Bioleaching of heavy metal from woody biochar using Acidithiobacillus ferrooxidans and activation for adsorption.

A woody biochar which was the byproduct of gasification of sawdust was treated with bioleaching by Acidithiobacillus ferrooxidans. After bioleaching, most heavy metal was removed from biochar. Leaching efficiency of heavy metal was efficient in a wide pulp density range from 1% to 10% (w/v) and decreased only a little with the increase in pulp density. It made application of biochar free of heavy metal risk. Benefitting from the improvement in functional group composition and pore structure after bioleaching, adsorption capacity of biochar to methylene blue and heavy metal was enhanced greatly. Adsorption of methylene blue could be described by pseudo-second-order model and Langmuir equation and the enhancement was mainly caused by the modification of physical character of biochar. Adsorption of heavy metal could be described by Freundlich equation and was mainly determined by chemical character of biochar.