Ultrasonic-Electrocoagulation method for nitrate removal from water

Abstract

Abstract Water contamination with nitrates is a serious problem due to the detrimental effects of nitrates on both human life and the global ecosystem; therefore, it is essential to remove nitrates using efficient methods. Accordingly, various methods have been used to treat nitrate-containing solutions, but recent studies focused on electrocoagulation (ELE) as it produces high quality water at low cost and it is environmentally friendly. However, passive layers are growing on the aluminum anodes after short time of treatment, which substantially affects the efficiency of ELE. In this investigation therefore, ultrasonic filed was used to remove these passive layers, and consequently improves the efficiency of ELE. This new method, ultrasonic-assisted ELE (U-ELE), was used to remove nitrates from water under various operational conditions. In particular, the impacts of water initial pH (WIP) (4.0-8.0), applied current densities (ACD) (6.0-9.0 mA/cm2), flow rates (FR) (60-100 ml/min), and initial nitrate concentrations (INC) (100-200 mg/L), which were optimized using the Central Composite Design (CCD). The ultrasonic irradiation time (UT) has been kept at 10 minutes for all experiments. The best possible removal of nitrate using only ELE method was about 77% at WIP of 6, UT of 10 minutes, FR of 40 ml/min, INC of 150 mg/l and ACD of 7.5mA/cm2. However, it was found that exerting ultrasonic for 10 minutes, U-ELE method, has increased nitrates removal to 87.80% under the same conditions of ELE treatment.