A Novel Peony-shaped ZnO/Biochar Nanocomposites with dominant {100} facets for Efficient Adsorption and Photocatalytic Removal of Refractory Contaminants

Herein, a peony-shaped nanocomposite (P-ZnO/BC) was facilely developed by incorporating ZnO with Hemp stalk derived biochar (BC) via two-step sequential solvothermal procedure and used for photocatalytic degradation of organic contaminants. The as-prepared P-ZnO/BC presents preferential (100) crystal orientation, suitable electronic energy level, and distinct mesoporous distribution as well as large specific surface area. Thereby, the optimal P-ZnO0.3/BC (weight ratio of 3:7 for ZnO:BC) shows higher photocatalytic activity with degradation efficiency as high as 94.5% toward methylene blue (MB) within 120min, whereas the ZnO and BC merely deliver 6.3% and 63.5%, respectively. Obviously, the superior contaminants removal properties of P-ZnO0.3/BC can be attributed to the synergistic effect of adsorption of BC and photocatalysis of ZnO. Also, this can be associated with the improved adsorption, accelerated charges (e-/h+ pairs) transportation and reduced e-/h+ pairs recombination of P-ZnO0.3/BC. The reactive radicals scavenging experiments and ESR measurements confirm that the main reactive species are hydroxyl radicals (•OH) and holes (h+). Furthermore, P-ZnO0.3/BC displays desirable reusability and better universal applicability toward other organic dyes and antibiotics removal. Moreover, the possible degradation mechanism and pathway were also inferred by analyzing the intermediates via liquid chromatography mass spectrometry (LC-MS) technique. In conclusion, this work provides a fundamental insight via integrating ZnO with low-cost BC for efficient removal of the refractory organic pollutants.