Elimination of Pb2+ through electrocoagulation: Applicability of adsorptive stripping voltammetry for monitoring the lead concentration during its elimination

Removal of inorganic pollutants using electrocoagulation technology: A review of emerging applications and mechanisms

Electrocoagulation (ECoag) technique has shown considerable potential as an effective method in separating different types of pollutants (including inorganic pollutants) from various sources of water at a lower cost, and that is environmentally friendly. The EC method's performance depends on several significant parameters, including current density, reactor geometry, pH, operation time, the gap between electrodes, and agitation speed. There are some challenges related to the ECoag technique, for example, energy consumption, and electrode passivation as well as its implementation at a larger scale. This review highlights the recent studies published about ECoag capacity to remove inorganic pollutants (including salts), the emerging reactors, and the effect of reactor geometry designs. In addition, this paper highlights the integration of the ECoag technique with other advanced technologies such as microwave and ultrasonic to achieve higher removal efficiencies. This paper also presents a critical discussion of the major and minor reactions of the electrocoagulation technique with several significant operational parameters, emerging designs of the ECoag cell, operating conditions, and techno-economic analysis. Our review concluded that optimizing the operating parameters significantly enhanced the efficiency of the ECoag technique and reduced overall operating costs. Electrodes geometry has been recommended to minimize the passivation phenomenon, promote the conductivity of the cell, and reduce energy consumption. In this review, several challenges and gaps were identified, and insights for future development were discussed. We recommend that future studies investigate the effect of other emerging parameters like perforated and ball electrodes on the ECoag technique.

Study on the treatment of Cu2+-organic compound wastewater by electro-Fenton coupled pulsed AC coagulation

Electro-Fenton (EF) coupled with Pulsed alternating current coagulation (PACC) is an effective technology for the treatment of Cu²⁺-organic wastewater. In this study, the removal efficiency (R_e), electrical energy consumption (EEC) and removal mechanism of Cu²⁺-organic were analyzed and the optimal operation parameters were determined. SEM, EDS, XRD and FTIR were used to characterize the morphology, elemental composition, crystal structure, function groups of sludge produced in the EF-PACC. UV, ESR and GC-MS were employed to determine concentration of organic matter, existence of OH, middle products of decomposed organic matter in EF-PACC, respectively. The results show that under the optimal conditions of initial pH = 2.5, current density (j) = 2 A/m², initial c(Cu²⁺) = 50 mg/L, c(chemical oxygen demand, COD) = 500 mg/L, c[H₂O₂] = 10 mL/L, frequency (f) = 1 Hz, t = 20 min, the R_e(Cu²⁺) can reach 99.59%. R_e(COD) is 90.21%, EEC 1.695 × 10^-1 kWh/m³, and the amount of produced sludge (W_s) is 0.9283 kg/m³. Compared with single EF and PACC processes, the order of treatment efficiency is EF-PACC > EF > PACC. EF-PACC technique was a highly effective method in the treatment of Cu²⁺-organic compound wastewater. The EF-PACC coupled process includes that electrolyzed Fe³⁺ produces electrocoagulation and OH produces degradation of organic compounds. The combined action of the two effects can effectively remove Cu²⁺-organic from wastewater.

Composite wastewater treatment by aerated electrocoagulation and modified peroxi-coagulation processes

Treatment of composite wastewater generating from the industrial estates is a great challenge. The present study examines the applicability of aerated electrocoagulation and modified peroxi-coagulation processes for removing color and COD from composite wastewater. Iron plates were used as anodes and cathodes in both electrochemical processes and experiments were carried out in a working volume of 2 L. Aeration enhanced the efficiency of electrocoagulation process significantly. More than 50% of COD and 60% of color were removed after 1 h of electrocoagulation process operated at pH 3 and applied voltage of 1 V. Efficiency of the modified peroxi-coagulation process was significantly higher than that of aerated electrocoagulation. COD and color removal efficiencies of the modified peroxi-coagulation process were found as 77.7% and 97%, respectively after 1 h of electrolysis operated at 1 V, solution pH 3 and 50 mM hydrogen peroxide addition. This improved efficiency of modified peroxi-coagulation compared to aerated electrocoagulation is mainly due to the attack of in-situ generated hydroxyl radicals.

