Separation Of Precious Metals Research Articles

Intensifying separation of Pb and Sn from waste Pb-Sn alloy by ultrasound-assisted acid leaching: Selective dissolution and sonochemistry mechanism

Clean and efficient extraction and separation of precious metals from discarded Pb-Sn alloy is critical to the sustainable utilization of solid waste resources. Dense oxide layer and compact alloy texture in the waste Pb-Sn alloy pose challenges to the effective leaching process. Ultrasonic waves are demonstrated to improve separation efficiency via the favorable physical and chemical effects in solution system. In this study, ultrasound-assisted leaching technology is attempted to rapidly and selectively extract Pb from the waste Pb-Sn alloy, and gives emphasis on ultrasonic electrochemical behaviors. The Eh-pH diagrams of Sn-H2O and Pb-H2O systems were firstly analyzed to lay the selective dissolution foundation. It’s indicated that oxidizing HNO3 lixiviant is suitable to realize the selective separation of Pb. Both Sn and Pb can be dissolved to ionic Sn2+ and Pb2+ in the HNO3 solution. However, Sn2+ rapidly oxidizes to Sn4+ and Sn4+ further hydrolyzes to insoluble SnO2, which will agglomerate on unreacted materials to limit internal metal leaching in conventional leaching process. Due to the vibratory stripping of oxide layer by physical effect of ultrasound, the conventional acid leaching time for Pb extraction can be halved with the ultrasound assistance. About 99.12 % Pb and only 0.1 % Sn are dissolved in ultrasound-assisted leaching under the following optimal parameters: 0.5 mol/L HNO3, leaching temperature of 80 °C, time of 30 min, liquid-to-solid ratio of 20 mL/g, and ultrasound intensity of 0.52 W/cm2. Leaching kinetics of Pb, phase transition, microstructure evolution, Pb-Sn galvanic corrosion and dissolution polarization curve were studied to determine the ultrasonic enhanced dissolution mechanism. Notably, Pb and Sn form a microcorrosion galvanic cell in which Sn acts as a cathode and is protected while the Pb undergoes intensifying corrosion as the anode giving rise to the higher Pb dissolution efficiency. Eventually, it’s suggested that Pb can be rapidly extracted and separated from the waste Pb-Sn alloy during the ultrasound-assisted HNO3 leaching process via the ultrasound physical and chemical effects, especially the sonochemistry aspect of intensified spot corrosion and galvanic corrosion. The proposed ultrasonic electrochemical corrosion in this work were applicable to the extraction of valuable metals from various waste alloys through leaching method.

Study on the extraction and separation of precious metals from wastewater using a hydrophobic deep eutectic solvent

Efficient and sustainable recovery of precious metals from the acidic leaching solution of solid waste is considered to be the main solution to the scarcity of precious metal resources. In this study, a hydrophobic deep eutectic solvent (HDES) was synthesized using trioctylmethylammonium chloride (N263) and oleic acid (OA). HDES was then used for the efficient recovery of Ir, Pt, Ru, and Rh from leaching solution containing precious metals. The effects of different molar ratios between N263 and OA, the initial pH of the aqueous phase, the oscillation time, and the phase ratio O/A of the extraction process were investigated. The organic phases were characterized analytically using ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, and electrospray ionization–mass spectrometry to further investigate the reaction mechanisms of the extraction process. The single-stage extraction percentages of Ir(IV), Ru(III), Pt(IV), and Rh(III) ions were 97.57%, 94.26%, 99.55%, and 15.1%, respectively. The high saturation extraction capacity of HDES enabled a high precious metal load, reaching 18.44 g L−1. Hydrogen bonds were formed between Cl-, which was bound by electrostatic force in the N263 structure, and H in the -COOH group in the OA molecule. During the extraction process, metal chloride complex ions replaced Cl- and entered the organic phase as 2[C17H33-COOH···N263+]IrCl62-, 3[C17H33-COOH···N263+]RuCl63-, 2[C17H33-COOH···N263+]PtCl62-, and 3[C17H33-COOH···N263+]RhCl63-. After scrubbing for effective removal of Cu and Fe in the loaded organic phase, different systems were used for stripping. The stripping percentage of precious metal ions reached more than 96.3%, providing efficient separation of the four precious metals from wastewater.

