Determination of hexavalent chromium in solid waste hypochlorite treated leachates by headspace gas chromatography

Abstract

This article reported a new headspace gas chromatography (HS-GC) for the determination of hexavalent chromium Cr(VI) in solid waste hypochlorite treated leachates. The method was based on the reaction between Cr(VI) and an excess potassium hydrogen oxalate in a pH buffer solution in the headspace vial at 60℃, followed by HS-GC measuring the carbon dioxide produced. To eliminate the interference from hypochlorite in the leachates, two reaction times, i.e., 6 and 7 min, were selected. At pH = 1.50, it was found that the reaction of oxalate with Cr(VI) was partly achieved in 6 min and fully achieved in 7 min, and the reaction of oxalate with hypochlorite was achieved in 6 min. Based on two separate HS-GC measurement on the CO2 signals at 6 and 7, respectively, the amount of Cr(VI) in the sample can be calculated. The results showed that the present method has a good measurement precision (RSD<4.70%) and accuracy (the recoveries were in the range of 92.5% - 107% and the relative differences were within 8.66% when compared with the data measured by the reference method). The present method can become a valuable tool in the Cr(VI) containing solid waste treatment related applications.