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(1) Objectives: To investigate the deviations between the morphological dimensions of finished cores and desired dimensions made by three available fabricating techniques. To assess the precious metal loss in custom precious metal post and core restorative treatment in the dental clinic. (2) Methods: Titanium posts and cores were fabricated using three different techniques: digital scanning impression technology, digital scanning wax-pattern technology, and the traditional lost-wax casting method. Geomagic Studio was used to fit the scanned model data to the digital design data of the expected preparation and to analyze the 3D deviations between the two. Precious metal debris from the precious metal post and core was collected, processed, weighed and analyzed for precious metal elements by energy-dispersive X-ray spectroscopy layered images. (3) Results: In all 48 pairs of models, there were positive and negative deviations, with the largest mean positive deviation of (0.752 ± 0.037 mm) for models made by the semi-digital scanning wax-pattern technique. A total of 7001.3 mg of metals was recovered from the waste streams collected, which contained precious metals—mainly gold, silver, and platinum. (4) Conclusions: There were discrepancies between the custom core and the expected preparation regardless of the fabrication process used. The digital scanning impression technology showed better dimensional rationality of crown cores. Custom precious metal posts and cores can have an average precious metal loss of 129.7 mg per case in the dental clinic.

This paper presents a process for efficiently recovering palladium (Pd) from spent Pd/Al2O3 catalysts used for hydrogenation reactions, using ultrasound-assisted leaching (UAL). A system composed of H2SO4 and NaCl was investigated under ultrasound-enhanced conditions and compared to regular leaching methods to demonstrate the superiority of UAL. Single-factor experiments were conducted to determine the optimal conditions for leaching, which included an ultrasound power of 200 W, a liquid–solid ratio of 5:1, a leaching time of 1 h, a leaching temperature of 60 °C, H2SO4 concentration of 60%, and 0.1 mol of NaCl. The leaching rate under these conditions was found to be 99%. Additionally, kinetic analysis of the UAL process showed that the apparent activation energy of the Pd leaching reaction was 28.7 kJ/mol, and it was found that Pd leaching from spent catalysts was controlled by diffusion. The tailings were analyzed by SEM, revealing that during ultrasonic leaching, the specific surface area of the spent catalyst increased, the mass transfer rate of the solution was accelerated, the passivation film on the surface of the spent catalyst was peeled off, and a new reaction interface was formed. This improved the leaching rate of Pd and provided a new approach to efficiently leach precious metals such as Pd from spent catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • An eco-friendly technology for precious metal recovery was developed. • Ag/Au enrichment and CuCl synthesis were achieved in one step. • CuCl synthesis process promoted recovery of Ag and Au. • Leaching of Au and Ag was achieved under mild conditions. • Less reagents and time were required for Au and Ag recovery. The present study reports a sequential, non-acid process for effective recovery of copper and precious metals from mobile phone printed circuit boards. In this process, gold and silver were first enriched during the synthesis process of cuprous chloride and then leached by thiosulfate method. Results indicated that the distribution of gold and silver in the liquid and solid phases during the synthesis of cuprous chloride process was affected by the [Cu]/[Cu2+] ratio. Enrichment of gold and silver in the residue after the cuprous chloride synthesis could be achieved by the adjusting the [Cu]/[Cu2+] ratio. The silver and gold leaching rates of the residue after cuprous chloride synthesis (93.8 % silver and 99 % gold) were much higher than those of the raw PCB sample (27.0 % silver and 14.2 % gold) under the same conditions. This process has the advantages of high leaching efficiency, high leaching rate and avoiding the use of HNO 3 or aqua regia commonly used for copper, gold and silver recovery. Thus, this study offers a promising and environmentally friendly method for recovering valuable metals from e-waste. [ABSTRACT FROM AUTHOR]

