Adsorption behaviors and mechanisms of gold recovery from thiosulfate solution by ion exchange resin

The adsorption behaviors and mechanisms of gold from thiosulfate solution on strong-base anion exchange resin were systematically investigated.The comparison experiment of adsorption ability and selectivity for gold showed that gel Amberlite IRA-400 resin with Type Ⅰ quaternary ammonium functional group had better adsorption performance.The increases of resin dosage,ammonia concentration and solution pH were favorable to gold adsorption,whereas the rises of cupric and thiosulfate concentrations were disadvantageous to gold loading.Microscopic characterization results indicated that gold was adsorbed in the form of [Au(S_(2)O_(3))_(2)]^(3–) complex anion by exchanging with the counter ion Cl^(–) in the functional group of the resin.Density functional theory calculation result manifested that gold adsorption was mainly depended on the hydrogen bond and van der Waals force generated between O atom in [Au(S_(2)O_(3))_(2)]^(3–) and H atom in the quaternary ammonium functional group of the resin.

Thiosulfate oxidation and autotrophy potential by marine prevalent heterotrophic bacteria of genus Marinobacter

The genus Marinobacter is very broadly distributed in global environments and is considered as aerobic heterotroph.In this study,six Marinobacter strains were identified with autotrophic thiosulfate oxidation capacity.These strains,namely Marinobacter guineae M3B^(T),Marinobacter aromaticivorans D15-8PT,Marinobacter vulgaris F01^(T),Marinobacter profundi PWS21^(T),Marinobacter denitrificans JB02H27T,and Marinobacter sp.ST-1M(with a 99.93%similarity to the 16S rDNA sequences of Marinobacter salsuginis SD-14B^(T)),were screened out of 32 Marinobacter strains by autotrophic thiosulfate oxidization medium.The population of cells grew in a chemolithotrophic medium,increasing from 105 cells/mL to 10^(7) cells/mL within 5 d.This growth was accompanied by the consumption of thiosulfate 3.59 mmol/L to 9.64 mmol/L and the accumulation of sulfate up to 0.96 mmol/L,and occasionally produced sulfur containing complex particles.Among these Marinobacter strains,it was also found their capability of oxidizing thiosulfate to sulfate in a heterotrophic medium.Notably,M.vulgaris F01^(T)and M.antarcticus ZS2-30^(T)showed highly significant production of sulfate at 9.45 mmol/L and 3.10 mmol/L.Genome annotation indicated that these Marinobacter strains possess a complete Sox cluster for thiosulfate oxidation.Further phylogenetic analysis of the soxB gene revealed that six Marinobacter strains formed a separate lineage within Gammaproteobacteria and close to obligate chemolithoautotroph Thiomicrorhabdus arctica.The results indicated that thiosulfate oxidizing and chemolithoautotrophic potential in Marinobacter genus,which may contribute to the widespread of Marinobacter in the global ocean.

Cyanide-free silver electroplating process in thiosulfate bath and microstructure analysis of Ag coatings

Cyanide-free silver electroplating was conducted in thiosulfate baths containing AgNO3 and AgBr major salts, respectively. The effects of major salt content and current density on surface quality, deposition rate and microhardness of Ag coatings were investigated. The optimized electroplating parameters were established. The adhesion strength of Ag coating on Cu substrate was evaluated and the grain size of Ag coating was measured under optimized electroplating parameters. The optimized AgNO3 content is 40 g/L with current density of 0.25 A/dm2. The deposited bright, smooth, and well adhered Ag coating had nanocrystalline grains with mean size of 35 nm. The optimized AgBr content was 30 g/L with current density of 0.20 A/dm2. The resultant Ag coating had nanocrystalline grains with mean size of 55 nm. Compared with the bath containing AgBr main salt, the bath containing AgNO3 main salt had a wider current density range, and corresponding Ag coating had a higher microhardness and a smaller grain size.

