Degradation of atrazine by cobalt-mediated activation of peroxymonosulfate: Different cobalt counteranions in homogenous process and cobalt oxide catalysts in photolytic heterogeneous process

The degradation of atrazine (ATZ) by cobalt-mediated activation of peroxymonosulfate (PMS) has been studied in this work. For the homogenous process, different cobalt counteranions: cobalt(II) nitrate Co(NO3)2, cobalt(II) sulfate CoSO4, cobalt(II) chloride CoCl2, and cobalt(II) acetate Co(CH3COO)2, have been examined. The inhibitory effect was observed in the process initiated by CoCl2. For the pH test, wide range of pH level (2–10) has been investigated. It was found that the higher rates were obtained in the normal pH levels. At extreme pH levels, the process was impeded by inactivation of PMS at acidic pH and prohibited by precipitation at basic pH. On the other hand, the recycling capability of cobalt oxide and the oxidative potential of cobalt-immobilized titanium dioxide Co–TiO2 catalyst were analyzed in the heterogeneous process. It was found that the higher the cobalt content in the catalyst, the better the removal performance was resulted. At last, the Co–TiO2 catalyst synthesized in this work was found to be very effective in transforming ATZ as well as its intermediate in the presence of UV–vis irradiation.