In situ stabilization of the adsorbed Co2+ and Ni2+ in rice straw biochar based on LDH and its reutilization in the activation of peroxymonosulfate.

Abstract

The stabilization of heavy metals adsorbed in the spent biochar remains a challenge, and the risk of secondary pollution under environmental changes will rise under inadequate post-treatment. Moreover, the safe and sufficient re-utilization of the spent biochar with heavy metals loaded have attracted extensive attention. In this research, the performance and mechanism of rice straw biochar (RSBC) pyrolyzed at different temperature for nickel and cobalt adsorption were investigated, and the stabilization of the adsorbed heavy metals was achieved via a simple two-step strategy: the adsorption of metal ions and the hydrothermal process to form the stable layered double hydroxides (LDH) on biochar, with a leaching rate below 0.005% evaluated by EPA toxicity characteristic leaching procedure (TCLP). Meanwhile, the stabilized RSBC-LDH can be reused as an excellent catalyst in the activation of peroxymonosulfate (PMS) to degrade organic pollutants efficiently. This work eliminated the risk of heavy metal desorption from the spent biochar, and enabled a new strategy for the optimized utilization of biochar in environmental remediation.