A quantitative investigation of the reaction of ozone with p-toluenesulfonic acid in aqueous solution as a model compound for anionic detergents

Abstract

Abstract The reaction of ozone with p-toluenesulfonic acid (PTA) at initial pH 3 and 12 in aqueous solutions (25°C) has been studied at initial concentration 1 mmol l−1 and ozone dose is 24 mg min−1 1. and 11 mg min−1 1. respectively. The substrate elimination follow a zero order rate law. A 98% p-toluenesulfonic acid reduction requires at least 7 mol O3 per mol PTA, however to remove 100% PTA the consumption of ozone increases to 16 mmol O3 per mmol PTA. At this point a 28% reduction of DOC and a 74% COD reduction was achieved. The PTA decomposition is quicker at higher ozone flow rate, but the specific ozone consumption increases also. As oxidation products the following compounds were identified and their quantitative variations as function of ozonation time were measured: methylglyoxal, acetic acid, formic acid, pyruvic acid, oxalic acid, H2SO4 and H2O2. As byproduct mesoxalic acid was identified. At pH 12 lactic acid as a further oxidation product was observed. Balances of carbon, sulfur and methyl as well of the acid equivalents indicate one or more intermediates with a sulfonic acid group. These intermediates with a proportion of about 20% disappear after 100% PTA elimination. On account of these results a reaction mechanism is discussed.