Separation Enrichment And Determination Methods Of Gallium In Vanadium Titanium Magnetite

With the development of science and technology, despersed element gallium as support material of high-tech industries have been widely applied in electronics, communications, medical and other fields. The comprehensive development and utilization of gallium has become the focus of study in order to meet the increasing needs. A variety of separation enrichment and determination methods of gallium have been reported at present, however, the samples are mainly limited to fly ash and waste residue of bauxite and sphalerite after smelting. Vanadium titanium magnetite is one of the important mineral resources in the west with a large number of non-ferrous metals, and the gallium content in ore and tailings are high, reaching the level of comprehensive utilization. However, the separation enrichment and determination of gallium in vanadium titanium magnetite with complex matrix are rare reported. Therefore, a series of enrichment and separation methods were established to study gallium in ore, ore concentrate and tailings of vanadium titanium magnetite. The main research work and results were shown below:The Ga(III) in vanadium titanium magnetite was determinated by alkali fusion and 1-(2-pyridylazo)-2-naphthol(PAN) spectrophotometry. The best chromogenic condition was that: in a buffer solution of potassium hydrogen phthalate- hydrochloric acid(KHP-HC l)(p H 3.2), 3.0 mL of 95% ethanol and 4.0 mL of 0.5 g/L PAN solution were added.The complex of Ga(III) and PAN was red at room temperature. The complex exhibited maximum absorption peak at 545 nm with an apparent molar absorption coefficient of 3.0×104 L?mol-1?cm-1. The concentration of Ga(III) in the range of 0.05 to 3 μg/mL was linear, the detection limit was 0.033 μg/mL and the relative standard deviation(RSD) was 1.6%(n=7). In order to improve the selectivity of method, sodium hydroxide and sodium dioxide alkali fusion, filtering, acidification, butyl acetate extraction, water re-extraction were conducted, then a large number of interference ions were eliminated.In order to improve the selectivity of method, the Ga(III) in vanadium titanium magnetite had been determined using spectrophotometry connected polyethylene glycol(PEG-2000)- ammonium sulphate((NH4)2SO4) two-phase extraction. The best condition was investigated. The aqueous two-phase extraction system was prepared by mixing 3.0 mL of potassium hydrogen phthalate- hydrochloric acid(KHP-HC l) buffer solution and 7.0 mL of PEG-2000 solution, adding Ga(III) and PAN to form complex. After mixed thoroughly, the system was allowed to add 8.0 g of(N H4)2SO4 with vigorous oscillation to separate PEG-2000 solution and water into two phases. The complex of Ga(III) and PAN dispersed in PEG-2000 phase and exhibited maximum absorption peak at 545 nm with an apparent molar absorption coefficient of 1.26×105 L·mol-1·cm-1. The method for Ga(III) determination gave a detection limit of 0.0033μg/mL and the linear ranges was from 0.01 to 1μg/mL. Compared with the method 1, the sensitivity was improved; the detection limit declined 10 times.In order to reduce the dosage of organic solvent and improve the sensitivity and the selectivity of the method, a new method of ultrasonic assisted-dispersive liquid liquid microextraction combined with flame atomic absorption spectrometry to determinate trace gallium in vanadium titanium magnetite was determined. In the proposed approach, 1-(2-pyridineazo)-2-naphthol was selected as a complex agent and chlorobenzene was chosen as extraction solvent. The complex formation and microextraction condition was that: in a buffer solution of potassium hydrogen phthalate-hydrochloric acid(KHP-HC l)(pH 3.5), 2.0 mL of 0.5 g/L PAN solution and 500 μL of chlorobenzene were added, then the extraction time was 10 minutes under the temperature of 30 ℃.Under optimal conditions, series of Ga(III) standard solution for enrichment and determination were instructed, the linear range of working curve was 0.1-1 μg/mL with detection limit of 0.07 μg/mL, the enrichment factor reached 124 times and the relative standard deviation(RSD) was 13.54%.A new method was established using strong-acid cation exchange fiber for separation and enrichment of trace of gallium. When the column flow velocity was 2 mL/min, 1000 mL of 0.1 μg/mL gallium solution in p H=3 could be quantitatively enriched by 0.1000 g of strong-acid cation exchange fiber, and the gallium adsorbed could be eluted by 10 mL of 1.6 mol/L nitric acid solution. The enriching times was 100. With the increase of temperature, the adsorption efficiency of gallium by fiber increased. The adsorption of gallium by ion exchange fiber was mainly liquid film diffusion. The apparent activation energy was 38.71 kJ/mol calculated by the Arrhenius formula. The saturated adsorption capacity was 209.4 mg/g. The ion exchange process was well described by Freundlich equation, and the fitting results showed that the adsorption of gallium easily occured. Under the best adsorption and elution conditions, trace gallium in tap water or water of the river could be determined after separation and enrichment with fiber, while the results of experiment were that standard addition recovery of gallium was between 86.3~104.4% with relative standard deviation(RSD) between 0.1~1.7%.The three methods had been applied to the determination of Ga( III) in vanadium titanium magnetite GBW07224, GBW07226 a and GBW07227, respectively. The relative error for the determination of Ga(III) was between-4.3% to 2.4%, the results conformed to the requirements of trace analysis in analytical chemistry. In addition, a new method was established for separation and enrichment of trace gallium using strong-acid cation exchange fiber. It was benefited for the comprehensive utilization and follow-up study of gallium in vanadium titanium magnetite.