Effects of radical scavengers on humic acid removal by electron beam irradiation

Despite many efforts to remove humic acid (HA) in water resources, this problem is not overcome, especially in underdeveloped countries. The aim of this study is to evaluate the effects of inorganic anions (Cl-) as radical scavenger on the efficacy of electron beam (EB) irradiation for the removal of HA from aqueous solutions. In this study, stock HA solution was prepared in alkaline condition; furthermore, different concentrations of anions were added to all HA samples. Here, the effect of different electron beam absorbed doses (1, 3, 6, 9, and 15kGy) on the removal of HA is studied. HA concentration was measured using UV-vis spectrophotometer at 254nm. The results showed that by increasing absorbed dose from 1 to 15kGy, HA removal efficiency increased from 28.2 to 77.7%, respectively. While, by increasing different inorganic anion concentrations from 25 to 100mg/L, the removal efficiency decreased. According to the results, nitrate has more inhibitory effect on the hydroxyl free radicals and HA removal efficiency in the presence of EB irradiation compared with chloride, bicarbonate, and sulfate anions. Furthermore, the kinetic model fitted the pseudo-second-order kinetics well.