Enhanced Photocatalytic Degradation of Humic Acid in Fe2O3 Aqueous Suspension by Increasing Ca²+ Strength under a Blue Light Irradiation

Abstract-This study aimed at improving the photocatalytic oxidation of humic acids (HA) in α-Fe
₂
O
₃
suspensions by adding calcium cationic ion (Ca
²⁺
). A visible light photocatalyst of α-Fe
₂
O
₃
was prepared by co-precipitation method and characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). First a set of tests was conducted in the dark to study the adsorption of HA onto α-Fe
₂
O
₃
in suspensions at different calcium concentrations. Then the photocatalytic degradation of HA under blue light irradiation was investigated in the presence of calcium ion. A set of comparison of photolysis, adsorption, photocatalysis was also studied. The results showed that the adsorption behavior between HA and α-Fe
₂
O
₃
played a very important role during the photocatalytic oxidation process. The photocatalytic oxidation could be enhanced at neutral pH by increasing the cation strength. The present findings may be valuable for the treatment of HA in natural water under solar light irradiation.