Effect of humic acid on the degradation of methylene blue by peroxymonosulfate

Abstract

Methylene blue dye has been widely used in many industries and usually released in natural water sources, which become a health thereat to human-beings and microbes. This paper demonstrates an oxidation method to remove methylene blue in water. The effect of natural organic matter humic acid, on the degradation of methylene blue using PMS was investigated. The results show that PMS could effectively degrade 50 mg/L methylene blue (>95%) when the PMS concentration was larger than 1.0 mM. Humic acid had either negative or positive impact on the degradation processes because of the co-existence of several competitive degradation mechanisms (I: humic acid competes with methylene blue for PMS; II: humic acid activates PMS to produce sulfate radicals; III: Cl-1 competes with methylene blue for sulfate radicals). This study is expected to provide valuable information to improve in situ remediation of dye-contaminated wastewater in the existence of natural organic matters.