Oxidation of clofibric acid in aqueous solution using a non-thermal plasma discharge or gamma radiation

TL;DR

This study compares the effectiveness of non-thermal plasma and gamma radiation in degrading the pharmaceutical compound clofibric acid in water, revealing differences in mineralization and energy efficiency.

Contribution

It introduces a new kinetic model for CFA degradation and compares two advanced oxidation technologies in terms of efficiency and by-products.

Findings

Gamma radiation achieves higher energy yield.

Limited mineralization despite high CFA conversion.

Degradation follows a quasi-exponential decay model.

Abstract

In this work, we study degradation of clofibric acid (CFA) in aqueous solution using either ionizing radiation from a $^{60}$Co source or a non-thermal plasma produced by discharges in the air above the solution. The results obtained with the two technologies are compared in terms of effectiveness of CFA degradation and its by-products. In both cases the CFA degradation follows a quasi-exponential decay in time well modelled by a kinetic scheme which considers the competition between CFA and all reaction intermediates for the reactive species generated in solution as well as the amount of the end product formed. A new degradation law is deduced to explain the results. Although the end-product CO$_2$ was detected and the CFA conversion found to be very high under the studied conditions, HPLC analysis reveals several degradation intermediates still bearing the aromatic ring with the chlorine substituent. The extent of mineralization is rather limited. The energy yield is found to be higher in the gamma radiation experiments.