Engineered biochar supported bismuth tungstate: Unveiling the influence of precursor concentrations and biochar dosage for the solar photocatalysis of 1,3-diphenylguanidine in secondary municipal effluent

In this work, engineered hierarchal structures of biochar-supported bismuth tungstate are synthesized for wastewater treatment applications. The integration of biochar supports resulted in an increase in the surface area, reduction in crystallite size, and exposure of the active facets of Bi2WO6. Controlled Bi2WO6 morphologies were obtained by varying the precursor concentrations, causing a remarkable transition from mixed microspheres to flower-like structures and, ultimately, to nanosheets. The optimal composite demonstrated its efficiency in a spiked wastewater secondary effluent, achieving 97.74 % degradation of 1,3-diphenylguanidine (DPG) under 8 h of simulated solar light irradiation. The treatment also reduced the toxicity and COD of the spiked secondary effluent matrix. The primary reactive oxygen species detected were O2•– and h+. Additionally, the photocatalytic degradation mechanism and possible degradation by-products of DPG were identified. These results highlight the significant influence of the biochar supports and synthesis parameters on the activity of biochar-supported photocatalysts, paving the way for the design of superior photocatalyst materials for wastewater treatment applications.