Recovery Of Silver Research Articles

Total Integration of the Sample Injection, Microdroplet Reaction, Phase Separation, Real‐Time Optical Detection, and Recovery of Diverse Silver–Gold Bimetallic Nanoalloys in a Continuous Process (Part. Part. Syst. Charact. 1/2021)

Total Integration of the Sample Injection, Microdroplet Reaction, Phase Separation, Real‐Time Optical Detection, and Recovery of Diverse Silver–Gold Bimetallic Nanoalloys in a Continuous Process (Part. Part. Syst. Charact. 1/2021)

Study of The Applications of Alkaline Protease Produced by Soil-Isolated Bacillus cereus FT 11

Proteases, enzymes widely utilized in industries such as food, pharmaceuticals, detergents, leather, among others, represent the highest-selling enzyme category globally. This study investigates the industrial applications of an alkaline protease enzyme derived from Bacillus cereus FT11, isolated from soil. The enzyme, after partial purification, demonstrated significant keratinolytic activity by degrading human hair and chicken feathers. Moreover, it effectively degraded various natural proteins including blood clots, meat, and coagulated egg albumin. Furthermore, the enzyme exhibited the capability to degrade gelatin extracted from used x-ray films, facilitating the recovery of silver, and it successfully dehaired goat skin without causing visible damage. In addition to its proteolytic properties, the enzyme proved adept at removing stubborn stains such as blood, turmeric, and plant extracts from fabrics. Notably, it displayed antibacterial activity against clinical pathogens, underscoring its potential for diverse industrial applications.Collectively, these findings highlight the enzyme's suitability for a broad array of industrial processes. Its ability to degrade complex proteins, recover valuable materials, and exhibit antimicrobial properties suggests promising practical implications. This research underscores the enzyme's potential as a versatile tool in various industrial sectors, emphasizing its role in enhancing efficiency and sustainability in processes ranging from waste management to textile and pharmaceutical production.

Economic analysis of electronics waste materials: A region based study

Effective electronic waste (E-Waste) management is necessary for maintaining the green environment. The process of recycling of e-waste material is a common practice in green manufacturing as it can enhance the productivity of an organization. In present work, the economic analysis of e-waste materials such as silver, aluminium, copper, plastic etc. is presented to justify the need of e-waste management in the current scenario. The amount of material recovery per product from common electronic equipment is discussed and it has been noticed that the highest recovery of ferrous and plastic material can be received from the refrigerator. The highest recovery of silver and copper can be received from a computer and air-conditioner respectively. A questionnaire based study was performed to gather the information of discarded electronic equipment. The approximate revenue which can be generated from E-waste from three states viz. Haryana, Punjab and Himachal Pradesh of India are presented. The results showed that maximum revenue from E-waste can be generated in Punjab and followed by Haryana.

A Deep Eutectic Solvent as Leaching Agent and Electrolytic Bath for Silver Recovery from Spent Silver Oxide Batteries

It is shown for the first time that the deep eutectic solvent, DES, formed by acetylcholine chloride and urea can be successfully used for Ag recovery from the cathode powder of spent silver oxide batteries. This DES performs two important functions namely, as selective leaching liquor to extract Ag(I) ions from the remaining Ag2O, leaving intact the metallic Ag in the solid phase, and as electrolytic bath for silver electrodeposition onto a glassy carbon electrode or graphite. Using potentiodynamic and potentiostatic electrochemical measurements, it was possible to quantify both: the Ag(I) leaching rate and the concentration of Ag(I) ions leached after 24 h. From this value, it was possible to estimate that about 7% of the original mass of the cathode powder corresponds to Ag2O and the rest to metallic Ag. Moreover, from potentiostatic current density transients, recorded during Ag electrodeposition, it was shown, for the first time in this DES, that this process occurs via multiple 3D nucleation with diffusion-controlled growth and valuable practical information i.e. the diffusion coefficient of Ag(I) ions in this media was quantified. From scanning electron microscopy images and energy-dispersive X-ray spectroscopy, the morphology and composition of the resulting deposits were characterized.

