Abstract: Twelve types of biochars were prepared by pyrolyzing rice husk and sawdust at different temperatures (200-700 ℃), which were referred as DBC200-DBC700 and MBC200-MBC700, respectively. The characteristics of these biochars and their Cu²⁺ adsorption performance were investigated, including the adsorption isotherms, kinetics and dynamic leaching. Results indicate that biochars derived from higher temperature showed better performance for Cu²⁺ adsorption, and those produced at 700 ℃ showed the highest sorption capability. The sawdust biochar had higher adsorption capacity than rice husk biochar derived under the same pyrolysis temperature. There was significant correlation between Cu²⁺ adsorption and each of the parameters, such as pH, specific surface area, carboxyl group content, and pore volume for rice husk biochars. For sawdust biochar, there was significant correlation between Cu²⁺ adsorption and the total acid groups, and obviously significant correlation between Cu²⁺ adsorption and pH as well as the carboxyl group content. Adsorption isotherms of Cu²⁺ by DBC700 and MBC700 were well fitting with Freundlich model, and the adsorption kinetics were greatly fitting to both pseudo-first-order model and pseudo-second-order model. The average amount of Cu²⁺ adsorption by DBC700 and MBC700 from dynamic adsorption experiment reached 7.58 and 16.12 mg·g^-1, respectively. The results indicate that rice husk and sawdust biochars could be used as efficient adsorbents to remove Cu²⁺ from wastewater.

Key words: biological carbon, adsorption, temperature, leaching, Cu²⁺