Study On Determination Of Inorganic Chlorine Species In Water By Ion Chromatography

Chlorine- containing oxidants include chlorine, hypochlorite, chlorine dioxide, chlorite and chloramines. They were found wide use in different applications such as fabric and pulp bleaching, wastewater treatment, drinking water disinfecting, industrial circle water for cooling sterilizing and so on. Toxincological research on by-product in the process of using these oxidants indicated that they have more or less effect on environment and human health. Trihalomethane(THMs) and dioxins in chlorine-treated water are dangerous carcinogen. As a substitute, chlorine dioxide is more safe, but studies showed that by-products in chlorine dioxide-treated water were suspected to be health hazards and so ClO2, ClO2,ClO3 concentrations are currently under consideration for regulation. Therefore, It is important that a rapid and sensitive analytical method is available for quantifying chlorine species in water.In this paper, a simple, effective and precise ion chromatography method has been developed for the determination of chlorine dioxide, chlorine, chlorite and chlorate in water. In neutral medium containing NaHCO3 buffer, chlorine dioxide and chlorine were reduced to chlorite and chloride by added sodium nitrite. Chlorine dioxide and chlorine were determined by IC determination of varied chlorite and nitrate. Thiacetamide(TAA) was used as masking agent for chlorite. The detection limits of C1O2, Cl2, C1O2 and C1O3 were respectively 0.15,0.13,0.072,0.14 mg/L, relative standard deviation at the 1 mg/L level were respectively 1.2, 4.3, 2.0, 3.9%, relative error were respectively 5.5, 4.4, 4.5, 2.3%, linear range were respectively 0.5-20, 0.8-50, 0.3-30, 0.8-50 mg/L. Compared with continuous iodimetry, the analytical method described in this paper was more suitable for analysis of low concentration of chlorine, chlorine dioxide, chlorite and chlorate.A application of this IC procedure was determination of chlorine species in pool water which was treated by chlorine dioxide disinfectant to kill algate and harmful microorganisms. Results showed there were ClO2, Cl2,ClO2 in the sample, Recovery of analyte from actual sample ranged between 96 and 100% with R.S.D less than 3%. The results were satisfactory.Another application of this IC procedure was determination of inorganic chlorine species after reactive brilliant red K-2BP solution were decolored by chlorine dioxide.Results indicated that by-products of chlorine dioxide were mainly ClO2 and ClO3. There were a few Cl2 in acidic media. Similarly, the IC method had good recovery, which was 91.5-104.5%. This paper also investigated stability of inorganic chlorine species. Chlorite were unstable in weak acidic media and gradually separated. Chlorate were stable in weak acidic media or alkalescent media and didn't react with products of the dye.