Fabrication of expanded graphite-embedded biopolymer-based composite membrane for chromate ion removal from aqueous solutions.

Chromate ion is considered as a potential pollutant due to its carcinogenic, mutagenic, and teratogenic effects. A newly fabricated chitosan-based composite membrane with expanded graphite shows effective and fast (within 40 min) adsorption of the chromate ion from aqueous solution. The percentage of removal of this membrane is about 91.68 ± 2%. Regeneration of the membrane is possible within 15 min, after which the removal efficiency of the membrane increases to 94.52 ± 1% and shows 89.62% removal up to seven cycles. Adsorption analyses were conducted by using UV spectroscopy. Removal of the chromate from aqueous solution was optimised for various parameters. Thermodynamic parameters of the adsorption indicate spontaneity, feasibility, and the exothermic nature of the adsorption. The value of ∆G° is between 0 and -20 kJ/mol, indicating that the adsorption is predominantly physical nature. Chromate ion adsorption on the membrane was best described by D-R model (R2 = 0.998). Membrane characterisations were done by I.R. spectroscopy, XRD, SEM, Raman spectroscopy, and TGA. Compared with conventional adsorbents such as activated carbon and ion-exchange resins, our newly fabricated membrane combines adsorption and filtration in a single system. The newly fabricated membrane is composed of environment friendly polymers and inexpensive expanded graphite, which can be regenerated rapidly, making it a promising and sustainable alternative for chromate removal from aqueous solutions.