Photocatalytic Degradation of Humic Acids Using LaFeO3

Abstract

TiO2 photocatalytic degradation of dissolved organic matter (DOM), namely humic substances composed of humic (HA) and fulvic acids, has been investigated for decades. However, the application of non-TiO2 photocatalysis for this purpose has only received recent attention. Aiming to fill this gap, this study was performed to elucidate the photocatalytic degradation of HAs using the novel photocatalyst LaFeO3 (LF) under simulated solar light irradiation. HA was selectively fractionated by ultrafiltration to two different molecular size fractions representing high molecular fraction as 100 kDa and lower molecular size fraction comprised of humic components expressing size fractions smaller than 30 kDa. Photocatalyst LF was prepared by the citrate auto-combustion method and characterized by using various techniques and Brunauer–Emmett–Teller (BET) surface area. Ultraviolet (UV)-vis and excitation-emission matrix (EEM) fluorescence spectroscopic features were used to characterize the treated HA and photocatalytic mineralization extend was followed by dissolved organic carbon (DOC) contents. Photocatalytic performance of LF was compared to the metal modified version as Cu-doped LF. Highest mineralization was achieved upon the use of a photocatalyst dose of 0.25 mg/mL of LaFe0.90Cu0.10O3−δ (Cu-LF) for 30 kDaHA, whereas lowest mineralization was attained for 100 kDaHA upon the use of LF. Photocatalytic degradation kinetics indicated the possible use of LF and Cu-LF for the degradation of HA.