Titanium dioxide-mediated photocatalytic degradation of humic acid under natural sunlight

In this article, photocatalytic degradation of humic acid, a predominant type of natural organic matter present in ground and surface waters, was conducted using a commercial titanium dioxide catalyst under natural sunlight irradiation in a batch photoreactor. Various parameters, such as photocatalyst loading, pH value, irradiation intensity, initial concentration, and illumination time, had a significant influence on humic acid removal. The adsorption isotherm of TiO2 dosage fit to Langmuir's isotherm equation well, and the reaction kinetics of initial dissolved organic carbon (DOC) concentration increased with the increase of TiO2 dosage but decreased with the increase of initial DOC. The mineralization of humic acid revealed that the large molecular weight organics with aromatic and hydrophobic properties were removed, while the most persistent components were the shortest UV-absorbing and hydrophilic low-molecular-weight compounds. This study indicates that the solar/ TiO2 photocatalytic degradation is a promising process for humic acid removal from water.