Adsorption/Reduction Behaviors of Modified Cellulose Aerogels for the Removal of Low Content of Cr(VI)

Abstract

Removal of low content of Cr(VI) from water is a critical challenge for water environment protection. Herein, an acrylamide-thiosemicarbazide cellulose aerogels (ATC) was designed by dissolving, grafting and freeze-drying to introduce thiosemicarbazide onto acrylamide-cellulose aerogels (AMC) via Schiff based reaction. The resultant ATC was further employed as an efficient adsorbent to remove low content of Cr(VI) from wastewater by adsorption and reduction. The SEM, FT-IR, and BET results showed that the ATC was composed of well-developed pore structure and owned functional groups such as –NH2, C–S and C=S groups. Experimental results indicated that ATC exhibited excellent removal efficiency for 99% under low initial concentration (0.1–10 mg/L). The adsorption isotherms demonstrated ATC adsorbent according to a monolayer adsorption behavior following the Langmuir model with a calculated maximum adsorption capacity of 83.40 mg/g at pH 3, and the adsorption kinetics well obeyed the pseudo-first-order kinetic model. Importantly, the maximum effluent concentration of Cr(VI) was lower than 0.045 mg/L, meeting the standard of WHO (50 μg/L). Furthermore, the main removal mechanisms involved the synergistic effect of electrostatic interactions, reduction and chelation between the positively charged functional groups of adsorbent and the anionic Cr(VI) ions.