Journal of Environmental Sciences 2010, 22(11) 1800–1806 Efficient microwave-assisted photocatalytic degradation of endocrine disruptor dimethyl phthalate over composite catalyst ZrO x /ZnO Wenchao Liao, Tong Zheng, Peng Wang ∗ , Sisi Tu, Weiqian Pan State Key Laboratory ofUrban Water Resource andEnvironment, School of Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin 150090, China. E-mail: liaowenchao@gmail.com Received 21 December 2009; revised 30 March 2010; accepted 06 April 2010 Abstract A highly active ZrO x /ZnO catalyst for microwave-assisted photocatalytic (MW/PC) degradation of endocrine disruptor dimethyl phthalate (DMP) has been prepared via cetyltrimethylammonium assisted hydrothermal method. The ZrO x /ZnO was characterized by XPS, XRD, UV-Vis, BET and SEM techniques. The XPS result showed that Zr oxides with different valences (+2, +3, +4) co-existed in ZrO x /ZnO. By using the ZrO x /ZnO (0.1 g), the TOC removal efficiency of DMP (100 mL of 50 mg/L) was 88% after 30 min reaction, which was about 15% higher than P25 TiO 2 . It was found that the removal process of DMP by MW/PC followed pseudo first-order kinetics in all cases, and ZrO x /ZnO significantly accelerated the degradation of DMP. The degradation half-life time of DMP was shortened 45% compared with P25 TiO 2 . A possible catalytic mechanism was proposed based on microwave response and interfacial charge transfer. ZrO x /ZnO could be reused for six times without obvious decrease in catalytic activity. The study offers new insights into designing highly efficient catalysts for MW/PC process and is applicable for MW/PC environmental remediation. Key words: ZrO x /ZnO; microwave-assisted photocatalysis; dimethyl phthalate DOI: 10.1016/S1001-0742(09)60322-3 Introduction Dimethyl phthalate (DMP), one of the priority pollutants listed by some regulatory agencies including the United States Environmental Protection Agency, is an endocrine disrupting compound which can disturb the endocrine system of humans and wildlife even with very low concen- trations. DMP is widely used as plasticizer and is hardly biodegradable (Wang et al., 1998; Adhoum and Monser, 2004). It is frequently identified in diverse environmental samples (Marttinena et al., 2003). Therefore, decomposi- tion of DMP is not only of scientific interests but also of industrial and medicinal importance. In recent years, microwave irradiations have been confirmed to be potent for accelerating many kinds of advanced oxidation processes (Zhang et al., 2005; Bi et al., 2008). In particular, it has been reported that microwave- assisted photocatalytic (MW/PC) process is extraordinarily effective for decomposition of unbiodegradable organic compounds in contaminated water (Horikoshi et al., 2002; Horikoshi et al., 2003; Horikoshi et al., 2004; Zhang et al., 2005; Ai et al., 2005; ˘ Zabov´ a et al., 2009). According to our previous research, photocatalytic degradation of DMP could be significantly enhanced when coupled with microwave irradiation (Liao et al., 2009). However, to the best of our knowledge, the catalyst commonly used * Corresponding author. E-mail: pwang73@vip.sina.com in the MW/PC process mainly focused on the traditional photocatalyst Degussa P25 TiO 2 and some modified TiO 2 (Horikoshi et al., 2006; ˘ Zabov´ a et al., 2009), and not enough attention has been paid to the microwave response ability of catalyst. Thus, developing a characteristic cat- alyst with strong response to both microwave and UV is indispensable for the application of MW/PC process. Zirconia is a wide bandgap semiconductor with big po- tential for photocatalytic degradation of pollutants (Fresno et al., 2008; Alvarez et al., 2007). However, it can not be effectively activated by long wavelength UV light irradia- tion, which to some extent restricts the application of it. As is well known, composite semiconductor can extend the photon-response range and improve the separation of photo-generated electrons-holes pairs (Tian et al., 2009; Dorraji et al., 2009; Liao et al., 2004). ZnO is a widely focused and explored photocatalyst for its high oxidative capacity, low cost, high chemical stability and low toxicity. It also offers some advantages over TiO 2 that ZnO can simultaneously sense and destroy pollutants (Hariharan, 2006; Gouvea et al., 2000; Gouvea et al., 2000; Afzaal et al., 2007). Furthermore, ZrO 2 and ZnO possess stronger microwave absorption ability than TiO 2 , according to report (Durka et al., 2009). In this article, we prepared a ZrO x /ZnO catalyst using a surfactant-assisted hydrothermal method and studied the MW/PC degradation of DMP over ZrO x /ZnO. The effect