Simultaneous leaching and separating of palladium from spent palladium catalyst by tribromide ionic liquids as non-volatile oxidizing solvents

The recovery of palladium (Pd) from secondary resources has attracted much attention because of its unique environmental effects and economic value. A novel technique for the oxidation, dissolution, and separation of precious metals is presented in this paper. Tribromide ionic liquids (ILs) with low viscosity, high stability, and strong oxidation were synthesized and applied for the one-step leaching and separation of Pd from spent Pd-Al2O3 catalysts. Through the preliminary performance test, [C1C12PYR]Br3 was selected as the optimal leaching agent from three kinds of tribromide ILs, and the reasons for the obvious difference in leaching ability were analyzed from the perspective of quantum chemistry.The optimum leaching conditions were determined as follows: leaching time was 12 h, leaching temperature was 45 °C, and the dosage of [C1C12PYR]Br3 was 0.8 g (the mass of fixed Pd was 20 mg). Under these conditions, the leaching efficiency (η%) can reach 94.82%. By optimizing the response surface methodology (RSM) model, the leaching temperature in the actual system was determined to be 50.28 °C, and the dosage of [C1C12PYR]Br3 was 0.74 g, which achieved the best economic value of the system. Using XPS, HPLC, and EDS, the leaching mechanism of Pd was demonstrated to be a process that combined redox with coordination and complexation. The kinetic study shows that the rate control step of the leaching process was a chemical reaction process. The 20% hydrazine hydrate can achieve efficient (99%) stripping of Pd in the IL phase. As a result of the leaching agent's good selectivity and reusability when used to recover spent Pd-Al2O3 catalyst, [C1C12PYR]Br3 is regarded as a promising precious metal leaching agent.

2-Mercaptobenzimidazole derivative of chitosan for silver sorption – Contribution of magnetite incorporation and sonication effects on enhanced metal recovery

The recycling of precious and strategic metals from secondary resources (including E-wastes) is of critical importance for the recovery of scarce metals widely used in High-Tech devices. Therefore, the development of efficient and selective sorbents is of great importance. The grafting of 2-mercaptobenzimidazole onto chitosan microparticles allows developing highly selective sorbents. The incorporation of magnetite particles is also a strategic aspect for facilitating the use and recovery of microparticles. Sonication (at two different frequencies: 37 kHz and 80 kHz) shows high potential for improving both kinetic and thermodynamic aspects associated with silver uptake on 2-MBI-chitosan materials. Sorption capacities as high as 3 mmol Ag g−1 can be obtained with contact times as low as 20–30 min. The sorption isotherms are successfully fitted by the Langmuir and the Sips equations, while the kinetic profiles are modeled using the pseudo-second order rate equation and the resistance to intraparticle diffusion. The sorption process is exothermic: the sonication (and the frequency of sonic generator) strongly changes the thermodynamic parameters. The sonication also speeds up metal desorption, which is highly efficient using acidic thiourea solutions: the sonication allows also reducing the concentration of thiourea in the eluent required for complete silver elution. The sorbent shows remarkable stability is terms or sorption and desorption for five successive recycling runs. The acid leachates of printed circuit board are efficiently treated with the 2-MBI-chitosan sorbent for the recovery, enrichment and separation of precious metals (Ag, Au and Pd) from base metals (major elements: iron copper, aluminum, tin).

Separation of precious metals by split-anion extraction using water-saturated ionic liquids

Split-anion extraction with water-saturated ionic liquids is a benign, efficient and selective process for recovery of precious metals from chloride media.

Sustainable extraction and separation of precious metals from hydrochloric media using novel ionic liquid-in-water microemulsion

A novel ionic liquid-in-water microemulsion (IL101/TX100/water) was developed for sustainable extraction and separation of precious metals (i.e., Au, Pd, and Pt) in acidic chloride media. Five-step protocol is composed of (i) mixing the feed solution containing precious metals with the ionic liquid based microemulsion; (ii) heating for phase splitting; (iii) phase separation; (iv) stripping; (v) regeneration. The aqueous microemulsion combines green properties of ionic liquid and advantages of microemulsion, and thus affords significant environmental benefits. Phase behaviour and structure of the microemulsion were determined by measuring the conductivity. Effect of various parameters was investigated for the complete extraction and selective recovery of highly pure precious metals (>99.9% w/w). Based on anion exchange mechanism and micellar structure of the aqueous microemulsion phase, the extraction of Au(III), Pt(IV) and Pd(II) from chloride media characterized by 31P NMR spectroscopies was proposed as{(([P66614]+)m([A]n−)q(Cl−)m-nq)(TX-100)p} where [A]n− refers to the anionic metal species to be extracted, p denotes the average aggregation number of the TX-100 micelles, m the average number of [P66614]+Cl− molecules in each (TX-100)p micelle and q the average number of [A]n− species extracted per micelle. Two-step stripping strategy was successfully adapted to treat the loaded ionic liquid-surfactant-rich (ILSR) phases with low aggressive media for the selective recovery of Au(III) with Na2S2O3 and Pd(II) and Pt(IV) with thiourea/HCl. The possible recirculation of regenerated ILSR phase without loss of performance was examined within five extraction-stripping cycles. Finally, a flow-sheet towards “zero-waste” concept was proposed for the complete extraction and selective recovery of individual precious metals using environmentally friendly aqueous microemulsion.