Effect of arsenopyrite on thiosulfate leaching of gold

Arsenopyrite was artificially added into the thiosulfate leaching solution to clarify the role of arsenopyrite on the thiosulfate leaching of gold.The effect of arsenopyrite on the thiosulfate leaching of gold was studied by the thermodynamic calculation,mineral dissolution test,leaching test and XPS analysis.The results show that the thiosulfate consumption slightly increases with increasing the concentration of arsenopyrite,but the gold dissolution is obviously hindered.This may mainly attribute to the catalytic effect of arsenopyrite on the thiosulfate decomposition and the formation of passivation layer on the gold foil surface.The passivation layer likely consists of Cu2S or Cu（S2O3）35-,element S,FeOOH and iron arsenate,which is deduced from the XPS analysis.However,the negative effect of arsenopyrite can be eliminated by adding additives.It is found that both additives of sodium carboxymethyl（CMC） and sodium phosphate（SHPP） can not only decrease the thiosulfate consumption but also improve the gold dissolution.

Review of gold leaching in thiosulfate-based solutions

Numerous non-cyanide leaching lixiviants have been developed,among which thiosulfate is considered the most promising alternative to cyanide due to its non-toxicity,low price,high leaching rate and excellent characteristics in dealing with carbonaceous and copper-bearing gold ores.The traditional copper−ammonia−thiosulfate system has been studied extensively.However,with many years of process development,there are still some problems and challenges with this gold leaching system.A series of studies using nickel-,cobalt-and ferric-based catalyst to substitute copper have been conducted with the purpose of reducing the consumption of thiosulfate.A variety of non-ammonia thiosulfate leaching systems including oxygen−thiosulfate,copper−thiosulfate,copper−EDA−thiosulfate,ferric−EDTA−thiosulfate,and ferric−oxalate−thiosulfate leaching systems have been also developed to eliminate the potential side-effect of ammonia.In this review,the basic theory and process development of some main gold leaching systems based on thiosulfate solutions were systematically summarized to illustrate the research status on thiosulfate leaching process.The potential effects of various additives such as organic ligands containing amino,carboxyl or hydroxy functional groups on gold thiosulfate leaching were described in detail.The potential opportunity and challenge for promoting the industrial development of thiosulfate-based gold leaching systems were also discussed.

Effects of Sodium Thiosulfate on the Occurrence of a Novel Glycolipid in Cyanobacterium Synechocystis sp. PCC 6803 Cells Grown in the Presence of Glucose

A novel lipid occurred when cyanobacterium Synechocystis sp. PCC 6803 cells were grown in BG-11 medium with glucose applied. This lipid was determined to be a glycolipid, designated glycolipid-x (Glyco-x), by staining with alpha-naphthol and concentrated sulfuric acid. The occurrence of Glyco-x accompanies the disappearance of other lipids, especially DGDG. Glyco-x can also be observed in cells grown in BG-11 medium with the application of other carbon sources: fructose, maltose and lactose. Sodium thiosulfate, an effective scavenger of reactive oxygen intermediates, showed strong capability to inhibit glucose-induced occurrence of Glyco-x. In the presence of 0.3% sodium thiosulfate, Glyco-x could only be detected in cells grown in BG-11 medium with 100 mmol/L glucose applied in late-exponential phase. These results suggest that reactive oxygen species might be involved in the occurrence of Glyco-x in cyanobacterium Synechocystis sp. PCC 6803 cells grown in the presence of glucose.

Effect of mechanical activation on thiosulfate leaching of gold from complex sulfide concentrate

The use of mechanical activation to enhance gold recovery from a CuPbZn complex sulfide concentrate was investigated. The effects of milling time, ball size, sample to ball ratio and milling speed on thiosulfate leaching were studied. Under optimum conditions of milling time 1 h, ball size 20 mm, sample to ball ratio 1/15 and mill speed 600 r/min, nearly 78% of sample is amorphized, particle size decreases from d100=30 μm to d100=8 μm, specific surface area increases from 1.3 m2/g to 4.6 m2/g and gold recovery enhances from 17.4 % in non-activated sample to 73.26 %.

