Hong-ying Yang

Control method of chalcopyrite passivation in bioleaching

Passivation is a common phenomenon on the surface of chalcopyrite in the process of bioleaching. The ordinary leaching and strengthening leaching by adding glass beads were carried out. The results show that the passivation of chalcopyrite was greatly weakened in strengthening leaching due to the change of leaching conditions. The copper leaching efficiency was increased from 50% to 89.8% through adding beads. The SEM and X-ray diffraction (XRD) analyses illustrate that there are few jarosite precipitates and weak passivation on the surface of chalcopyrite in strengthening leaching. In contrast, there are thick and compact jarosite precipitate and obvious passivation in ordinary leaching, which hinders further dissolution of chalcopyrite.

Sequential removal of selenium and tellurium from copper anode slime with high nickel content

Abstract A process using soda roasting–alkaline leaching–acid leaching to remove selenium, tellurium and copper sequentially from the copper anode slime with high content of Ni was tested. The mechanism of this process was outlined based on thermodynamic analysis and the change in the XRD patterns of different intermediate products. During soda roasting, copper which occurs as Cu 4 SeTe in the slime was oxidized to CuO and Cu 3 TeO 6 , while selenium and tellurium were oxidized to Ag 2 SeO 4 and Cu 3 TeO 6 , respectively. Ag 2 SeO 4 in the calcine is easily leached in the subsequent alkaline leaching, but CuTeO 3 resulted from the decomposition of Cu 3 TeO 6 remains inactive in this process through which selenium is leached out in preference to tellurium. The CuTeO 3 and CuO in the alkaline leaching residue can be leached in the following sulfuric acid leaching process. More than 97% of selenium was leached with little tellurium leached under the optimal condition. Then, more than 96% of copper and almost all the tellurium were leached out in the following acid leaching process.

Research status of carbonaceous matter in carbonaceous gold ores and bio-oxidation pretreatment

Carbonaceous gold mines are important refractory gold ores. The previous results demonstrate that the carbonaceous matter is mainly composed of elemental carbon, organic acid and hydrocarbons. The dissolved aurocyanide complex is robbed by adsorption of carbonaceous matter, which is similar to activated carbon in cyanide leaching of gold. The pretreatment methods of carbonaceous gold ores were introduced, including high temperature roasting, bio-oxidation, chemical oxidation, competitive adsorption, barrier inhibition and microwave roasting. Recently, bio-oxidation was developed rapidly due to its advantages such as mild conditions, simple processes, low energy consumption and friendly environment. The known microorganisms related with bio-oxidation pretreatment mainly are chemolithotroph bacteria such as Thiobacillus ferrooxidans, Thiobacillus thiooxidans and Leptospirillum ferrooxidans. The researches on decomposing and passivating carbonaceous matter were commenced by Phanerochaete chrysosporium, Pseudomonadaceae and Streptomyces setonii. Finally, the main problems were analyzed and the application prospect of this technique was looked forward.

Feasibility of lead extraction from waste Cathode-Ray-Tubes (CRT) funnel glass through a lead smelting process.

A novel and effective process for extracting lead from the hazardous waste Cathode Ray Tubes (CRT) funnel glass is presented. The technological breakthrough of this process is introducing the discarded CRT funnel glass to traditional lead smelting. In this study, the influences of amount of carbon addition, calcium-silicate ratio, temperature, holding time and funnel glass addition on lead extraction efficiency were investigated to determine the optimal operational parameters. With a glass addition of less than 30wt%, a high extraction yield of 97.5% of lead from the mixture of funnel glass and lead slag was successfully obtained by controlling the C/PbO molar ratio, CaO/SiO2 ratio, temperature, treatment time at 0.9, 0.8, 1200°C, 60min, respectively. The main crystalline phases of the residues were calcium silicate slag, and an amorphous glass phase appears at a glass addition more than 30wt%. Thermodynamic calculation shows that the proportion of liquid phase in the slag first increased and then decreased, when the addition of glass is increased, while the viscosity of the slag exhibited a continuous decrease. Thus, based on all the results, it is concluded that the process proposed in this paper is an effective and promising approach for reutilization of obsolete CRT funnel glass.

Valence variation of arsenic in bioleaching process of arsenic-bearing gold ore

Abstract The concentration and variational trend of As 3+ and As 5+ , the bacterial resistance for the As 3+ and As 5+ and converting conditions from As 3+ to As 5+ were analyzed. The additive was used to prompt the bacterial leaching efficiency by changing valence state of arsenic. The results show that the concentration of As 3+ is larger than that of As 5+ in the lag phase. The concentration of As 3+ decreases in the log phase, and is lower than that of As 5+ . HQ-0211 typed bacteria express better resistance for As 3+ and As 5+ and remain growing when the concentrations of As 3+ and As 5+ are above 6.0 g/L and 12.0 g/L, respectively. It is found that Fe 3+ cannot oxidize As 3+ singly as strong oxidant in the leaching system, but can cooperate with pyrite or chalcopyrite to do that. The oxidation of As 3+ is prompted with addition of H 2 O 2 . The bacterial activity is improved in favor of bacterial leaching efficiency. NaClO restrains the bacterial growth to depress leaching efficiency because of the chloric compounds affecting bacterial activity.

