Electrocoagulation using a novel reactor design for removal of selected inorganic pullutants

Abstract

The issue of water scarcity due to the effects of climate change and rapid population growth poses a serious threat in many countries in the world, especially in arid regions such as the Middle East. Water treatment has become increasingly important for drinking water supplies. In the present study, the selected types of inorganic pollutants such as sulfate (SO4 2−), chloride (Cl−), bromine (Br−) were eliminated by using a novel electrocoagulation (EC) reactor. Several parameters were estimated to set the optimum operating conditions in a batch system. These parameters effects such as rotation speed (rpm), reaction time (min), current density (mA/cm2), inter space distance (cm), pH solution, recirculation flow rate (L/hour), and continuous flow system (L/min) were optimized. This study critically discussed major and minor reactions of electrocoagulation technique with several significant operational parameters, emerging designs of EC cell, and operating conditions. It was found that the optimization of the operating parameters has significantly enhanced the efficiency of the EC technique and reduce overall operating costs. The aim of this study was to evaluate the ability of the electrocoagulation (EC) process with combined aluminum electrodes in removing some types of inorganic pollutants from water samples collected at Sawa Lake, Al-Muthanna, Iraq. Initial results showed the following optimum operating conditions: I = 2 mA/cm2, RT = 80 min, pH = 8, T = 25 °C, IED = 1 cm and Mrpm = 500. The optimum value of removal efficiency of SO4 2−, Cl− and Br− and were 90%, 93% and 92% respectively. Operation cost during primarily step of the study was 8.49 (kwh/m3) and 0.1 (kg/m3) for each of Energy consumption and Electrode consumption respectively. A novel rotating anode-based reactor (RAR) was designed to evaluate and improve its effectiveness in removing selected types of inorganic pollutants. Two configurations of an impeller’s rotating anode (rod and plate) with various operation factors, such as operating time (min), rotating speed (rpm), current density (mA/cm2), temperature (°C), pH, and inter-electrode space (cm), were used in the EC process. Results showed that the optimal adjustments for treating lake water were carried out at the following conditions: 150 and 75 rpm rotating speeds for the impeller’s rod anode and plate anode designs, respectively; 2 mA/cm2 current density (I), 1 cm2 inter-electrode space, 25 °C temperature, 10 min operation time, and pH 8. The results indicated that EC technology with impeller plates of rotating anode can be considered a very cost-effective technique for treating lake water. Moreover, EC continuous reactor with a rotating anode was used and the effect of impellers plate anode was validated. Several variables were estimated to set the optimum operating conditions in a batch system. These variable effects such as rotation speed (rpm), retention time (min), recirculation flow rate, current density (mA/cm2), inter space distance (cm), pH solution, and continuous flow system were optimized. These operational parameters were set at 75 rpm, 10 min, 8 L/hour, 2 mA/cm2, pH 8, 1 cm2, and 0.25 L/min, respectively. Electrodes geometry has been recommended to be used to reduce a passivation phenomenon, promote the conductivity of the cell, and reduce energy consumption. Moreover, the integration of EC technique with other advanced technologies (microwaves and ultrasonic) has been recommended to achieve high removal efficiencies and to remove refractory pollutants. In this thesis, several challenges and gaps were identified, and insights for future development were discussed. We recommend that future studies need to investigate the effect of emerging parameters i.e. rotating electrodes on the electrocoagulation process.