A novel hydrometallurgical treatment for the recovery of copper, zinc, lead and silver from bulk concentrates

Nowadays sulphide ores exploitation is undergoing some troubles, which are hindering the treatment through traditional routes. Bulk flotation followed by a novel hydrometallurgical process can dodge these difficulties. In this work, an integral hydrometallurgical process consists of two ferric leaching steps, followed by a hot brine leaching stage, is proposed to recover target metals from a bulk sulphide concentrate (2.9% Cu, 7.4% Zn, 2.5% Pb, 67 ppm Ag and 37.2% Fe). In the first ferric leaching step, sphalerite, galena and copper secondary sulphides are dissolved and, in the second leaching step, a silver salt is added in order to catalyse chalcopyrite oxidation. If silver salt is added at the beginning of the process, sphalerite passivation is observed, and therefore zinc recovery is not possible. However, when catalytic leaching is performed after a previous ferric leaching, copper and zinc recoveries higher than 95% are achieved. The leached concentrate (0.3% Cu, 0.8% Zn, 3.3% Pb, 1438 ppm Ag, 38.0% Fe and 6.6% S0), is treated by a hot brine leaching. When hot brine leaching is performed at high pulp density, elemental sulphur removal is necessary to recover all silver added as a catalyst. Extractions higher than 95% for Zn, Cu and Pb are achieved as well as the total recovery of catalyst. The proposed process is silver surplus; therefore, this agent can be recirculated.

Total Integration of the Sample Injection, Microdroplet Reaction, Phase Separation, Real‐Time Optical Detection, and Recovery of Diverse Silver–Gold Bimetallic Nanoalloys in a Continuous Process

AbstractMicrofluidic droplet generators have garnered great attention due to the uniformity, high‐throughput capability, and facile experimental setup. To maximize the potentials of droplet technology as a chemical/biological nanoliter‐scale reactor, the downstream processes such as separation of the aqueous and oil phase, real‐time monitoring of the products formed in droplets, and the final product recovery from the droplets is necessary. In this study, the droplet is utilized as a chemical reactor to synthesize a variety of Ag and Au bimetallic nanoalloys in a fully integrated microsystem including sample injection, a T‐junction droplet generator, droplet reaction, water–oil phase separation, real‐time UV–vis absorbance detection, and product recovery. The flow rate of the Ag nanoparticle (NP) solution and the HAuCl4 solution was tuned to generate different molar ratios of Ag and Au components. The in‐line UV–vis absorbance spectrometer displays a peak shift of the Ag/Au bimetallic alloys depending on the molar ratio of Ag/Au in the continuous process, enabling to judge the kind of the Ag/Au alloys in situ and collect a variety of Ag/Au nanoalloys. Thus, the desired nanomaterials can be obtained with minimal trial and error, saving time and cost.

Recovery of lead and silver from zinc acid-leaching residue via a sulfation roasting and oxygen-rich chlorination leaching method

A large amount of acid-leaching residue is produced during the conventional Zn hydrometallurgy process, and this residue has a large concentration of a variety of valuable metals. The purpose of this study was to evaluate the ability of a procedure that entails the use of sulfation roasting, water leaching, and chlorination leaching (blowing oxygen technique) to recover Pb and Ag, followed by cooling crystallization and the replacement of Ag with lead sheet, to realize the full recovery of all valuable metals from zinc acid-leaching residue; consequently, good results were achieved. The best results were obtained under the following conditions: a sulfuric acid at 70% of the raw material quality, roasting temperature of 300 °C and roasting time of 2 h, followed by the process of leaching the roasted residue for 1 h by applying a water-to-solid ratio of 5:1 at room temperature. The recovery rates of Zn and Fe were 98.69% and 92.36%, respectively. The main parameters of the chlorine salt leaching system were as follows: Cl− concentration of 300 g/L, Fe3+ concentration of 25 g/L, acid concentration of 2 mol/L, liquid-to-solid ratio of 9 mL:1 g, temperature of 90 °C, and leaching time of 0.5 h; this leaching process was followed by filtration separation. These conditions resulted in high extents of leaching for Pb and Ag (i.e., 98.87% and 96.74%, respectively). Finally, the kinetics of the process of Ag leaching using Cl− ions in an oxygen-rich medium was investigated. It was found that the leaching process was controlled by the diffusion of the product layers, and the activation energy was 19.82 kJ/mol.

Silver Recovery from Silver Fluoride Solution Using Electrowinning

As solar technology becomes more popular, more modules with limited lifetimes will be manufactured. By 2050 there are expected to be 78 million tons of waste modules, which are rarely recycled today. Each module contains approximately 6 grams of silver, which is the most precious metal found in silicon modules. Hydrofluoric acid is proposed as the leaching agent to remove silver and other metals from the surface of the silicon, while electrowinning is used to recover the silver from the leachate and plate it onto a cathode. The electrowinning setup uses a three-electrode configuration with a pseudo reference electrode to control the half-cell potential. A silver pseudo-reference electrode was found to be sufficient for achieving a high mass recovery rate. Variable voltage trials were conducted and 0.7 V with reference to silver achieved a high mass recovery rate of 96.4% with a high purity of silver. Current efficiency is below 7% for all the voltages tested, which suggests parasitic reactions in the reaction vessel such as O2(g) + 4H+ + 4e− ⇌ 2H2O. The trials at 0.7 V vs silver in a nitrogen purge environment eliminated corrosion at the vapor-liquid interface on the cathode but did not improve the current efficiency. It is possible that the nitrogen purge environment still contains residual oxygen.