Function of microorganism and reaction pathway for carrollite dissolution during bioleaching

Abstract The function of microorganism and dissolution reaction pathway of carrollite in the bioleaching process were investigated. The results showed that both indirect and contact mechanisms influenced the leaching process. The dissolution of carrollite was significantly accelerated when bacteria were adsorbed on the mineral surface, indicating that the contact mechanism significantly affected the dissolution of carrollite. During bioleaching, the sequence of oxidation state of the sulfur moiety of carrollite was as follows: S−2→S0→S+4→S+6. Elemental sulfur precipitated on the mineral surface, indicating that the dissolution of carrollite occurred via the polysulfide pathway. The surface of carrollite was selectively corroded by bacteria, and oxidation pits with different sizes were observed at various sites. Elemental sulfur, sulfate and sulfite were present on the surface of carrollite during the leaching process, and may have formed a passivation layer on mineral surface.

Influence of Phanerochaete chrysosporium on degradation and preg-robbing capacity of activated carbon

Abstract The effect of Phanerochaete chrysosporium on degradation and preg-robbing capacity of activated carbon, which was used as a substitute of carbonaceous matter in carbonaceous gold ores, was studied. After 14 d treatment with Phanerochaete chrysosporium , the degradation rate of activated carbon reached 27.59%. The XRD and FTIR analyses indicate that Phanerochaete chrysosporium can distort the micro-crystalline structure of activated carbon, increase the number of oxygen-containing groups and aliphatics and make the aromatic structures be oxidized and exfoliated. The gold-adsorption tests show that Phanerochaete chrysosporium can reduce the preg-robbing capacity of activated carbon by 12.88%. This indicates that Phanerochaete chrysosporium is an available microorganism, and it can be employed to reduce the preg-robbing capacity of carbonaceous matter and improve the gold leaching rate. The combined effect of passivation, alkalization and oxidation of biological enzymes-free radicals of Phanerochaete chrysosporium on carbonaceous matter was also discussed.

Catalytic performance of biological method seeds on jarosite process

Abstract The catalytic performance on jarosite process of jarosite seeds via biosynthesis and chemical processes were studied, respectively. The SEM and XRD results showed that biosynthetic jarosite seeds (BIO seeds) had smooth surface and mainly consisted of potassium jarosite. The chemical synthesis jarosite seeds (CHM seeds) had a loose cauliflower-like surface and mainly consisted of hydronium jarosite. The catalytic performance of BIO seeds was better than that of CHM seeds on the formation of final jarosite product. The induction time can be shortened to 20 min, the reaction temperature can be reduced to only 75 °C, and the initial reaction speed was enhanced obviously, up to 3.933%/min. The crystallinity of final jarosite product using BIO seeds can achieve 97.22%, while it was only 12.89% without seeds. This indicates that the precipitation process of jarosite is more complete with BIO seeds.

Effect of potential on characteristics of surface film on natural chalcopyrite

Abstract Electrochemical behavior of natural chalcopyrite in electrolyte solution containing 5×10 −4 mol/L ethyl xanthate, and the effect of potential on the composition and characteristics of surface film were studied by cyclic voltammetry (CV), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The adsorption of xanthate (X − ) occurred on the mineral surface at open-circuit potential (OCP). In the potential range from −0.11 to 0.2 V, the electrochemical reaction related to the formation of the hydrorphobic film of dixanthogen (X 2 ) occurred on natural chalcopyrite surface. This surface film had high coverage and large thickness at the potential of 0 V, but it had low coverage and small thickness at the potentials of 0.1 V and 0.2 V. Electrochemical activation started to occur when the potential was higher than 0.2 V, and the film of X 2 transformed to plenty of Cu(II) and Fe(III) oxygen-containing species which had the porous and loose characteristics.

Gold occurrence of Jiaojia gold mine in Shandong province

Abstract The microscopy and scanning electronic microscopy (SEM) were used to study the gold occurrence of Jiaojia gold mine, Shandong province. The results show that the gold-bearing minerals are composed of pyrite, chalcopyrite, gangue, sphalerite and galena. 77.12% of gold minerals are the sulphides and 22.88% are the gangues. The gold occurrence is composed of 60.28% fissure gold, 21.63% inclusion gold and 18.09% crystal fractured gold. The morphology of gold mineral is composed of sphere, triangle, rectangle, strip and erose. The Jiaojia gold mineral owns large grain size range from 3-5 μm to 100 μm. 1.5% of gold grains is more than 0.104 mm, 5.26% is 0.074-0.104 mm, 23.31% is 0.043-0.074 mm, 3.76% is 0.043-0.037 mm and 64.29% is less than 0.037 mm. The occurrence of gold mineral is composed of native gold, electrum, native silver, iron-bearing native silver, goldcuprid and acanthite. Electrum is the most important mineral, accounting for 71.56%. The average quality is 641.26% for gold and silver mineral.