This paper presents a process for efficiently recovering palladium (Pd) from spent Pd/Al2O3 catalysts used for hydrogenation reactions, using ultrasound-assisted leaching (UAL). A system composed of H2SO4 and NaCl was investigated under ultrasound-enhanced conditions and compared to regular leaching methods to demonstrate the superiority of UAL. Single-factor experiments were conducted to determine the optimal conditions for leaching, which included an ultrasound power of 200 W, a liquid–solid ratio of 5:1, a leaching time of 1 h, a leaching temperature of 60 °C, H2SO4 concentration of 60%, and 0.1 mol of NaCl. The leaching rate under these conditions was found to be 99%. Additionally, kinetic analysis of the UAL process showed that the apparent activation energy of the Pd leaching reaction was 28.7 kJ/mol, and it was found that Pd leaching from spent catalysts was controlled by diffusion. The tailings were analyzed by SEM, revealing that during ultrasonic leaching, the specific surface area of the spent catalyst increased, the mass transfer rate of the solution was accelerated, the passivation film on the surface of the spent catalyst was peeled off, and a new reaction interface was formed. This improved the leaching rate of Pd and provided a new approach to efficiently leach precious metals such as Pd from spent catalysts.

[Display omitted] • First study of MOFs for the recovery of noble metal NPs using a fixed bed column. • Rietveld refinement of the Zr4+-mercaptosuccinate MOF, first time presented here. • Quantitative recovery of both noble metal nanoparticles and ions. • Efficient capture of noble metal nanoparticles and ions from real water samples. The increasing use of nanomaterials in commercial products has raised concerns regarding their potential effects on water quality and living organisms. So far, most sorbents available for removing nanosized inorganic pollutants from water rely on electrostatic interactions or entrapment in the sorbent pores. However, this limits their applicability in real wastewater samples containing nanomaterials with variable surface properties and sizes, along with high concentrations of competitive species such as inorganic salts and organics. Little attention has also been paid to the recovery of nanoparticles after sorption. In this work, a Zr4+-mercaptosuccinate metal organic framework (MOF) with free thiol groups was investigated as a sorbent for the removal of Au nanoparticles and Au3+ ions from water. Sorption occurs on the surface of the MOF via the formation of strong metal-thiolate chemical bonds enabling the fast uptake of noble metal nanoparticles and noble metal ions from water (within <1 h). The maximum sorption capacity was found to depend on the size of the Au nanoparticles and ranged from 8 to 41.5 mg/g. The surface functionalization of nanoparticles did not influence sorption performance, which was also maintained in natural waters of variable matrix complexity. The material was also efficient in fixed bed columns with an estimated maximum Au sorption capacity of approximately 7 mg/g, which is significantly higher than the environmental concentrations of Au nanoparticles and adequate for their removal from industrial wastewater. Importantly, the sorbed nanoparticles could be quantitatively recovered (>90 %), at the expense of material degradation, enabling their potential reuse. [ABSTRACT FROM AUTHOR]

It is a great challenge to refine precious metals from e‐wastes under mild conditions without hazardous reagents. Herein, black phosphorus (BP) was covalently functionalized with poly(N‐isopropylacrylamide) (PNIPAM) to obtain thermo/near‐infrared (NIR)‐responsive BP−P for precious metal recovery. Precious metals (Au, Ag, and Pd) with higher redox potentials than BP−P could be efficiently recovered by reduction‐driven enrichment. Taking Au as an example, the recovery process presented fast kinetics (<15 min), excellent selectivity, and high efficiency (≈98 %). Remote operation with NIR light could generate heat by BP, which induced the hydrophilic‐to‐hydrophobic transition of PNIPAM, allowing the spontaneous gathering, facile collection, and practical recycle of BP−P following Au extraction. Thanks to the unique features of BP−P, not only could high‐quality Au nanoparticles (20–30 nm) be economically extracted (cost: $0.731–1.222 g−1 Au nanoparticles; 5–6 orders of magnitude lower than the market price), but also the formed BP−P‐Au nanocomposites have potential application in hydrogen evolution reaction. [ABSTRACT FROM AUTHOR]

