Researchers have developed a new biochar zinc oxide (BC/ZnO) composite, derived from wood waste, that significantly improves the photocatalytic degradation of naphthenic acids (NAs) found in oil sands process water (OSPW). These acids pose notable risks to both aquatic and mammalian species due to their toxicity. The study demonstrates that the BC/30%ZnO composite not only outperforms pure ZnO in terms of degradation efficiency but also maintains its effectiveness after multiple uses.

The introduction of the BC/ZnO composite marks the first use of such material for the simultaneous degradation of a complex mixture of NAs, showcasing over 95% degradation efficiency after just six hours of solar irradiation. The superior performance of the BC/ZnO composite is attributed to the biochar’s porous structure which serves as a robust platform enhancing the stability and durability of the ZnO particles. This structural advantage prevents the rapid recombination of photogenerated electron-hole pairs, a common issue in photocatalysis, and allows for a sustained generation of hydroxyl radicals, the main agents responsible for the breakdown of the NAs.

Extensive tests reveal that optimal conditions for the composite’s use involve a concentration of 0.5 g/L of BC/30%ZnO and an exposure time of four hours under simulated solar light, achieving a remarkable 93.7% degradation of cyclohexanecarboxylic acid, one of the prevalent NAs. Even after four cycles of reuse, the composite’s degradation efficiency impressively stands at 92.9%.

This innovative approach not only leverages the photocatalytic properties of ZnO but also incorporates sustainable practices by utilizing wood waste, presenting a promising and environmentally friendly solution for the treatment of OSPW. The study’s findings offer significant implications for the practical application of photocatalytic materials in environmental remediation, particularly in treating complex pollutant mixtures with varied chemical compositions.