Innovative electro-filtration process achieves efficient wastewater treatment
image: (a) Illustration of a typical electrochemical membrane reactor (EMR) system for simultaneous denitrification and decarbonization of a practical hypersaline wastewater containing 503.5 mg·L−1 ammonia. Arrows indicate the direction of water flow. (b) Schematics of the RuO2@PbO2-M electro-filtration membrane reactor system. The system includes the pre-filtration (1st unit) and electro-filtration (2nd and 3th units) processes. (c) Photographs of the permeate of different units. (d) Applied voltage (left y-axis) and current (right y-axis) of the electro-filtration system for treating the practical wastewater. (e) EnC and ACE of the electro-filtration system. (f) Metal leaching in the first and second units of the membrane reactor. (g) COD of the permeate of the three electro-filtration stages (top layer left y-axis). TN concentration (bottom layer left y-axis) and NH3-N removal rates (bottom layer right y-axis) of the permeate of the three electro-filtration stages. The inset shows the photos of the RuO2@PbO2-M used in the three units of the membrane reactor. Ucell was used to denote the cell voltage, and I was used to represent the current.
Credit: Bin Zhao et al.
A recent study published in Engineering presents a novel electro-filtration process that simultaneously achieves denitrification and decarbonization of wastewater through the in situ generation of chlorine oxide radicals (·ClO). This method, developed by researchers from the Chinese Academy of Sciences and Tsinghua University, offers an efficient and environmentally friendly solution for wastewater treatment.
The primary challenge in wastewater treatment involves the removal of organic pollutants and nitrogen compounds, which are often resistant to traditional treatment methods. The study introduces an electrochemical approach using a specially designed electro-reactive membrane (RuO₂@PbO₂-M) that facilitates the rapid conversion of ammonia nitrogen to nitrogen gas while reducing the chemical oxygen demand (COD) in the effluent. This membrane is fabricated using an electrodeposition-coupled template approach, integrating ruthenium dioxide (RuO₂) and lead dioxide (PbO₂) to enhance electrocatalytic performance.
The research highlights the critical role of chlorine oxide radicals (·ClO) in the electrochemical oxidation process. These radicals, generated near the anode, react rapidly with ammonia nitrogen, achieving high removal efficiency. The study demonstrates that the RuO₂@PbO₂-M membrane can achieve nearly 100% removal of ammonia nitrogen within a retention time of just 1.2 minutes. This ultra-efficient process also results in significant reductions in COD and total nitrogen (TN) levels, with a 68% COD removal rate and a 99.6% TN removal rate observed during continuous operation over 70 h.
The electro-filtration system’s efficiency is attributed to the synergistic effects of the RuO₂ and PbO₂ components. The incorporation of RuO₂ significantly enhances the oxygen evolution potential (OEP) of the membrane, inhibiting undesired oxygen evolution reactions and improving electrocatalytic oxidation efficiency. Additionally, the presence of chloride ions in the wastewater further boosts the generation of active chlorine species, which play a crucial role in ammonia nitrogen removal.
The study also investigates the impact of various operational parameters on the system’s performance, including current density, initial ammonia concentration, chloride ion concentration, and pH levels. Optimal conditions were identified as a current density of 20 mA/cm², a chloride ion concentration of 100 mg/L, and an acidic pH, which collectively maximize ammonia nitrogen removal efficiency.
Furthermore, the research explores the simultaneous denitrification and decarbonization of amino-containing pollutants using acetaminophen (APAP) as a model contaminant. The results indicate that the RuO₂@PbO₂-M membrane effectively removes both nitrogen and carbon from the wastewater, demonstrating its potential for treating complex industrial effluents.
This innovative electro-filtration process not only addresses the challenges of wastewater treatment but also offers a sustainable and energy-efficient solution. By eliminating the need for chemical precursors and minimizing energy consumption, this technology could significantly enhance the efficiency of wastewater treatment systems, contributing to environmental protection and resource recovery.
The paper “Simultaneous Denitrification and Decarbonization of Wastewater over In Situ Generation of ·ClO Radicals Through a Fast, High-Performance Electro-Filtration Process,” is authored by Bin Zhao, Jialin Yang, Ruiping Liu, Jiuhui Qu, Meng Sun. Full text of the open access paper: https://doi.org/10.1016/j.eng.2025.07.016. For more information about Engineering, visit the website at https://www.sciencedirect.com/journal/engineering.