This paper aims to use in-situ adsorptive pyrolysis combined with ultrasonication and solvent extraction for precious metal recovery from e-waste. The pyrolysis of discarded printed circuit board (PCB) and waste cable (WC) resulted in pyrolysis oil yields of 4.2–13.0 and 6.8–13.5%, respectively. Aliphatic and single-ring compounds were the major components of the pyrolysis oil. The pyrolysis char was ultrasonicated at 40 kHz for 20, 30, and 40 min at 35 °C to separate precious metals in pyrolysis char. The amounts of Au and Ag recovered by solvent extraction experiments with 2%vol HCl/2%vol HNO 3 , 2%vol HNO 3 and 2%vol I 2 /2%vol H 2 O 2 were 36.3–61.4 and 60.7–79.9%, respectively. The total energy recovery from the pyrolysis char, oil, and gas obtained from the pyrolysis of PCB was 9.0–9.2 MJ/kg. These results indicated that in-situ adsorptive pyrolysis with ultrasonication and solvent extraction could potentially facilitate e-waste conversion for energy and metal recovery processes at a lower cost. • Fly ash from lignite coal and rice husk were used in in-situ adsorptive e-waste pyrolysis. • The discarded printed circuit board (PCB) and waste cable (WC) were used as e-waste. • Pyrolysis oil yield of PCB and WC were 4.2–13.0 and 6.8–13.5 wt%, respectively. • Au and Ag in residue solid were 36.3–61.4%, and 60.7–79.9% by solvent extraction. • The energy recovery values obtained from pyrolysis of PCB were 9.0–9.2 MJ/kg. [ABSTRACT FROM AUTHOR]

[Display omitted] • Investigation of photoactivated adsorption and reduction of precious metal ions. • Fabrication of tannin-grafted porous silica with a high grafting density. • Study of selectivity towards precious metals among common metals in wastes. • Utilization of captured precious metals for metal recovery and pollutant removal. The escalating demand and dwindling reserves of precious metals request efficient recycling techniques from electron waste. Addressing this need, we introduce a new method utilizing tannin-grafted mesoporous silica for the sunlight-boosted recovery of precious metals. Our strategy leverages the inherent photoreactivity of tannins, enabling metal–ligand complexation and plasmonic enhancement of chemical reduction. The result is a marked increase in the adsorption capacity and the high selectivity towards precious metal ions in electronic waste. Our robust covalent bonding approach concentrated tannic acids onto silica at a high density (500,000 per square micrometer), which significantly boosted the adsorption of gold ions up to an 11-fold increase, even amidst a mixture of nine other metal species. Impressively, we achieved a maximum adsorption capacity of 68.4 mmol per gram, equivalent to 13.4 g of gold per gram of adsorbent. Also, the adsorption rates for platinum and palladium ions were enhanced by 2.6 and 3.0 times, respectively. The underlying mechanism includes the visible-light-driven plasmonic hot electron transfer that affords nearly perfect selectivity for gold ions (approximately 99%). These findings not only advance the field of metal recovery from electronic waste but also offer an environmentally benign and cost-effective solution that harnesses renewable solar energy. [ABSTRACT FROM AUTHOR]

Solid waste, especially electronic waste is increasingly considered as secondary sources of base, critical, precious, rare and heavy metals. Some microorganisms that possess specific metabolic pathways, adapted to the recycling of these materials, have been shown to be a cost-effective resource in the bioleaching of such secondary sources. Bioleaching not only provides an efficient alternative to extract and recuperate metals, but it also provides a green approach for tackling environmental challenges. As such, while environmental concerns have limited the use of chemical cyanidation, biocyanidation is a more sustainable approach that utilises cyanogenic organisms that are able to solubilise gold and other noble metals via cyanogenesis and through the production of specific metabolites and siderophores. To illustrate this process, this review describes cyanogenesis and explores its use and associated challenges through the cyanogenic metabolic pathways (i.e. enzymes and intracellular functions), biocyanidation and metal complexation. In addition, the following process of metal-cyanide complex formation is also summarised. Finally, recent biotechnological developments, which promote recovery and provide guidance for the improvement of downstream processes for recovery from pregnant solutions, will be described. [ABSTRACT FROM AUTHOR]

