Efficient Removal of Cr(VI) by Protonated Amino-Bamboo Char Prepared via Radiation Grafting: Behavior and Mechanism

Abstract

Biochar is considered to be the most promising substrate for the preparation of environmentally functional materials. The modification of bamboo char can significantly improve the removal rate of toxic ions from wastewater; however, there are few reports that focus on the radiation grafting method. Here, glyceride methacrylate (GMA) is successfully grafted onto bamboo char through electron beam radiation, followed by amination using the existing epoxide group in diethyltriamine, and finally, treated with hydrochloric acid to obtain protonated diethyltriamine-functionalized bamboo char (CDGBC). The results of IR, TG, XRD, and SEM prove the successful fabrication of a CDGBC biosorbent. The results show that the solution pH has a great effect on the adsorption capacity, and a maximum adsorption capacity of 169.13 mg/g is obtained at pH = 2 for Cr(VI). In addition, the adsorption behavior of Cr(VI) onto CDGBC is demonstrated to obey the pseudo-second-order kinetic and Freundlich isotherm models, and thermodynamic analysis exhibits that Cr(VI) adsorption is an endothermic spontaneous process. A possible adsorption mechanism based on the electrostatic interaction, reduction, and surface complexation is proposed, according to the obtained results. This work confirms that radiation-induced grafting modification can effectively transform biochar into a high-performance adsorbent for Cr(VI) removal, offering a new approach to synthesizing an efficient biosorbent.