The comparative assessment of photolysis, sorption and photocatalysis processes to humic acids removal from water [articol]

Abstract

Taking into account the photosensitive character of humic acids and the sorption as prerequisite step to reach an effective degradation by photocatalysis application for removal of humic acids from water, the assessment of photolysis and adsorption contribution to overall photocalysis process using TiO2-modified zeolite catalyst with 1% TiO2, w/w (TiO2-Z) is necessary. The results obtained at low concentration of humic acid (25 mg·L-1) using TiO2-Z, indicated that in comparison with adsorption process, the photocatalysis application did not improve removed amount of humic acid. Though, the functionalization of zeolite with TiO2 led to improve the adsorption capacity for humic acid. The best results were achieved for photolysis due to fact that humic acids act as natural photosensitizers. At higher concentrations of humic acids (100 mg·L-1), better results were achieved on TiO2-Z for photocatalytic process (41.8 mg) than the sorption (28.7 mg) and photolysis (27.3 mg) processes, but no a cumulative effect of sorption and photolysis was noticed. The similar results obtained through application of photocatalysis using both TiO2-Z and Z-Na catalysts and taking into account the photoinert character of Z-Na and enhanced sorption capacity of TiO2-Z for HA proved the significant contribution of both photolysis and sorption processes.