1 Objectives: To investigate the deviations between the morphological dimensions of finished cores and desired dimensions made by three available fabricating techniques. To assess the precious metal loss in custom precious metal post and core restorative treatment in the dental clinic., 2 Methods: Titanium posts and cores were fabricated using three different techniques: digital scanning impression technology, digital scanning wax-pattern technology, and the traditional lost-wax casting method. Geomagic Studio was used to fit the scanned model data to the digital design data of the expected preparation and to analyze the 3D deviations between the two. Precious metal debris from the precious metal post and core was collected, processed, weighed and analyzed for precious metal elements by energy-dispersive X-ray spectroscopy layered images., 3 Results: In all 48 pairs of models, there were positive and negative deviations, with the largest mean positive deviation of (0.752 ± 0.037 mm) for models made by the semi-digital scanning wax-pattern technique. A total of 7001.3 mg of metals was recovered from the waste streams collected, which contained precious metals-mainly gold, silver, and platinum., 4 Conclusions: There were discrepancies between the custom core and the expected preparation regardless of the fabrication process used. The digital scanning impression technology showed better dimensional rationality of crown cores. Custom precious metal posts and cores can have an average precious metal loss of 129.7 mg per case in the dental clinic., Competing Interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Haifeng Xie reports financial support was provided by Jiangsu Commission of Health. Haifeng Xie reports financial support was provided by 10.13039/501100013058Jiangsu Provincial Key Research and Development Program. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors. Published by Elsevier Ltd.)

• Evaluated the environmental impacts of PM and REE recovery from electronic waste. • Conducted comparative LCA of three different e-waste recycle methods. • Electrochemical recovery method has lower environmental impacts in most categories. • Hydrometallurgical and pyrometallurgical methods have comparable impacts. • The impact of REE recovery from e-waste was evaluated in different scenarios. There is an ever-increasing concern regarding the electronic waste (e-waste), which is the fastest growing waste stream in the world. Incentivized by various legislations and the intrinsic value of critical metals inside, recycling of e-waste is becoming an attractive business opportunity that also benefits the environment. A novel electrochemical recovery (ER) process has been developed as a promising alternative to the existing pyrometallurgical and hydrometallurgical processes based technologies to recover base metals, precious metals, and rare earth elements (REEs) from e-waste. Experimental results indicate that the ER process has lower chemical consumption, enhanced control, and reduced energy demand compared to the pyrometallurgical and the hydrometallurgical processes. To quantify and compare the environmental performances of the three technologies, life cycle analysis has been conducted. Results show that the ER process outperforms the other two processes in almost all impact categories adopted in TRACI and ILCD while there is no clear winner between the hydrometallurgical and the pyrometallurgical processes. The highest impactful input for the ER method is hydrochloric acid, and for the pyrometallurgical method is copper scrap, while for the hydrometallurgical method, it is hydrogen peroxide, an oxidizer that accelerates base metal extraction process, that dominates the overall environmental footprint. The environmental viability of the ER process warrants the further development of ER process at industrial scale. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pt, Pd, and Rh in dilute solution were extracted by Fe-EC. • PGM ions are reduced to elemental form by flocs. • Selective mechanism of PGMs extraction by Fe-EC was discussed. • Fe-EC process can recover PGMs efficiently and simply with low cost. The recovery of platinum group-metals (PGMs) has attracted increasing attention owing to their scarcity, economic importance, and criticality. Traditional techniques for PGM recovery often involve the use of toxic reagents and require strict extraction conditions, posing challenges for their implementation in complex environments. In this paper, a novel method based on iron electrocoagulation (Fe-EC) is proposed for PGM extraction. The Fe-EC process generates iron (hydr)oxide flocs in situ, which spontaneously and uniformly adsorb and reduce PGM ions. The selectivity of PGM recovery is attributed to the higher electronegativity and standard reduction potential of PGM ions compared to base metal ions. Efficient extraction of Pt, Pd, and Rh ions from aqueous solutions was achieved using Fe-EC, with extraction efficiencies of 81.26 %, 81.32 %, and 99.66 %, respectively. These results were obtained at a voltage of 2 V and residual concentrations of 0.3072, 0.0051 and 0.0049 mg L–1. TEM-EDS and XPS characterizations of the Fe-EC flocs showed that Pt, Pd, and Rh were present in the elemental form particles. The extraction performance of base metal such as Ni, Zn, Mg and Mn ions by Fe-EC was found to be poor, with minimal reduction to elemental form. Finally, the Fe-EC flocs were subjected to acid washing and filtration, resulting in the selective recovery of Pt, Pd, and Rh products with high purities of 97.43%, 97.12%, and 97.92%, respectively. This study presents a new and environmentally friendly method for the recycling of PGMs, offering a promising approach for sustainable PGM recovery. [ABSTRACT FROM AUTHOR]

