Novel determination method for chemical oxygen demand in water based on sulphate radical digestion and turbidimetry

Sulphate radical-based advanced oxidation processes (SR-AOPs) have gained considerable popularity in the fields of organic contaminant degradation and industrial wastewater treatment. However, there are few reports focusing on study and application of such promising technology in determination or online monitoring of chemical oxygen demand (COD) in water quality. Herein, a novel determination method of COD based on photoactivated SR-AOPs and barium sulphate turbidimetry is proposed, in which, sulphate radicals (SO4 center dot-) are mainly responsible for the digestion of organic pollutants, not hydroxyl radicals (center dot OH). For improving the precision and accuracy of this determination method, all the parameters affecting on the digestion and detection were investigated. Performance verification results showed that this method has a good linearity (R-2 = 0.9988), precision (2.26%), accuracy (0.43%) and low method detection limit (2.4431 mg/L) within a range of 5 similar to 200 mg/L, under the optimised process conditions.