A method for removing persulfate interference in the analysis of the chemical oxygen demand in wastewater

• Published in: Environmental chemistry letters Vol. 17; no. 2; pp. 1085 - 1089
• Main Authors: Yang, Jieyang, Liu, Zile, Zeng, Zequan, Huang, Zhanggen, Cui, Yan
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.06.2019; Springer Nature B.V
• Subjects: Analytical Chemistry; Chemical oxygen demand; Coal industry; Coal industry wastewaters; Contamination; Deviation; Earth and Environmental Science; Ecotoxicology; Environment; Environmental Chemistry; Geochemistry; heat; Heating; industrial wastewater; Interference; Methods; Organic chemistry; Original Paper; Oxidation; phenol; Phenols; Pollution; Potassium; Potassium persulfate; Sodium; Sodium sulfite; Sulfates; Sulfite; Treated water; Wastewater; Wastewater treatment; Water analysis; Water sampling; Advanced oxidation processes; Na; heating treatment; Chemical oxygen demand; Interference elimination; Calibration curve method; Persulfate; SO
• ISSN: 1610-3653; 1610-3661
• DOI: 10.1007/s10311-018-00832-2

In recent years, sulfate radical-based advanced oxidation has received increasing attention for the treatment of water and wastewater. However, the chemical oxygen demand (COD), a common measure of gross organic contamination, is subject to interference from residual persulfate in the treated water. In this study, a new method, based on addition of sodium sulfite (Na 2 SO 3 ) and heating, has been developed to eliminate the interference of remaining potassium persulfate (PS k ) on COD analysis. Results of batch experiments show that potassium persulfate can be efficiently removed with molar ratio of Na 2 SO 3 /potassium persulfate ≥ 2 and heating at 90 °C for 60 min. This method (Na 2 SO 3 –heating treatment) was further tested in a phenol wastewater and a coal industry wastewater. The deviation of COD values of Na 2 SO 3 –heating treatment was lower than  5%, which was much lower than the deviation of the calibration curve method, of more than 14%. This new method could be applied to water samples containing persulfate and organic substances and help researchers to accurately evaluate performance of sulfate radical-based advanced oxidation processes.