The recycling of precious metal ions is highly desirable to the environment and economy. In this work, zeolitic imidazolate framework-8 (ZIF-8), a porous and relatively stable adsorption material, was explored for the adsorption of Au from water. Important conditions affecting the adsorption performance were investigated, including pH, adsorption time, initial concentration, and temperature. In consequence, the ZIF-8 adsorbent exhibits excellent adsorption performance toward Au(III) with high adsorption capacity of 1192 mg g−1 at pH 2.5 and 298 K. In addition, the study of recycling use indicated that the stable adsorption performance being maintained after recycle twice. The adsorption process of Au(III) onto ZIF-8 undergoes a spontaneous endothermic process and fits well with the Freundlich isotherm model. Kinetics studies indicated that the kinetics follows pseudo-second-order model and the intraparticle diffusion is the adsorption rate-determining step. Mechanism studies suggested that the electrostatic interaction and partial reduction of Au(III) play vital roles in the adsorption process. This work introduces a promising adsorbent for Au separation due to its considerable adsorption capacity, outstanding stability, and facile regeneration. [ABSTRACT FROM AUTHOR]

Exergy analysis is one of the useful decision-support tools in assessing the environmental impact related to waste emissions from fossil fuel. This paper proposes a thermodynamic-based design to estimate the exergy quantity and losses during the recycling of copper and other valuable metals out of electronic waste (e-waste) through a secondary copper recycling process. The losses related to recycling, as well as the quality losses linked to metal and oxide dust, can be used as an index of the resource loss and the effectiveness of the selected recycling route. Process-based results are presented for the emission exergy of the major equipment used, which are namely a reduction furnace, an oxidation furnace, and fire-refining, electrorefining, and precious metal-refining (PMR) processes for two scenarios (secondary copper recycling with 50% and 30% waste printed circuit boards in the feed). The results of the work reveal that increasing the percentage of waste printed circuit boards (PCBs) in the feed will lead to an increase in the exergy emission of CO2. The variation of the exergy loss for all of the process units involved in the e-waste treatment process illustrated that the oxidation stage is the key contributor to exergy loss, followed by reduction and fire refining. The results also suggest that a fundamental variation of the emission refining through a secondary copper recycling process is necessary for e-waste treatment.

[Display omitted] • The ionic COF had an high gold capture capacity from diluted aqueous solutions. • The gold capture process on the COF was extremely fast and highly selectively. • Freestanding nanopapers consisting of cellulose fibers and COF were prepared. • The nanopapers enabled efficient gold recovery from E-waste leaching solution. • The CF-COF nanopapers can be prepared with a relatively low cost. The ever-increasing production of electronic devices generates a huge amount of electronic waste (E-waste). Therefore, there is an urgent need for advanced recycling technology for E-waste that provides both economic and environmental benefits. Herein, we describe the preparation of flexible, freestanding CF-COF nanopapers consisting of cellulose fibers (CFs) and guanidinium-based ionic covalent organic framework (COF) that can be used for recovering gold from E-waste leaching solutions via a membrane separation technique. Due to the synergetic effects of physical adsorption, ion exchange and chemical reduction, the COF has an extremely high capture capacity (up to 1,794 mg of Au per gram of COF), is highly selective and has fast kinetics for adsorbing trace amounts of [AuCl 4 ]− in aqueous solution. The high COF loadings (∼50 wt%) and hierarchical porosity of the CF-COF nanopapers resulted in excellent performance when capturing gold species from the E-waste leaching solution. This study provides new possibilities for developing sustainable membrane materials, and highly efficient and cost-effective techniques for the recovery of precious metals from E-waste. [ABSTRACT FROM AUTHOR]

Rational design of functional material interfaces with well-defined physico-chemical-driven forces is crucial for achieving highly efficient interfacial chemical reaction dynamics for resource recovery. Herein, via an interfacial structure engineering strategy, precious metal (PM) coordination-active pyridine groups have been successfully covalently integrated into ultrathin 1T-MoS 2 (Py-MoS 2 ). The constructed Py-MoS 2 shows highly selective interfacial coordination bonding-assisted redox (ICBAR) functionality toward PM recycling. Py-MoS 2 shows state-of-the-art high recovery selectivity toward Au 3+ and Pd 4+ within 13 metal cation mixture solutions. The related recycling capacity reaches up to 3343.00 and 2330.74 mg/g for Au 3+ and Pd 4+ , respectively. More importantly, above 90% recovery efficiencies have been achieved in representative PMs containing electronic solid waste leachate, such as computer processing units (CPU) and spent catalysts. The ICBAR mechanism developed here paves the way for interface engineering of the well-documented functional materials toward highly efficient PM recovery.

