No abstract

No abstract

A rapid gelation method was used to fabricate magnetic chitosan/graphite/polyvinyl alcohol (m-CGPA) hydrogel beads crosslinked with glutaraldehyde. A thorough characterization was carried out by FTIR, SEM-EDX, XRD, VSM, and TGA. Studies with batch experiments indicated that m-CGPA removes more than 95% of reactive orange 16 (RO 16) dye with a Langmuir monolayer adsorption capacity of 196.3 mg/g at pH 4.0 in just 90 min of contact time. Langmuir isotherm model fitted well with the experimental data. Pseudo-second order kinetics was proposed for the adsorption process. Adsorption thermodynamics evidenced the fact that the process was spontaneous, exothermic, and enthalpy-driven in nature. The saturation magnetization of the material as obtained from VSM analysis was found to be 7.2 emu/g in comparison with that of pure Fe3O4 at 66.4 emu/g. In light of its excellent decontamination efficiency, low cost, and rapid adsorption, this material was found to be an excellent decontaminant for RO16. In addition to enhanced adsorption capacity, the magnetic behavior was an added advantage as it could be easily separated with the help of an external magnet. Fixed bed column studies revealed that the column method can be applied to large-volume treatment. Also, it was possible to regenerate m-CGPA using a 5% NaOH solution and reuse it in multiple cycles.

Polymers have been proven to be an interesting class of adsorbents applied in water treatment. Biopolymers are of special interest due to their unique properties such as biocompatibility, biodegradability, and reusability. This work reports a composite formed by a chitosan biopolymer and activated charcoal using sodium citrate as a crosslinking agent. The chitosan–citrate-activated charcoal composite (CCA) was characterized using FT–IR, SEM, EDAX, XRD, TGA–DTA and BET surface area analysis. The material was found to be microporous in nature with a surface area of 165.83 m2/g that led to high adsorption capacities toward both the targeted pollutants. In an aqueous phase, the dye adsorption studies were carried out with reactive orange 16 (R-16) dye, while in a gaseous phase, CO2 adsorption capacity was evaluated. Under optimum solution conditions, maximum R-16 dye removal capacity was found to be 34.62 mg g−1, while in the gas phase the CO2 adsorption capacity was found to be 13.15 cm3g−1. Intrinsic microporosity of CCA resulted in an enhanced capture capacity for R-16 dye and carbon dioxide in the respective phases. Material sustainability studies were carried out to evaluate various sustainability parameters.

Cellulose-Sn(IV) (CSn) biocomposite was synthesized by cellulose and stannic chloride in ethanol medium using microwave irradiation for 2 min with 30 s of intermittent time intervals. The incorporation of Sn(IV) into the cellulose matrix was confirmed through FT-IR, XRD, TGA, SEM- EDS, and BET. The prepared composite CSn has been used for the adsorptive removal of As(III) from water. Parameters, such as initial concentration, adsorbent dose, initial As(III) concentration, and time required for the adsorption process, were optimized through the batch-adsorption process. The adsorption capacity of the CSn for As(III) adsorption was found to be 16.64 mg/g at pH 7.0. Freundlich isotherm was found to be more suitable for the adsorption process based on regression coefficient values. Pseudo-second-order kinetic model was found to be more suitable for understanding the kinetics of the adsorption of As(III). Weber–Morris model with non-zero intercept revealed that the mechanism of adsorption was not limited to the diffusion process only. The adsorption process was spontaneous and exothermic and showed a decrease in randomness. Chloride ions decreased the percentage removal of As(III) when the concentration of chloride ions was ten times that of As(III) concentration according to the results obtained through the effect of co-anions study. In this study, 5% (w/v) NaCl solution has been used for the regeneration of the material, and during up to five adsorption–desorption cycles, there was a gradual decrease in percentage removal of As(III) from 95% to 78% only, which proves the greener aspect of the CSn. The breakthrough volume of 1.25 L of 10 mg/L of As(III) in column studies revealed that the CSn could be applicable for larger sample volumes also.