phase analysis

There are many kinds of tungsten minerals in nature, but most of them are very few, so the phase analysis of tungsten minerals is generally only aimed at wolframite (WO3), scheelite (CaWO4) and wolframite [(Fe, Mn)WO4]].

Tungsten flower is soluble in ammonium hydroxide solution, but wolframite and scheelite are insoluble, so it can be separated and determined.

When the scheelite content in the sample is more than 4%, (5+95)HCl is used for leaching, while wolframite is insoluble or slightly soluble. When the content is less than 4%, 1mol/L oxalic acid is used as leaching solution.

The wolframite is calculated by subtracting the total amount of tungsten trioxide in the sample.

See fig. 55. 1 for the process of tungsten phase analysis.

reagent

Hydrogen peroxide.

Ammonium hydroxide.

Sulfuric acid.

Sodium hydroxide solution (0.7 mol/L).

Ammonium chloride solution (20g/L).

Aluminum trichloride-acetic acid solution Weigh 40gAlCl3 and dissolve it in water, add 1 17.5mLHAc, transfer it to 1000mL volumetric flask, and dilute it to scale with water.

Fig. 55. 1 Flowchart of Tungsten Phase Analysis

Aluminum trichloride-acetic acid washing solution 1 part aluminum trichloride-acetic acid solution, and add 2 parts water.

Oxalic acid solution (1mol/L) Weigh 126g of oxalic acid (H2C2O4 2H2O) and dissolve it in water, then dilute it with water to 1000mL.

Methyl orange solution (1.0g/L).

Potassium permanganate standard solution (calibrated with sodium oxalate).

Analytical method

(1) wolframite

Weigh 1g (accurate to 0.0002g) sample, put it in a 250mL conical flask, add 50mL(2+98)NH4OH, plug it with a rubber stopper with a long glass tube, put it in water at 80 ~ 90℃ and heat it for 2h. When shaking, take it out and let it cool a little, add 0.2gNH4Cl and stir it evenly. Immediately filter with slow filter paper, and wash the conical flask and residue with hot (2+98)NH4OH lotion for 4 times. Heat and evaporate the filtrate until it is nearly dry, add a small amount of sodium hydroxide solution and heat until the soluble salt is completely dissolved. Cool, transfer into a 50 ml volumetric flask, dilute to scale with sodium hydroxide solution, and mix well.

Absorb the clear liquid and determine the amount of tungsten trioxide by potassium thiocyanate spectrophotometry (see 55.3.4 in this chapter), which is the content of wolframite in the sample.

(2) Scheelite

A hydrochloric acid leaching method (suitable for the determination of scheelite containing more than 4% tungsten). Rinse the insoluble matter of wolframite with aluminum trichloride-acetic acid solution in a 400mL beaker to make the volume of the solution about 65438±000ml, cover it with watch glasses, heat it in water at 80 ~ 90℃ for 65438 0 h, and stir it regularly. Cooling, filtering with slow filter paper, washing insoluble matter with aluminum trichloride-acetic acid lotion for 20 times, heating and evaporating the filtrate until it is nearly dry, adding a small amount of sodium hydroxide solution, and heating until the soluble salt is completely dissolved. After cooling, transfer to a 1000mL volumetric flask and dilute to scale with sodium hydroxide solution. The content of tungsten trioxide is determined by potassium thiocyanate spectrophotometry (see 55.3.4 in this chapter), and added to the result obtained by dissolving the residue with hydrochloric acid, which is the content of scheelite in the sample.

Put the residue leached in the above steps into the original beaker, add 200mL(5+95)HCl, mash the filter paper, and heat it in water at 80 ~ 90℃ for 2h while stirring. Take it off, filter it, wash the insoluble matter 10 times with hot (1+99)HCl, collect the filtrate in a 400mL beaker, when the ammonium hydroxide is alkaline and exceeds 3mL, add 1+9 H2O2 and heat it to boiling. Filtering, washing the beaker with ammonium chloride solution and precipitating 10 times, collecting the filtrate in a 400mL beaker, acidifying with hydrochloric acid and concentrating to about 200mL, and heating to boiling. Take it out, cool it a little, add 15~20mL oxalic acid solution, use methyl orange as indicator, neutralize it with ammonium hydroxide until it is slightly alkaline, and keep it warm overnight if it exceeds 15 ~ 20ml.

