Zhe-nan Jin

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.

Fine debismuthizing with calcium, magnesium and antimony

In order to achieve fine debismuthizing of lead bullion, the effects of temperature, adding amount of calcium and magnesium and antimony on the bismuth removal from lead bullion were investigated. The mechanism of debismuthizing was also discussed. The results show that when adding amounts of calcium and magnesium reach 0.112% and 0.395%, respectively, bismuth level of 0.001% (mass fraction) in the final lead is achieved at 330 °C, without the need for antimony addition. Maintaining addition amount of magnesium at 0.155%, when calcium addition amount is less than 0.09%, the concentration of peritectic reaction point, the bismuth concentration can be easily decreased to 0.001% by the following antimony treatment. But the effect of antimony treatment on debismuthizing gets bad if the calcium addition exceeds 0.09%.

Mechanism of debismuthizing with calcium and magnesium

Abstract In order to further understand the debismuthizing mechanism with calcium and magnesium, the influence of adding amount of calcium on the bismuth removal from lead was examined. A part of the debismuthizing dross samples were studied by electron probe microanalysis (EPMA). The results show that the calculated bismuthide governing debismuthizing process is Ca3Mg7Bi8, which may be a mixture of Ca3Bi2, CaBi, CaBi3 and Mg3Bi2. And the bismuthide formed during the debismuthizing process exists in two states: one is free bismuthide in the matrix of dross, and the other is symbiotic with Pb–Ca phase.

Lead extraction and glass-ceramics synthesis from waste cathode ray tube funnel glass through cooperative smelting process with coal fly ash

In this study, a novel process was developed for extracting lead from the hazardous waste cathode ray tube (CRT) funnel glass and simultaneously producing glass-ceramics. CRT funnel glass was mixed with coal fly ash and subjected to carbon thermal reduction with the addition of CaO. The homogeneous glass melt and reduced metallic lead were quenched in water. Glass-ceramics were produced from the parent glass through an appropriate heat treatment. The optimum carbon loading amount (calculated as the molar ratio of C/PbO), CaO/SiO2 ratio, smelting temperature and holding time for lead recovery were 1.0, 0.3-0.6, 1450 °C and 2 h, respectively. Under these conditions, more than 95% of lead can be extracted from the funnel glass and a low lead content of the resultant parent glass below 0.6 wt% was successfully achieved. CaO behaved as a network modifier to reduce the viscosity of the glass and also acted as a substitution to release lead oxide from the silicate network structure, resulting in a high lead separation efficiency. X-ray diffraction (XRD) analysis revealed that the main crystalline phase was gehlenite when 50-70 wt% funnel glass was added. Scanning electron microscopy (SEM) observation showed that well-crystallized crystals occurred in the specimens with 50-70 wt% funnel glass additions, whereas the specimens with 40 wt% and 80 wt% glass additions exhibited a relative low crystallization degree. Furthermore, property measurements, chemical resistance tests and leaching characteristics of heavy metals confirmed the possibility of engineering and construction applications of the superior glass-ceramic products. Overall results indicate that the process proposed in this paper is an effective and promising approach for reutilization of obsolete CRT funnel glass.

Extraction of selenium from copper anode slimes in a sealed leaching system

A new method was proposed for extracting selenium from copper anode slimes with a low concentration of nitric acid in a sealed sulfuric acid leaching system. It is performed under an atmosphere of oxygen which allowed for a cyclic utilization of nitric acid. The effects of main parameters on selenium leaching were studied. The mineralogical characterizations of the typical samples were investigated by XRD and SEM. The results showed that the optimal conditions of the process are considered to be total gas pressure of 0.1 MPa, leaching temperature of 388 K, solid-liquid ratio of 0.20 g mL–1, H2SO4 concentration of 2 mol L–1, HNO3 concentration of 0.07 mol L–1 and leaching time of 2 h. The high selenium leaching efficiency of 99.23% was obtained under these conditions. According to the results of XRD and SEM-EDS, Cu–Ag selenide in the raw anode slimes is difficult to be leached with sulfuric acid alone; copper can be leached more easily from Cu-Ag selenide than silver; selenide is oxidized into the solution, undergoing the intermediate product of elemental selenium.

Selenium Leaching from Copper Anode Slimes Using a Nitric Acid–Sulfuric Acid Mixture

Based on the Eh–pH diagram for the Se–H2O system, a new method is proposed for leaching selenium from copper anode slimes using a nitric acid–sulfuric acid mixture. The effects of solid/liquid ratio, HNO3 and H2SO4 concentrations, leaching temperature, and reaction time on the leaching efficiency of selenium were investigated. Samples were mineralogically characterized by x-ray diffraction and scanning electron microscopy with energy-dispersive spectroscopy to study the transformation of selenium-containing phases during the leaching process. The results showed that the optimal conditions comprised a solid/liquid ratio of 0.25 g/ml, HNO3 concentration of 0.5 M, H2SO4 concentration of 2 M, leaching temperature of 363 K, and reaction time of 3 h. A selenium leaching efficiency of 97.79% was obtained under these conditions. Mineralogical characterization indicated that selenium occurred as Cu–Ag selenide in the raw copper anode slimes. This was first converted to elemental selenium and then to selenite ions in solution.

Effect of the CaO/SiO2 mass ratio and FeO content on the viscosity of CaO–SiO2–“FeO”–12wt%ZnO–3wt%Al2O3 slags

An effective process for recycling lead from hazardous waste cathode ray tubes (CRTs) funnel glass through traditional lead smelting has been presented previously. The viscous behavior of the molten high lead slag, which is affected by the addition of funnel glass, plays a critical role in determining the production efficiency. Therefore, the viscosities of the CaO–SiO2–“FeO”–12wt%ZnO–3wt%Al2O3 slags were measured in the current study using the rotating spindle method. The slag viscosity decreases as the CaO/SiO2 mass ratio is increased from 0.8 to 1.2 and also as the FeO content is increased from 8wt% to 20wt%. The breaking temperature of the slag is lowered substantially by the addition of FeO, whereas the influence of the CaO/SiO2 mass ratio on the breaking temperature is complex. The structural analysis of quenched slags using Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy reveals that the silicate network structure is depolymerized with increasing CaO/SiO2 mass ratio or increasing FeO content. The [FeO6]-octahedra in the slag melt increase as the CaO/SiO2 mass ratio or the FeO content increases. This increase can further decrease the degree of polymerization (DOP) of the slag. Furthermore, the activation energy for viscous flow decreases both with increasing CaO/SiO2 mass ratio and increasing FeO content.

A method for calculation of ion distribution in reaction system forming hydroxide

Abstract A formula was proposed to calculate the distribution of metal ions quantitatively in chemical reaction system forming hydroxide where precipitation and complex are formed together. The effects of some factors on formation of precipitation and complex were investigated, and the corresponding precipitation rates of zinc, iron (III), aluminum, copper and magnesium were calculated. As a result, it shows that the proposed formula is reliable. By the proposed formula, the existence state of metal ions in hydroxides reaction system with any metal ions can be well described and the effects of some factors on the distribution of metal ions were determined.