Solvent Extraction Of Gold Research Articles

Comparison of the Reactivity for the Solvent Extraction of Gold(iii) from Concentrated HCl Solutions Among D2EHPA, PC 88A, and Cyanex 272

ABSTRACT In this study, the chemical reactivity of three organophosphorus acidic extractants (D2EHPA, PC 88A, and Cyanex 272) was compared for the extraction of the anionic gold(III) complex, AuCl4 −, from the concentrated hydrochloric acid solutions. The extraction behavior was examined by varying the hydrochloric acid concentration from 1 to 9 M. Among the three extractants, only Cyanex 272 showed significant efficiency in extracting Au(III) with the extraction percentage was proportional to hydrochloric acid concentration. In contrast, the extraction of Au(III) by D2EHPA and PC 88A was not significant. FT-IR spectra analysis indicated that the P=O bond in Cyanex 272 weakened after extraction, suggesting its involvement in the process. Based on the structural differences between the extractants and the observed dependence of gold(III) extraction on the hydrochloric acid concentration, a nucleophilic addition reaction was proposed as the extraction mechanism. Specifically, the phosphoryl oxygen of protonated Cyanex 272 likely forms a coordinate bond with the gold ion in AuCl4 −, facilitating its extraction. This mechanism was supported by both extraction and spectroscopic data, making Cyanex 272 a promising candidate for the selective extraction of Au(III) from highly acidic solutions. The findings offer insights into the extraction of metal ions using organophosphorus extractants in highly acidic environments.

Solvent Extraction of Gold(III) by 2-Ethylhexanol and Modeling of Facilitated Transport across a Supported Liquid Membrane

The solvent extraction of gold(III) by undiluted 2-ethylhexanol or dissolved in toluene from a HCl solution has been investigated in this paper. The numerical analysis of gold distribution data suggests the formation of HAuCl4·L and HAuCl4·2L (L = 2-ethylhexanol) species in the organic phase, with formation constants K11 = 38 and K12 = 309, respectively. The results derived from gold(III) distribution have been implemented in a solid-supported liquid membrane system. The influence of several variables on gold transport has been considered: feed and receiving phases’ stirring speeds, HCl and gold concentrations in the feed phase, and carrier concentration in the membrane phase as well as the presence of base metals (Fe, Cu, Ni) and platinum-group metals (PGMs) in the feed phase. Gold transport is influenced by the stirring speed of the feed phase and the variation in HCl and gold (feed phase) and carrier (membrane phase) concentrations. Also, diffusional resistances to mass transfer are estimated, and the contribution of each resistance to gold transport is estimated. Gold is recovered as zero-valent nanoparticles.

Sustainable solvent extraction of gold and other metals with biomass chemicals

Metal purification by solvent extraction using a sustainable alternative to petroleum kerosene is demonstrated using gold and other metals as examples.

Solvent extraction of gold from a chloride-hypochlorite leached solution of waste printed circuit boards

ABSTRACT This study reveals the reclamation process of gold from a brine-leached solution of waste printed circuit boards (WPCBs) after the maximum leaching of base metals in a nitric acid medium. The brine leaching performed in the presence of hypochlorite yielded leach liquor of 152 ppm Au, 86 ppm, Cu, and 62 ppm Ni that underwent solvent extraction with tri-butyl phosphate (TBP) in Exxol D80. The gold extraction process was observed to be selective over base metal impurities, while the effect of TBP concentration, equilibrium pH, temperature, and organic-to-aqueous phase ratio was optimized. Experimental results showed the formation of complex into the extraction phase with the negative enthalpy change value of −98.7 kJ/mol. Thiosulphate mobilized stripping of gold from the loaded-TBP could give about 99% recovery efficiency of the solvent extraction process along with a good regeneration of the organic extractant to be re-used.

On the Use of Pseudo-Protic Ionic Liquids to Extract Gold(III) from HCl Solutions.

Solvent extraction of gold(III) from HCl media using pseudo-protic ionic liquids (PPILs) dissolved in toluene as the extractant phase is investigated. Three PPILs are generated from the reaction of commercially available amines and 1 M HCl solution and named as pri-NH2H+Cl- (derived from the primary amine Primene 81R), sec-NHH+Cl- (derived from the secondary amine Amberlite LA2) and ter-NH+Cl- (derived from the tertiary amine Hostarex A327). In the above structures, -NH2H+Cl-, -NHH+Cl- and -NH+Cl- represented the active groups (anion exchangers) of the respective PPIL. In the case of gold(III) extraction, the experimental variables investigated included the equilibration time (2.5-30 min), temperature (20-60 °C), HCl concentrations (1-10 M) in the aqueous phase, gold(III) concentration (0.005-0.05 g/L) in this same phase, and PPILs concentrations in the organic phase. From the experimental data, and using the Specific Interaction Theory, the interaction coefficients (ε) for the pair AuCl4-, H+ are estimated for the systems involving the three PPILs. Gold(III) is recovered from the metal-loaded organic phases using sodium thiocyanate solutions, and from these, gold is finally recovered by the precipitation of zero-valent gold (ZVG) nanoparticles.

