Removal of lead by rice husk biochars produced at different temperatures and implications for their environmental utilizations

Rice husk is a common agricultural waste. The utilization of rice husk biochar depends on the characteristics of biochar and its interaction mechanisms with heavy metals. In the present study, rice husk biochars at three different temperatures 300, 500, and 700 °C were produced (RH300, RH500, and RH700). The characteristics of these rice husk biochars and their interaction mechanisms with lead (Pb) were investigated, in order to reveal the potential environmental applications of the biochars. It was observed that the surface area (from 0.632 to 193.149 m2/g) and pH (from 7.13 to 9.80) of the rice husk biochars significantly increased as production temperature rose from 300 to 700 °C, while the number of functional groups (e.g., carboxyl) decreased. The Langmuir maximum removal capacity (Qmax) values for Pb are in the order of RH300