Thin-film composite nanofiltration membrane based on polyurea for extreme pH condition

Multifunctional Bacterial Cellulose/Covalent Organic Framework Composite Membranes with Antifouling and Antibacterial Properties for Dye Separation

Covalent organic frameworks (COFs) have a wide application prospect in wastewater treatment because of their unique structure and properties; however, the preparation of pure COF membranes remains a great challenge by reason of the insolubility and unprocessability of COF powders formed at high temperature and high pressure. In this study, a continuous and defect-free bacterial cellulose/covalent organic framework composite membrane was prepared by using bacterial cellulose (BC) and a porphyrin-based COF with their unique structures and hydrogen bonding forces. The dye rejection rate of this composite membrane toward methyl green and congo red was up to 99%, and the permeance was about 195 L m^-2 h^-1 bar^-1. It showed excellent stability under different pH conditions, long-time filtration, and cyclic experimental conditions. In addition, the hydrophilicity and surface negativity of the BC/COF composite membrane made it have certain antifouling performance, and the flux recovery rate can reach 93.72%. More importantly, the composite membrane exhibited excellent antibacterial properties due to the doping of the porphyrin-based COF, and the survival rates of both Escherichia coli and Staphylococcus aureus were less than 1% after exposure to visible light. The self-supporting BC/COF composite membrane synthesized by this strategy also has outstanding antifouling and antibacterial properties, in addition to excellent dye separation effects, which greatly broaden the application of COF materials in water treatment.

From Trace to Pure: Pilot-Scale Scandium Recovery from TiO2 Acid Waste

Scandium (Sc), declared a critical raw material in the European Union (EU), could face further supply issues as the EU depends almost entirely on imports from China, Russia, and Ukraine. In this study, a tandem nanofiltration-solvent extraction procedure for Sc recovery from titania (TiO₂) acid waste was piloted and then augmented by antisolvent crystallization. The new process, comprising advanced filtration (hydroxide precipitation, micro-, ultra-, and nanofiltration), solvent extraction, and antisolvent crystallization, was assessed in relation to material and energy inputs and benchmarked on ScF₃ production. From ∼1 m³ of European acid waste containing traces of Sc (81 mg L^-1), ∼13 g of Sc (43% yield, nine stages) was recovered as (NH₄)₃ScF₆ with a purity of approximately 95%, demonstrating the technical feasibility of the approach. The production costs per kilogram of ScF₃ were lower than reported market prices, which underscores a competitive process at scale. Although a few technical bottlenecks (e.g., S/L separation and electricity consumption) need to be overcome, combining advanced filtration with solvent extraction and antisolvent crystallization promises a future supply of this critical raw material from European secondary sources.

Recent Advanced Development of Acid-Resistant Thin-Film Composite Nanofiltration Membrane Preparation and Separation Performance in Acidic Environments

Membrane filtration technology has attracted extensive attention in academia and industry due to its advantages of eco-friendliness related to environmental protection and high efficiency. Polyamide thin-film composite nanofiltration (PA TFC NF) membranes have been widely used due to their high separation performance. Non-acid-resistant PA TFC NF membranes face tremendous challenges in an acidic environment. Novel and relatively acid-resistant polysulfonamide-based and triazine-based TFC NF membranes have been developed, but these have a serious trade-off in terms of permeability and selectivity. Hence, how to improve acid resistance of TFC NF membranes and their separation performance in acidic environments is a pivotal issue for the design and preparation of these membranes. This review first highlights current strategies for improving the acid resistance of PA TFC NF membranes by regulating the composition and structure of the separation layer of the membrane performed by manipulating and optimizing the construction method and then summarizes the separation performances of these acid-resistant TFC NF membranes in acidic environments, as studied in recent years.

Synchronous Engineering for Biomimetic Murray Porous Membranes Using Isocyanate

Highly permselective and durable membranes are desirable for massive separation applications. However, currently most membranes prepared using nonsolvent-induced phase separation (NIPS) suffer from low permeability and a high fouling tendency due to the great challenges in a rational design and also practical approach for membrane optimization. Inspired by the natural Murray network from vascular plants, we developed a hierarchical membrane via a straightforward yet robust strategy, using isocyanate as a multifunctional additive. Thanks to the integrated functions of a phase separation regulator, blowing agent, cross-linker, and functionalization anchor of isocyanate, our strategy is featured as a perfect combination of a phase separation and chemical reaction, and it enables synchronous engineering of the membrane hierarchy on porosity and components. The representative membrane exhibits superior water permeance (334 L/m²·h·bar), protein retention (>98%), and antifouling ability (flux recover ratio ∼ 98%). This work highlights a versatile path for pursuing a highly enhanced performance of NIPS-made membranes, from the fancy perspective of Murray bionics.