Fen Jiao

Flotation separation of chalcopyrite from galena by sodium humate and ammonium persulfate

Abstract The flotabilities of chalcopyrite and galena with sodium humate (HA) and ammonium persulfate (APS) as the depressant were studied by flotation test, adsorption measurement and infrared spectroscopic analysis. Single mineral flotation test shows that the slurry oxidation environment and the proper oxidation of galena surface are prerequisites for the depression of galena by sodium humate. The closed-circuit flotation test of copper/lead bulk concentrate shows that the grade and recovery of Cu reach 30.47% and 89.16% respectively and those of Pb reach 2.06% and1.58% respectively in copper concentrate, and the grade and recovery of Pb reach 50.34% and 98.42% and those of Cu reach 1.45% and 10.84% respectively in lead concentrate with HA and APS. The selective depression effect of HA and APS is more obvious than that of potassium dichromate. The results of FTIR analysis and adsorption measurements indicate that the adsorption of sodium humate on the fresh surface of galena is negligible, while after oxidation, sodium humate can be chemically adsorbed on the surface of galena. According to the theory of solubility product, the sodium humate can display the oxidation product PbSO 4 , after then, adsorb on the surface of lead chemically to produce inhibitory effect. Thus, it can be seen that the combination of HA and APS is an efficient non-toxic reagent to achieve cleaning separation copper/lead bulk concentrate by flotation. The combination of HA and APS is an efficient non-toxic reagent to achieve cleaning for copper/lead bulk concentrate by flotation.

Mechanism study on the sulfidation of ZnO with sulfur and iron oxide at high temperature

The mechanism of ZnO sulfidation with sulfur and iron oxide at high temperatures was studied. The thermodynamic analysis, sulfidation behavior of zinc, phase transformations, morphology changes, and surface properties were investigated by HSC 5.0 combined with FactSage 7.0, ICP, XRD, optical microscopy coupled with SEM-EDS, and XPS. The results indicate that increasing temperature and adding iron oxide can not only improve the sulfidation of ZnO but also promote the formation and growth of ZnS crystals. Fe2O3 captured the sulfur in the initial sulfidation process as iron sulfides, which then acted as the sulfurizing agent in the late period, thus reducing sulfur escape at high temperatures. The addition of carbon can not only enhance the sulfidation but increase sulfur utilization rate and eliminate the generation of SO2. The surfaces of marmatite and synthetic zinc sulfides contain high oxygen due to oxidation and oxygen adsorption. Hydroxyl easily absorbs on the surface of iron-bearing zinc sulfide (Zn1−xFexS). The oxidation of synthetic Zn1−xFexS is easier than marmatite in air.

Effects of galvanic interaction between galena and pyrite on their flotation in the presence of butyl xanthate

Abstract The effects of galvanic interaction between galena and pyrite on their flotation and electrochemical characters were studied by electrochemical, adsorption, flotation and FTIR techniques, respectively. Electrochemical tests indicate that galena is electrochemically more active than pyrite and serves as an anode in galvanic combination with pyrite. The galvanic current density from a mixture of galena and pyrite is 4 times as high as the self corrosion current density of galena, which indicates that the corrosion rate of galena is accelerated. Adsorption tests show that the adsorption of butyl xanthate on galena surface is enhanced, and affected by a combination of pyrite–galena mixtures and conditioning time. Compared with individual mineral particles, galvanic interaction reduces the floatability difference between galena and pyrite. The flotation recovery of galena decreases while that of pyrite increases when two minerals are mixed together due to the influence of galvanic interaction on the formation of hydrophilic/hydrophobic product. The FTIR results show that the formation of dixanthogen on pyrite surface is depressed due to the galvanic interaction.

Sulfur composition on surface of chalcopyrite during its bioleaching at 50 °C

Abstract The composition of passive layer of chalcopyrite was investigated by X-ray photoelectron spectroscopy (XPS), accompanied with cyclic voltammetry (CV). The leaching experiment shows that the extraction rates of Cu with leaching for 30 d by sterile control and microorganisms are 4.0% and 21.5%, respectively. In comparison, 3.8% and 10.5% Fe are leached by sterile control and microorganisms, respectively. The results of XPS studies suggest that Fe atoms dissolve preferentially from the chalcopyrite lattice, and disulfide (S 2 2− ), polysulfide (S n 2- ) and elemental sulfur (S 0 ) are identified on the chalcopyrite surfaces leached by sterile control and microorganisms. Additionally, sulfate (SO 4 2- ) is detected on the chalcopyrite surfaces leached by microorganisms, and most of it probably originates from jarosite. The analysis of CV results reveals that metal-deficient sulfide (Cu 1- x Fe 1- y S 2- z , y > x ) and elemental sulfur (S 0 ) passivate the surface of chalcopyrite electrode. The elemental sulfur and/or jarosite coating on the chalcopyrite surface may have impact on the leaching process; however, the disulfide, polysulfide or metal-deficient sulfide plays a more key role in the chalcopyrite leaching.

