Treatment of landfill leachate using photocatalytic based advanced oxidation process - a critical review

Landfill leachate is a discrete volumetric component of municipal solid waste; hence, researchers and professionals are more concerned about it because of its obscurity. Innovative treatment and emerging technologies are being scrutinized to address the treatment of landfill leachate challenges. The leading target of this review was to examine the possibility of removing recalcitrant organic pollutants from landfill leachate by photocatalytic-based advanced oxidation processes. A summary of the systematic applicability of conventional treatment for landfill leachate is provided, with a focus on physico-chemical and biological processes. The biological treatment, such as aerobic and anaerobic digestion, is an excellent technique for treating highly concentrated organic pollutants in the wastewater. However, Leachate can scarcely be treated using conventional techniques since it is enriched with refractory organics and inorganic ions. It is clear from the literature review that none of the available combinations of physico-chemical and biological treatments are entirely relevant for the removal of recalcitrant organic pollutants from leachate. Recently, the photo-assisted TiO₂/ZnO oxidation has shown an excessively potential and feasible way to treat landfill leachate. TiO₂/ZnO photocatalysis is currently developing to treat recalcitrant organic pollutants from landfill leachate. The effect of operating parameters reveals that pH and temperature affect the reaction rate. The addition of oxidant H₂O₂ to the TiO₂/ZnO suspension suggests that TiO₂ leads to an increase in the rate of reaction when compared to ZnO. Photocatalytic remediation technique of landfill leachate would support the goal of environmental sustainability by greatly enhancing the effectiveness of treated leachate reutilization. In this review, the selection of the best photocatalytic treatment for leachate based on its systematic relevance and potential conditions, characteristics, cost-effectiveness, essential controlling, discharge limit, long-term environmental effects, and its future study perspectives are emphasized and discussed.