Mineral cathodic electro-precipitation and its kinetic modelling in thin-film microfluidic reactor during advanced electro-oxidation process

Electrosorption of phenolic compounds from olive mill wastewater: Mass transport consideration under a transient regime through an alginate-activated carbon fixed-bed electrode

Olive mill wastewater (OMWW) is an environmentally critical effluent, specifically due to its high content of phenolic compounds (PCs), which are hazardous due to their antimicrobial activities in water. However, their properties have good health effects at suitable doses. For the first time, the electrosorption of PCs from actual OMWW has been proposed for their possible recovery as value-added compounds, while decontaminating OMWW. A bio-sourced alginate-activated carbon (AC) fixed-bed electrode was prepared based on the reuse of olive pomace solid waste as powdered AC. At the optimal AC content (1% w/v), the internal ohmic drop voltage was lower (2.26 V) and the mass transport coefficient was higher (9.7 10^-5 m s^-1) along with the diffusivity (7.3 10^-9 m² s^-1), which led to enhanced electrosorption rates. Afterward, an optimal electrode potential was obtained (-1.1 V vs. Ag/AgCl), while higher voltages led to faradaic reactions. Moreover, the adsorption capacity was lower (123 mg g^-1) than that of electrosorption (170 mg g^-1) and was even higher (307 mg g^-1) with actual effluents. This was probably due to the influence of electromigration, which was confirmed by new models that could predict the electrosorption kinetics well considering mass transport and acid dissociation constants.

A critical review on the electrosorption of organic compounds in aqueous effluent - Influencing factors and engineering considerations

Despite being an old process from the end of the 19^th century, electrosorption has attracted renewed attention in recent years because of its unique properties and advantages compared to other separation technologies and due to the concomitant development of new porous electrode materials. Electrosorption offer the advantage to separate the pollutants from wastewater with the possibility of selectively adsorbing and desorbing the targeted compounds. A comprehensive review of electrosorption is provided with particular attention given to the electrosorption of organic compounds, unlike existing capacitive deionization review papers that only focus on inorganic salts. The background and principle of electrosorption are first presented, while the influence of the main parameters (e.g., electrode materials, electrode potential, physico-chemistry of the electrolyte solutions, type of compounds, co-sorption effect, reactor design, etc.) is then detailed and the modeling and engineering aspects are discussed. Finally, the main output and future prospects about recovery studies and combination between electro-sorption/desorption and degradation processes are given. This review particularly highlights that carbon-based materials have been mostly employed (85% of studies) as porous electrode in organics electrosorption, while existing studies lack of electrode stability and durability tests in real conditions. These electrodes have been implemented in a fixed-bed reactor design most of the time (43% of studies) due to enhanced mass transport. Moreover, the electrode potential is a major criterion: it should be applied in the non-faradaic domain otherwise unwanted reactions can easily occur, especially the corrosion of carbon from 0.21 V/standard hydrogen electrode or the water oxidation/reduction. Furthermore, there is lack of studies performed with actual effluents and without addition of supporting electrolyte, which is crucial for testing the real efficiency of the process. The associated predictive model will be required by considering the matrix effect along with transport phenomena and physico-chemical characteristics of targeted organic compounds.