Solvent Extraction of Gold(III) with Diethyl Carbonate

Diethyl carbonate (DEC) was evaluated as a green, renewable alternative to methyl isobutyl ketone and dibutyl carbitol for the recovery of gold from copper-rich sources, such as anode slimes, by solvent extraction from chloride solutions. DEC is a powerful extractant at high chloride concentrations and can be used to sequester and concentrate gold from large volumes of dilute aqueous solutions containing high concentrations of copper. Stripping can be performed using pure water. Different variables were investigated: DEC concentration, chloride concentration, chloride source, phase volume ratio, and equilibration time. The selectivity and phase disengagement times were studied, and possible mechanisms of extraction are discussed and evaluated. In addition, the stability of DEC against hydrolysis was measured.

Development of novel solvent extraction method for determination of gold(III) using 4-heptylaminopyridine: Application to alloys and environmental analysis

In this paper, the solvent extraction of gold(III) from malonate media (0.04molL−1) has been studied by equilibrating aqueous phase having pH 2.5 with 10mL of 0.07molL−1 4-heptylaminopyridine (4-HAP) as a novel anion exchanger diluted in xylene for 2min. The extracted metal from organic phase was separated by stripping with 5.0molL−1 NH3 solution (2×10mL). The effect of various parameters, such as pH, extractant concentration, weak acid concentration, equilibrium time, stripping agents, aqueous to organic volume ratio and diluents on the extraction of gold(III) was investigated. The extracted species has been evaluated from log D vs log C and species appears to be 1:2:1 (metal: acid: extractant). The selectivity of the method was checked by separating gold(III) from binary and ternary mixtures of associated metal ions as well as platinum group metals(PGMs). The separation of gold(III) from synthetic alloys and environmental samples was also carried out.

Solvent Extraction of Gold(I) from Alkaline Cyanide Solution with Furfuryl Thioalcohol

A facile approach was designed to extract gold(I) from alkaline cyanide solution via a hydrometallurgy method. The performances of gold(I) extraction with furfuryl thioalcohol were investigated. The results revealed that gold(I) extraction increased with increasing extractant concentration and phase ratio but decreased with increase of pH value and god(I) concentration. The transfer speed of gold(I) between two phases was rather fast, and the extraction equilibrium could be established within 2 min. The extraction of gold(I) reached 92.7% with 15% (V/V) extractant. Gold(I) loaded in organic phase was stripped by NaOH solution, and stripping of gold(I) reached 90.2% with 0.08 mol · L−1.

Solvent Extraction of Gold(I) from Alkaline Cyanide Solution with Synthesized Sulfoxide MSO under Assistance of TBP

Solvent Extraction of Gold(I) from Alkaline Cyanide Solution with Synthesized Sulfoxide MSO under Assistance of TBP

Thiocyanate hydrometallurgy for the recovery of gold. Part IV: Solvent extraction of gold with Alamine 336

Solvent extraction with amines has been evaluated as a possible method to purify and concentrate gold from thiocyanate solutions. No significant difference was observed in gold extraction with commercially available tertiary amines (Alamine 336, Alamine 308, and Alamine 304–1). The effects of Alamine 336 and thiocyanate concentrations were examined for gold extraction. Gold extraction isotherms were established at different thiocyanate concentrations. The extraction and stripping of gold showed satisfactory results at an organic/aqueous (O/A) ratio of 1:5 for extraction (~100%) and 5:1 for stripping (~92%), in the presence of decanol. Possible solvent extraction reactions and stripping reactions with thiourea are discussed in order to better understand the system chemistry. Sodium hydroxide/thiocyanate, ammonium hydroxide, and acidic thiourea were examined for the stripping of gold from the loaded organic phase. Acidic thiourea gave the best results (with complete stripping of gold) under the conditions studied.

Radiotracer study of synergic effect of trioctyl phosphine oxide on the solvent extraction of gold(III)-β-diketonates

Liquid–liquid extraction of gold(III) with two β-diketones e.g. Benzoyl acetone (BZAC) and theonyl trifluoro acetone (TTA) and enhancement effects of trioctyl phosphine oxide on such extractions in various organic media have been studied by radiotracer technique. Strong ternary adduct complex formation were reported in chloroform (BZAC chelate) and carbontetrachloride (TTA chelate) media. Effect of temperature variation established such processes as spontaneous, enthalpy favoured with net loss in entropy. Synergic effects were reported to be strongly diluent dependent and Hildebrand’s regular solution theory was found to be applicable in such systems.