Silver(I) recovery on sulfur-containing polymeric sorbents from chloride solutions

Silver(I) recovery on sulfur-containing polymeric sorbents from chloride solutions

Phytoremediation potential of aquatic plants in Uzbekistan for the treatment of cyanide-containing wastewater

For over a century now, the mining industry has been using cyanides for gold and silver recovery. Cyanides are highly toxic for human beings, animals, and aquatic organisms. The available physical and chemical methods of wastewater treatment are cost-ineffective. Certain microorganisms are capable of use cyanides as sources of carbon and nitrogen and turn those into ammonia and carbonate. Some plants are also efficient for the processes of cyanides destruction. Phytoremediation of cyanides may be efficient, cost-effective, environmentally friendly, and be used as an attractive alternative to traditional physical and chemical processes. This article considers the capability of aquatic plants, which grow in the valley of Zerafshan River on the territory of Uzbekistan, to dispose of cyanides and recover the cyanides-contaminated tailings of Navoi Mining & Metallurgical Combinat. Such aspects as the mechanisms of enzymatic detoxification of cyanides by aquatic plants and microorganisms are discussed. The most promising plants to be bedded in the tailings dump are selected.

The environmental performance of enhanced metal recovery from dry municipal solid waste incineration bottom ash

This study assesses the environmental performance of the municipal solid waste (MSW) incineration bottom ash (IBA) treatment plant in Hinwil, Switzerland, a large-scale industrial plant, which also serves as a full-scale laboratory for new technologies and aims at an optimal recovery of metals in terms of quantity and quality. Based on new mass-flow data, we perform a life cycle assessment that includes the recovery of iron, stainless steel, aluminium, copper, lead, silver and gold. Fraction-specific modelling allows for investigating the effect of the metal fraction quality on the subsequent secondary metal production as well as examining further metal recycling potentials in the residual IBA. In addition, the implications on the landfill emissions of IBA residues to water were quantified. The impact assessment considered climate change, eco- and human toxicity and abiotic resource depletion as indicators.Results indicate large environmental savings for every impact category, due to primary metal substitution and reduction of long-term emissions from landfills. Metal product substitution contributes between 75% and >99% to these savings in a base scenario (1′000-year time horizon), depending on the impact category. Reductions in landfill emissions become important only when a much longer time horizon was adopted. The metal-based analysis further illustrates that recovering heavy non-ferrous metals – especially copper and gold – leads to large environmental benefits. Compared to the total net savings of energy recovery (215 kg CO2-eq per tonne of treated waste, average Swiss plant), enhanced metal recovery may save up to 140 kg CO2-eq per tonne of treated waste.

Selective recovery of silver and palladium from acidic waste solutions using dithiocarbamate-functionalized cellulose

The efficient extraction and recovery of precious metals (PMs) such as silver (AgI) and palladium (PdII) from waste sources are of high importance, as natural reserves are limited, and the metals pose an environmental concern. Consequently, a biomass-based adsorbent, dithiocarbamate-modified cellulose (DMC), was used for the selective capture of AgI and PdII from complex aqueous matrices. DMC was found to be an efficient material for the quantitative adsorption of AgI, and PdII from weak to strongly acidic media. The adsorption kinetic data of AgI and PdII were well described by the pseudo-second-order (PSO) model, and the times required to reach equilibrium were 60 min and 90 min, respectively. The Langmuir isotherm model provided the best fitting for the PM ions adsorption, and the maximum uptake capacities of DMC were evaluated as 10.97 and 4.28 mmol g−1 for AgI and PdII, respectively. After extraction, the PM ion-loaded DMC was incinerated and the metals were recovered in their pure and elemental form (Ag0 and Pd0), with a yield of >99%. The proposed technique is more straightforward than the typical adsorption–desorption-based recovery method, as employed in commercial operations. Other advantages include process simplicity, high efficiency, non-utilization of toxic eluents, and recovery of the metals in their elemental form without the use of any reductants. Furthermore, the excellent performance (extraction rate: ~99%) of DMC towards the recovery of Ag and Pd from actual waste solutions indicates the potential for the application of the process at a larger scale.

