Use of ultraviolet and ultraviolet /peroxide hydrogen processes for degradation of humic substances from aqueous solutions

Abstract

In this study, the degradation of humic acid was studied using advanced photochemical oxidation by exposing humic acid aqueous solution with low-pressure mercury vapor lamp as a UV light source after the addition of hydrogen peroxide. The effect of different parameters such as H 2 O 2 dosage, pH, and initial concentration of humic acid on the removal effi ciency of UV/H 2 O 2 was evaluated and investigated in detail. Increase of initial H 2 O 2 dosage (up to optimum dosage) and also increase of humic acid concentration resulted in the decrease of humic acid degradation. The residual concentrations of humic acid were measured for assessing the process performance and understanding the process reaction behavior. The results showed that humic acid was degradable in the presence of hydrogen peroxide under UV irradiation. In the absence of H 2 O 2 , the degradation effi ciency was very negligible. The results show 91% humic acid removal in 60 min of reaction time when 30 mmol L-1 of H 2 O 2 aqueous solution was added to the solution compared with only 20% of removal in similar conditions and in the absence of H 2 O 2. Investigation of the kinetics of the UV/H 2 O 2 process demonstrated that the semi-log plot of the humic acid concentration versus time was linear, which suggested a fi rst order reaction.