Fixed bed recirculation type photocatalytic reactor with TiO2 immobilized clay beads for the degradation of pesticide polluted water

A recirculation type photocatalytic reactor (RTPR), using ultraviolet radiations (Blue black lamp) and filled with titanium dioxide (TiO2) coated local clay beads, has been designed and used for the degradation of extremely toxic and water persistent pesticide Monocrotophos (MCP). Further, the present study has made an effort to use low cost, easily available, eco-friendly clay material as the support for the immobilization of catalyst for treating the pesticide polluted water by photocatalytic degradation. The economic viability of the developed reactor has been addressed in terms of electrical energy per order (E-EO ) for photocatalytic degradation of MCP, which is found to be very less compared to the literature values. The effect of various parameters like light conditions, recirculation rate, light intensity and initial MCP concentration has been determined for optimization of the designed RTPR. MCP degradation of 78.57% was obtained with optimum conditions as 25 mg/L MCP, 600 beads and pH 5. In addition to this, the recyclability of the immobilized TiO2 over clay beads in the developed RTPR was studied up to 30 continuous cycles without reactivation of catalyst. The mineralization of the MCP was studied using COD and was determined to be 73.75% and the degradation pathway is also proposed. Further, the degradation obeys pseudo first order kinetics.