Removal of chromium from aqueous solution by CLCh/Fe/MWCNT/ TiO2-Ag magnetic composite film: Simultaneous Cr(VI) reduction and Cr (III) adsorption

A catalyst CLCh/Fe/MWCNT/TiO2-Ag film was prepared using multi-walled carbon nanotubes (MWCNT) impregnated with magnetic iron oxide and silver-doped titanium dioxide (TiO2-Ag), being deposited on crosslinked chitosan (CLCh). The physicochemical characterization of the catalyst was performed by various analytical techniques such as ICP-MS, XRD, FTIR, SEM, EDS, Raman spectroscopy, N-2 adsorption/desorption and UV-Vis diffuse reflectance spectra (DRS). A solution of Cr(VI) (30 mg/L) was used in the evaluation of the photoreduction of (Cr(VI) to Cr(III)) using UV-visible light (filter cut-off for lambda > 300 nm). The composite film allowed, when applied in a solution of 30 mg/L of Cr(VI) at pH 2, the removal and simultaneous photoreduction of 97 % of Cr(VI) to Cr(III) in 120 min. The cationic Cr(III) generated remains retained in the composite film by adsorption on the hydroxyl and carboxyl groups of MWCNTs. The CLCh/Fe/MWCNT/TiO2-Ag film can be mechanically removed from the aqueous solution or by magnetic attraction. In ten consecutive cycles of reuse, the CLCh/Fe/MWCNT/TiO2-Ag film showed an efficiency of 84 % in the photoreduction of Cr(VI).