The next day, the precipitate was filtered with slow filter paper and washed with water until there was no oxalate reaction (tested with silver nitrate). Stick the filter paper on the original beaker wall, rinse the precipitate with water, add 50mL( 1+9)H2SO4, dilute it to 200mL with water, heat it to 70 ~ 80℃, titrate it to reddish with potassium permanganate standard solution, immerse the filter paper in the solution, and continue to titrate to reddish.

Analysis of Rock Minerals Volume III Analysis of Nonferrous, Rare, Dispersed, Rare Earth, Precious Metal Ores and Uranium Thorium Ores

Where: W (scheelite WO3) is the mass fraction of scheelite WO3,%; Is the concentration of potassium permanganate standard solution, mol/l; V is the volume of consumed potassium permanganate standard solution, ml; 23 1.8 is the numerical value of the molar mass of tungsten trioxide in g/mol; M is the sample mass, g; H is the mass fraction of tungsten trioxide in the original sample of aluminum trichloride-acetic acid leaching solution,%.

B oxalic acid leaching method (suitable for the determination of tungsten with scheelite less than 4%). Put the residue after leaching wolframite into a 250mL beaker, add 50 ml of 0.5mol/L oxalic acid solution, mash the filter paper, soak it for 30min at room temperature (shake it frequently), take it off, filter it with slow filter paper in a 100mL volumetric flask, wash the beaker and residue with 0.5 mol/L oxalic acid solution, and fix the volume. Absorb the clear solution, determine tungsten trioxide by potassium thiocyanate spectrophotometry (see 55.3.4 in this chapter), and calculate the scheelite content in the sample according to the following formula:

Analysis of Rock Minerals Volume III Analysis of Nonferrous, Rare, Dispersed, Rare Earth, Precious Metal Ores and Uranium Thorium Ores

Where: W (scheelite WO3) is the mass fraction of scheelite WO3,%; A is the mass fraction of WO3 in the sample measured by this method,%; B is WO3 in the sample minus the total amount of wolframite and scheelite measured by this method,%; 0. 1 is the wolframite dissolution correction coefficient.

(3) wolframite

The total amount of tungsten trioxide in the sample minus tungsten trioxide in wolframite and scheelite is regarded as wolframite.

Matters needing attention

Determination of wolframite. Reagent bottle should be used for ammonium hydroxide. If carbonate is contained, a small amount of scheelite will dissolve. Equipped with a long glass tube, it can reduce the volatilization rate of water and ammonium hydroxide and ensure the complete dissolution of tungsten oxide. If the sample contains copper, after adding sodium hydroxide solution, add formaldehyde to remove copper.

2) Determination of scheelite. When scheelite is leached with dilute hydrochloric acid, scheelite is partially dissolved; When the wolframite content is high and the scheelite content is low, the error of scheelite measured is very large. Wolframite is slightly soluble in oxalic acid solution. When scheelite: wolframite in tungsten ore is ≤ 10: 1, this method is not applicable.

refer to

Jiangxi provincial bureau of geology and mineral resources experimental testing center. Analysis of tungsten ore [M]. Beijing: Geological Publishing House.

Jing, Zhang Boyi, Liu. 1990. determination of tungsten and tin by thin filter paper sample-wavelength dispersive x-ray fluorescence spectrometry [J]. rock and ore testing, 9(4):272-273.

King, cow,. 1999. A simple method for determining WO3(%) in tungsten concentrate by XRF [J]. Spectroscopy and spectral analysis, 19( 1):93.

Technical conditions of tungsten concentrate [s] (ys/t231-1994). Beijing: China Standards Publishing House.

Methods for chemical analysis of tungsten concentrates (GB/T 6150-1985). Beijing: China Standards Publishing House.

Code for Geological Exploration of Tungsten, Tin, Mercury and Antimony Mines [S] (DZ/T0201-2002). 2003. Beijing: Geology Press.

Xu, Yuan Jizu,, et al. Handbook on the development and utilization of industrial mineral resources [M]. Wuhan: Wuhan University of Technology Press, 248-25 1.

Zhang Jing. 199 1. Determination of fifteen elements in tungsten ore by inductively coupled plasma atomic emission spectrometry [J]. Rock and mineral testing,10 (1): 41-43.

This chapter is written by Chen Jinbao (Experimental Testing Center of Jiangxi Geological Exploration Bureau).