Silver sulfide leaching with a copper-thiosulfate solution in the absence of ammonia

Leaching from silver sulfide.using a copper-thiosulfate solution in the absence of ammonia was investigated. It is found that silver sulfide could be effectively dissolved in the copper-thiosulfate system without ammonia. The effects of thiosulfate concentration, cop- per-to-thiosulfate ratio, agitation vigorousness, pH values, and dissolved gases on the leaching of silver sulfide with the copper-thiosulfate solution were studied. A maximum extraction of 95.1% was achieved with the 0.12 mol/L thiosulfate and the 0.048 rnol/L copper sulfate. It is shown that copper-to-thiosulfate ratio is an important factor in silver sulfide dissolution and oxygen is not needed to leach silver sulfide, which leads to the instability of the leaching system at high copper-to-thiosulfate ratio. On the other hand, the silver extraction is not affected by the pulp pH values.

Biooxidation-thiosulfate leaching of refractory gold concentrate

A process of biooxidation followed by thiosulfate leaching of gold from refractory gold concentrate was investigated.Mineralogical studies on the concentrate showed that very fine gold grains(<10μm)were encapsulated in pyrite and arsenopyrite,while the proportion of monomer gold was only 21%.The gold-bearing sample was identified as a high-sulfur fine-sized wrapped-type refractory gold concentrate.The gold leaching efficiency obtained by direct cyanidation was only 59.86%.After biooxidation pretreatment,the sulfide minerals were almost completely decomposed,92 wt%of the mineral particles of the biooxidation residue were decreased to<38μm,and the proportion of monomer gold in the biooxidation residue was over 86%.Meanwhile,the gold content in the biooxidation residue was enriched to 55.60 g/t,and the S,Fe,and As contents were reduced to approximately 19.8 wt%,6.97 wt%,and 0.13 wt%,respectively.Ammoniacal thiosulfate was used for gold extraction from the biooxidation residue of the refractory gold concentrate.The results showed that the optimal reagent conditions were 0.18 M thiosulfate,0.02 M copper(II),1.0 M ammonia,and 0.24 M sulfite.Under these conditions,a maximum gold leaching efficiency of 85.05%was obtained.

Pretreatment and thiosulfate leaching of refractory gold-bearing arsenosulfide concentrates

A hydrometallurgical process for refractory gold-bearing arsenosulfide concentrates at ambient temperature and pressure was presented, including fine grinding with intensified alkali-leaching （FGIAL）, enhanced agitation alkali-leaching （EAAL）, thiosulfate leaching and displacement. Experimental results on a refractory gold concentrate showed that the total consumption of NaOH in alkaline leaching is only 41% of those theoretically calculated under the conditions of full oxidization for the same amount of arse- nides and sulfides transformed into arsenates and sulfates, and 72.3% of gold is synchro-dissoluted by thiosulfate self-generated during alkaline leaching. After alkaline leaching, thiosulfate leaching was carried out for 24 h. The dissolution of gold is increased to 91.9% from 4.6% by cyanide without the pretreatment. The displacement of gold by zinc powder in the solution gets to 99.2%. Due to an amount of thiosulfate self-generated during alkaline leaching, the reagent addition in thiosulfate leaching afterwards is lower than the normal.

Thiol-free route to diaryl sulfides by Cu catalyzed coupling of sodium thiosulfate with aryl halides

A method for the synthesis of diaryl sulfides from aryl halides in polyethylene glycol was reported.Inodorous Na2S2O3·5H2O,which is readily available as a stable salt,is an effective source of sulfur in the presence of Cu I as catalyst.

