Study On Microwave Digestion Of Vanadium And Titanium Magnetite And Determination Of Micro Amounts Of Vanadium By Polarography

Iron ore was the resource that largely used in national construction process. The quality problem of iron ore would not be igored with minings and imports of plenty of iron ore. Vanadium and titanium magnetite was one of the inport iron ores in our country, and it was hard to digest, so the vanadium and titanium magnetite was representative. This topic had studied microwave digestion and determination of main element of vanadium and titanium magnetite standard sample. The main research content and results were followed:1. Four kinds of microwave digestion system had been established:(1) Mixed system of sulfuric acid and phosphoric acid: 0.2000g of vanadium and titanium magnetite sample, 3.00mL of concentrated H₂SO₄, 9.00mL of concentrated H₃PO₄, 5 droplets of HNO₃, The digestion procedure was: holding 2min in microwave power of 350W and holding 6min in microwave power of 560W, holding 2min in microwave power of 350W at last.(2) Mixed system of hydrofluoric acid and phosphoric acid: 0.1000g of vanadium and titanium magnetite sample, 10.00mL of mixed acid (VH₃PO₄ / V_HF was 2:8), The digestion procedure was: holding 6min in microwave power of 280W and holding 2min in microwave power of 350W.(3) Digestion system with complex: 0.1000g of vanadium and titanium magnetite, 0.0400g of complexant(8-hydroxyquinoline), 12.00mL of concentrated HCl, digestion time was 10¹2min, microwave power was 385W.(4) Alkali fusion: 0.1000g of vanadium and titanium magnetite, 3.000g of total mixed-flux (m_NaOH/m_Na2O2 was 1:2), holding 10 min in microwave power of 385W. Titanium and iron were determined one after another in the first and second system. Iron was determined by dichromatemethod in the third and forth system. The level of digestion was judged by the concentrations of titanium and iron in samples. The results showed that the four systems could digest vanadium and titanium magnetite completely and the consequences had met the analytical chemistry requirements.2. A new method had been developed for the determination of micro amounts of vanadium in a buffer solution of HAc-NaAc.Optimization reagent conditions: 5.00mL of buffer solution of HAc-NaAc at a pH of 4.5, 3.00mL of 1.00g/L phenanthroline(Phen) solution, then final volume was 25.00mL through adding distilled water. Optimization instrument conditions: determination waveform was the first order derivative wave, starting potential was -0.20V, scanning rate was 1.00V/s, scanning times was four and static time was 14s. Under the optimal condition, the linear range of vanadium determination was 0.050-5.0μg/mL, the linear equation was Ip'(×10⁴nA) = 13.631-1.7678c(μg/mL) (n=7,R² = 0.9953), the detection limit was 0.0042μg/ml. The method had the advantage of the high sensitivity, wide linear range, simpleness and celerity. This method had been successfully applied to determination of micro amounts of vanadium in vanadium and titanium magnetite. The results had met with requirements of analytical chemistry.The mechanism of electrode reactant had been also studied. The results showed that the main electrode reactant was protonated Phen, and the polarographic wave was an irreversible adsorption wave.