Hydrothermal-assisted acid-etching of oil shale semi-coke for preparation of mineral/biochar nanocomposites and selective adsorption toward mycotoxins

Due to the continuous increase in the mycotoxin pollution in various cereals, animal feeds and water body, it is crucial to develop efficient mycotoxin adsorption materials. This study employed hydrothermal-assisted acid-etching of oil shale semi-coke (OSSC) to fabricate mineral/biochar nanocomposites based on full-component synchronous utilization of OSSC for the adsorption of mycotoxins, and the structural evolution and structure-activity relationship of mineral/biochar nanocomposites for adsorption of mycotoxins were studied from the mineral material perspective. XRD and Raman results indicated that the acid-etching process affected the crystalline structures of the minerals, while Zeta potential and FTIR spectra demonstrated that this process increased the number of active adsorption sites on the nanocomposites for selective adsorption of mycotoxins. By contrast, the obtained mineral/biochar nanocomposites presented good adsorption properties toward zearalenone and aflatoxin B1 with a maximum removal ratio of 95.59% and100% after being treated with 4 mol/L of HCl for 12 h, while almost no zearalenone adsorption was observed for raw OSSC. The adsorption mechanism involves the formation of hydrogen bond, van der Waals force, π-π interaction, and π-dipole interaction derived from the synergistic effect between silicate and carbon species. This study provides a feasible strategy for the preparation of mineral/biochar nanocomposites with excellent adsorption performance, and a reference for understanding the structural evolution and structure-activity relationship of mineral/biochar nanocomposites to realize the popular strategy of "Treating the wastes with wastes".