Pyrolysis combined ball-milling for the preparation of biochar from Chinese Baijiu distillers' grains for the adsorption of heavy metal ions

The facile and feasible method for the valorization of distillers' grains (DGs) is a pressing demand of Chinese Baijiu industries to realize the sustainable manufacturing process. In this work, pyrolysis combined MgO ball -milling was applied to convert distillers' grains into MgO-biochar (BMBCx) for the efficient adsorption of Co2+ and Ni2+. MgO was highly dispersed on BMBCx and Mg-Si complex was synthesized after ball-milling. The adsorption capacity of BMBCx for Co2+ and Ni2+ raised approximately 16-77 and 12-29 times compared with pristine biochar, respectively, implying MgO and Mg-Si complex enhanced the adsorption capacity enormously, which was confirmed by DFT analysis. The adsorption of BMBCx on Co2+ and Ni2+ was pH-dependent and could be described by pseudo-second-order kinetic and Freundlich models. The maximal adsorption capacity of BMBCx on Ni2+ was 469.3 mg/g, which was accomplished by multiple synergistic effects of Van der Waals force, metal ion exchange, metal-& pi; interaction and surface functional group complexation. Thus, this facile MgO-loaded biochar fabrication method can realize the valorization of DGs and promote the ecofriendly development of Baijiu industry.

Automated summary

In this study, a facile and feasible method for the valorization of distillers' grains was developed. MgO-biochar was prepared through pyrolysis and ball-milling, and it showed significantly enhanced adsorption capacity for Co2+ and Ni2+. The adsorption mechanism was elucidated, and the maximal adsorption capacity for Ni2+ was determined to be 469.3 mg/g. This method provides a promising approach for the sustainable manufacturing process in Chinese Baijiu industries.