The effects of various parameters, such as initial dye concentration, nanophotocatalyst concentration, initial pH of dye solution, and reaction kinetics were studied. According to the Pseudo-first-order kinetic model, photodegradation data followed the first-order reaction rate (R2 > 0.95) of degradation of dyes. In conclusion, a simple and low-cost synthesis process, speedy degradation and excellent stability of polyaniline-coated Co1-xZnxFe2O4 nanophotocatalyst could be used as a promising photocatalyst for dye-wastewater treatment.