Photoconversion of endocrine disruptors (parabens) using zinc oxide photocatalyst

Abstract

Parabens are widely used as preservatives in drugs, cosmetic products, and foodstuffs. They are found in water bodies, food stuffs, cosmetics, pharmaceutical and personal care products. These parabens cause breast cancer and reproductive issues due to their absorption through the skin. Safety concerns have recently increased due to their potential health risks associated with exposure to these parabens. The purpose of this study is to photoconvert ethylparaben, a member of the paraben’s family, and a potential endocrine disruptor into less toxic substances using cost effective and efficient methods involving light. Photocatalytic degradation experiments were carried out in the sunlight and UV light irradiation under magnetic stirring conditions. HPLC analysis was done and it was found out that the ethylparaben used was pure. UV-Visible absorption spectra analysis was done to monitor the degradation pattern and the maximum absorption wavelength was =256 nm for different concentrations. Kinetic study conducted gave the apparent rate constant to be 0.0041014 molL-1min-1, the absorption coefficient was 0.56874 mol-1 and R2 = 0.9959 using the Langmuir–Hinshelwood (L–H) kinetic model. The photocatalytic reaction obeys the first order kinetics as R2 was greater than 0.96. The degradation % of the Sunlight/ZnO was 63.16 % and that of the UV-Vis/ZnO was 82.2 % for a concentration of 0.0361 mM. The degradation of ethylparaben was less efficient in acidic medium and highly efficient in basic medium. At pH 10.4 (basic), the degradation percentage was 73.9 % and at pH 3.3 (acidic), the degradation percentage was 4.87%. The natural solution pH was 6.7, gave a degradation % of 63.16%. GC-MS analysis was done and some of the products and their mass to charge ratio (m/z) were obtained.