KINETICS OF GOLD LEACHING FROM SULFIDE GOLD CONCENTRATES WITH THIOSULFATE SOLUTION

The reaction process for leaching gold from sulfide gold concentrates containing copperwith ammonia-ammonium thiosulfate solution containing copper（Ⅱ）can be divided into initialstage and later stage of reaction.Initial stage of reaction is controlled by interface reaction.Lat-er stage of reaction is controlled by diffusion process of reaction through solid products layer.Whole leaching process is under the control of corrosion reaction of pyrite bearing gold.Actionof ammonium sulfate in the system is probably as follows:（1）NH4+ and NH3 forms a buffer so-lution;（2）SO42-ion inhibites the oxidation and decomposition of S2O32-ion.Cu2+ion in thesystem acts as an oxidant and oxygen makes the Cu2-regenerate.

Pharmacokinetics of sodium thiosulfate in Guinea pig perilymph following middle ear application

Hypothesis： To determine the pharmacokinetics of sodium thiosulfate in the inner ear perilymph following middle ear application in Guinea pigs. Background： Cisplatin chemotherapy is often associated with a dose-dependent high frequency senso- rineural hearing loss. Sodium thiosulfate has been shown to reduce cisplatin-induced ototoxicity when given intravenously, but this may limit the tumoricidal effects of the chemotherapy. Recent animal studies looking at middle ear application of sodium thiosulfate have shown prevention of outer hair cell and hearing loss, but the perilymph pharmacokinetics have not yet been established. Methods： Twenty Guinea pig ears were split into two groups and administered sodium thiosulfate to the middle ear at either a concentration of 250 mg/mL or 50 mg/mL for 30 min. Perilymph samples were then obtained serially through the round window over 6 h. Sodium thiosulfate concentrations were obtained using high-pressure liquid chromatography. Results： The 250 mg/mL group had a maximum perilymph concentration of 7.27 mg/mL （±0.83） that decreased to 0.94 mg/mL （±0.03） over 6 h. The 50 mg/mL group had an initial concentration of 1.63 mg/mL （±0.17） and was undetectable after 1 h. The half-life of sodium thiosulfate within perilymph was 0.74 h. Conclusions： and Relevance： The results of this study show that sodium thiosulfate is capable of diffusing through round window and into the inner ear perilymph. Peak levels decline over several hours after exposure. This has a potential application as a localized therapy in the prevention of cisplatin induced ototoxicity.

Electrocatalytic oxidation of thiosulfate at 2,7-bis(ferrocenylethyl)-fluoren-9-one-modified carbon paste electrode(2,7-BFEFMCPE):Application to the catalytic determination of thiosulfate in real sample

Electrocatalytic oxidation of thiosulfate at the 2,7-BFEFMCPE occurs at a potential about 460 mV less positive than that unmodified carbon paste electrode.The diffusion coefficient（=5.6×10^-5）cm^2 s^-1）,the kinetic parameters such as electron transfer coefficient,（=0.5） and kh（=1.21×10^-3 cm s^-1） of thiosulfate oxidation at the surface of,2,7-BFEFMCPE were determined.The electrocatalytic oxidation peak current of thiosulfate showed two linear dynamic ranges（0.0006-0.009 mmol/L and 0.009- 0.900 mmol/L） and a detection limit of 0.00015 mmol/L.This method was also examined as a new electrochemical sensor for the determination of thiosulfate in real sample.

Novel Reduction of Sodium Alkyl Thiosulfates to Disulfides with TiCl_4/Sm System

Sodium alkyl thiosulfates(Bunte salts) can be readily reduced to the corresponding disulfides with TiCl4/Sm system in good to excellent yields under mild conditions

Anti-proliferative potential of sodium thiosulfate against HT 29 human colon cancer cells with augmented effect in the presence of mitochondrial electron transport chain inhibitors

