Enhanced removal of Cr(VI) by cation functionalized bamboo hydrochar

Chemical modification on hydrochars can significantly improve their ability of removing heavy metal ions from wastewater, but so far no research has focused on the chemical modification through free radical reaction. In this work, a cation functionalized hydrochar (CFHC) bearing - N⁺H₂R was synthesized by grafting-polymerization of glycidyl methacrylate (GMA) onto bamboo hydrochar under initiation by benzoyl peroxide, followed by the amination with the introduced epoxy group and diethylenetriamine and a subsequent hydrochloric acid treatment. The resulted CFHC exhibited a superior removal capacity of 424.09 mg·g^-1 for Cr(VI), and the highest sorption occurred at pH of 2. Combining a series of characterizations and tests, it was concluded that the sorption conformed to the pseudo-second-order and Freundlich equations, indicating a multilayer chemisorption process that mainly driven by electrostatic reaction, reduction, and surface complexation. This research proved that a free radical polymerization treatment could effectively transform hydrochars into super adsorbents for wastewater treatment.