Precious Metals in Municipal Solid Waste Incineration Bottom Ash

Municipal solid waste incineration (MSWI) bottom ash contains economically significant levels of silver and gold. Bottom ashes from incinerators at Amsterdam and Ludwigshafen were sampled, processed, and analyzed to determine the composition, size, and mass distribution of the precious metals. In order to establish accurate statistics of the gold particles, a sample of heavy non-ferrous metals produced from 15 tons of wet processed Amsterdam ash was analyzed by a new technology called magnetic density separation (MDS). Amsterdam’s bottom ash contains approximately 10 ppm of silver and 0.4 ppm of gold, which was found in particulate form in all size fractions below 20 mm. The sample from Ludwigshafen was too small to give accurate values on the gold content, but the silver content was found to be identical to the value measured for the Amsterdam ash. Precious metal value in particles smaller than 2 mm seems to derive mainly from waste of electrical and electronic equipment (WEEE), whereas larger precious metal particles are from jewelry and constitute the major part of the economic value. Economical analysis shows that separation of precious metals from the ash may be viable with the presently high prices of non-ferrous metals. In order to recover the precious metals, bottom ash must first be classified into different size fractions. Then, the heavy non-ferrous (HNF) metals should be concentrated by physical separation (eddy current separation, density separation, etc.). Finally, MDS can separate gold from the other HNF metals (copper, zinc). Gold-enriched concentrates can be sold to the precious metal smelter and the copper-zinc fraction to a brass or copper smelter.

Recovery and Separation of Precious Metals Using Waste Paper

Abstract An adsorption gel was prepared from waste paper by immobilizing iminodiacetic acid so as to investigate its adsorption behavior for various metal ions from chloride media. The gel was found to be selective for AuIII and PdII over PtIV and other base metal ions including CuII, FeIII, NiII and ZnII at varying concentrations of hydrochloric acid. Moreover, AuIII was reduced by the gel giving rise to clearly recognizable beautiful elemental gold particles which was confirmed by means of the XRD-spectrum and SEM-images of the adsorbent after adsorption. This result has increased the prospect for mutual separation of AuIII and PdII from coexisting PtIV and base metals.

Extraction and Separation of Precious Metals by a Column Packed with Divinylbenzene Homopolymeric Microcapsule Containing Tri‐n‐octylamine

The separation of palladium, platinum, and gold was investigated using a column packed with divinylbenzene homopolymeric microcapsules containing tri‐n‐octylamine (TOA). The extraction of precious metals except platinum using the microcapsules progresses by means of the same reaction proposed in a solvent extraction system. The microcapsules also effectively extracted precious metals from an aqueous hydrochloric acid medium in the column operation. The breakthrough point is delayed in the following order: platinum, palladium, and gold. Almost all TOA molecules enclosed in the microcapsules can act on the extraction reaction with precious metals, which was confirmed by the calculation of the concentration of precious metals extracted into the microcapsules based on the breakthrough curve of each precious metal. By selecting the appropriate eluent, palladium, gold, and platinum were successfully eluted from the column using an 8.0 mol/dm3 aqueous HCI solution, a 0.1 mol/dm3 thiourea in 0.1 mol/dm3 aqueous HCI solution, and a 0.5 mol/dm3 ethylenediamine in 0.1 mol/dm3 aqueous NaOH solution, respectively. By feeding the eluent stepwise into the column in this order, the mutual separation of precious metals can be successfully achieved.

貴金属のリサイクル技術

The separation and purification methods of precious metals from the scrap containing precious metals are introduced in this review. The solid waste containing precious metals first is dissolved by the solution comprising oxidation agents and ligands, such as aqua regia, Cl2 + HCl and NaCN + O2. The separation of precious metals in the leached solution or wasted solution is carried out by using various methods like classic precipitation, cementation, ion exchange resin, activated carbon adsorption and solvent extraction. It depends on the concentration and combination of precious metals what kind of separation method is applied. Generally, adsorption and ion exchange methods are applicable to the dilute solution, while precipitation, cementation and solvent extraction are used for the concentrated solution. In the recovery of the precious metals in automobile catalyst, the collection of the platinum group metals in Cu or Fe metal melted by a plasma melting method is performed as one of the recovery techniques by the pyro-metallurgy.The fundamental of separation and purification methods, and some commercial plant examples are described for recycling of precious metals.

