Hydrophobic Deep Eutectic Solvent-Embedded Polymer Membranes for Selective Preconcentration and Rapid Quantification of Cr(VI) in Water Sources

Hexavalent chromium, a pollutant arising from both natural processes and anthropogenic activities, is commonly found in water sources, prompting significant attention for its monitoring and remediation. In this study, a hydrophobic deep eutectic solvent (HDES)-immobilized membrane was used to preconcentrate Cr(VI) from aqueous solutions and a tannery effluent. EDXRF and ICP-OES were employed to analyze the membranes and equilibrated solutions, respectively. AFM, contact angle, SEM, FTIR, and other techniques were used for a detailed characterization of the membrane. Uptake studies revealed that the ideal pH for Cr(VI) removal was 3. The sorption process obeyed the Langmuir adsorption isotherm model and followed pseudo-first-order kinetics during the initial period, which transitioned to pseudo-second-order kinetics at higher duration. Using EDXRF, the Cr retained on the membrane could be directly analyzed across a broad concentration range (0.1-10 mg L^-1) with a detection limit of 0.04 mg L^-1. Interferences from various anions were also evaluated. The performance of the HDES-cellulose triacetate (HDES-CTA) membrane was further evaluated by measuring chromium concentrations in diverse water samples.