Microalgal residue was chemically modified by immobilizing a functional group of dithiooxamide to prepare a novel type of adsorbent. This adsorbent exhibited high adsorption affinity and selectivity for Pd(II) and Pt(IV) whereas the adsorption of coexisting base metal ions was negligible. From the adsorption isotherms, this adsorbent was found to exhibit remarkably high adsorption capacity. The thermodynamic parameters indicated that the adsorption is governed by an endothermic reaction. The effective separation of Pd(II) and Pt(IV) from Cu(II) was confirmed also by a dynamic adsorption test. The effectiveness of elution of adsorbed Pd(II) and Pt(IV) was 85% and 96%, respectively. [ABSTRACT FROM PUBLISHER]

• The high extractability (yield of 99.07%) and selectivity (purity of 94.02%) for the Pd over other metal ions. • The RSM optimization approach was used to determine the optimal conditions of operational parameters (with error of 0.32%). • The CCD revealed that the predicted data were in good agreement with the observed ones (R2 = 0.9762). In this study, electrometallurgy recovery of Pd from the spent petrochemical unit Pd/Al 2 O 3 catalyst has been reported. The electrochemical deposition of Pd from the acid solution (HCl/H 2 O 2) was developed using flat plate graphite electrodes. The effect of the operating variables was assessed and optimized by employing the central composite design of the response surface methodology. The recovery efficiency of Pd was obtained 99.07% at the optimum condition of, reaction temperature of 67.0 °C, electrolysis time of 3.4 h, liquid/solid ratio of 24.7 ml/g, a current density of 196 A/m2 and stirring speed of 572 rpm. The results of the statistical analysis indicated that the anticipated data were in good suitable with the observed ones (R2 = 0.9762), in which the average deviation from experimental data was 0.32% for optimum condition. It indicates that the deposited Pd has spherical nanoparticles shape with a purity of 94.02%. The present study can provide a reliable process for extraction of Pd from the solid waste by the high efficiency and purity. [ABSTRACT FROM AUTHOR]

Precious metals, such as platinum group metals (PGMs) with distinct catalytic activity, are widely used as active components in various industrial catalysts. It is, therefore, highly desirable to recover these valuable components from the end-of-life products. We explored treatment of refining wastewater from precious metals recovery using direct contact membrane distillation (DCMD). The role of various initial pH of refining wastewater on DCMD performance was assessed. Results suggested that hydrochloride acid (HCl) and high-quality water can be reclaimed from the real refining wastewater by adjusting initial pH. Furthermore, DCMD water flux decline was mainly caused by silica and chromium (III) scaling, which was dependent on initial pH of refining wastewater. Silica scaling was responsible for the decrease of DCMD performance when the initial pH of refining wastewater increased from original 0.03 to 5 and 7. Silica oligomers in the concentrated feed with various initial pH were identified using mass spectra. Dichlorotetraaquochromiun was identified by X-ray photoelectron spectroscopy and ultraviolet and visible absorbance spectra as the main species contributing to the green colour and scaling on the PTFE membrane surface. Our results suggest that DCMD can be used as a promising and feasible solution for resource recovery from acidic refining waste stream. Image 1 • DCMD process was first applied to the treatment of real refining waste stream. • High-quality hydrochloride acid (HCl) was recovered. • System performance was negatively influenced by silica and chromium (III) scaling. • Chromium (III) scaling was dependent on initial pH of feed. • Chemistry of silica and chromium (III) in membrane scaling was elucidated. [ABSTRACT FROM AUTHOR]

