The removal efficiency and degradation pathway of IPMP and IBMP in aqueous solution during ozonization

Abstract

2-isopropyl-3-methoxypyrazine (IPMP) and 2-isobutyl-3-methoxypyrazine (IBMP) are two of main taste and odor compounds in drinking water. The removal efficiency and possible degradation pathway of IPMP and IBMP by ozonization were studied by evaluating experimental parameters including ozonization time, initial concentration of IPMP and IBMP, and solution pH. At pH 6.8 the removal efficiency of IPMP and IBMP (100 ng L−1) were both found over 90% within 15 min ozonization, and a higher pH value (8.6) helped to accelerate the degradation in some degree. In both neutral and acidic media, the degradation followed the pseudo first order kinetics. In contrast, at lower pH range, e.g. pH 5.0, more than 10% of the title compounds were still existing even after 30 min ozonization. With increasing the initial concentration from 100 to 200 and to 400 ng L−1, the removal efficiency of the title compounds was decreased successively. The intermediate by-products of IPMP and IBMP by ozonization were mainly acid esters and carboxylic acids as identified by GC–MS, and accordingly the possible degradation pathway was proposed.