An effective strategy for dual enhancements on bioethanol production and trace metal removal using Miscanthus straws

Lead (Pb) is one of the most hazardous substances contaminating water source and agricultural lands, and Miscanthus is a leading bioenergy crop providing enormous lignocellulose residues convertible for bioethanol and biochemicals. Using two distinct Miscanthus straws, this study compared various chemical pretreatments to obtain relatively high cellulosic ethanol production. All remained solid wastes were then employed for Pb adsorption under different incubation conditions (pH, initial concentration, temperature, etc). By comparison, the solid residues were of remarkably higher Pb adsorption capacity and removal rates than those of raw materials. Notably, the optimal one-step alkali pretreatment could not only lead to high bioethanol yield, but the remaining solid residues from final yeast fermentation were of the highest Pb adsorption among all pretreatments performed in this study. Chemical analyses revealed that the solid residues from the optimal alkali pretreatment could act as active biosorbents for Pb adsorption via typical chemical binding manner, and they also exhibited much larger surface area and pore volume relative to the raw materials, interpreting why they were of significantly higher Pb adsorption. Hence, this study has demonstrated a powerful strategy to use full Miscanthus straws for both enhanced cellulosic ethanol production and improved biosorbent activity for trace metal removal without any biomass waste release into the environment.