Adsorption of Cr(VI) from wastewater by iron-modified coconut shell biochar Jiangping Bu, Wenyu Li, Ning Niu, Ning Guo, Hao Zhou, Cheng Chen and Aifang Ding E3S Web Conf., 248 (2021) 01059 Published online: 12 April 2021 DOI: 10.1051/e3sconf/202124801059