Polyethylene glycol-polyvinylidene fluoride/TiO2 nanocomposite polymer coatings with efficient antifouling strategies: Hydrophilized defensive surface and stable capacitive deionization.

Capacitive deionization (CDI) is flourishing as an energy-efficient and cost-effective water desalination method. However, challenges such as electrode degradation and fouling have hindered the practical deployment of CDI technology. To address these challenges, the key point of our strategy is applying a hydrophilic coating composed of polyethylene glycol (PEG)-functionalized nano-TiO2/polyvinylidene fluoride (PVDF) to the electrode interface (labeled as APPT electrode). The PEG/PVDF/TiO2 layer not only mitigates the co-ion depletion, but also imparts the activated carbon (AC) electrode hydrophilicity. As anticipated, the APPT electrode possessed an enhanced desalination capacity of 83.54 µmol g-1 and a low energy consumption of 17.99 Wh m-3 in 10 mM sodium chloride solution compared with the bare AC electrode. Notably, the APPT maintained about 93.19 % of its desalination capacity after 50 consecutive adsorption-desorption cycles in the presence of bovine serum albumin (BSA). During the trial, moreover, no obvious overall performance decline was noted in concentration reduction (Δc), water recovery (WR) and productivity (P) over 50 cycles. This strategy realizes energy-efficient, antifouling and stable brackish water desalination and has great promise for practical applications.

Easily scale 3D conductive gradient fiber membrane for contaminants removal and fouling mitigation under electrochemical assistance.

An electrochemical membrane filtration system provides an innovative approach to enhance contaminant removal and mitigate membrane fouling. There is an urgent need to develop portable, versatile, and efficient electrochemical membranes for affordable wastewater treatment. Here, a 3D conductive gradient fiber membrane (CC/PVDF) with a gradient porous structure was prepared using a two-step phase inversion method. Methyl orange (MO) was utilized as model organic substance to investigate the electrochemical performance of the CC/PVDF membrane. At applied potentials of +2 V, +3 V, -2 V and -3 V, the removal efficiency of MO was 5.1, 5.3, 4.8, and 5.1 times higher than at 0 V. A dramatic flux loss of 35.02% occurred on the membrane without electrochemistry, interestingly, whereas the flux losses were only 23.59%-10.24% in the applied potential after 30 min of filtration, which were approximately 1.18, 1.28, 1.29 and 1.38 times as high as that without electrochemistry, respectively. The enhanced removal and anti-fouling performances of the membranes were attributed to the functions of electrochemical degradation, electrostatic repulsion, and electrically enhanced wettability. Electrochemical generation of Hydrogen peroxide, along with HO• radicals, was detected and direct electron transfer and HO• were proved to be the dominant oxidants responsible for MO degradation. The intermediate oxidation products were identified by mass spectrometry, and an electrochemical degradation pathway of MO was proposed based on bond-breaking oxidation, ring-opening reactions, and complete oxidation. All the findings emphasize that the ECMF system possesses superior efficiency and creative potential for water purification applications.