TiO2-Assisted Photocatalytic Degradation of Herbicide 4-Chlorophenoxyacetic Acid: Slurry and Fixed-Bed Approach
The photocatalytic degradation of a recalcitrant herbicide 4-chlorophenoxyacetic acid (4-CPA) was investigated using suspended and supported TiO2. The photocatalytic process was intensified with optimization of various operating parameters in slurry mode-like dose of TiO2, H2O2, A/V ratio of reactor, pH, and UV intensity. An almost 93% degradation of 4-CPA was achieved after 2 h of UV irradiations while it enhanced to 99% under natural solar irradiations within the same treatment time. For fixed-bed studies, novel TiO2 immobilized spherical clay beads were used which yielded approximately 97% degradation of 4-CPA after 5 h of treatment. Excellent stability and durability of the immobilized catalyst were confirmed through SEM/EDS analysis. TiO2-coated clay beads were successfully recycled for more than 30 cycles without any significant reduction in the degradation efficiency of 4-CPA. The mineralization studies of 4-CPA were carried out by monitoring the generation of chloride ions along with reduction in COD. The intermediates formed during the degradation of 4-CPA were identified through GC-MS analysis. The results obtained in this study especially in fixed-mode using highly durable TiO2 immobilized clay beads can open up new channels in this particular field for the removal of recalcitrant pollutants present in aquatic environment.
KeywordsPhotocatalysis 4-chlorophenoxyacetic acid Clay beads Degradation Mineralization
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