Search

The CaCO3 interlayer was grown in situ on PK membrane through mineralization process, which plays a multi-functional role in the process of regulating IP and facilitating the formation of a thinner selective layer with rough and loose structure.

Interfacial polymerization (IP) and self-assembly are two thermodynamically different processes involving an interface in their systems. When the two systems are incorporated, the interface will exhibit extraordinary characteristics and generate structural and morphological transformation. In this work, an ultrapermeable polyamide (PA) reverse osmosis (RO) membrane with crumpled surface morphology and enlarged free volume was fabricated via IP reaction with the introduction of self-assembled surfactant micellar system. The mechanisms of the formation of crumpled nanostructures were elucidated via multiscale simulations. The electrostatic interactions among m -phenylenediamine (MPD) molecules, surfactant monolayer and micelles, lead to disruption of the monolayer at the interface, which in turn shapes the initial pattern formation of the PA layer. The interfacial instability brought about by these molecular interactions promotes the formation of crumpled PA layer with larger effective surface area, facilitating the enhanced water transport. This work provides valuable insights into the mechanisms of the IP process and is fundamental for exploring high-performance desalination membranes.

Covalent organic frameworks (COFs) have evinced a potential solution that promises for fast and efficient molecular separation due to the presence of orderly arranged pores and regulable pore apertures. Herein, the synthesized COF (TPB-DMTP-COF) with the pore aperture matching the pore size of the nanofiltration (NF) membrane was utilized to modulate the physicochemical characters of the polyamide (PA) membranes. It is demonstrated that COFs with superior polymer affinity and hydrophilicity not only circumvent the nonselective interfacial cavities but also improve the hydrophilicity of the resultant thin-film nanocomposite (TFN) membranes. Furthermore, the predeposited COF layer is able to slow down the diffusion rate toward the reaction boundary through hydrogen bonding, which is consistent with the results of molecular dynamic (MD) and dissipative particle dynamic (DPD) simulations. In this context, COF-modulated TFN membranes show a roughened and thickened surface with bubble-shaped structures in contrast to the nodular structure of original polyamide membranes. Combined with the introduced in-plane pores of COFs, the resultant TFN membranes display a significantly elevated water permeance of 35.7 L m

6:2 chlorinated polyfluorinated ether sulfonate (F-53B), a Chinese PFOS alternative, has recently been identified in river water, sewage sludge, wildlife and humans, causing great concerns about its potential toxic effects. Here, we report the first investigation of the toxicokinetics and oxidative stress of F-53B in adult zebrafish. Adult male and female zebrafish were exposed to 10 and 100 μg/L of F-53B for 7 days followed by a 5-d depuration period to examine bioaccumulation, distribution, and depuration of F-53B in fish. The results showed that F-53B was readily accumulated in fish tissues with log BCF values of 2.36–3.65, but was eliminated slowly (t1/2 = 152.4–358.5 h). F-53B accumulation was greater in males than in females and the concentration in tissues decreased in the following order: gonad ≈ liver ≫ gill ≫ brain in females and liver ≈ gill ≫ gonad ≫ brain in males, showing sex- and tissue- specific accumulation of F-53B in fish. After chronic exposure to F-53B for 28 days, a significant dose-dependent increase in histopathological changes in the liver were mainly manifested by vacuolation. Furthermore, F-53B also significantly reduced the enzyme activity (or content) of most of the measured oxidative stress-related markers (e.g., SOD, CAT and MDA) except for an increase in GSH-Px activity, indicating that oxidative stress was induced in zebrafish after treatment with F-53B. The results of this study provide important information on the toxicokinetics and toxic effects of F-53B, which will contribute to the ecological risk assessments of F-53B released into surface waters.

Nanofiltration has been applied as a promising way in water treatment because of its special separation mechanisms. As the main class of nanofiltration membranes available on the market, most thin-film polyamide nanofiltration membranes obtained by interfacial polymerization possess active layer containing amine and carboxylic acid groups that are distributed in a highly non-uniform fashion, leading to an inhomogeneous fixed charge distribution. This feature has been reported only under consideration of steric hindrance and electric repulsion while the intensity of dielectric exclusion is worth being taken into account. The primary objective of this work was to investigate the influence of dielectric exclusion on the relationship between fixed charge distribution and electrolyte rejection performance. CaCl2 rejection rate has been computed as a function of different dielectric constants inside the pore for various inhomogeneous charge distributions with an identical average volume charge density. Electric field behavior and ion concentration distribution inside the nanopore reflect that the variation of dielectric effect affects the repulsive force to co-ions so that the electrolyte rejection performance has been changed. The simulations performed in this work supplement the theoretical research of nanofiltration separation mechanism to support the accuracy of rejection performance prediction and the results drawn in this work are beneficial for the comprehension of fixed charge distribution and dielectric effect.

International audience; The current treatment for firefighting waters containing fluorinated surfactants is incineration. A process for purifying firefighting water was proposed in a previous paper: electrocoagulation and filtration followed by reverse osmosis. Here the objective was to demonstrate the efficiency of reverse osmosis to reduce the fluorinated surfactant concentration from 30 to 0.1 mg L À 1 at large scale and over several days. A polyamide thin film membrane was selected. Retention rate, obtained at laboratory and industrial scale for fluorinated surfactant (RR¼0.994–0.999), was sufficient to reach the limit concentration in permeate defined in the project. Permeability (0.5 L h À 1 m À 2 bar À 1) and retention rates were stable for several days. The flux decline observed was governed by the accumulation of surfactants. The fouling due to adsorption of the surfactant mixture was successfully described by a combination of the resistance-in-series and Langmuir adsorption models.