Preparation of bamboo-based oxidized biochar for simultaneous removal of Cd(II) and Cr(VI) from aqueous solutions

Abstract

Cd(II) and Cr(VI) are highly toxic heavy metal ions, which commonly coexist in industrial wastewater. In this study, simultaneous removal of Cd(II) and Cr(VI) by a bamboo-based oxidized biochar (BZ-APS24h) was investigated. The biochar was modified by ZnCl2 and oxidized with (NH4 )2 S2 O8, and its structures as characterized by SEM, BET, elemental composition and X-ray photoelectron spectroscopy. Batch adsorption experiments for Cd(II) and Cr(VI) were carried out to explore the effects of oxidation time, pH, contact time, temperature and coexisting ions on its adsorption process. The results showed that the BZ-APS24h exhibited excellent adsorption performance for the removal of Cd(II) (0.27 mmol/g) and Cr(VI) (0.65 mmol/g). The adsorption data were fitted well with pseudo-second-order model and Langmuir isotherm. The pH of the solution had a great influence on the adsorption process. The coexistence of Cd(II) and Cr(VI) affected the equilibrium pH after adsorption, and synergistic adsorption was also observed.