An energy-efficient air-breathing cathode electrocoagulation approach for the treatment of arsenite in aquatic systems

Optimum parameters for humic acid removal and power production by Al-air fuel cell electrocoagulation in synthetic wastewater

Although humic acid (HA) is a complex natural organic matter, it can potentially harm the environment and human health. In this study, aluminum-air fuel cell electrocoagulation (AAFCEC) was used to remove HAs from water while generating electricity. Initial pH, electrolyte concentration, HA concentration electrode distance and external resistance were investigated to determine the power generation and removal efficiency. The results showed that the better performance of power generation has been acquired in the alkaline solution and larger electrolyte concentration and short electrode distance. Further, Al-Ferron complexation timed spectrophotometry was used to determine the Al speciation distribution in the solution under different parameters. The power density of the cell reached 313.47 mW/cm² for the following conditions: 1 g/L NaCl concentration, 3 cm electrode distance, 20 Ω external resistor, and pH 9. After about an hour of electrolysis, the optimum removal rate of HA was above 99%. The results demonstrated that the AAFCEC is an efficient and eco-friendly water treatment process, and it could be further developed and disseminated in the rural areas and households.

Electrocoagulation technology for water purification: An update review on reactor design and some newly concerned pollutants removal

Water shortage and quality deterioration are plaguing people all over the world. Providing sustainable and affordable treatment solutions to these problems is a need of the hour. Electrocoagulation (EC) technology is a burgeoning alternative for effective water treatment, which offers the virtues such as compact equipment, easy operation, and low sludge production. Compared to other water purification technologies, EC shows excellent removal efficacy for a wide range of contaminants in water and has great potential for addressing limitations of conventional water purification technologies. This review summarizes the latest development of principle, characteristics, and reactor design of EC. The design of key parameters including reactor shape, power supply type, current density, as well as electrode configuration is further elaborated. In particular, typical water treatment systems powered by renewable energy (solar photovoltaic and wind turbine systems) are proposed. Further, this review provides an overview on expanded application of EC in the removal of some newly concerned pollutants in recent years, including arsenite, perfluorinated compounds, pharmaceuticals, oil, bacteria, and viruses. The removal efficiency and mechanisms of these pollutants are also discussed. Finally, future research trend and focus are further recommended. This review can bridge the large knowledge gap for the EC application that is beneficial for environmental researchers and engineers.

Domestic wastewater treatment by real-scale electrocoagulation process

In this study, domestic wastewaters originating from a settlement with a population of 17,500 were treated by electrocoagulation process in a real-scale EC plant and the economic applicability of the process was investigated. The removal efficiencies of control parameters in the influent and effluent of the real-scale treatment plant such as suspended solids (SS), biological oxygen demand (BOD), chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP) and changes of pH and conductivity parameters were monitored for 12 months. The obtained data were evaluated according to European Urban Wastewater Treatment Directive, Turkish Water Pollution Control Regulation and Turkish Urban Wastewater Treatment Regulation. According to the results obtained, the removal efficiencies of the pollutant parameters were achieved in the range of 72-83% for SS, 67-80% for COD, 69-81% for BOD, 21-47% for TN and 27-46% for TP. Considering the Turkish wastewater discharge regulations, it can be concluded that the discharge standards for SS, COD and BOD parameters were achieved while they were not achieved in certain periods for TN and TP. In addition, the energy consumption and the operating cost of this real-scale plant were determined to be 0.49-0.54 kWh/m³ and 0.24-0.28 EUR/m³, respectively.

Nanomaterials-based treatment options for chromium in aqueous environments

Sustainable development and the restoration of ecosystems are the important goals for civilization. Currently, heavy metal contamination of aquatic environments has become a serious issue. Chromium (Cr) is simultaneously an essential metallic element and one of 20 chemicals posing a maximum threat to living beings. To mitigate that threat, various treatment methods have been developed, including adsorption, electrocoagulation, photoelectrocatalysis, fuel cells, bioremediation, chemical precipitation, ultrafiltration, ion exchange, and co-precipitation. However, selection of the most energy- and cost-efficient wastewater treatment option has proven challenging, as each approach is subject to shortcomings involving energy consumption, treatment capacity, and efficiency. This review describes the potential role of diverse functional nanomaterials (e.g., iron/iron oxide nanoparticles, carbon nanostructures, metal organic frameworks, and their commercial counterparts) in treatment of Cr in aqueous environments with respect to key figure of merits, such as, adsorption capacity, removal efficiency, and partition coefficient. In addition, their performance was compared with the most common treatment options. The results of this study will help determine the most effective and economical options for control of Cr in aquatic environments.