Hydrometallurgical recovery of copper and silver from flotation concentrates obtained from mixed ore

Hydrometallurgical recovery of copper and silver from flotation concentrates obtained from mixed ore

Recovery of High-Purity Silver from Spent Silver Oxide Batteries by Sulfuric Acid Leaching and Electrowinning

A sustainable and effective sulfuric acid-based process with the combination of facile acid leaching and electrowinning has been developed for the recovery of valuable elements from spent silver ox...

An alternative to cyanide leaching of waste activated carbon ash for gold and silver recovery via synergistic dual-lixiviant treatment

This study reports the development of a hydrometallurgical treatment for activated carbon ash (ACA); a waste product of the carbon-in-pulp (CIP) process used in the gold mining industry, rich in adsorbed precious metals. After an initial screening of known leaching chemistries, the research focusses on dual-lixiviant (thiourea and thiocyanate) and thiourea systems, both of which have lower environmental impact than traditional cyanide leaches. Comparing ferric sulfate and hydrogen peroxide as oxidants showed that a thiourea leach is more suited to ferric sulfate whereas the dual-lixiviant leach achieved greater extraction with hydrogen peroxide. This was believed to be due to a more favourable effective [thiourea]:[thiocyanate] molar ratio in solution. The latter demonstrated faster kinetics and improved efficiency for dissolution of gold and silver. However, both leaches had issues with silver extraction due to formation of passivating layers on the surface of the silver nanoparticles. Kinetic modelling showed both systems tended towards a mixed-controlled process. Gold extraction of 89%, with leaching reaching equilibrium within 100min, using the dual-lixiviant process demonstrated that there is an alternative to cyanide leaches employed in gold recovery.

Nitric acid leaching of the copper-bearing arsenic sulphide concentrate of Akzhal

This paper examines the possibility of using the hydrometallurgical process of nitric acid leaching to process the refractory sulphide concentrate of Akzhal. The study that looked at the structure and composition of this material confirmed that the studied material has a complex mineralogy due to dissemination of gold-bearing sulphides (mainly pyrite and arsenopyrite) in the gangue and their interpenetration, as well as the presence of finely dispersed gold (10 μm) in tight assemblage with the host minerals. A series of laboratory tests, as well as mathematical experimental design techniques, helped identify the most critical parameters governing the leaching efficiency. The following process parameters are recommended: nitric acid concentration — 5 mol/dm3, L/S = 5:1,  = 1 h. A high recovery into solution can be achieved in the above conditions, %: >98 Fe; >96 As; >90 S. The authors propose to use atmospheric deposition of scorodite to dispose of leach liquors. This is achieved by means of staged neutralization until the concentration of arsenic in the liquor reaches 20 mg/dm3. Sorption techniques are applied to recover copper and zinc from leach liquors. Leach cakes are subjected to sorption cyanidation with the total recoveries of gold and silver of >94 and >64%, correspondingly. The nitrous gas recovery stage proved highly efficient — >90%. A series of pilot tests was carried out to verify the findings. Thus, the developed hydrometallurgical process was applied to the copper-bearing arsenic sulphide concentrate of Akzhal at the testing facility of KazGidroMed, a research centre for innovative technology. The tests enabled to conduct a feasibility study, which proved the proposed processing techniques to be efficient and feasible.This research study was funded by the Russian Science Foundation (Project no. 18-19-00186).The study of arsenic precipitation from leach liquor was funded by the Russian Foundation for Basic Research under the Research Project no. 18-38-00914\18.

Synthesis, silver (I) extraction and silver (I) binding studies of novel N1,N3-bis(2-(benzylthio)ethyl)propanediamide derivatives

Solvent or liquid–liquid extraction represents a highly valuable technique for the selective recovery of metals from the aqueous phase due to the ease of operation and short turnaround times. Ligands bearing soft donor atoms including nitrogen and sulfur are ideal candidates for selective silver recovery due to their preference for silver binding. Herein, novel N1,N3-bis(2-(benzylthio)ethyl)propanediamide derivatives bearing sulfur and nitrogen donor atoms were prepared in low to high yields and tested for Ag+ extraction from ternary aqueous solutions also containing Cu2+ and Pb2+ following a well-established solvent extraction protocol. It was observed that electronics effects at the 4-aryl position in the propanediamide (or malondiamide) derivatives had a significant effect on the selectivity, but little effect on the efficiency of Ag+ extraction with the 4-methoxy analogue proving the most selective. Steric hindrance provided by dimethyl substitutions at the α-positions to the sulfur atoms had negative effects on Ag+ extraction efficiency and selectivity, while diethyl steric hindrance at the methylene center lowered selectivity but increased extraction efficiency for Ag+. Detailed binding studies reveal that one of the malondiamide derivatives which lacked the electronic and steric hindrance groups studied coordinated Ag+ in a 1:1 fashion suggesting a tetrahedral complex geometry. Overall, the results show that simple modification of the electronics and sterics of the N1,N3-bis(2-(benzylthio)ethyl)propanediamides, can improve their selectivity for Ag+ recovery from the aqueous phase.

