Acid decomposition and thiourea leaching of silver from hazardous jarosite residues: Effect of some cations on the stability of the thiourea system

Choque, Dandy Calla; Nava‐Alonso, F.; Fuentes-Aceituno, J.C.

doi:10.1016/j.jhazmat.2016.05.085

Cited by 72 publications

(22 citation statements)

References 30 publications

(33 reference statements)

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“…At low pH, hematite rather than goethite is the stable Fe(III) oxide. [68][69][70] Synthesis of 3 removed 82 % of Tc from solution. A duplicate synthesis of 3 ended with a slightly higher pH, 3.4, and contained goethite in addition to hematite.…”

Section: Resultsmentioning

confidence: 99%

Facile incorporation of technetium into magnetite, magnesioferrite, and hematite by formation of ferrous nitratein situ: precursors to iron oxide nuclear waste forms

Lukens

Saslow

2018

Dalton Trans.

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The fission product, 99Tc, presents significant challenges to the long-term disposal of nuclear waste due to its long half-life, high fission yield, and to the environmental mobility of pertechnetate (TcO4-), the stable Tc species in aerobic environments. Migration of 99Tc from disposal sites can potentially be prevented by incorporating it into durable waste forms based on environmentally stable minerals. Since Tc(iv) and Fe(iii) have the same ionic radius, Tc(iv) can replace Fe(iii) in iron oxides. Environmentally durable iron oxides include goethite (α-FeOOH), hematite (α-Fe2O3), and magnesioferrite (MgFe2O4). The incorporation of Tc into two of these, hematite and magnesioferrite, as well as magnetite (Fe3O4) by means of simple, aqueous chemistry is presented starting from TcO4- in 5 M nitric acid. A combination of X-ray diffraction and X-ray absorption fine structure spectroscopy reveals that Tc(iv) replaces Fe(iii) within the iron oxide structures. Following incorporation, Tc doped samples were suspended in deionized water under aerobic conditions, and the release rates of Tc were determined. The results of this work show that Tc leaches more quickly from Fe3O4 than from α-Fe2O3 or MgFe2O4. Modeling the leach rates and comparison with the leach rate of Tc from TiO2 indicate that release of Tc is controlled by solid state diffusion.

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Section: Resultsmentioning

confidence: 99%

Facile incorporation of technetium into magnetite, magnesioferrite, and hematite by formation of ferrous nitratein situ: precursors to iron oxide nuclear waste forms

Lukens

Saslow

2018

Dalton Trans.

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“…[91,92] or pre-leaching of other metals included in the composition of the Au-containing secondary material [93] help to increase the efficiency of the following Au-leaching process. Pre-leaching of Fe and Cu is especially important for Au mobilization by thiourea since the dissolution of these metals increases the redox potential of acidic leachate thereby oxidizing thiourea and forming formamidine disulfide [90,[94][95][96]. Different inorganic acids HCl, HNO 3 and H 2 SO 4 with or without additional oxidants (e.g., O 2 , H 2 O 2 ), organic acids (e.g., citric acid, oxalic acid and acetic acid), and other lixiviants (e.g., EDTA, sodium acetate and sodium hydroxide) can be used for the recovery of Fe and Cu from Aucontaining secondary materials [68,97,98].…”

Section: Use Of Secondary Materials For Au Leachingmentioning

confidence: 99%

Thiourea leaching of gold from processed municipal solid waste incineration residues

Abramov

Wimmer

et al. 2022

J Mater Cycles Waste Manag

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Incineration is one of the key technologies in disposal of municipal waste, which produces municipal solid waste incineration (MSWI) residues with high valuable metal contents. The recycling strategy for the MSWI residues is typically focused on the recovery of scrap metals yielding processed municipal solid waste incineration residues (PIR) as the main byproduct. However, the PIR still contains valuable metals, particularly gold, which cannot be extracted by conventional methods. Here, we evaluated the feasibility of using the 0.5–2.0 mm grain size fraction of PIR containing 28.82 ± 1.62 mg/kg of gold as raw material for a two-stage extraction process. In the first stage the alkalic fine-grained PIR was acidified with a solution of 20% (v/v) of HCl-containing flue gas cleaning liquid that is obtained by the municipal waste incineration plant itself as a waste product. In the second stage we leached the acidified fine-grained PIR by thiourea with Fe3+ as an oxidant. Application of the thiourea-Fe3+ leaching system resulted in recovery of 16.4 ± 1.56 mg/kg of gold from the fine-grained PIR within 6 h of incubation. Due to high gold market prices, upscaling of the suggested technology can represent a suitable strategy for gold recovery from PIR and other MSWI residues.

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“…Nevertheless, the leaching of Fe and Cu increased from 16.2% to 33.5% and 39.2% to 60.3% with a further increase in acidity (from pH 1.0 to 0.5). This, in turn, would increase the consumption of thiourea and have a detrimental effect on any subsequent solution purification step (Calla-Choque et al, 2016). Consequently, in order to decrease the adverse effect of impurities on the recovery of Ag and Hg and to improve the recovery of all valuable metals from the waste residues, it was determined that a stepwise leaching process was preferable.…”

Section: Stepwise Leaching Of Ag and Hg From Hazardous Zinc Refinery Residuesmentioning

confidence: 99%

“…Furthermore, the addition of ferric sulfate to the thiourea solution results in a rapid increase of the initial silver leaching kinetics, although the presence of excessive amount of ferric ions leads to the oxidation of thiourea, which increases its overall consumption (Li et al, 2012). In contrast to thiosulfate, thiourea is much more stable under acidic conditions, nonetheless, presence of high levels of impurities like Fe 3+ , Cu 2+ and metal oxides has a negative impact in terms of thiourea decomposition, which affects the leaching metal kinetics (Li et al, 2006;Calla-Choque et al, 2016). Consequently, it is necessary that some type of pre-treatment protocol be adopted in order to separate such impurities prior to treatment with thiourea-based chemistries.…”

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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Acid decomposition and thiourea leaching of silver from hazardous jarosite residues: Effect of some cations on the stability of the thiourea system

Cited by 72 publications

References 30 publications

Facile incorporation of technetium into magnetite, magnesioferrite, and hematite by formation of ferrous nitratein situ: precursors to iron oxide nuclear waste forms

Facile incorporation of technetium into magnetite, magnesioferrite, and hematite by formation of ferrous nitratein situ: precursors to iron oxide nuclear waste forms

Thiourea leaching of gold from processed municipal solid waste incineration residues

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

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