Cotton stalk derived carbon pretreated by microbial fermentation for selective uranium extraction

Microbial fermentation pretreatment is an effective strategy to solve the problem of low uranium adsorption capacity of traditional biochar materials by introducing some porous structures and special functional groups in the fermentation process. Here, five different microorganisms ( Bacillus licheniformis , Aspergillus oryzae , Lactobacillus acidophilus , Bacillus subtilis, and Saccharomyces cerevisiae ) were selected to pretreated cotton stalk biochar to find the most suitable microorganism to increase surface area and effective functional groups. Cotton stalk biochar fermented by Aspergillus oryzae has a highest specific surface area and more functional groups than other groups. U(VI) adsorption efficacy of five fermentation biochars and blank control was tested for different contact times and initial concentrations of U(VI). Cotton stalk biochar fermented by Aspergillus oryzae had the best uranium adsorption performance with an adsorption capacity of 100.31 mg/g. Mechanism analysis showed that the adsorption of U(VI) on cotton stalk biochar fermented by Aspergillus oryzae was mainly attributed to the ion exchange with Ca 2+ and the complexation with phosphate groups. Based on the above analysis, cotton stalk biochar fermented by Aspergillus oryzae possessed the potential to be applied for removing U(VI) from wastewater.