Abstract 

Water pollutants, such as industrial wastes, mining activities and radioactive waste, have gathered much attention in the last few years, due to the negative impact pollutants can have on the quality of water. Such substances can be easily transferred through water to humans, animals and the environment causing severe health issues. Among the different water-treatment processes, adsorption is of high interest for metal ion removal from wastewater (Crini et al. 2019). Moreover, over the different sorbent materials that can be employed, functionalized electrospun fibers can demonstrate strong uptake capacities and high selectivity among various metal ions.

Electrospinning is a simple, low-cost, and highly versatile technique that can be employed in the fabrication of fibers with tunable morphology and diameters. Properties including the high surface-to-volume ratio, high porosity, and high affinity towards specific kinds of metal ions, set such materials as excellent candidates in various water treatment applications ranging from adsorption of precious metal ions, removal of heavy metal and radioactive elements, to oil-water separation (Guo et al., 2022; Cheng et al., 2023). Moreover, the possibility of functionalization of the fibers with various functional groups can lead to a higher affinity of the fibres with the metals, achieving even higher adsorption capacities.

The current work describes the preparation and functionalization of fibrous membranes, using the electrospinning method, that can be potentially used as sorbent materials for the wastewater treatment and recovery of Precious Metals (PM) from aqueous solutions. For this purpose, a combination of two polymers namely Polyethylene oxide (PEO) and Polymethyl methacrylate (PMMA) was used, along with the incorporation of an active component (i.e. a dithioester compound), to further enhance the ability of the fibers to form strong complexes with PM ions in acidic conditions. The produced fibers were characterized in terms of morphology and chemical stability and evaluated as potential sorbent materials for the effective Palladium (Pd) recovery from acidic aqueous model solutions.

Crini, G., & Lichtfouse, E. (2019). Advantages and disadvantages of techniques used for wastewater treatment. In Environmental Chemistry Letters (Vol. 17, Issue 1, pp. 145–155). Springer Verlag.

Guo, W., Guo, R., Pei, H., Wang, B., Liu, N., & Mo, Z. (2022). PAN/PEI Nanofiber Membrane for Effective Removal of Heavy Metal Ions and Oil–Water Separation. Journal of Polymers and the Environment, 30(11), 4835–4847.

Cheng, N., Zhang, L., Wang, M., Shu, J., Shao, P., Yang, L., Meng, X., Fan, Y., & Li, M. (2023). Highly effective recovery of palladium from a spent catalyst by an acid- and oxidation-resistant electrospun fibers as a sorbent. Chemical Engineering Journal, 466, 143171.

#Electrospinning #ElectrohydrodynamicAtomisation #ESEE2024 #Research #Innovation #MaterialsScience #Sustainability #PalladiumRecovery 

Abstract 

Introduction – The electric and electronic industry heavily consumes gold, driving constant device upgrades. Mining, predominant in over 100 countries, faces challenges like geopolitical tensions and environmental concerns. Recycling is crucial to supplementing the gold supply. Extensive studies reveal high gold content in electric and electronic waste (WEEE), particularly in Printed Circuit Boards (PCBs), making them valuable for secondary gold recovery efforts. The work is part of the Italian project PRIN Green and Sustainable Urban Mining of Noble Metals (DURABLE Project), which aims is the secondary production of gold and other precious metals from spent catalysts and WEEE. In this study, hydrometallurgical treatment of PCBs has been identified as the most suitable extraction process. Conversely, adsorption has been deemed the optimal refining process owing to its procedural simplicity and the availability of promising materials.

Experimental - The main aim was to assess the adsorption capacities of four sorbents: three electrospun nanofibers (α, β, and γ EFs) made of Polyethylene oxide (PEO) and polymethyl methacrylate (PMMA) with varying Dithioester percentages (0%, 5%, and 10%), and 𝑈𝑖𝑂 − 66 − 𝑁𝐻2, a Zirconium-based metal-organic framework (MOF). These were tested with two model leaching solutions: one containing only gold (Au) and another with gold and copper (Au/Cu) in a 1:1000 molar ratio. Since copper is prevalent in real leaching solutions, testing with copper was crucial due to its impact on gold recovery. Three matrix conditions with different HCl concentrations (1M, 0.1M, and 0.01M) were examined. Adsorption equilibrium was evaluated under various operating conditions for both leaching solutions.

Results and Discussion - MOFs and electrospun nanofibers displayed differing behaviours: 𝑈𝑖𝑂 − 66 − 𝑁𝐻2 showed increased uptake capacity with decreasing HCl molarity, whereas membranes exhibited the opposite trend. Among the membranes, 𝛾 consistently outperformed others. Specifically, 𝑈𝑖𝑂 − 66 − 𝑁𝐻2 exhibited twice the uptake capacity of 𝛾 in the Au leaching model solution but was four times less efficient in the presence of copper in the Au/Cu leaching model solution. Interestingly, the presence of copper substantially boosted the uptake capacity of all electrospun nanofibers, while membranes showed minimal variation in copper concentration after the tests. Selectivity in gold adsorption is crucial for facilitating subsequent metal separation steps.

