Comparison of radical-driven technologies applied for paraben mixture degradation: mechanism, biodegradability, toxicity and cost assessment

Marta Gmurek,João F Gomes,Rosa M Quinta-Ferreira,Rui C Martins

doi:10.1007/s11356-019-06703-9

Abstract

Parabens (esters of p-hydroxybenzoic acid) are xenobiosis belonging to endocrine disruptors and commonly used as a preservative in cosmetics, food, pharmaceutical, and personal care products. Their wide use is leading to their appearance in water and wastewater in the range from ng/L to mg/L. In fact, the toxicity of benzylparaben is comparable to bisphenol A. Therefore, it is important to find not only effective but also ecofriendly methods for their removal from aqueous environment since the traditional wastewater treatment approaches are ineffective. Herein, for the first time, such extended comparison of several radical-driven technologies for paraben mixture degradation is presented. The detailed evaluation included (1) comparison of ozone and hydroxyl peroxide processes; (2) comparison of catalytic and photocatalytic processes (including photocatalytic ozonation); (3) characterisation of catalysts using SEM, XRD, DRS, XPS techniques and BET isotherm; (4) mineralisation, biodegradability and toxicity assessment; and (5) cost assessment. O3, H2O2/Fe2+, H2O2/UVC, O3/H2O2, O3/UVA, O3/H2O2/UVA, UVA/catalyst, O3/catalyst and O3/UVA/catalyst were selected from advanced oxidation processes to degrade parabens as well as to decrease its toxicity towards Aliivibrio fischeri, Corbicula fluminea and Lepidium sativum. Research was focused on the photocatalytic process involving visible light (UVA and natural sunlight) and TiO2 catalysts modified by different metals (Ag, Pt, Pd, Au). Photocatalytic oxidation showed the lowest efficiency, while in combining ozone with catalysis and photocatalysis process, degradation efficiency and toxicity removal were improved. Photocatalytic ozonation slightly improved degradation efficiency but appreciably decreased transferred ozone dose (TOD). Results indicate that the degradation pathway is different, or different transformation products (TPs) could be formed, despite that the hydroxyl radicals are the main oxidant.Graphical abstract

Highlights

Xenobiotics are organic compounds foreign to living organisms, which do not occur in the form of neither primary nor secondary metabolites
They are included in personal protective equipment or pharmaceuticals, referred as pharmaceuticals and personal care products (PPCPs), whose presence in water reservoirs is a serious environmental problem (Yang et al 2017)
The concentration of paraben in the mixture was followed by HPLC (UFLC, Shimadzu) with a C18 (SiliaChrom) column at 40 °C

Summary

Introduction

Xenobiotics are organic compounds foreign to living organisms, which do not occur in the form of neither primary nor secondary metabolites. While some xenobiotics are natural compounds, most of them are from anthropogenic source (Hashmi et al 2017; Yang et al 2017). They are included in personal protective equipment or pharmaceuticals, referred as pharmaceuticals and personal care products (PPCPs), whose presence in water reservoirs is a serious environmental problem (Yang et al 2017). Many of xenobiotics have been classified as compounds that disrupt the hormonal balance of the body (xenooestrogenic or endocrine compounds) called endocrine-disrupting compounds (EDCs) (Nakada et al 2007; Esplugas et al 2007; Giulivo et al 2016; Wang and Wang 2016). Numerous studies have confirmed the harmful effect of xenobiotics on disturbing the hormonal balance of organisms, hepatotoxic effects damaging liver cells and the possibility of producing free radicals which cause oxidative stress (Vilela et al 2018)

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