Cementation Behavior of Gold and Silver Onto Zn, Al and Fe Powders from Acid Thiourea Solutions

Lee, Hwa Young; Kim, Sung Gyu; Oh, Jong Kee

doi:10.1179/cmq.1997.36.3.149

Cited by 14 publications

(14 citation statements)

References 2 publications

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“…The temperature of the electrolyte is fixed to 35°C, and the time of experiments is kept at 30 min. Before the experiment, all solutions were de‐aerated with high purity nitrogen (99.5% purity) before the experiment for 20 min, and this atmosphere is maintained during the process (Lee et al, 1997). The used sacrificial metal is an iron grid shown in Figure 3.…”

Section: Methodsmentioning

confidence: 99%

“…The inherent advantage of this technology consists in its environmental compatibility due to the fact that the main reagent, the electron, is the “clean reagent” (Nosier and Sallam, 2000). The cementation process is one of the electrochemical techniques very often used in the removal of toxic or precious metals (Lee et al, 1997). The cementation process was already known from the ancient times of human culture but the early knowledge about the process was spread in Europe at the beginning of the middle Ages.…”

Section: Introductionmentioning

confidence: 99%

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Optimization of silver cementation yield in fixed bed reactor using factorial design and central composite design

2010

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This work deals with cementation of silver onto iron grid in fixed bed reactor. The influence of several parameters is studied namely: initial concentration of silver [Ag + ] 0 , flow rate, solution pH, and mass of iron. Moreover, their influence on the yield of the reaction of cementation is investigated statistically by the experimental design in view of industrial application. The estimation and the comparison of the parameter's effects are realised by using two-level factorial design. The analysis of these effects permits to state that the most influential factor is the mass of iron with an effect of (+5.642), the second in the order is the initial concentration of silver ions (Ag + ) with an effect of (+4.005), the third is the flow rate of the electrolytic solution with an effect of (+3.824). A central composite design methodology is employed to determine the optimum conditions for a silver cementation yield onto iron grid. For this end, the experimental results were approximated by a second-order model as well as the surface contour plots and surface responses are drowned. The optimal conditions found for initial silver concentration, such as a flow rate, pH of the solution and mass of iron, are respectively: 21.25 mg/L, 4.43 L/min, 3.6 and 50 g. Under these conditions, the obtained silver cementation yield is 96.851%.Ce travail concerne la cémentation de l'argent sur une grille de fer dans un réacteurà lit fixe. L'influence de plusieurs paramètres estétudiée, a savoir: la concentration initiale d'argent [Ag + ] 0 , le débit, le pH de la solution et la masse du fer. De plus, leur influence sur le rendement de la réaction de la cémentation est analysée de façon statistique par le plan expérimental enégardà l'application industrielle. L'estimation et la comparaison des effets des paramètres sont réalisées en utilisant un plan factorielà deux niveaux. L'analyse de ces effets permet de déclarer que le facteur présentant le plus d'influence est la masse du fer avec un effet de (+5.642), le deuxième dans l'ordre est la concentration initiale d'ions argent (Ag + ) avec un effet de (+4.005), le troisième est le débit de la solutionélectrolytique avec un effet de (+3.824). Une méthodologie de plan composite centrale est utilisée pour déterminer les conditions optimales pour un rendement de cémentation de l'argent dans la grille en fer. A cette fin, les résultats expérimentaux ontété approximés par un modèle de deuxième ordre ainsi que les tracés de lignes hypsométriques et les réponses de surface sont inondées. Les conditions optimales que l'on trouve pour la concentration d'argent initiale, comme le débit, le pH de la solution et la masse de fer sont respectivement: 21,25 mg/L, 4,43 L/min, 3,6 et 50 g. Dans ces conditions, le rendement de cémentation d'argent obtenu est de 96,851%.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Optimization of silver cementation yield in fixed bed reactor using factorial design and central composite design

2010

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“…The diminishing availability of mineral resources and the increasing demand for gold metal emphasize the importance of its recovery from waste solutions and scrap materials 2,3 . During the past three decades, many recovery methods have been used, such as cementation 4 , precipitation 5 , ion-exchange 6 and solvent extraction [7][8][9] , and adsorption [10][11][12][13] . Both precipitation and cementation techniques result in higher efficiencies, but they generally do not ensure a complete purification, i.e., further treatment is inevitably necessary.…”

