Photocatalytic Bactericidal Performance of LaFeO3 under Solar Light: Kinetics, Spectroscopic and Mechanistic Evaluation

Abstract

Lanthanum orthoferrites are a versatile class of catalysts. Here, the photocatalytic bactericidal performance of LaFeO3 (LF) to inactivate pathogenic microorganisms, i.e., Escherichia coli (E. coli), in water under simulated solar irradiation conditions was investigated. Various competing and contributing factors were covered to visualize the reaction medium consisting of E. coli K12 cells, organic sub-fractions formed by cell destruction, and LF surface. LF solar photocatalytic inactivation (SPCI) kinetics revealed the highest inactivation rate in ultrapure water as expected, followed by distilled water (DW), aqueous solution containing anions and cations (WM) and saline solution (SS). Characterization of the released organic matter was achieved by UV-vis and fluorescence spectroscopic techniques as well as organic carbon contents (DOC). Upon SPCI, significant amounts of K+ along with released protein contents were detected expressing cell wall destruction and lysis. Under the specified experimental conditions, in the presence of released intracellular organic and inorganic components via cell lysis, a significant count of E. coli was still present in SS, whereas almost all bacteria were removed in other matrices due to various challenging reasons. Based on the presented data, SPCI of E. coli using LF as a novel photocatalyst was successfully demonstrated as an alternative and promising method for disinfection purposes.

New Perspectives in Photocatalytic Water Treatment

“…The grant provided to Bekbolet while a visiting professor at the University of Bergamo, Department of Engineering and Applied Sciences, in May 2019, is highly acknowledged. This cooperation supported significant contributions to the realization of the studies denoted by [2,3].…”

“…In this respect, two complementary studies were presented by Birben and colleagues covering the effect of NOM analog compounds [2,3]. Besides sole E. coli inactivation kinetics, characterization of the released organic matter was also presented by UV-vis, fluorescence, and FTIR spectroscopic techniques as well as mineralization extents.…”

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

“…The ashes were then calcined at 600 • C to get rid of the residual organic matter. More detailed information about the preparation and characterization of LF has been previously presented elsewhere [6][7][8].…”

“…2.1.3. Indicator Organism: E. coli An E. coli K12 (ATCC 23716) suspension was prepared in Luria-Bertani broth displaying an initial count of colony forming units as 10 5 -10 6 CFU/mL [6].…”

“…Among perovskites, lanthanum orthoferrite (LaFeO 3 ) is reported to be a promising solar photocatalyst. Detailed information related to the application of perovskites and perovskite-like materials to solar photocatalytic antimicrobial activities was presented previously by Birben et al [6]. Moreover, in this previous study, solar photocatalytic inactivation kinetics of E. coli using LaFeO 3 as the photocatalyst was investigated profoundly by the consideration of various aqueous medium matrices.…”