Combined nanofiltration and advanced oxidation processes with bifunctional carbon nanomembranes.

Wastewater reclamation is becoming a top global interest as population growth and rapid industrialization pose a major challenge that requires development of sustainable cost-effective technologies and strategies for wastewater treatment. Carbon nanomembranes (CNMs)-synthetic 2D carbon sheets-can be tailored chemically with specific surface functions and/or physically with nanopores of well-defined size as a strategy for multifunctional membrane design. Here, we explore a bifunctional design for combined secondary wastewater effluent treatment with dual action of membrane separation and advanced oxidation processes (AOP), exploiting dissolved oxygen. The bifunctional membrane consists of a CNM layer on top of a commercial ultrafiltration membrane (Microlon™) and a spray-coated reduced graphene oxide (rGO) thin film as the bottom layer. The CNM/support/rGO membrane was characterized by helium ion and atomic force microscopy, FTIR, XPS with a four-point conductivity probe, cyclic voltammetry, galvanostatic measurements, and impedance spectroscopy. Combined treatment of water by nanofiltration and AOP was demonstrated, employing a unique three electrode-dead end filtration setup that enables concurrent application of potential and pressure on the integrated membrane. For the model organic compound methylene blue, oxidation (by the Fenton reaction) was evaluated using UV-vis (610 nm). The rejection rate and permeability provided by the CNM layer were evaluated by dissolving polyethylene glycol (400 and 1000 Da) in the feed solution and applying pressure up to 1.5 bar. This demonstration of combined membrane separation and AOP using an integrated membrane opens up a new strategy for wastewater treatment.

Capacitive deionization for wastewater treatment: Opportunities and challenges.

Capacitive deionization (CDI) is an emerging method for removal of charged ionic species from aqueous solutions, based on electrostatic interactions between (mostly) inorganic ions and porous carbon electrodes. Inspection of recent publications related to CDI processes, revealed that the majority of the publications are related to the removal of salt (NaCl) from the water (desalination) or electrosorption processes. However, such a water desalination is only one process in the improvement of the quality water, it is interesting to review the literature in the context of CDI processes for other water treatment processes. Herein wastewater treatments are discussed. In this paper, we critically review the last publications that relate to capacitive deionization with wastewater treatments. Since wastewater treatments may involve broad aspects, we address in this review four specific water treatment processes that are thought to be connected with CDI processes: organic fouling of CDI cells, removal of heavy metals by CDI processes, removal of organic micropollutants with CDI processes and disinfection with CDI processes. We also evaluate herein the status of several research efforts in this area and suggest future directions.

Bromide Ions Specific Removal and Recovery by Electrochemical Desalination.

Removal and recovery of bromide ions by electro-oxidation and electro-reduction are presented using hybrid physical adsorption and capacitive deionization cells, which contain activated carbon cloth electrodes. This is a proof of concept research with results, which indicate that when comparing the removal and recovery quantities of bromide and chloride ions (starting with the same initial concentration of 0.05 M for both salts), the desalination capacity of the bromide ions is larger by almost 2 orders of magnitude than that of the chloride ions; thus, we obtained specific desalination of bromide ions from a solution containing chloride ions. Removal and recovery of 3.5 mmol of bromide ions were achieved by a working electrode with 1 g of activated carbon cloth, and the calculated energy consumption for the removal and recovery of 1 g of bromide ions was about 2.24 kJ/g.