The behaviours of complexation and dissolution of PbCl2 on the surface of galena were investigated to explore the process of hydro-chemical conversion of galena(PbS)in chloride media.By means of solution chemistry calculation,the production and dissolution of the products PbCl2 were studied.And the passivation of the galena was studied by Tafel curve.The results show that PbCl4 2-is the main form of PbCl2 presented in the saturated potassium chloride(KCl)solution.The PbCl2 crystal is easy to precipitate when the total concentration of chloride ion([Cl -]T)is equal to 0.92 mol/L,and it is inclined to dissolve when[Cl -]T is more than 0.92 mol/L.The chloride complexing reaction rate strongly depends on the Fe3 +ion concentration when it is less than 6× 10-4mol/L,while passivation occurs on the surface of the electrode when Fe 3+concentration is larger than 6×10 -4mol/L.The reaction rate increases obviously when KCl is added,since the activity of Cl-increases;thus accelerates the dissolution of PbCl2.
The co-extraction behavior of galena-pyrolusite in a sodium chloride solution and the electrochemical mechanism of this process were investigated,and some factors affecting the leaching rate of Pb and Mn were optimized.The results show that all the factors such as the concentration of NaCl,HCl and pyrolusite ore,reaction time,temperature,adding times of HCl,affect the leaching rate of Pb.The main affecting factors are the concentration of NaCl,reaction time and temperature.The Tafel polarization curves and EIS plots of the galena and pyrolusite in the NaCl solution demonstrate that during the oxidation process of galena mineral electrode,film forms on the galena surface,which prevents galena from deeper oxidation.However,the film resistance can be greatly reduced in the presence of sodium chloride,thus promoting the reaction rate of galena.
Solvent extraction experiments were conducted from acidic solutions containing germanium(IV) and other metal ions, such as Ga 3+ , Fe 3+ , Zn 2+ and Fe 2+ in hydrometallurgical process of zinc. The purpose of this work was to enhance the efficiency of the extraction and stripping processes and the selectivity of germanium and other metals, while making the method as simple as possible. Germanium was recovered from sulfuric acid, using di-(2-ethylhexyl) phosphoric acid (P204) as an extractant, tributyl phosphate (TBP) as modifier diluted in sulfonate kerosene and stripped by NaOH aqueous solution. Extraction studies were carried out under different acid concentrations and solvent concentrations, and optimized conditions were determined. The numbers of stages required for extraction and stripping of metal ions were determined from the McCabe-Thiele plot. The results show that the extracting and stripping efficiencies are 94.3% and 100%, respectively, through two-stage extraction and two-stage strip. Moreover, the synergistic effect of TBP on the system P204/kerosense/Ge 4+ is revealed with respect to the extraction of germanium.
Two reagents including salicylhydroxamic acid(SHA) and tributyl phosphate(TBP) were tested as collectors either separately or together for electro-flotation of fine cassiterite(<10 μm).Subsequently,the flotation mechanism of the fine cassiterite was investigated by adsorbance determination,electrophoretic mobility measurements and Fourier transform infra-red(FT-IR) spectrum checking.Results of the flotation experiments show that with SHA as a collector,the collecting performance is remarkably impacted by the pulp pH value as the floatability of cassiterite varies sharply when the pH changes,and flotation with SHA gives distinct maximum at about pH 6.5.Additionally,the floatability of cassiterite is determined by using SHA and TBP as collectors.The range of pulp pH for good floatability is broadened in the presence of TBP as auxiliary collector,and the utilization of TBP improves the recovery of cassiterite modestly.Moreover,the optimum pH value for cassiterite flotation is associated with adsorbance.The results of FT-IR spectrum and the electrophoretic mobility measurements indicate that the adsorption interaction between the collectors and the cassiterite is dominantly a kind of chemical bonding in the form of one or two cycle chelate rings due to the coordination of carbonyl group,hydroxamate and P=O group to the metal tin atoms,where the oxygen atoms contained in carbonyl group,hydroxamate and P=O group of the polar groups have the stereo conditions to form five-membered rings.In addition,the adsorption interactions of SHA and TBP on the surfaces of cassiterite are also dominated by means of hydrogen bonds.
In the flotation process,bubble is a key factor in studying bubble-particle interaction and fine particle flotation.Knowledge on size distribution of bubbles in a flotation system is highly important.In this study,bubble distributions in different reagent concentrations,electrolyte concentrations,cathode apertures,and current densities in electroflotation are determined using a high-speed camera.Average bubble sizes under different conditions are calculated using Image-ProòPlus(Media Cyberneticsò,MD,USA)and SigmaScanòPro(Systat Software,CA,USA)software.Results indicate that the average sizes of bubbles,which were generated through 38,50,74,150,250,420,and 1000 lm cathode apertures,are 20.2,29.5,44.6,59.2,68.7,78.5,and 88.8 lm,respectively.The optimal current density in electroflotation is20 A/m2.Reagent and electrolyte concentrations,current density,and cathode aperture are important factors in controlling bubble size and nucleation.These factors also contribute to the control of fineparticle flotation.
The floatability of different crystalline structures of pyrrhotite(monoclinic and hexagonal) was studied.It is shown that the floatability of monoclinic and hexagonal has obvious difference,and that the flotation recovery of monoclinic pyrrhotite is larger than that of hexagonal pyrrhotite using different collectors.When butyl dithiophosphate is used as the collector,the recovery is larger than that by sodium butyl xanthate and sodium diethyl dithiocarbamate.At the pH values ranging from 6 to 9,monoclinic pyrrhotite can be floated well,and the flotation recovery is higher than 90%.Monoclinic and hexagonal pyrrhotites are more easily activated by Cu2+ in acidic conditions than in alkaline conditions.But Cu2+ cannot activate hexagonal pyrrhotite using sodium diethyldithiocarbamate as the collector.By the measurement of contact angle,it is indicated that monoclinic and hexagonal pyrrhotites float well and are easily activated by Cu2+ when dithiophosphate is used as the collector.Using sodium diethyl dithiocarbamate as a collector,the relationship between potential and pH range for pyrrhotite flotation is established.At pH 5,the optimal potential range for flotation of monoclinic pyrrhotite is about 125-580 mV(vs SHE),with the maximum flotation occurring at about 350 mV(vs SHE);the optimal potential range for flotation of hexagonal pyrrhotite is 200?580 mV(vs SHE),with the maximum flotation occurring at about 300 mV(vs SHE).