Solvent Extraction of Gold(I) Directly from Alkaline Cyanide Solution with Dibutyl Sulfoxide and n-Octanol

The direct extraction of gold from alkaline cyanide solution with dibutyl sulfoxide and n-octanol diluted in kerosene was investigated. It has been indicated that the gold extraction percentage increases by increasing dibutyl sulfoxide concentration, n-octanol concentration, and organic-to-aqueous (O/A) phase ratio, but decreases with the increase of initial gold concentration and equilibrium pH of the aqueous phase. No gold extraction was observed using n-octanol alone as an extractant, but n-octanol had an obvious synergistic effect on gold extraction with dibutyl sulfoxide. The extraction reaction was rapid for the extraction equilibrium and could be established within 3 minutes. Gold loaded in the organic phase could be stripped effectively by Na2S2O3 solution. It was indicated that at Na2S2O3 concentration 0.12 mol·L−3, aqueous-to-organic (A/O) phase ratio 1.0, and retention time of 5 minutes, the gold stripping percentage reached 92.6 pct.

Solvent extraction of gold(I) from alkaline cyanide solutions by the cetylpyridinium bromide/tributylphosphate system

This paper explores the solvent extraction of KAu(CN) 2 from alkaline cyanide solutions using quaternary ammonium cetylpyridinium bromide (CPB) as an extractant with the addition of tributylphosphate (TBP) as a modifier. It also investigates the influence of several variables on gold extraction, including the molar ratio ( β) of CPB to Au(I), the volume percentage of TBP ( φ TBP), NaCl concentration, phase ratio (AQ/ORG), and gold concentration in the aqueous phase. The results indicate that nearly all of the Au(I) (>98%) was transferred from the aqueous phase into the organic phase when β = 1 and φ TBP = 30 vol%. We also carried out experiments for treating 20 L synthetic aurocyanide solution containing 10 mg/L Au(I) with column-shaped extraction equipment. The results demonstrated the recovery of more than 94.5% of Au(I) after two successive stages of extraction, and the Au(I) concentration in the raffinate was less than 0.5 mg/L. KSCN solution was used to strip the gold-loaded organic phase, and about 90% of Au(I) could be reverse extracted into the aqueous phase when the KSCN concentration reached 3.0 mol/L. The results obtained in this paper establish that the CPB/TBP extraction system has potential for practical application in the extraction and separation of gold from alkaline aurocyanide solutions.

Continuous Laboratory Gold Solvent Extraction from Cyanide Solutions using LIX 79 Reagent

AbstractContinuous laboratory solvent extraction of gold from cyanide solutions has been investigated by using LIX 79 guanidine‐based extractant. Different variables that affected the extraction included aqueous pH, extractant concentration and modifier concentration. Extraction isotherms of the aurocyanide complex with respect to the other cyanoanions were compared, and the following order of selectivity was observed: Au > Ag > Cu > Zn > Fe. According to the pH isotherms, aurocyanide can be extracted in alkaline media, and a better separation with respect to other cyano anions was obtained in the pH range 10.5–11.2. From the McCabe‐Thiele diagrams, better recovery was observed when using LIX 79 and tridecanol at 10 vol.‐%. Stripping gold from the loaded organic was carried out at pH > 12 by using NaOH and NaCN solutions. The pilot plant tests indicate that a two‐stage extraction followed by one strip step are more than adequate to obtain an overall process efficiency of 92 %. However, for those cases where copper is present significantly, a copper wash stage is recommended before gold stripping. In this case, stripping of copper is accomplished at a pH 10.8, whereas the gold stripping was done at a pH of 12.0.

Assessment of gold exposure and contamination in galvanizing workplace by neutron activation analysis

Gold is not included in the current list of elements considered essential to humans and there are many controversies related to its toxicity. According to the chemical characteristics of the element, Au1+ is favored for binding at sites with S donor, such as sulfhydryl group (-SH) in proteins in biological systems. This tendency raises the possibility of health-related risk, mainly linked to a long-term exposure to high and low levels of gold. This paper highlights the determination of gold by instrumental neutron activation analysis (INAA) during the assessment of exposure levels to metals and possible workers’ contamination in three galvanizing factories applying the same processes. This assessment is aimed at giving support to Worker’s Health Awareness Program of the Municipal Department of Health of Belo Horizonte, Minas Gerais, Brazil. INAA, mix of k 0 and monostandard methods was applied to air filter, hair and toenail samples, and to urine samples. Solvent extraction of gold was carried out followed by comparative INAA. The results revealed that gold was present in all matrixes, indicating the exposure in the workplace and suggesting endogenous contamination. Is gold playing a role as a toxic element?

