Xingbin Li

Recovery of H2SO4 from an acid leach solution by diffusion dialysis

Diffusion dialysis with a series of anion exchange membranes was used to recover H(2)SO(4) from an acid leach solution produced during the vanadium manufacturing process. The effects of sulfuric acid, FeSO(4) and VOSO(4) concentration, flow rate and flow rate ratio on the recovery of H(2)SO(4) were investigated. The results showed that sulfuric acid permeated well through the membranes used, while metal ions were efficiently rejected. The recovery of H(2)SO(4) increased as the sulfate concentration of the feed increased and the flow rate ratio of water to feed increased. More than 80% of the H(2)SO(4) could be recovered from the leach solution which contained 61.7 g/L free H(2)SO(4), 11.2 g/L Fe and 4.60 g/L V at a flow rate of 0.19x10(-3) m(3)/h m(2). V and Fe ion rejection were within 93-95 and 92-94%, respectively. A preliminary economic evaluation revealed that an investment in this process could be recovered within 27 months.

Molybdenum blue photometry method for the determination of colloidal silica and soluble silica in leaching solution

An improved analytical procedure has been described for the spectrophotometric determination of colloidal silica in leaching solution by means of adding fluoride to convert colloidal silica into reactive silica. The method is a variation of the classical molybdenum blue method, and the optimal wavelength, temperature, ratio of H3BO3/NH4F, pH and ammonium molybdate in the colorimetric process has been determined. The pH especially needs to be fairly strictly controlled. The linear equation is established as: C = 3.15956A − 0.51912, and R is more than 0.9992. Its feasibility and reproducibility have been confirmed by ICP-OES; the average relative error is 1.5%. The detection scope of silicon concentration extends almost 1000 times higher in a leaching solution, so the method in this paper can be used to detect leaching samples with a high silica concentration.

Simultaneous determination of progestogens, androgens, estrogens and phenols in water, sediment and biological samples by enolisation–silylation with ASE-GPC-SPE-GC/MS

This research has developed an enolisation–silylation with accelerated solvent extraction (ASE)-automated gel permeation chromatography (GPC)-solid phase extraction (SPE)-gas chromatography/mass spectrometry (GC/MS) analytical method for the simultaneous determination of twelve steroidal and phenolic endocrine disrupting chemicals (EDCs) in water, sediment and biological samples. The parameters of ASE have been optimized as follows: ethyl acetate as the extraction solvent, a static extraction time of 5 min, and 3 extraction cycles at 80 °C and 60 °C for sediment and biological samples, respectively. Clean-up of extracts was carried out by GPC with Sep-Pak C18 cartridges. The target compounds were eluted in the fraction from 7–14 min retention time, and then the extracts were obtained by solid phase extraction with Sep-Pak C18 cartridges after elution with 15 mL ethyl acetate. The final sample extracts were derivatized using N-methyl-N-(trimethylsilyl)trifluoroacetamide (MSTFA)/trimethyliodosilane (TMIS)/dithioerythreitol (DTE) (1000 : 2 : 5; v/v/w) as a derivatization reagent. Quantification was performed by gas chromatography-mass spectrometry (GC-MS) with electron ionisation (EI) and selected ion monitoring (SIM) mode. The method was validated by spiking experiments which showed low method detection limits, good recovery (60.28% to 95.46%) and reproducibility (RSD < 10%). The proposed methods were successfully applied to the determination of the target EDCs in environmental samples taken from the Laoyu River and a local market in Yunnan, China. This method had better practicability and feasibility for simultaneous determination of progestogens, androgens, estrogens and phenols in water, sediment and biological samples. This technique is more fast, simple and precise than some other methods, and has a wide range of applications. It is beneficial to study the occurrence, fate and bioaccumulation of these compounds in the environment.

An optimized method based on MAE-SPE-GC-MS for the analysis of thirteen PBDEs in airborne particles

An efficient and reliable analytical method has been developed for the determination of polybrominated diphenyl ethers (PBDEs) in atmospheric particulates collected by ultra-fine glass fibre filters. Thirteen PBDEs in atmospheric particulates were extracted through a developed method and determined by gas chromatography-mass spectrometry (GC-MS). Compared with the classical Soxhlet method and multi-layer silica column purification procedure, the developed method, including microwave assisted extraction (MAE) and solid phase extraction (SPE) procedures, made the pretreatment procedure of atmospheric particulates samples more automatic and faster. The four important conditions of MAE procedure (extraction solvent, solvent volume, extraction temperature and holding time) and three important conditions of SPE procedure (SPE cartridge, elution solvent and pH) were carefully studied and improved. The method achieved good repeatability and reproducibility with RSDs ranging from 2.0% to 11% for all target PBDEs in atmospheric particulate samples. Satisfactory recoveries for spiked particulate samples ranged from 74.0% to 112%. The limits of detection (LOD) and limits of quantification (LOQ) ranges for filter samples were from 0.11 (BDE-17) to 1.23 ng g−1 dw (BDE-209) and from 0.37 (BDE-17) to 4.10 ng g−1 dw (BDE-209), respectively. The developed method has been successfully demonstrated to determine the concentrations of the target PBDEs in atmospheric particulates from one of the state air quality controlling sites in Kunming, China. The results showed that the concentration range of target PBDEs was from 4.97 to 376 ng g−1 dw. BDE-28 (27.9 ng g−1 dw), BDE-71 (35.4 ng g−1 dw), BDE-190 (265.4 ng g−1 dw) and BDE-209 (375.6 ng g−1 dw) were the four dominant PBDEs at the sampling site.

