Double-edged sword effect of nano-biochar for Cd2+ adsorption on zeolite

Nano-biochar (NBC) is an effective material for environmental relevance due to its larger specific surface area and richer functional groups than bulk biochar. However, the interaction between NBC and Cd2+ when they coexist with environmental media, in addition to the mechanism of this action, is still unknown. In this study, adsorption experiments and characterization of zeolite and NBC were carried out for revealing the interaction of NBC and Cd2+ on zeolite. The results of isothermal adsorption demonstrated that the Sips model best fitted the co-adsorption of NBC and Cd2+ on zeolite. The adsorption capacity of NBC increased by 10.2% & PLUSMN; 0.03% as opposed to that of Cd2+ decreased by 24.8% & PLUSMN; 0.07% in the co-existence of NBC and Cd2+. It was found that the coexistence of NBC had a dual effect on the environmental behavior of zeolite and contaminant, acting as a double-edged sword. The positive effect was that the adsorption of NBC on zeolite tended to make zeolite more accessible to organic functional groups and inorganic salts. The negative effect was that NBC inhibited contaminant adsorbing on zeolite when NBC coexisted with Cd2+. This study revealed that the coexisting NBC can also enhance the migration risk of Cd2+ in the environment by affecting the adsorption behavior of Cd2+ on zeolite.