Evaluating the Efficiency of the Fenton-Ultrasonic Process in Degradation of Trihalomethanes Precursors from Aqueous Environments Using Zero Iron by Response Surface Method

Background: The reaction of natural organic matters (NOMs) with chlorine in the conventional disinfection process results in disinfection by-products (DBP) such as trihalomethanes and haloacetic acids. Due to the potential health risks of trihalomethanes for public health, it has attracted a lot of attention. The purpose of this study is to investigate the performance of combined Fenton-ultrasonic processes in removing the precursors of trihalomethanes from aqueous environments using zero iron. Method: In this procedure, the effect of independent variables including initial concentration of pollutant, reaction time, amount of catalyst, hydrogen peroxide dose, and pH, in the specified level was studied. The diagrams and figures to determine the kinetics of reactions will be drawn using Excel software and the optimal conditions of the process and analysis of variance will be done using Design Expert software and the CCD-RSM method. According to the output of this software, 340 samples were tested in this study. Results: The results demonstrate that with constant humic acid concentrations of 64.75 mg/L and catalyst concentrations of 106.76 mg/L as well as pH of 4.39, the highest degradation efficiency happens when the hydrogen peroxide and the reaction time are at their maximum values ​​of 35 mmol/L and 88.75 min in this condition, the amount of degradation efficiency has increased from 80% to 92%. The highest percent of humic acid degradation was 74.09% by using the Fenton process and it is 93.17% by using Fenton/ultrasonic process. Conclusion:  In the mentioned ultrasonic/Fenton process under laboratory conditions, iron ion as a catalyst reacts with an oxidant such as hydrogen peroxide in an acidic environment and produces hydroxyl radicals. The efficiency of this method is affected by various factors such as pH, concentration of iron and hydrogen peroxide, initial concentration of pollutant and reaction time.