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Associate Professor Zhang Yi, Associate Professor He Hongxing & Researcher Nie Zhifeng from Kunming University: Ionic Liquid-Modified PVC Nanofibers Enhance Gold Recovery from Wastewater through Light-Enhancing Effect
With rapid industrial development, gold as a precious metal has been widely used in various industrial fields. However, wastewater from metallurgical industries contains gold, and direct discharge causes resource waste and economic losses. While novel adsorbents like MOFs, COFs and functionalized polymers demonstrate satisfactory gold adsorption capabilities, they face limitations including complex synthesis, high costs, poor acid/alkali resistance, and difficult recycling. In contrast, electrospun nanofibers offer simpler preparation, cost-effectiveness, and easier recyclability. Their unique long fibrous morphology provides extensive grafting areas for functional adsorption sites, ensuring effectiveness and feasibility. Therefore, developing functional electrospun nanofibers for efficient gold recovery from wastewater is crucial for precious metal recycling.
Recently, Associate Professor Zhang Yi, Associate Professor He Hongxing and Researcher Nie Zhifeng from Yunnan Key Laboratory of Metal-Organic Molecular Materials and Devices at Kunming University published their latest electrospinning research in Chemical Engineering Journal: "An ionic liquid-modified PVC nanofiber facilitates gold recovery from wastewater by a light-enhancing effect." The team prepared light-responsive ionic liquid-modified polyvinyl chloride (IL-PVC) nanofibers via electrospinning and chemical grafting for efficient gold recovery from metallurgical wastewater. Under light irradiation, IL-PVC achieved 1243.75 mg/g Au(III) adsorption within 18 hours - 1.6 times higher than in darkness. IL-PVC also showed high Au(III) selectivity (distribution coefficient: 531.08 L/g) in simulated wastewater and maintained stable adsorption efficiency through six cycles.
Figure 1: Morphological and structural characterizations of IL-PVC nanofibers.
IL-PVC nanofibers were fabricated via electrospinning and chemical grafting. As shown in Figure 1, pristine PVC nanofibers exhibited uniform diameters without beading. Modified fibers showed rougher surfaces and increased diameters. Successful 4,4'-bipyridine grafting was confirmed by SEM, FTIR and ssNMR. XRD and EDS verified gold adsorption on IL-PVC surfaces.
Figure 2: Effects of pH and temperature on the adsorption process.
Figure 3: Adsorption kinetics and isotherm fitting of the adsorption process.
Figure 4: Selectivity and recyclability of IL-PVC for Au(III) adsorption.
Figure 5: XPS spectra (under dark and light conditions respectively).
Figure 6: Electrochemical and EPR characterizations of IL-PVC.
Figure 7: Relevant DFT calculations of the adsorption process.
Studies on pH, temperature, initial concentration and time revealed spontaneous endothermic adsorption with capacity increasing with temperature. Kinetic and isotherm analyses indicated monolayer chemical adsorption dominated the process. In simulated industrial wastewater, IL-PVC demonstrated remarkable Au(III) selectivity and adsorption efficiency.DFT calculations and XPS analysis revealed synergistic electrostatic, coordination and redox mechanisms. Electrochemical and EPR characterizations confirmed photo-generated electrons enhanced gold reduction, boosting adsorption. This light-enhanced strategy provides novel insights for gold recovery from wastewater.
This work comprehensively investigated IL-PVC's gold recovery phenomenon and mechanism through experiments and theoretical calculations, offering an effective approach for precious metal recycling using functional electrospun nanofibers.
