Insights on the influence of natural co-contaminants on the photocatalytic performance of biochar supported p-n heterojunction photocatalyst in an aqueous media

In last few decades, photocatalysis have been extensively studied in a simulated wastewater under laboratory conditions to degrade wide range of organic pollutants. To transfer this technology into a large scale, several approaches have been made focusing on developing novel photocatalyst for maximizing the generation of reactive species and efficient photocatalytic reactor for maximizing photon usage. However, there are some fundamental issues exist with the presence of natural co-contaminants such as competitive ions and natural organic matter (NOM) which can significantly reduce efficiency of the photocatalytic process. Hence, this study investigated role of competitive ions and NOM on photocatalytic oxidation of DMP using p-n heterojunction photocatalyst (O2-TiO2/CuO) decorated on biochar. The study revealed that competitive ions showed quenching effect towards photogenerated charged pairs and significantly reduces degradation efficiency. Similarly, presence of NOM in small amount could enhance or does not have substantial impact on the removal efficiency of DMP. However, at higher NOM concentration, DMP removal dropped significantly by screening of photons, blocking of adsorption sites of the catalyst and scavenging of positive holes (h+). In addition, Electron Spin Resonance (ESR) analysis was performed as an evidence for the generation of radicals and quenching experiment was conducted to identify the major contributing radical in the degradation process among multiple radicals generated from the photocatalysis. The findings revealed that among different reactive species OH• is the dominant species in the degradation process and O2-• has least contribution to the degradation of DMP.