Preparation and Characterization of Fe-Mn Binary Oxide/Mulberry Stem Biochar Composite Adsorbent and Adsorption of Cr(VI) from Aqueous Solution

This study details the preparation of Fe-Mn binary oxide/mulberry stem biochar composite adsorbent (FM-MBC) from mulberry stems via the multiple activation by potassium permanganate, ferrous chloride, triethylenetetramine, and epichlorohydrin. The characteristics of FM-MBC had been characterized by SEM-EDS, BET, FT-IR, XRD, and XPS, and static adsorption batch experiments such as pH, adsorption time, were carried out to study the mechanism of Cr(VI) adsorption on FM-MBC and the impact factors. The results indicated that in contrast with the mulberry stem biochar (MBC), the FM-MBC has more porous on surface with a BET surface area of 74.73 m(2)/g, and the surface loaded with alpha-Fe2O3 and amorphization of MnO2 particles. Besides, carboxylic acid, hydroxyl, and carbonyls functional groups were also formed on the FM-MBC surface. At the optimal pH 2.0, the maximum adsorption capacity for Cr(VI) was calculated from the Langmuir model of 28.31, 31.02, and 37.14 mg/g at 25, 35, and 45 degrees C, respectively. The aromatic groups, carboxyls, and the hydroxyl groups were the mainly functional groups in the adsorption of Cr(VI). The mechanism of the adsorption process of FM-MBC for Cr(VI) mainly involves electrostatic interaction, surface adsorption of Cr(VI) on FM-MBC, and ion exchange.