Conventional chemical and physical methods to remove antibiotics from wastewater consume large amount of energy and chemicals, and the efficiency of biological process in converting antibiotics is relatively low. Microbial electrolysis cell (MEC) has been employed to degrade recalcitrant organic compounds recently. Given it is an energy consuming device, it would be more sustainable if driven by renewable energy, e.g. power from microbial fuel cell (MFC). Here, chloramphenicol (CAP) was chosen as a representative antibiotic that is abundant in the environment, and Ag ion contained wastewater as electron acceptor in MFC, to demonstrate the feasibility of a self-driven system for recalcitrant removal and resource recovery. It was found that CAP removal in MEC can be successfully driven by Ag(I) reduced MFC without external energy consumption. Method of one-factor-at-a-time (OFAT) and response surface methodology (RSM) with central composite design were used to evaluate the system performance. Under the optimum condition, 99.8% of Ag(I) in MFC and 98.8% of CAP in MEC can be converted. EDX and XPS revealed that pure silver was obtained on the surface of electrode in MFC, reflecting Ag(I) was reduced to valuable product. The concept and methods developed in this study can be also applied to design other types of self-driven BES systems for simultaneous pollutants removal and resources recovery. Unlabelled Image • CAP degradation MEC was successfully driven by Ag(I) reduced MFC. • System performance was optimized using response surface methodology. • Pure silver was recovered in MFC. • CAP was completely degraded in MEC. [ABSTRACT FROM AUTHOR]

The use of precious metals in many areas, such as printed circuit boards, catalysts, and targeted drugs, is increasing due to their unique physical and chemical properties, but their recovery remains a great challenge. Here, we report a sandwiched Ti 3 C 2 T x MXene/carbon nanotube (CNT) hybrid membrane, where the CNT isolates and supports the MXene sheets, which act as a reducing agent. The hybrid membrane shows excellent ability to capture precious metal ions in solution with a high flux. The water permeability of the membrane reaches 437.6 L m -2 h -1 bar -1 (2.46 × 10 -18 m 2 ), about 202 times higher than that of a pure Ti 3 C 2 T x membrane, and captures 99.8% Au(III) from a solution with an extremely low concentration of 20 ppm. The desirable precious metal trapping capability of the Ti 3 C 2 T x -CNT film is due to the high redox activity of C-Ti-OH. This work provides an efficient way for the recovery of precious metal ions from wastewater.

Exergy analysis is one of the useful decision-support tools in assessing the environmental impact related to waste emissions from fossil fuel. This paper proposes a thermodynamic-based design to estimate the exergy quantity and losses during the recycling of copper and other valuable metals out of electronic waste (e-waste) through a secondary copper recycling process. The losses related to recycling, as well as the quality losses linked to metal and oxide dust, can be used as an index of the resource loss and the effectiveness of the selected recycling route. Process-based results are presented for the emission exergy of the major equipment used, which are namely a reduction furnace, an oxidation furnace, and fire-refining, electrorefining, and precious metal-refining (PMR) processes for two scenarios (secondary copper recycling with 50% and 30% waste printed circuit boards in the feed). The results of the work reveal that increasing the percentage of waste printed circuit boards (PCBs) in the feed will lead to an increase in the exergy emission of CO2. The variation of the exergy loss for all of the process units involved in the e-waste treatment process illustrated that the oxidation stage is the key contributor to exergy loss, followed by reduction and fire refining. The results also suggest that a fundamental variation of the emission refining through a secondary copper recycling process is necessary for e-waste treatment. [ABSTRACT FROM AUTHOR]

Precious metals such as palladium (Pd) and platinum (Pt) are marvelous materials in the fields of electronic and catalysis, but they are tapering day by day. Zr(IV)-based metal-organic frameworks (MOFs) are competent for their recovery, notably in harsh environments, while the general powder form limits their practical application. Porous MOF-based membranes with ultraefficient metal ion permeation, strong stability, and high selectivity are, therefore, strikingly preferred. Herein, a set of polymeric fibrous membranes incorporated with the UiO-66 series are fabricated; their adsorption/desorption capabilities toward Pd(II) and Pt(IV) are evaluated from strongly acidic solutions; and the MOF-polymer compatibilities are investigated. Polyurethane (PU)/UiO-66-NH 2 showed strong acid resistance and high chemical stability, which are attributable to strong π-π interactions between PU and MOF nanoparticles with a high configuration of energy. The as-fabricated MOF membranes show extremely good adsorption/desorption performances without ruptures/coalitions of nanofibers or leak of MOF nanoparticles, and successfully display the efficacy in a gravity-driven or even continuous-flow system with good recycle performance and selectivity. The as-fabricated MOF membranes set an example of potential MOF-polymer compatibility for practical applications., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)