Solvent extraction of gold from polysulfide solution

The extraction of Au(I) from a polysulfide solution with TBP, amine alkyl extractants and their mixture was studied. The results show that Au(I) could be extracted with TBP or amine alkyl extractants, under the same condition, the extraction capacity of primary alkyl amine is better than that of tertiary alkyl amines. A mixture of N 1923-TBP showed a synergistic effect. Separation of gold and copper from the polysulfide solution was readily achieved using 0.5 mol/L N 1923–0.5 mol/L TBP/ n-octane as the organic phase at pH < 8 or pH > 11 and the extraction rate of gold is very high.

Solvent Extraction of Gold from Alkaline Cyanide Solution with a Tri‐n‐octylamine/Tri‐n‐butyl phosphate/n‐heptane Synergistic System

Solvent extraction of KAu(CN)2 from alkaline cyanide solution by using the pre‐acidified tertiary amine, tri‐n‐octylamine(TOA) as extractant with the addition of tri‐n‐butyl phosphate (TBP) as a synergist has been studied. The influence of several variables such as the molar ratio of TOA to KAu(CN)2 (n r ), the volume percentage of TBP (ϕ TBP ), the phase ratio of the organic phase to the aqueous phase and the pH value of the aqueous phase were investigated. The results indicated that, at a certain pH range, while ϕ TBP is above 20%(v/v) and n r is bigger than 1, the organic phase can extract gold from the aqueous phase completely. The relationship between the extraction percentage of gold (E) against n r and the logD − logϕ TBP plot indicate that the stoichiometry of the extracted species is a 1:1:3 complex, namely, [TOA · H+] · [Au(CN)2 −] · 3TBP. Dynamic laser scattering (DLS) method reveals that the organic phase tends to self‐assemble to form aggregations when the concentration of gold in the organic phase reaches a certain limiting value. The stripping of the loading organic phase by NaOH and inorganic salts, such as NH4SCN, NaClO4 and potassium halides, has also been investigated.

Improved kinetics-based gold cyanide extraction with mixture of LIX79+TOPO utilizing hollow fiber membrane contactors

Dispersion-free solvent extraction of gold(I) (Au(CN) 2 −) from alkaline cyanide media was performed using porous hydrophobic hollow fibers with mixtures of membrane extractants. The organic extractant used for gold(I) extraction was LIX79 ( N, N′-bis(2-ethylhexyl)guanidine) alone and a mixture of trioctylphosphine oxide (TOPO)+LIX79 diluted with n-heptane. The mixture of LIX79+TOPO affords a better performance than LIX79 alone. It took 300 s to extract more than 95% gold with equimolar LIX79+TOPO (0.125 M), whereas pure LIX79 (0.375 M) took 1860 s to reach the same percentage level of gold extraction (over six times slower). The mass transfer coefficient’s ( K Au E) value was around four times higher with the equimolar mixture of 0.125 M LIX79+0.125 M TOPO than with LIX79/ n-heptane alone. Extraction of Au(CN) 2 − from alkaline cyanide solutions with TOPO alone was also observed, indicating that gold(I) complexation takes place probably by a solvation reaction mechanism (M +⋯Au(CN) 2·S n ). A model is presented which describes the extraction mechanism, indicating different rate-controlling steps. The validity of this model was evaluated with experimental data and was found to tie in well with theoretical values.

塩化トリオクチルメチルアンモニウムを用いたチオ硫酸アンモニウム水溶液からの金の溶媒抽出(第一報)

Hydrometallurgical process as like a solvent extraction is very important to recovery precious metals from raw materials and metals scraps. Recently, authors have ever indicated the leaching process of gold by using ammonium thiosulfate solution from sponge gold, low concentrate ore and electronics scrap.In this study trioctylmethylammonium chloride (TOMAC, (C8H17)3CH3NCl) was used as an extractant to extract gold from ammonium thiosulfate leaching solution. The influence of TOMAC concentration, retention (shaking) time, stripping process, multi stage extraction tests were investigated. It was found that the effective conditions for gold solvent extraction by TOMAC, such as 0.18 mol / l TOMAC diluted with n-octane at organic and water phase ratio of 1 : 1 could extract more than 99% of gold from the ammonium thiosulfate leaching solution at standard leaching condition (1.0 mol / l S2O32-, 0.03mol / l Cu2+ ion and 3.0mol / l NH3/NH4+ at pH10.5).

Solvent extraction of gold(III) by octadecyldimethylbenzylammonium chloride (ODMBAC) from chloride solution

The mechanism of solvent extraction of gold(III) in hydrochloric acid media with quaternary ammonium salt octadecyl dimethyl benzyl ammonium chloride dissolved in chloroform was studied. The influences of temperature, NaCl and HCl concentraction on the extraction equilibrium were also investigated. The extraction reaction is exothermic (ΔH° = -28.53±0.15 kJ/mol) and log Kex = 5.47±0.04.