KCS

The in situ chemical oxidation (ISCO) technique for the treatment of various chemical contaminants like halogenated aromatic and aliphatic compounds, other emerging contaminants and heavy metals is a new area for environmental chemists. An important and emerging ISCO agents is persulfate ion, which can produce strong oxidizing species like sulfate radical and hydroxyl radical for the fast degradation of organic contaminants in the presence of various activators. The most common and economically efficient activator is transition metals and their minerals. There are many reports on the activation of persulfate by zero valent iron nano particles (ZVI) also. However, the nZVI would completely exhaust within a short period of time and therefore their reusability is questioned. In this study we adopt a multicomponent nanoparticle, Fe/FeS for the activation of persulfate ion for the degradation of most abundant organic contaminant benzoic acid from aqueous medium. The degradation efficiency of Fe/FeS-PS system is compared with that in the presence of various ligands like EDTA, NTA, oxalic acid and citric acid at three different [Fe/FeS]:[Ligand] concentration like, 1:0.5, 1:1 and 1:2. The iron dissolution study (both Fe²⁺ and total dissolved iron) were also carried out in the presence of these ligands. The degradation efficiency at lower concentration of ligands is found to be in the order EDTA > citric acid > oxalic acid >NTA. Moreover, when the concentration of the ligands is increased the order becomes citric acid > oxalic acid > NTA > EDTA. This difference in the degradation is mainly visible in the iron dissolution study. The Fe²⁺ and the total dissolved concentration in the presence of ligands are in the order citric acid > oxalic acid > NTA > EDTA. The recent studies reported that the Fe(III)-ligands complex could enhance the formation of reactive oxygen species and there by enhanced the reaction rate. This report also supports our observed result.