Synergistic sorption/photo-Fenton removal of typical substituted and parent polycyclic aromatic hydrocarbons from coking wastewater over CuO-Montmorillonite

Polycyclic aromatic hydrocarbons (PAHs) and substituted PAHs (SPAHs) are commonly persistent organic pollutants that are found in different industrial and agricultural wastewaters. In the present research study, we investigated the purification of coking wastewater containing mixed 16 PAHs and 18 SPAHs using CuO decorated montmorillonite (CuO-M) under solar light. For better removal efficiency, H2O2 was added to make the photo-Fenton reaction into action. Due to the complexity of this coking wastewater, the purification was carried out in two runs. The results showed that, by using CuO-M/H2O2/light, 66% of the total yield of PAHs and SPAHs was removed from coking wastewater within 4 h. The second treatment run led to a further increase in the removal rate up to 91% of total pollution. Different synergetic mechanistic pathways such as the adsorb & shuttle process, generation of reactive oxygen species (ROSs) by photoactive CuO on the montmorillonite surface, and photo-Fenton ROSs generation in bulk water catalyzed by CuO and H2O2 are responsible for the effective removal of PAHs and SPAHs. Even though the study was established under well-controlled lab conditions, we should say that the CuO-M/H2O2/light system showed excellent performance in removing a significant part of PAH and SPAH compounds that might make it a potential alternative/cooperative to be involved in wastewater treatment plant (WWTP) to purify the same coking wastewater.