Determination of vanadium content in vanadium carbide

Vanadium carbide is an important alloy additive, which can improve the corrosion resistance, wear resistance, strength and other comprehensive properties of hard alloys, so it is widely used in alloys. At present, the main methods for the determination of high vanadium content are REDOX titration, inductively coupled plasma atomic Emission spectrometry (ICP-AES), X-ray fluorescence spectrometry and spectrophotometry, but they all have their shortcomings. Chemical titration is widely used because of its high accuracy, easy to master and low operating cost.

Vanadium titration method according to the use of oxidants can be divided into ammonium persulfate oxidation – ammonium ferric sulfate titration method, potassium permanganate oxidation – ammonium ferric sulfate titration method, perchloric acid oxidation – ammonium ferric sulfate titration method, the former two main, the latter application is less. Potassium permanganate oxidation – ammonium ferric sulfate titration method only at room temperature can oxidize vanadium, of which excess potassium permanganate at room temperature can also be reduced by sodium nitrite; However, the ammonium persulfate oxidation – ammonium ferric sulfate titration method can only be vanadium oxide under heating conditions, in which the excess ammonium persulfate can be completely destroyed under boiling conditions, and the next step can only be carried out after cooling to room temperature. The operation is relatively more complicated.

Wang Lufeng, Wang Binbin and other researchers from Vanadium and Titanium College of Panzhihua University and National Vanadium and Titanium Product Quality Supervision and Inspection Center added nitric acid solution to Vanadium carbide samples, dissolved, cooled, filtered, collected filtrate and adjusted to neutral, and the obtained filtrate was stored as the main solution. After cooling, sulfuric acid solution and hydrofluoric acid are added. After heating and evaporating at low temperature, hydrochloric acid solution is added to continue heating to extract the molten substance. The resulting leaching solution is combined in the main solution.

Add sulfuric acid solution into the solution obtained above, heat until white smoke, add phosphoric acid after dilution, drop potassium permanganate solution to pink, then add manganese sulfate solution, oxalic acid solution, shake until pink disappeared. Add sulfuric acid solution and a few drops of N-phenylamino-benzoic acid solution, immediately titration with ammonium ferrous sulfate standard titration solution, the solution from purple red to bright green is the end point of titration, record the volume of ammonium ferrous sulfate standard titration solution consumed at this time.

At present, the preparation method of vanadium carbide in China mainly uses metallurgical grade vanadium pentoxide, which is mixed with carbon and prepared by reaction at high temperature. In the production of hard alloy, the requirement of raw material impurities is high. The vanadium carbide used in this experiment is prepared by ammonium metadadate. According to the test results, the phase of vanadium carbide is V 8 C 7. Vanadium carbide samples were selected and decomposed by acid dissolution method and acid dissolution realkali fusion residue method respectively. According to the results, acid dissolution realkali fusion residue method was selected as the sample decomposition method. The main elements affecting the determination of vanadium are manganese, chromium, cerium and tungsten. The test results show that the determination of vanadium in vanadium carbide sample does not consider interference. Through precision test, method comparison and recovery test, it can be seen that this method has good precision and high accuracy, and the method is basically consistent with the determination results of GB/T 24583.1 — 2019.