Objective:To compare the anti-proliferative effect of sodium thiosulfate on human colorectal cancer cells(HT-29)and normal small intestine cells(IEC6).Methods:Cells(HT-29 and IEC6)were treated with different concentrations of sodium thiosulfate ranging from 0.5 m M to 80 m M for 24 h.Cell viability was measured via crystal violet and MTT assays.HT-29 cells were further treated in the presence and absence of mitochondrial electron transport chain(ETC)inhibitors,KATP channel opener and closer and H2S inhibitors for 24 h followed by sodium thiosulfate in order to study their respective roles in the anti-proliferative activity of sodium thiosulfate.Results:The IC50 values of sodium thiosulfate on HT-29 cells were 40.93 m M and 42.45 m M by crystal violet and MTT assay whereas,in the case of IEC6 cells,the values were 45.17 m M and 47.22 m M.The inhibition of endogenous H2S enzymes and KATP channel induced no change in the anti-proliferative capacity of sodium thiosulfate.However,the anti-proliferative activity of sodium thiosulfate was enhanced in the presence of mitochondrial ETC inhibitors.Conclusions:HT-29 cell growth is effectively attenuated by sodium thiosulfate and the anti-proliferative activity of sodium thiosulfate is enhanced in the presence of mitochondrial ETC inhibitors.

ANODIC OXIDATION OF THIOSULFATE IONS IN GOLD LEACHING

The regularities of anodic oxidation of thiosulfate ions on a gold electrode have been investigated using electrochemical methods in order to improve gold extraction. Effects of ammon, copper-ammon ions, pH and sulphite on anodic oxidation of thiosulfate ions have been examined in details. Results show that the anodic oxidation of thiosulfate ions is an inreversible reaction whose oxidizing peak potential is 620 mV/SCE in the absence of ammon. Oxidation rate increases with concentration of thiosulfate ions, but not in linear relation. It is also shown that ammon has significant effects on the oxidation of thiosulfate ions by causing great decrease in oxidation rate and negative shift of peak potential. The degrees of the rate decrease and negative shift increase with ammon concentration. When ammon concentration is increased to 1. 0 mol/L, the oxidation rate decreases to one fourth of that without ammon and the peak potential shifts from 620 mV/SCE to 350 mV/SCE.

LEACHING GOLD BY LOW CONCENTRATION THIOSULFATE SOLUTION

The effects of the concentrations of thiosulfate,copper and ammonia on the extraction of gold from sulfide gold concentrate have been studied.The results show that it is possible to reduce thiosulfate concentration.More than 95%of the gold could be extracted by a 0.2 mol/L thiosulfate leaching solution in two hours under suitable conditions.Therefore,the process of washing the residue was simplified,and the consumption and loss of thiosulfate carried by the washing residue were reduced.

Ammonium Thiosulfate Ecological Viable Alternative to Replace Sodium Cyanide in Gold and Silver Dissolution Ores

The southern region of the state of Chihuahua is mining by origin, as this has been proved ghost towns of Minas Nuevas, it is also called Villa Escobedo, Emerald and Blue. Minerals are nonrenewable resources. There are only reserves and waste deposited in tailings ponds of low-rade precious metals （gold and silver）. A conventional method for recovering gold and silver ore is low-grade cyanidation and the solvent consider toxic and highly dangerous for the flora, fauna, humans and the environment. The mechanism of cyanide poisoning is inhibition of cytochrome oxidase--an enzyme needed for cell respiration. Without compromising efficiency, sensitivity and cost of the process, the toxic solvent is replaced by a less aggressive one, which helps the environment, public and occupational health. （NH4）2S203 has no appreciable damage to conservative amounts, is a selective aqueous solvent for leaching gold and silver, easy to get and manipulate. This work is done in the Technological Institute of Parral in a low-grade ore from the southern region of the state of Chihuahua. This document has been enriched presented in the IMEC 2014, with the increase of series Ⅴ and Ⅵ.

Novel Reduction of Arylsulfonyl Chlorides and Sodium Alkyl Thiosulfates to Disulfides with TiCl_4/Zn System

T1Cl4/Zn system reduces arylsulfonyl chlorides and sedium aldyl thiosulfates to corresponding disulfides in moderate to good yields