Photocatalytic degradation of the herbicide chloridazon on mesoporous titania/zirconia nanopowders

Advanced oxidation processes using semiconducting photocatalysts for the degradation of organic pollutants are a promising approach for the remediation of pesticide-contaminated wastewater. High photodegradation efficiency and stability of the photocatalyst are of key importance for practical application of the semiconductor. In this study, mesoporous TiO₂/ZrO₂ nanopowders were synthesized via two techniques; evaporation-induced self-assembly (EISA) and sol-gel using triblock copolymers Pluronic P123 and F127. The photodegradation activities of the composites were determined by employing the herbicide chloridazon as a model compound. Due to well-developed mesoporosity, the TiO₂/ZrO₂ nanocomposite synthesized by EISA displays high surface area and small crystallite sizes leading to higher photocatalytic activity than pristine TiO₂ prepared under similar condition and commercial Degussa P25 nanopowder. The optimum amount of zirconium required for the highest activities was identified and found to be 0.14 and 0.05 mol% for the EISA and sol-gel-prepared samples, respectively. Systematic studies of the post-thermal treatment step for both samples show that Zr inhibits an anatase-to-rutile phase transition only up to 600 °C, at higher temperature phase separation occurs. Samples synthesized by EISA method showed enhanced degradation activity than sol-gel-synthesized samples.