Potential of virgin and calcined wheat bran biomass for the removal of chromium(VI) ion from a synthetic aqueous solution

Virgin wheat bran (WB) and calcined wheat bran were prepared at 500 or 1000 degrees C (WB500 or WB1000, respectively), and their physicochemical properties (such as morphological, thermal, specific surface area, point of zero charge pH, and surface functional groups) were investigated to assess their chromium(VI) ion adsorption capability. The amount of chromium(VI) ion adsorbed was in the order WB < WB500 < WB1000. These results showed that the chromium(VI) ion adsorption was related to the WB surface characteristics. Additionally, the amount of chromium (Cr) and oxygen (O) on the WB1000 surface increased after adsorption, which indicated chromium(VI) ions were adsorbed onto the WB1000 surface. Adsorption isotherm and adsorption kinetic data fit the Freundlich (0.879-0.991) and pseudo-second-order models (0.979-0.997), respectively. The optimal pH condition for the removal of chromium(VI) ion from aqueous solution was approximately 2. Finally, WB1000 could be useful for repetition of chromium(VI) ion adsorption/desorption using sodium hydroxide at 1000 mmol/L (at least five times). It was shown that WB1000 has the potential for adsorption and recovery of chromium(VI) ion from aqueous solution using sodium hydroxide.