Simultaneous removal of cadmium, zinc and manganese using electrocoagulation: Influence of operating parameters and electrolyte nature

In the present study, the influence of operating parameters and electrolyte nature on the simultaneous removal of toxic metals (cadmium, zinc and manganese) from synthetic smelting wastewater by batch electrocoagulation was investigated. This wastewater contained high concentrations of anion-cation electrolytes. Results indicated that the efficiency of heavy metals removal can be enhanced by increasing the solution pH and current density. The Fe-Fe electrode combination is more effective than the other combinations (Al-Al, Al-Fe and Fe-Al). The interaction of heavy metal ions showed that the increase of initial Zn²⁺ concentration adversely affects on Cd²⁺ removal. In addition, the single chloride system exhibits the optimum removal efficiency on Mn²⁺. Single sulfate and binary anion systems exert a more positive effect on Cd²⁺ and Zn²⁺ removal because of the stronger charge neutralization and destabilization of iron hydroxide flocs. Increases of Ca²⁺ and Mg²⁺ ions exert a significant negative effect on metal removal. However, the addition of a small amount of sodium chloride into a high sulfate and hardness solution can accelerate the removal of heavy metals. Finally, the sludge samples generated from electrocoagulation were characterized by XRD and SEM-EDS analyses.

Removal of Pb, Cu, Cd, and Zn Present in Aqueous Solution Using Coupled Electrocoagulation-Phytoremediation Treatment

This study presents the results of a coupled electrocoagulation-phytoremediation treatment for the reduction of copper, cadmium, lead, and zinc, present in aqueous solution. The electrocoagulation was carried out in a batch reactor using aluminum electrodes in parallel arrangement; the optimal conditions were current density of 8 mA/cm2 and operating time of 180 minutes. For phytoremediation the macrophytes, Typha latifolia L., were used during seven days of treatment. The results indicated that the coupled treatment reduced metal concentrations by 99.2% Cu, 81.3% Cd, and 99.4% Pb, while Zn increased due to the natural concentrations of the plant used.

Continuous flow electrocoagulation in the treatment of wastewater from dairy industries

Dairy industry wastewater contains high levels of organic matter, consisting mainly of fat, protein and products of their partial microbial decomposition. In the present study, the use of continuous electrocoagulation is proposed for the primary treatment of dairy wastewater. The electrochemical treatment was carried out in a continuous flow cell with aluminum electrodes. The influence of the voltage, the distance between the electrodes and the hydraulic residence time (HRT) on the process performance was assessed, by measuring the removal of color, turbidity, total organic carbon (TOC) and chemical oxygen demand (COD). The optimum voltage, distance between the electrodes and HRT were 10 V, 1 cm and 90 min, respectively, yielding a current density of 13.3 A.m(-2). Under these conditions, removal of color, turbidity, TOC and COD were 94%, 93%, 65% and 69%, respectively, after a steady state was reached in the continuous flow reactor.

Optimization of electrocoagulation (EC) process for the purification of a real industrial wastewater from toxic metals

In the present work, the efficiency evaluation of electrocoagulation (EC) in removing toxic metals from a real industrial wastewater, collected from Aspropyrgos, Athens, Greece was investigated. Manganese (Mn), copper (Cu) and zinc (Zn) at respective concentrations of 5 mg/L, 5 mg/L and 10 mg/L were present in the wastewater (pH=6), originated from the wastes produced by EBO-PYRKAL munitions industry and Hellenic Petroleum Elefsis Refineries. The effect of operational parameters such as electrode combination and distance, applied current, initial pH and initial metal concentration, was studied. The results indicated that Cu and Zn were totally removed in all experiments, while Mn exhibited equally high removal percentages (approximately 90%). Decreasing the initial pH and increasing the distance between electrodes, resulted in a negative effect on the efficiency and energy consumption of the process. On the other hand, increasing the applied current, favored metal removal but resulted in a power consumption increase. Different initial concentrations did not affect metal removal efficiency. The optimal results, regarding both cost and EC efficiency, were obtained with a combination of iron electrodes, at 2 cm distance, at initial current of 0.1 A and pH=6. After 90 min of treatment, maximum removal percentages obtained were 89% for Mn, 100% for Cu and 100% for Zn, at an energy consumption of 2.55 kWh/m(3).

Large disk electrodes of Ti/TiO2-nanotubes/PbO2for environmental applications

Large disk electrodes of Ti/TiO₂-nanotubes/PbO₂(65 cm²of geometrical area) were successfully synthesized by anodization and electrodeposition procedures.