Photocatalytic Bactericidal Performance of LaFeO3 under Solar Light in the Presence of Natural Organic Matter: Spectroscopic and Mechanistic Evaluation

Nazmiye Cemre Birben,Renato Pelosato,Nazli Turkten,Ezgi Lale,Miray Bekbolet,Isabella Natali Sora

doi:10.3390/w13192785

Abstract

Solar photocatalytic inactivation (SPCI) of E. coli as the indicator microorganism using LaFeO3 (LF) has already been investigated under various experimental conditions, excluding any role of natural organic matter (NOM). However, comprehensive information about the behavior of E. coli and its inactivation mechanism in the presence of NOM, as well as the behavior of NOM components via solar photocatalysis using LF as a photocatalyst, has prime importance in understanding real natural water environments. Therefore, in this study, further assessment was devoted to explore the influence of various NOM representatives on the SPCI of E. coli by using LF as a novel non-TiO2 photocatalyst. The influence of NOM as well as its sub-components, such as humic acids (HA) and fulvic acids (FA), was also investigated to understand different NOM-related constituents of real natural water conditions. In addition to spectroscopic and mechanistic investigations of cell-derived organics, excitation emission matrix (EEM) fluorescence spectra with parallel factor multiway analysis (PARAFAC) modeling revealed further information about the occurrence and/or disappearance of NOM-related and bacteria-related fluorophores upon LF SPCI. Both the kinetics as well as the mechanism of the LF SPCI of E. coli in the presence of NOM compounds displayed substrate-specific variations under all conditions.

Highlights

Natural organic matter (NOM) is known to be originated from the residues of plants and microbial components or could be derived from water cycles and/or various decomposition pathways [1]
NOM in natural waters comprises a variety of amphiphilic components, of which the major fraction (>50% of total organic carbon) is related to hydrophobic acids, including humic acids (HA), fulvic acids (FA), and humin
Almost all of the bacteria were inactivated in 30 min following the trend Suwannee River fulvic acids (SRFA) ≈ Suwannee River humic acids (SRHA)

Summary

Introduction

Natural organic matter (NOM) is known to be originated from the residues of plants and microbial components or could be derived from water cycles and/or various decomposition pathways [1]. NOM in natural waters comprises a variety of amphiphilic components, of which the major fraction (>50% of total organic carbon) is related to hydrophobic acids, including humic acids (HA), fulvic acids (FA), and humin. Differentiation of HA and FA could be ascribed to variations in molecular weight, the number of functional groups (carboxyl and phenolic OH), and the extent of polymerization. NOM components and other organic and inorganic constituents of aquatic environments. Being regarded as the major organic fraction of natural water sources, NOM components would have a critical function in the physicochemical as well as photochemical reaction pathways. The performance of unit processes, the application of chemicals in water treatment processes, and the biological stability of water are all dependent on the

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