Conclusions - This study highlights the efficacy of recycling electronic waste, particularly PCBs, for secondary gold recovery. Hydrometallurgical treatment of PCBs and adsorption emerged as promising methods. MOFs exhibited enhanced uptake capacity with decreasing HCl molarity, while electrospun nanofibers showed increased capacity in the presence of copper. Selectivity in gold adsorption is crucial for efficient metal separation. Overall, this research contributes to sustainable resource management and circular economy efforts.

#GreenChemistry #SustainableEngineering #UrbanMining #CircularEconomy #WEEE #Research #Collaboration #GoldRecovery #CopperRecovery #NextGenerationEU 

Abstract 

Rapid technological advances have led to an increase in Waste Electrical and Electronic Equipment (WEEE), which contains hazardous elements such as lead, mercury and flame retardants that release dioxins when incinerated, posing serious environmental and health risks [1]. WEEE is rich in valuable metals such as copper, iron, nickel, silver, gold and platinum. For example, one tonne of e-waste can contain up to 0.2 tonnes of copper, and discarded mobile phones have high concentrations of gold. Therefore, WEEE is an important source for precious metals recovery, which is essential to meet sustainable demand for metal resources and support the circular economy. 

This work investigates a biosustainable method for the recovery of precious metals from WEEE, focusing on the valorisation of biowastes, using biomolecules such as humic acids (HA). Specifically, two types of HA extracted from different biowastes were tested as potential sorbents for precious metal ions. The study evaluated the uptake capacity of these biomolecules for three metal ions - Au³⁺, Pd²⁺ and Cu²+, under different conditions, including changes in pH, temperature and metal ion concentrations. Both biosorbents exhibited excellent adsorption capacities for both gold and palladium ions, especially at pH 3, reaching adsorption efficiency of about 300 mg/g of biosorbent and 200 mg/g of biosorbent of Au3+ and Pd2+ ions, respectively, while they showed no significant interaction with copper ions. The selectivity of the sorbents was evaluated in multi-metal solutions, confirming that effective adsorption requires simultaneous adsorption and reduction processes.

The use of biowaste-derived sorbents for metal recovery from WEEE is a promising technological solution in line with circular economy principles. In addition, this approach offers an environmentally friendly and cost-effective alternative to traditional electrochemical reduction processes.

#MYCS2024 #SCIgiovani #Sustainability #EWaste #humicacids #MetalRecovery #CircularEconomy #Innovation #UniNA #DICMaPI 

Abstract 

Gold is a key material for the electronics industry due to its valuable properties such as corrosion resistance, stability, and conductivity. The growing demand for gold, driven by advancements in electronics, has raised concerns over the environmental impact of traditional mining processes and generates increasing attention toward urban mining, i.e. the recovery of secondary gold from waste materials. Hydrometallurgical recycling methods are increasingly employed to recover gold from the waste of electrical and electronic equipment (WEEE), where gold is particularly abundant in printed circuit boards (PCBs). Hydrometallurgical processes involve a leaching step to dissolve metals in acidic aqueous solutions, followed by a refining step, often carried out by solvent extraction, precipitation, and adsorption. In this work, we will report experimental findings on using new electrospun fibers for the adsorption of gold in hydrochloric acid-based leaching solutions. Electrospun fibers stand out due to their unique properties: high porosity, permeability, and surface area, along with chemical resistance. Electrospinning allows for the use of diverse polymers and the incorporation of functional groups to enhance the adsorption of specific metal ions: this study focuses on the fabrication and performance of electrospun fibers made from polyethylene oxide (PEO) and polymethyl methacrylate (PMMA) functionalized with dithioester (2-cyano-2-propylbenzodithioate). These fibers were tested with two acidic model leaching solutions: one containing gold (Au) alone and another with gold and copper (Au/Cu), simulating real hydrometallurgical conditions for WPCBs. The results showed high stability of the membranes in the acidic solutions and high adsorption capacities, overcoming 100 mg/g under different operating conditions and for dissolved gold concentration even below 20 mg/L. Besides, the experiments indicated that the presence of copper enhanced the fibers' overall adsorption efficiency while maintaining strong selectivity for gold ions. These findings emphasize the potential of functionalized electrospun fibers as highly effective and sustainable materials for recovering gold from WEEE. This offers a promising solution to reduce dependence on mining practices. Additionally, these sorbents can serve as valuable options for producing new functional materials, such as waste-derived catalysts.

#DURABLEproject #ESEE2025 #GoldRecovery #CircularEconomy #Ewaste #Sustainability #Electrospinning #GreenChemistry