Biochar with nanoparticle incorporation and pore engineering enables enhanced heavy metals removal

Biochar is a desirable candidate for environment remediation of heavy metals in water due to wide availability and environmental-friendliness. In practical application, however, biochar suffers from inferior adsorption capacity owing to poor surface properties and limited pore structure. Herein, a combined strategy of nanoparticle incorporation and pore engineering was proposed to synthesize KOH activated porous biochar embedded MgO composite (K-MgO-RB) derived from waste ramie. Specifically, KOH as the chemical activator developed regular porous structures, which not only facilitated the increase in surface area and the MgO incorporation, but also effectively suppressed the aggregation of MgO nanoparticles due to the nanoconfinement effect. Thanks to the favorable nanostructures and incorporation of nano-MgO, K-MgO-RB presented superior adsorption capacities for Pb2+ (1276.46 mg/g) and Cd2+ (861.82 mg/g), which was approximately 100 and 19 times higher than those of the pure RB, respectively. The adsorption mechanism study indicated that electrostatic effect, precipitation, ion exchange, and cation-pi electrons complexation were the dominant adsorption driving force of Pb2+ and Cd2+. Further, outstanding dynamic adsorption performance of 3480 mL (174 BV) for Pb2+ and 2520 mL (126 BV) for Cd2+ in fixed-bed column experiment, exceptional reusability as well as low economic cost demonstrated the excellent potential of K-MgO-RB for practical application.