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In capacitive deionization (CDI), the functionalization or modification of carbon electrodes and the mitigation of positive electrode oxidation are effective methods to improve desalination capacity and stability for practical application. Here, the covalent bond attached three-dimensional (3D) graphene/carbon nanotubes hybrid (G-CNTs) with rich conductive channels was chosen as electrode material, and a periodically alternated (positive and negative) voltage operation (1.2/0/–1.2/0 V) was applied that aims to enhance the efficiency and stability of capacity deionization. The desalination capacity of the G-CNTs electrode increased gradually over the first few cycles in this operation, while the usage cycle of CDI could be pronouncedly extended almost six times, compared with the CDI of regular applied voltage operation (1.2/0 V). Through the characterization of electrode and CDI cell, this enhancement of the desalination performance is attributed to the synergistic benefits of alternating oxidation of negative and positive electrode, which can mitigate the oxidation of the positive electrode as well as achieve negative surface charge enhanced negative electrode. Therefore, a periodically alternated voltage operation is an economical and efficient method to control the oxidation of electrodes for enhancing the desalination performance. [ABSTRACT FROM AUTHOR]

Flow-electrode capacitive deionization (FCDI) is a new desalination technology that delivers sustainable desalination performance. However, higher desalination rate and charge efficiency of FCDI are still desired for practical applications. In this study, voltages greater than 1.23 V – the minimum voltage for water electrolysis – were applied to enhance the driving force for ion migration and adsorption in an FCDI so as to achieve higher desalination rates. When the voltage was raised from 0.6 to 4.8 V, the desalination rate increased by nearly 7 times but the charge efficiency reduced from 92% to 69.5% due to the occurrence of Faradaic reactions such as water electrolysis. The other major factor that influenced the FCDI's charge efficiency was found to be concentration diffusion of ions between the FCDI's middle chamber and the two electrode chambers. To improve the charge efficiency, carbon black (CB) particles with an average diameter of 12 μm were added to the activated carbon flow electrodes at a mixing ratio of 1.5 wt%. With that, the FCDI's charge efficiency increased from 83.5% to 96.5% at 2.4 V. Electrochemical impedance spectrometry (EIS) analysis indicates that the addition of CB particles significantly reduced the FCDI's internal resistance, thereby leading to enhanced desalination performance. [ABSTRACT FROM AUTHOR]

Using microbial fuel cells (MFCs) to power a capacitive deionization (CDI) process enables simultaneous removal of salinity and organic matter in wastewater. The desalination performance of an MFC-CDI system can be influenced by not only the capacity of individual components but also the arrangement and operation of the MFC-CDI circuit. Five typical circuits (consisting of serial- or parallel-connected MFCs or CDIs) and two ion-desorption modes (short-circuit and reverse-voltage desorption) were compared. Results showed that the MFC-CDI system could be reasonably modeled (R 2 > 0.967) by a first-order resistor–capacitor circuit. The optimal arrangement of the MFC-CDI circuit depended on the electrical characteristics of selected MFCs and CDIs as well as operating conditions. When the system was powered by two MFCs of a larger internal resistance (146 Ω), the highest salt removal after 60 min ( m 60 ; 7.5 mg) was achieved by paralleling the two MFCs; with MFCs of a smaller resistance (12 Ω) being used, the highest m 60 (16.5 mg) was obtained when the two MFCs were connected in series. Further analysis revealed that the MFC's internal resistance and open-circuit voltage, along with the CDI's internal resistance and capacitance, were the chief factors affecting the charge transfer and accordingly desalination on the CDI electrodes. [ABSTRACT FROM AUTHOR]

A new technology (CDI-MFC) that combined capacitive deionization (CDI) and microbial fuel cell (MFC) was developed to treat low-concentration salt water with NaCl concentration of 60 mg/L. The water desalination rate was 35.6 mg/(L h), meanwhile the charge efficiency was 21.8%. Two desorption modes were investigated: discharging (DC) mode and short circuit (SC) mode. The desalination rate in the DC mode was 200.6 ± 3.1 mg/(L h), 47.8% higher than that in the SC mode [135.7 ± 15.3 mg/(L h)]. The average current in the DC mode was also much higher than that of the SC mode. The energy stored in the CDI cell has been reused to enhance the electron production of MFC by the discharging desorption mode (DC mode), which offers an approach to recover the electrostatic energy in the CDI cell. [ABSTRACT FROM AUTHOR]

• A comprehensive review of electro-driven technologies for phosphorus enrichment was provided. • Enrichment rate and energy consumption were important indicators for phosphorus enrichment. • Phosphorus enrichment promoted p recovery efficiency and vivianite formation. • Prospect and directions of electro-driven technologies for phosphorus enrichment and recovery were presented. The recovery of phosphorus from wastewater is a critical step in addressing the scarcity of phosphorus resources. Electro-driven technologies for phosphorus enrichment have gathered significant attention due to their inherent advantages, such as mild operating conditions, absence of secondary pollution, and potential integration with other technologies. This study presents a comprehensive review of recent advancements in the field of phosphorus enrichment, with a specific focus on capacitive deionization and electrodialysis technologies. It highlights the underlying principles and effectiveness of electro-driven techniques for phosphorus enrichment while systematically comparing energy consumption, enrichment rate, and concentration factor among different technologies. Furthermore, the study provides a thorough analysis of the capacity of various technologies to selectively enrich phosphorus and proposes several methods and strategies to enhance selectivity. These insights offer valuable guidance for advancing the future development of electrochemical techniques with enhanced efficiency and effectiveness in phosphorus enrichment from wastewater. [ABSTRACT FROM AUTHOR]

This study employed a titanium mesh-membrane assembly (MMA) as the current collector in flow-electrode capacitive deionization (FCDI) device (designated as M-FCDI), and obtained a much reduced charge transport distance as compared to traditional FCDI with plate-shaped current collectors located far from the exchange membrane. The average salt removal rate of M-FCDI was greatly improved by 76% under 10 wt% carbon content than the control experiment with graphite plate as current collector, and the charge efficiency remained over 75% even under low carbon loading. This improvement was attributed to the reduced resistance as revealed by electrochemical impedance spectroscopy tests. Further investigation on FCDI's performance with different specifications of titanium meshes showed that the implementation of MMA could provide a larger effective electron transfer area, which would lead to better desalting performance. Image 1 • Titanium mesh-membrane assembly (MMA) as current collector in FCDI. • Largely reduced charge transport distance with MMA than graphite plate. • Much increased salt removal rate up to 75% attributing to smaller cell resistance. • Stable operation over 24 h of FCDI with MMA and with lower energy consumption. [ABSTRACT FROM AUTHOR]