TiO2-assisted photocatalytic degradation of humic acids: effect of copper ions

摘要

The present study investigated the removal efficiency of aqueous humic acid solutions by TiO2nphotocatalytic degradation in the presence of Cu(II) species. The pseudo-first-order kineticsnrevealed rate constants as 9.87 ￡ 1023, 7.19 ￡ 1023, 3.81 ￡ 1023 min21 for Color436, UV254 andnTOC, respectively. Comparatively, lower rate constants were attained with respect tonphotocatalytic degradation of humic acid. Considering the source-dependent diverse chemicalnand spectral characteristics of NOM, a particular interaction would be expected for humic acidnwith Cu(II) species (0.1mgL21). The presence of copper ions significantly altered thenphotocatalytic degradation kinetics of humic acids in relation to the concentration effects ofnhumic acid as expressed by spectroscopic parameters and TOC. Batch equilibrium adsorptionnexperiments revealed a distinct Langmuirian-type adsorptive behavior of humic acid onto TiO2nboth in terms of UV254 and Color436 and a C-type adsorption isotherm was attained for TOC.nKF values displayed an inconsistent effect of Cu(II) species, while adsorption intensity factorn1 , 1 denoted a prevailing favorable type of adsorption for Color436 and UV254. Because of thenrole of intra- and intermolecular interactions between copper ions and humic molecular sizenfractions, spectroscopic techniques were also employed for the assessment of the adsorption asnwell as photocatalytic degradation efficiencies.