Rapid Photodegradation of Methyl Orange (MO) Assisted with Cu(II) and Tartaric Acid.

Jing Guo,Ying Shi,Xue Chen,Yeqing Lan,Chao Qin,Jingdong Mao

doi:10.1371/journal.pone.0134298

Abstract

Cu(II) and organic carboxylic acids, existing extensively in soil and aquatic environments, can form complexes that may play an important role in the photodegradation of organic contaminants. In this paper, the catalytic role of Cu(II) in the removal of methyl orange (MO) in the presence of tartaric acid with light was investigated through batch experiments. The results demonstrate that the introduction of Cu(II) could markedly enhance the photodegradation of MO. In addition, high initial concentrations of Cu(II) and tartaric acid benefited the decomposition of MO. The most rapid removal of MO assisted by Cu(II) was achieved at pH 3. The formation of Cu(II)-tartaric acid complexes was assumed to be the key factor, generating hydroxyl radicals (•OH) and other oxidizing free radicals under irradiation through a ligand-to-metal charge-transfer pathway that was responsible for the efficient degradation of MO. Some intermediates in the reaction system were also detected to support this reaction mechanism.

Highlights

Advanced oxidation processes (AOPs), which have superseded biological procedures proven to be ineffective for the treatment of some contaminated effluents under certain conditions, have been successfully demonstrated as efficient methods of degradation of organic pollutants [1,2,3]
Zuo and Hoigne [6] noted that photolysis of Fe(III)-oxalato complexes could lead to the formation of hydrogen peroxide (H2O2), which could react with Fe(II) to further yield Fe(III) and a hydroxyl radical (ÁOH)
A small increase in the methyl orange (MO) degradation efficiency (~9%) in the two-component system of MO and tartaric acid was observed, which was attributed to the possible oxidants (e.g., H2O2 and some free radicals) that were produced through the photolysis of tartaric acid

Summary

Introduction

Advanced oxidation processes (AOPs), which have superseded biological procedures proven to be ineffective for the treatment of some contaminated effluents under certain conditions, have been successfully demonstrated as efficient methods of degradation of organic pollutants [1,2,3]. UV-vis irradiation improves the efficiency of the process Alternative techniques such as photocatalysis of the novel iron sources, and complexes of Fe(III) and carboxylate anions for the degradation of organic contaminants have received considerable attention [6,7,8,9,10,11]. Hydroxyl radicals could non-selectively mineralize azo dyes to carbon dioxide and water due to their high oxidation potential [12]

Methods

Results

Conclusion