CHARACTERISATION OF METALFIX-CHELAMINE AND ITS APPLICATION IN PRECIOUS METAL ADSORPTION

ABSTRACT The physical and chemical characteristics of the chelating resin Chelamine, which contains a pentamine ligand, are investigated in order to consider its application in the separation of precious metals- Adsorption isotherm experiments for Pt, Pd and Au and kinetic experiments were carried out under batch procedures. The resin presents a high level of adsorption selectivity for Pt(IV), Au(III) and Pd(II) giving a capacity of 2.8 mmol/g, 3.1 mmol/g and 2.0 mmol/g respectively. Acidic solutions, complexing agents, lipophilic anions and ammonia were used for metal elution. NaClO4 solutions are the most effective eluting agents for Pt(IV) while thiourea is the best stripping agent for both Pd(II) and Au(III). Selective separation of the three metals can be achieved by sequential elution from the resin with NaClO4 solutions in different HCl concentrations and thiourea 0.5 M.

The recovery of palladium with the use of ion exchange resins

Separation of precious metals is possible with the use of ion exchange resins. Selective ion exchange resins are being developed by the industry for the chloride complexes of the precious metals. The loading isotherms and the kinetics of loading palladium onto an anion resin, Amberlite IRA 900, has been determined. Amberlite IRA 900 is a macro reticular polystyrene type I strongbase anion exchange rsein containing quaternary ammonium groups. Pure K 2PdCl 4 was used for the preparation of the single metal solution. The resin as well as the various test solutions were rolled in plastic bottles for 2 days to ensure equilibrium was attained. The best equilibrium fit was obtained with the Freundlich model. The Freundlich model also fit the kinetic data very well.

Separation of Precious Metals through a Trioctylamine Liquid Membrane

The extraction behavior of precious metals (PMs) from HCl media has been studied using trioctylamine (TOA) in kerosene. The extraction sequence of PMs was found to be Au(III) > Pd(II), Pt(IV), Ir(IV) > Ir(III). Ru. Transport of PMs was performed through a supported liquid membrane (SLM) impregnated with TOA as a mobile carrier from the HCl feed solution into the HClO4 or HNO3 product solution. Selective transport; and recovery of PMs from certain mixtures were accomplished across the TOA-SLM on the basis of differences in extraction equilibria and kinetics.

Solvent extraction of some base and precious metals using 1,3,4-thiadiazole-2-nonylmercapto-5-thiol

This investigation is one of a series of studies in which the fundamental chemistry which underlies the extraction and separation of precious metals is considered. The title compound (TNSTH) was used as a solvent extraction reagent and shows some promise for extracting and separating the chloro-anions of Au(III) and Pd(II) from strong hydrochloric acid solutions (ca. 5 M). The distribution coefficients from such media were in the order of 10 4. The title reagent may be used to separate the precious metals from each other. For example, the separation coefficients (i.e., ratios of distribution coefficients) for mixed solutions are 10 6 for Au(III)/Rh(III) and Pd(II)/Rh(III); 145 for Au(III)/Pd(II); 180 for Pd(II)/Cu(I or II); 10 6 for Pd(II)/Pt(IV). The time for half of the Pd(II) to be extracted is approximately 6 min, which is acceptable for a commercial process. The title reagent provides a means of separating precious metals from base metals as the latter, with the exception of copper, are not extracted. In the case of copper, the extraction is as Cu(I) rather than Cu(II). The stoichiometry of the Pd(II) extraction is Pd:TNSTH is 1:1.5. Some additional information concerning the nature of the complexes formed by the title compound and chloro-anions in alcoholic solution indicates that Cu(TNST), Ag(TNST), Pd(TNST) 2, and RhCl 3(TNST) 2 are formed. Most of the metals, with the notable exception of rhodium(III) and iridium(IV), can be stripped using a thiourea/HCl solution. The reagent TNSTH appears to be a chelating agent with donor N and S atoms.

Circular-paper chromatography in the separation of ions : Separation of precious metals

A. circular-paper Chromatographie method for separating the precious metals Pd +2, Pt +4, l r+4. Rh +3, Ru +3, Os +4 and Au +3, using several solvent mixtures with or without complexing agents, has been studied. Mixtures of microamounts of three or four of these metals can be effectively separated into distinct circular zones within one or two hours.

Electro-chromatography in the Separation of Inorganic Ions. Separation of Precious Metals

Electro-chromatography in the Separation of Inorganic Ions. Separation of Precious Metals