Adsorption mechanism of 2-mercaptobenzothiazole on chalcopyrite and sphalerite surfaces: Ab initio and spectroscopy studies

Abstract Interaction mechanism of the collector, 2-mercaptobenzothiazole (MBT), with chalcopyrite and sphalerite surfaces were investigated by Fourier transform infrared (FTIR) and density functional theory. Results of FTIR showed that some characteristic peaks of MBT were observed on the chalcopyrite surface, including C=N, C=N—S and C—S stretching vibration peaks, and the adsorption product was CuMBT. But there were no characteristic peaks of MBT on the sphalerite surface. The thione molecular form of MBT was the most efficient and stable, N and exocyclic S were the more favourable reactive sites for nucleophilic attacked by metal atoms. Compared with ZnS (110), MBT is more readily adsorbed on CuFeS 2 (112). Attachment of MBT occurs due to strong bonding through exocyclic S p and s orbits with Cu d orbit on CuFeS 2 (112) and electron transfer from Cu atom to S atom. Under the vacuum condition, MBT in the form of thione molecular cannot be adsorbed on ZnS (110) spontaneously.

Effect of surface oxidation on the flotation separation of chalcopyrite and galena using sodium humate as depressant

ABSTRACT This study investigated the influence of mineral oxidation on Cu-Pb separation using green reagent sodium humate as depressant for galena. The flotation tests showed that sodium humate had a poor selectivity when it was used alone, especially with high dosage of sodium humate chalcopyrite could be depressed as well. Long time stirring or the addition of oxidants could significantly enhance the depressant ability of NaHA for galena. Zeta potential, electrochemical, and XPS measurement were conducted, indicating that surface oxidation of galena was conducive to the adsorption of sodium humate and then enhanced its inhibitory ability and selectivity.

Effect of Fe2+ and Cu2+ Ions on the Electrochemical Behavior of Massive Chalcopyrite in Bioleaching System

The electrochemical behavior of massive chalcopyrite in presence of Acidithiobacillus caldus, Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans and Sulfobacillus thermosulfidooxidans has been studied by cyclic voltammetry. The effect of Fe2+ and Cu2+ ion addition on the electrochemical behavior of massive chalcopyrite in bioleaching system were also investigated. The voltammograms illustrated that current densities of peaks were obviously increased with adding Fe2+ into the electrolyte. A series of anodic peaks were observed at more than 0 V when adding Fe2+ and Cu2+ ions, and these peaks are similar to the peaks of the step oxidation of chalcocite, thus proving that the formation of intermediate CuS2. Especially, the 9 g/L Fe2+ and 1.5 g/L Cu2+ were added. Therefore, appropriate ferrous and cupric ions concentration could enhance the formation of intermediate CuS2 leading to accelerate dissolution of chalcopyrite.

Sulfidation mechanism of ZnO roasted with pyrite

Sulfidation is a widely used technology to improve the floatability of oxidized metal minerals or to stabilize the heavy metals in various wastes. The sulfidation mechanism of ZnO with pyrite was detailedly studied by thermodynamic calculation and roasting experiments. The sulfidation behaviors, phase transformations, microscopic morphology and surface properties were investigated by TG-DSC, ICP, XRD, SEM-EDS, and XPS analysis. The results indicate that the nature of the sulfidation is the reaction of ZnO with the gaseous sulfur generated by the decomposition of pyrite. Pyrite instead of sulfur as the sulfidizing agent can not only relieve the volatilization loss of sulfur but also enhance the formation of liquid phase and thus facilitate the growth of ZnS particles. The sulfidation reaction belongs to surface chemical reaction and relates to the migration of oxygen from the inside of ZnO to its surfaces. The presence of carbon not only eliminates the release of SO2, but also decreases the decomposition temperature of pyrite and promotes the sulfidation of ZnO. The addition of Na2CO3 promotes the sulfidation of ZnO at lower temperatures (below 850 °C) and enhances the growth of ZnS particles but has a negative effect on the sulfidation at higher temperatures.

Removal of Iron Impurity from Zinc Calcine after Magnetization Roasting

The removal of iron impurity from zinc calcine was studied by magnetization roasting and magnetic separation. The effects of roasting temperature, magnetic intensity, ore grinding, and leaching pretreatment on iron grade and recovery were investigated. The results indicated that iron recovery increased with the increase of roasting temperature or magnetic intensity, while iron grade was always less than 22%, depending on the fact that the magnetite were not liberated completely. The good liberation was difficult to be achieved by ore grinding but was easier by acid leaching, since the magnetite grains were very fine. After the leaching pretreatment, the recovery of 76.31% with iron grade of 53.24% was obtained by one roughing and cleaning. The SEM/EDS analysis showed that a part of sphalerite, zinc ferrite and other gangues were mixed into the iron concentrate, while some of fine magnetite was reported to the tailing.