Section: Introductionmentioning

confidence: 99%

Studies of Gold Adsorption from Chloride Media

et al. 2015

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In this paper, adsorption of gold from chloride media using commercial sorbent ) and biomass residue (rice hull (RH)) were investigated. The different adsorption parameters, sorbent dosage, contact time, temperature and pH of solution on adsorption (%) were studied in detail on a batch sorption. Before the RH was activated, adsorption (%) was poor compared with L-214. However, after the RH was activated at 1000 °C under an argon atmosphere, the gold adsorption (%) increased four-fold. X-ray fluorescence (XRF) was used to explore the feasibility this material as an adsorbent for the removal of gold from aqueous solutions. The adsorption equilibrium data were best fitted with the Langmuir isotherm model. The maximum adsorption capacities, Q max , at 25 °C were found to be 93.46 and 108.70 mg/g for the activated rice hull (ARH) and L-214, respectively. Thermodynamic calculations using ΔH°, ΔS°, ΔG° and E a values indicate that the adsorption process was spontaneous and endothermic.

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“…Whilst the leaching of Hg and Ag can be achieved simultaneously, the main challenge involves the effective recovery and separation of Hg and Ag as they are both very similar chemically. Methods including activated carbon adsorption (Bunney et al, 2010), cementation with base metals (Lee et al, 1997;Ku et al, 2002), direct electrowinning (Sheya et al, 1988), solvent extraction (Stankovic et al, 2008), sulfide precipitation (Gabby et al, 2013) and ion exchange (Grosse et al, 2003) have all been proposed for the recovery Ag and Hg from aqueous acid solutions. Of these, the cementation process has been widely used in industry for the removal of heavy metals from aqueous solution due to its relative ease of operation, low cost and the feasible recovery of valuable metals.…”

Section: Introductionmentioning

confidence: 99%

“…Of these, the cementation process has been widely used in industry for the removal of heavy metals from aqueous solution due to its relative ease of operation, low cost and the feasible recovery of valuable metals. Alternatively, investigations by Lee et al (1997) on the cementation behavior of Ag and Au with Zn, Al and Fe powder from acidic thiourea solution has demonstrated that recoveries of gold and silver can reach almost 100% after 5 min with 10 g/L Zn powder. In addition, it has also been found that 99% of Hg can be removed from a low Hg (30 mg/L) solution by a similar zinc powder cementation method at pH of 4 (Ku et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

Recovery and separation of silver and mercury from hazardous zinc refinery residues produced by zinc oxygen pressure leaching

et al. 2019

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Hazardous zinc refinery residues that contain Ag and Hg are a typical complex material obtained from zinc oxygen pressure leaching and currently there are few economically viable methods for disposal or reuse. The research presented here offers an effective approach for the comprehensive recovery of Zn, Fe, Cu, Ag and Hg from this highly toxic waste. During the initial hot-acid leaching stage, leaching efficiencies of 96.3% Zn, 96.0% Fe and 97.5% Cu were obtained, whereas the leaching of Ag and Hg were less than 0.2%. This resulted in the simultaneous separation of Zn, Fe and Cu and the enrichment of Ag and Hg ca. 300%. Subsequently, the leaching residues obtained from hot-acid leaching was further leached using acidic thiourea solution (pH = 1). The results of this second leaching step showed the almost 93% of Ag and 98% of Hg could be extracted using 20 g/L thiourea and 4 g/L Fe 3+ , with a L/S ratio of 8 and a temperature of 40 °C for 2 hours. The residue after thiourea leaching could be used as raw material in lead smelting. In the next step based on zinc powder cementation, the recovery of Ag and Hg both reached 99.0% and the cementation residue comprised of 53.1 wt. % Ag and 11.7 wt. % Hg. The main phases present included Ag, Hg3Ag2 and Ag2S and these can be further treated by vacuum distillation in order to separate Hg from Ag. These findings demonstrate that high recoveries of Zn, Fe, Cu, Ag and Hg from the toxic waste could be achieved with stepwise leaching followed by zinc powder cementation. This treatment protocol for toxic zinc refinery residues not only avoids the potential harm to the environment but also significantly improves the economics of the process.

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Cementation Behavior of Gold and Silver Onto Zn, Al and Fe Powders from Acid Thiourea Solutions

Cited by 14 publications

References 2 publications

Optimization of silver cementation yield in fixed bed reactor using factorial design and central composite design

Optimization of silver cementation yield in fixed bed reactor using factorial design and central composite design

Studies of Gold Adsorption from Chloride Media

Recovery and separation of silver and mercury from hazardous zinc refinery residues produced by zinc oxygen pressure leaching

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