Optimization of silver recovery from waste X-ray radiographic films by oxalic acid extraction with response surface methodology

Waste X-ray radiographic films contain an appreciable amount of silver (Ag) that can be recovered and reprocessed. Most of the existing methods of Ag recovery from waste radiographic films are expensive and harmful to the environment. In this study, the extraction of Ag from waste radiographic films was done using oxalic acid solution heated at 90–100 °C. XRD and SEM results reveal that the recovered residue contains pure metallic Ag spherical microparticles. According to the response surface methodology (RSM) based on three-level, three-factorial Box-Behnken design, the optimized stripping conditions are oxalic acid concentration of 9.97% w/v, extraction temperature of 99.51 °C, and extraction time of 16.62 min. The predicted and actual % Ag recovery are of 94.94 and 90.07%, respectively. Reusability study confirms that the oxalic acid solution can be reused for several runs of Ag extraction. Initial Ag recovery of ~68.9% decreased to ~28.2% after 4 cycles of reusing the extraction solution.

Silver production from spent zinc–silver oxide batteries via leaching–cementation technique

ABSTRACT Silver recovery from a spent submarine battery was investigated. The effect of different parameters including nitric acid concentration, temperature, solid to liquid ratio (w/v%) and time was studied and results revealed that recovery increased by increasing acid concentration, temperature (up to 55°C) and solid to liquid ratio (up to 40 g/L). Recovery of silver could reach 99.99% under optimum conditions and the activation energy was found to be 22.84 KJ/mol. Moreover, the effect of Cu/Ag ratio (w %), time, pH and temperature on the precipitation of silver from PLS was studied by surface response methodology (RSM).

Извлечение золота и серебра из упорного золотосодержащего мышьяковистого флотоконцентрата месторождения «Иккижелон» с добавлением хлорида натрия в процессе автоклавного окисления

This work was aimed at developing an effective method for processing a refractory gold-arsenic flotation concentrate using an autoclave-chloride technology followed by cyanidation to recover precious metals. The research object was a flotation concentrate obtained from mixed ores mined at the Ikkizhelon deposit (Northern Tajikistan), the main valuable components of which are gold and silver. In the concentrate, the main mass of gold is associated with iron sulfide minerals (total Fe content - 81.90%), among which pyrite and arsenopyrite predominate (total As content - 90.85%). Experiments on sulfuric acid autoclave oxidation of the flotation concentrate in the presence of NaCl were carried out in a Parr series 4532 laboratory autoclave at a temperature of 220 °C for 60 minutes. Cyanidation of the as-obtained cakes was carried out for 24 hours at a concentration of 0.2% NaCN. To determine the concentration of elements in the solution and the content of solid phase components, the method of optical emission spectrometry with inductively coupled plasma by a Varian 730-ES Axial Eur (Australia) instrument was used. It was found that, following sulfuric acid autoclave (with the addition of sodium chloride) oxidation of the flotation concentrate, precious metals were practically absent in the solution. The total recovery of gold and silver from the flotation concentrate to the cake was ~ 99.9% and 99.3%, respectively. The recovery of Au by cyanidation of the obtained oxidized cakes in all experiments was 96.5-98.13%. It is shown that, the addition of sodium chloride in the process of autoclave oxidation of the studied material increased the extraction of Ag to 54.9-62.1% during cyanidation and reduced the consumption of NaCN by 24.69%. The addition of NaCl to the process of sulfuric acid autoclave oxidation of the gold-containing arsenic flotation concentrate obtained from ores mined at the Ikkizhelon deposit reduces (in comparison with the conventional processing scheme) the formation of argentojarosite AgFe 3 (SO 4 ) 2 (OH) 6 due to the formation of silver chloride forms. As a result, a high level of metal recovery is achieved during the subsequent cyanidation of the solid product of autoclave oxidation under reduced reagent consumption.