Process Optimization of Electrochemical Treatment of COD and Total Nitrogen Containing Wastewater

In this work, an electrochemical method for chemical oxygen demand (COD) and total nitrogen (TN, including ammonia, nitrate, and nitrite) removal from wastewater using a divided electrolysis cell was developed, and its process optimization was investigated. This process could effectively relieve the common issue of NO3−/NO2− over-reduction or NH4+ over-oxidation by combining cathodic NO3−/NO2− reduction with anodic COD/NH4+ oxidation. The activity and selectivity performances toward pollutant removal of the electrode materials were investigated by electrochemical measurements and constant potential electrolysis, suggesting that Ti electrode exhibited the best NO3−/NO2− reduction and N2 production efficiencies. In-situ Fourier transform infrared spectroscopy was used to study the in-situ electrochemical information of pollutants conversion on electrode surfaces and propose their reaction pathways. The effects of main operating parameters (i.e., initial pH value, Cl− concentration, and current density) on the removal efficiencies of COD and TN were studied. Under optimal conditions, COD and TN removal efficiencies from simulated wastewater reached 92.7% and 82.0%, respectively. Additionally, reaction kinetics were investigated to describe the COD and TN removal. Results indicated that COD removal followed pseudo-first-order model; meanwhile, TN removal followed zero-order kinetics with a presence of NH4+ and then followed pseudo-first-order kinetics when NH4+ was completely removed. For actual pharmaceutical wastewater treatment, 79.1% COD and 87.0% TN were removed after 120 min electrolysis; and no NH4+ or NO2− was detected.

13 Electrochemistry in Laboratory Flow Systems

Organic electrosynthesis in flow reactors is an area of increasing interest, with efficient mass transport and high electrode area to reactor volume present in many flow electrolysis cell designs facilitating higher rates of production with high selectivity. The controlled reaction environment available in flow cells also offers opportunities to develop new electrochemical processes. In this chapter, various types of electrochemical flow cells are reviewed in the context of laboratory synthesis, paying particular attention to how the different reactor environments impact upon the electrochemical processes, and the factors responsible for good cell performance. Coverage includes well-established plane-parallel-plate designs, reactors with small interelectrode gaps, extended-channel electrolysis cells, and highly sophisticated designs with rapidly rotating electrodes to enhance mass transport. In each case, illustrative electrosyntheses are presented.

Direct Epoxidation of Propylene with Water at PtOx Anode Using a Solid-Polymer-Electrolyte Electrolysis Cell

Direct electro-oxidation of C3H6 was achieved using a solid polymer electrolyte (SPE) electrolysis cell. PtOx anode prepared by mild oxidation of Pt black exhibited superior activity for propylene oxide (PO)...

Versatile Bioelectrochemical system for heavy metals removal

Industrial activity has resulted in heavy metals anthropogenic contamination of groundwater, especially in industrial or mining areas. Bioelectrochemical systems (BES) can be used for metals removal and recovery from aqueous solutions. In the framework of GREENER project, double-chamber BES have been adopted to treat groundwater from industrial sites containing copper, nickel and zinc (Cu, Ni and Zn), among other contaminants. Two operation modes, (i) short-circuited microbial fuel cell (MFC), and (ii) power supply driven microbial electrolysis cell (MEC, poisoning the cathode at -0.4 V vs. Ag/AgCl), were studied for metals removal at lab-scale. Two control reactors were run to evaluate metals adsorption on cathodes and membranes, and the effect of anolyte composition. Synthetic water containing different concentrations of Cu, Ni and Zn were treated, and metals removal pathways were studied. MEC and MFC performed similarly and the highest removal efficiencies were 97.1±3.6%, 50.7±6% and 74,5% for Cu, Ni and Zn respectively, from initial concentrations in the range of 1.1-1.5 mM.

P2H Modeling and Operation in the Microgrid Under Coupled Electricity–Hydrogen Markets

The uncertainty and volatility of wind power have led to large-scale wind curtailment during grid connections. The adoption of power-to-hydrogen (P2H) system in a microgrid (MG) can mitigate the renewable curtailment by hydrogen conversion and storage. This paper conducts unified modeling for different types of P2H systems and considers the multi-energy trading in a hydrogen-coupled power market. The proposed bi-level equilibrium model is beneficial to minimize the energy cost of microgrids. Firstly, a microgrid operation model applied to different P2H systems including an alkaline electrolysis cell (AEC), a proton exchange membrane electrolysis cell (PEMEC), or a solid oxide electrolysis cell (SOEC) is proposed at the upper level. Secondly, an electricity market–clearing model and a hydrogen market model are constructed at the lower level. Then, the diagonalization algorithm is adopted to solve the multi-market equilibrium problem. Finally, case studies based on an IEEE 14-bus system are conducted to validate the proposed model, and the results show that the microgrid with a P2H system could gain more profits and help increase the renewable penetration.