This study aimed at investigating the photocatalytic degradation of humic acid (HA) as a representative of natural organic matter (NOM) by using Ce-doped ZnO as a novel material. Following photocatalysis, HA degradation was characterized by specified UV-vis and fluorescence spectroscopic parameters as well as by the dissolved organic carbon (NPOC) content. Excitation–Emission Matrix (EEM) fluorescence features were also evaluated by using advanced techniques. Comparison of Ce-doped ZnO photocatalysis to TiO₂ P-25 photocatalytic treatment of the HA samples was elucidated under similar experimental conditions. Kinetic modeling of the photocatalytic removal of HA expressed promising results indicating that Ce-doped ZnO could serve as an efficient catalyst for the degradation of NOM.

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.