Cross-linking of dehydrofluorinated PVDF membranes with thiol modified polyhedral oligomeric silsesquioxane (POSS) and pure water flux analysis

An anchor for help: a cross-linking moiety for block copolymer membrane stabilization for ultrafiltration applications in water

Block copolymer membranes are an exciting class of materials used to separate small contaminants from water. Covalent cross-linking of the membrane matrix is one approach to alleviate stability issues, which limit their application nowadays. In the current work, membranes from amphiphilic block copolymers are manufactured and cross-linked using a UV-active radical initiator moiety.

Fabricating novel PVDF-g-IBMA copolymer hydrophilic ultrafiltration membrane for treating papermaking wastewater with good antifouling property

Ultrafiltration membranes are widely used for the treatment of papermaking wastewater. The antifouling performance of polyvinylidene fluoride (PVDF) ultrafiltration membranes can be improved by changing the hydrophilicity. Here, a novel amphiphilic copolymer material, PVDF grafted with N-isobutoxy methacrylamide (PVDF-g-IBMA), was prepared using ultraviolet-induced Cu(II)-mediated reversible deactivation radical polymerization. The amphipathic copolymer was used to prepare ultrafiltration membrane via NIPS. The prepared PVDF-g-IBMA ultrafiltration membrane was estimated using ¹H NMR, FT-IR, and DSC. The contact angle, casting viscosity, and the permeation performance of the PVDF-g-IBMA ultrafiltration membrane were also determined. The pure water flux, bovine serum albumin removal rate, and pure water flux recovery rate of the PVDF-g-IBMA ultrafiltration membrane were 432.8 L·m^-2·h^-1, 88.4%, and 90.8%, respectively. Furthermore, for the treatment of actual papermaking wastewater, the chemical oxygen demand and turbidity removal rates of the membrane were 61.5% and 92.8%, respectively. The PVDF-g-IBMA amphiphilic copolymer ultrafiltration membrane exhibited good hydrophilicity and antifouling properties, indicating its potential for treating papermaking wastewater.

Functional PVDF ultrafiltration membrane for Tetrabromobisphenol-A (TBBPA) removal with high water recovery

Tetrabromobisphenol-A (TBBPA) is one of the most important brominated flame retardants (BFRs), accounting for 60% of the total commercial BFR market. Increasing amounts of TBBPA and byproducts are released to the aquatic environment due to their extensive utilization in various sectors. However, research on the treatment of TBBPA contaminated wastewater using membrane filtration is still lacked. Herein, a PVDF10-PAA-ZrO₂ membrane was successfully developed and applied for the treatment of high-concentration TBBPA wastewater with super-high water recovery. The membrane was obtained through surface functionalization with nano-ZrO₂ from commercial PVDF ultrafiltration (UF) membrane. Compared to the commercial PVDF membrane, the developed membrane exhibited 4 times of permeate flux which was up to 200 L/m² min with comparable TBBPA rejection rate. Furthermore, the mechanisms of membrane development and TBBPA rejection were explored through synchrotron-based ATR-FTIR and X-ray analyses. It was revealed that ZrO₂ NPs were immobilized into membrane surface through binding with PAA layer, where the O of the carboxyl group combined with the Zr⁴⁺ on the ZrO₂ NP surface to form C-O-Zr bond through monodentate and bridging-bidentate modes. The sieving function of membrane could be the main mechanism of TBBPA removal. This research demonstrated a practical route and solid insight toward the development of highly efficient membrane for TBBPA removal. The proposed PVDF10-PAA-ZrO₂ membrane can also be promising for other industrial separation and purification applications.

Cationic metal-organic framework based mixed-matrix membrane for extraction of phenoxy carboxylic acid (PCA) herbicides from water samples followed by UHPLC-MS/MS determination

A novel kind of cationic metal-organic framework(MOF) based mixed-matrix membrane(MMM) namely cationic MOF-MMM was firstly designed and used for simultaneous dispersive membrane extraction(DME) of six phenoxy carboxylic acid(PCA) herbicides from water samples followed by determination using ultrahigh-performance liquid chromatography tandem mass spectrometry. The cationic MOF-MMM was synthesized by soaking the zirconium-based MOFs in a polyvinylidene fluoride(PVDF) solution and further functionalization with quaternary amine groups, viz., UiO-66-NMe₃⁺ MMM. The well-prepared UiO-66-NMe₃⁺ MMM was characterized by FT-IR, SEM, XRD, XPS, NMR and etc. Several main variables influencing the MMM based DME efficiency were investigated and optimized in detail, such as dosage ratio of MOF/PVDF, solution pH, extraction time, coexistent anions and ionic strength. Electrostatic interactions dominated adsorption mechanism between anionic PCAs and cationic UiO-66-NMe₃⁺ MMM, along with ππ conjugation and cation-π bonding, leading to better adsorption performance. Low limits of detection in the range of 0.03-0.59 ng/L and satisfactory recoveries within 80.06-117.40 % for all the PCAs are a reliable witness to demonstrate supreme sensitivity and the applicability of the developed method. By relying on the obtained results, the present work implied cationic MOF-MMM based DME can be a versatile and worthy utility for extraction of pollutants from different water samples with high throughput.