Titanium dioxide mediated photocatalytic degradation of monocrotophos

Abstract

Titanium dioxide mediated photocatalytic oxidation of Monocrotophos (MCP) was studied under different conditions. At a flow rate of 30 ml/min and initial concentration of 50 mM, 51% of MCP was found to degrade after an hour. When small amounts of either oxygen or hydrogen peroxide was added to the system, the degradation was enhanced significantly. Changes in the rates of MCP degradation were studied with the addition of chloride, chlorate, nitrate, sulphate, and copper ions to the recirculating solutions. The addition of anions can cause either an increase or a decrease in the photocatalytic oxidation of MCP, depending on the type of anions used. Whereas chloride, chlorate, and nitrate were demonstrated to hinder the degradation of MCP, sulphate was found to have an enhancement effect. The behaviour of Cu 2+ ions was shown to have different effects on the photocatalytic degradation of MCP. It depends on the concentration of Cu 2+ ion added during the reaction. At low concentrations (< 10 −5 M) an enhancement in the degradation was found. However, at higher Cu 2+ concentrations, a dramatic lowering of the rate of degradation was observed. Fourier Transformed Infrared Spectroscopy (FTIR) indicated that different intermediates were formed during the photocatalytic oxidation of MCP. These intermediates were also degraded with prolonged reaction.