Star polymer-mediated in-situ synthesis of silver-incorporated reverse osmosis membranes with excellent and durable biofouling resistance

High-stable bimetallic AgCu nanoalloys with core-shell structures for sustainable antibacterial and biofouling mitigation in nanofiltration

Nanofiltration (NF) is crucial for advancing water purification and wastewater reuse technologies. Incorporating biocidal nanoparticles (NPs) such as AgNPs and CuNPs is promising for developing antibacterial and antibiofouling NF membranes, while their application is limited by NPs aggregation, high cost, and severe ion release. In this study, we developed novel NF membranes by integrating bimetallic AgCu nanoalloys via an in-situ reduction and coordination method facilitated by a polydopamine/polyethyleneimine (PDA/PEI) intermediate layer. The sequential deposition of Cu2+ onto nascent AgNPs formed uniform AgCuNPs with a unique core-shell structure. The Cu shell layer can shield the release of Ag+ from the Ag core and chelate with the PDA/PEI intermediate layer, thus controlling the release of biocidal ions and prolonging the biocidal properties of the membranes. As a result, the AgCuNP-modified membranes exhibited significantly improved membrane water permeability, salt rejection, and performance stability, along with reduced release of biocidal ions in the long-term operation. Notably, the bimetallic AgCuNP-modified membrane displayed superior antibacterial activity and biofouling reversibility compared to the commercial NF and monometallic Ag/Cu-modified membranes, achieving the highest sterilization rate (> 99 %), largest flux recovery rate (93 %), and lowest flux decline rate (16 %) in both static antibacterial and dynamic biofouling processes. The metal-semiconductor heterostructure of the AgCuNPs facilitated the electron transfer from the Ag core to the Cu shell, intensifying the substantial generation of reactive oxygen species (H2O2: 71.6 mmol l-1 m-2, •OH: 43.4 mmol l-1 m-2, and O2•-: 1.3 × 10-4) at the membrane-bacteria interface. The synergistic effects of the unique properties of AgCuNPs including microstructure, atomic composition, charge transfer, and ROS generation significantly enhanced the antibacterial capacity of the AgCuNP-modified membrane. This study presents a facile method for modifying NF membranes with bimetallic AgCuNPs to achieve enhanced antibacterial activity and biofouling reversibility, providing fundamental insights and promising potential for water treatment applications.

Efficient recovery and recycling/upcycling of precious metals using hydrazide-functionalized star-shaped polymers

There is a growing demand for adsorption technologies for recovering and recycling precious metals (PMs) in various industries. Unfortunately, amine-functionalized polymers widely used as metal adsorbents are ineffective at recovering PMs owing to their unsatisfactory PM adsorption performance. Herein, a star-shaped, hydrazide-functionalized polymer (S-PAcH) is proposed as a readily recoverable standalone adsorbent with high PM adsorption performance. The compact chain structure of S-PAcH containing numerous hydrazide groups with strong reducibility promotes PM adsorption by enhancing PM reduction while forming large, collectable precipitates. Compared with previously reported PM adsorbents, commercial amine polymers, and reducing agents, S-PAcH exhibited significantly higher adsorption capacity, selectivity, and kinetics toward three PMs (gold, palladium, and platinum) with model, simulated, and real-world feed solutions. The superior PM recovery performance of S-PAcH was attributed to its strong reduction capability combined with its chemisorption mechanism. Moreover, PM-adsorbed S-PAcH could be refined into high-purity PMs via calcination, directly utilized (upcycled) as catalysts for dye reduction, or regenerated for reuse, demonstrating its high practical feasibility. Our proposed PM adsorbents would have a tremendous impact on various industrial sectors from the perspectives of environmental protection and sustainable development.

Engraving Polyamide Layers by In Situ Self-Etchable CaCO3 Nanoparticles Enhances Separation Properties and Antifouling Performance of Reverse Osmosis Membranes

Nanovoids within a polyamide layer play an important role in the separation performance of thin-film composite (TFC) reverse osmosis (RO) membranes. To form more extensive nanovoids for enhanced performance, one commonly used method is to incorporate sacrificial nanofillers in the polyamide layer during the exothermic interfacial polymerization (IP) reaction, followed by some post-etching processes. However, these post-treatments could harm the membrane integrity, thereby leading to reduced selectivity. In this study, we applied in situ self-etchable sacrificial nanofillers by taking advantage of the strong acid and heat generated in IP. CaCO3 nanoparticles (nCaCO3) were used as the model nanofillers, which can be in situ etched by reacting with H+ to leave void nanostructures behind. This reaction can further degas CO2 nanobubbles assisted by heat in IP to form more nanovoids in the polyamide layer. These nanovoids can facilitate water transport by enlarging the effective surface filtration area of the polyamide and reducing hydraulic resistance to significantly enhance water permeance. The correlations between the nanovoid properties and membrane performance were systematically analyzed. We further demonstrate that the nCaCO3-tailored membrane can improve membrane antifouling propensity and rejections to boron and As(III) compared with the control. This study investigated a novel strategy of applying self-etchable gas precursors to engrave the polyamide layer for enhanced membrane performance, which provides new insights into the design and synthesis of TFC membranes.

Design of Microstructure-Engineered Polymers for Energy and Environmental Conservation

With the ever-growing demand for sustainability, designing polymeric materials using readily accessible feedstocks provides potential solutions to address the challenges in energy and environmental conservation. Complementing the prevailing strategy of varying chemical composition, engineering microstructures of polymer chains by precisely controlling their chain length distribution, main chain regio-/stereoregularity, monomer or segment sequence, and architecture creates a powerful toolbox to rapidly access diversified material properties. In this Perspective, we lay out recent advances in utilizing appropriately designed polymers in a wide range of applications such as plastic recycling, water purification, and solar energy storage and conversion. With decoupled structural parameters, these studies have established various microstructure-function relationships. Given the progress outlined here, we envision that the microstructure-engineering strategy will accelerate the design and optimization of polymeric materials to meet sustainability criteria.