Hematite Precipitation from High Iron Solution in Hydrometallurgy Process

Iron precipitation occupies a vital position in the metallurgy industry, especially for treating iron-bearing sphalerite in hydrometallurgical processes. This paper emphasizes techniques for removing iron from high-iron sphalerite via hematite precipitation, and describes the results of research performed to examine ferrous oxydrolysis and precipitation. The behavior and mechanism of conversion between the iron phase and hematite residue at elevated temperature under pressure is ascertained by investigating the dissolving characteristic and thermodynamics stable area of hematite at sulfate system. The results show hematite precipitation went through the process of crystallization, dissolve, oxidation and precipitation of ferrous sulfate, and the overall iron precipitation was determined to be controlled by the rate of ferric sulphate hydrolysis rather than the oxidation of ferrous sulphate or the re-dissolution of ferrous sulphate crystals, or the transformation of basic ferric sulphate.

Oxygen Pressure Leaching Behavior of Nickel from Black Shale

Ni–Mo ore is a black shale containing amorphous colloidal sulfides which have highly active. The oxygen pressure leaching behavior of nickel from black shale in aqueous media is presented. The effects of agitation speed, temperature, oxygen partial pressure and particle size on the rate of nickel leaching were determined. The results indicate that at low temperature hydrothermal and excess oxygen presence, the amorphous sulfides are easily oxidized to sulfuric acid and sulfate, and leaching nickel. The mathematical analyses of the experimental data for various experimental conditions indicated that the dissolution process was controlled by the chemical reaction during the early stage of dissolution, and was then controlled by liquid-film diffusion. In the initial stage of leaching, the reaction depends on oxygen partial pressure.

Separation of Iron (III) and Nickel (II) from Acidic Sulfate Leaching Solution of Molybdenum-Nickel Black Shale

Cooling crystallization was used to separate iron (III) and nickel (II) from acidic sulfate solution produced by leaching of molybdenum-nickel black shale. The effect of K2SO4 concentration, crystallization temperature, solution pH and crystallization time on recovery of nickel (II) and precipitation of iron (III) was investigated, in order to obtain effective separation of nickel and iron. The optimum parameters determined were as follows: 200 g/L K2SO4, 10 °C crystallization temperature, solution pH of 0.5 and 24 h crystallization. Under these conditions, 97.6% nickel (II) was recovered as K2Ni(SO4)2·6H2O crystals and only 2.0% of the total iron (III) was precipitated. Recrystallization yielded K2Ni(SO4)2·6H2O crystals with a purity of 98.4%.

Behaviour and characterization of hematite process for iron removal in hydrometallurgical production

ABSTRACT The separation of zinc and iron is essential in hydrometallurgical processes, especially for treating high-iron sphalerite. The hematite precipitation process for removing iron is an effective way to achieve the high-efficiency separation of zinc and iron. The authors studied the effect of temperature and time on the precipitation behaviour and characterised the precipitation products through X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and chemical analysis. The hematite precipitate contained more than 50% iron, less than 0.5% zinc, 0.1% arsenic and 5% sulfur; more than 95% K, 50% Na and 50%–60% F were co-precipitated, and less than 1% Zn, Mg, Mn and Cl remained in the residue. Because of the uncontrolled supersaturation conditions, jarosite and goethite were generated. Extension of the reaction time and increasing the reaction temperature enabled conversion of most of the goethite and sodium jarosite to hematite during the hematite precipitation process.

Pressure Leaching Behavior of Molybdenum-Nickel Sulfide from Black Shale

Molybdenum and nickel in black shale ore exists as amorphous sulfides which has highly active, and easily oxide to sulfuric acid and sulfate at low temperature in the presence of excess oxygen. Take advantage of the characteristic to leach molybdenum and nickel from black shale. Oxidation, conversion and dissolution behavior of amorphous colloidal molybdenum and nickel sulfide in pressure leaching process was studied. The effects of stirring speed, temperature, concentration of sulphuric acid, oxygen process and mineral granularity on molybdenum and nickel leaching were investigated. The results showed that dissolution rate increased with increasing temperature and stirring speed, but decreased with increasing concentration of sulphuric acid. And dissolution of molybdenum and nickel from ore only need oxygen without any other reagent.

Acid Leaching Zinc and Indium with Reduction Ferric Simultaneously from Marmatite and High-Iron Neutral Leaching Residue

Marmatite is an important resource of zinc, which exist in forms of high iron and high indium. In order to recycle the valuable metal from these ores, the testwork of simultaneous leaching on neutral residue mixed with zinc concentrate of high iron and high indium has been conducted. The primary objectives are to leach the zinc and indium remaining in the neutral leach residue as ferrite using acid, and to reduce the ferric iron in solution to the ferrous by zinc concentrate, thereby extracting the zinc and indium in the zinc concentrate. The results indicated that in the following conditions, mass ratio of neutral residue to zinc concentrate of 1:0.25, particle size of 74–58 µm, initial sulfuric acid concentration of 150 g/L, liquid to solid ratio of 8 L/kg, temperature of 90°C, reaction time of 4h, the leaching efficiency of zinc and indium were over 95%, nearly 90% Fe was Ferrous in the leaching solution. This process effectively extracted zinc and indium and converted Fe3+ into Fe2+ in solution, and simplified the traditional process of reduction after leaching.