Adsorption and photocatalytic degradation of metaldehyde in aqueous solution

Metaldehyde is best known as the main constituent of slug pellets. This organic compound has been found in relatively high levels in both surface and underground water. While many water treatment processes do not work with metaldehyde degradation, a photocatalytic degradation process has been proved to have a significant effect on metaldehyde stability. Nanosized ZnO/laponite composite (NZLC) was used as a photocatalyst in this investigation of metaldehyde degradation. The reactions were carried out in a ultraviolet C (UVC) lamp fitted batch reactor by considering the following parameters: initial metaldehyde concentration, pH of solution, and light intensity. A comparison of degradation efficiency between photolysis, photocatalysis, and adsorptive ability on NZLC indicated that the latter had the highest efficiency. Furthermore, higher metaldehyde degradation was observed as the initial concentration decreased. However, the fastest metaldehyde degradation rate in heterogeneous photocatalysis was obtained when pH values were greater than 7.0. Consequently, the findings suggest that the removal of metaldehyde by adsorption and photocatalytic degradation using NZLC under UV irradiation was a hybrid reaction process (i.e. photolysis, adsorption, and photocatalysis).