Photocatalytic Degradation of Geosmin with Zn-Al Multi-metal Oxide Composites Derived from Layered Double Hydroxide Precursors

Abstract

Geosmin is one of the typical odor compounds in water environment, it has a very low odor threshold (10ng/L), and difficult to degrade in natural environment. In this study, a Zn-Al multi-metal oxide, based on Zn-Al-LDH as a precursor, was prepared and used as photocatalyst to investigate the photocatalytic degradation performance of geosmin in the range of ng level in aqueous solution. Firstly, Zn-Al-LDH was synthesized by co-precipitation method, and the Zn-Al multi-metal oxide was produced after calcination of Zn-Al-LDH at 1023 K in air. The obtained Zn-Al multi-metal oxide showed a good photocatalytic degradation performance. In the condition of simulated solar light, 1g/L catalyst dosage and initial geosmin concentration of 200ng/L, the apparent rate constant kapp is 0.017min-1. After 3 hours of photocatalytic reaction, the residual concentration of geosmin decreased to lower than 10ng/L, which can meet the requirements of "Standards for Drinking Water Quality" (GB5749-2006). The result showed that the photocatalytic reaction efficiency was mainly related with the part of ultraviolet light. The photocatalytic activity of the Zn-Al-MMO was little affected by pH over the range of 4–10. The possible photocatalytic degradation mechanism of the geosmin was also discussed.