At present, the main raw materials for extracting vanadium are stone coal and vanadium slag. Stone coal contains low vanadium, and its leachate needs to be further decontaminated and concentrated to further precipitate vanadium. The ion exchange method can be used for separation and enrichment of substances in dilute solutions. The extraction of vanadium from stone coal leaching solution with weakly basic anion exchange resin has been studied. The effects of resin type, adsorption contact time and pH on the adsorption rate of vanadium have been investigated. Different types of resin have been studied for vanadium ( The ion exchange performance of V) proves that the ion exchange method can well enrich vanadium in the stone coal leaching solution.

When vanadium is leached from the vanadium slag, the concentration of vanadium in the leaching solution is relatively high, and generally no concentration is required, and vanadium can be directly recovered from the purified leachate by extraction-back extraction. However, after the leachate is extracted by solvent, the raffinate still contains a small amount of vanadium. In order to fully recover this part of vanadium, it is adsorbed by D301 macroporous weakly basic anion exchange resin, and the vanadium concentration in the desorbed liquid is high, which can be returned to the solvent extraction process.

First, the test part

(1) Test materials and instruments

The solution used in the test is a raffinate containing a small amount of vanadium after solvent extraction, that is, the vanadium slag is subjected to sodium sulphide roasting and leaching to obtain a raffinate aqueous phase obtained by purifying and extracting, wherein the vanadium mass concentration is 1 to 2 g/L. The vanadium solution was taken from Chengde Xinxin Vanadium and Titanium Co., Ltd., and the raffinate was obtained after purification and impurity removal in the laboratory and single-stage extraction.

Resin: D301 macroporous weakly basic anion exchange resin, provided by Hangzhou Zhengguang Resin Factory. Before use, treated with acid solution, transition to HSO ₄ ^- type. D301 resin is an anion exchange resin mainly containing a tertiary amino group [-N(CH ₃ ) ₂ ] on a macroporous structure of styrene-divinylbenzene copolymer, which is weakly alkaline and can be used in acidic near-neutral medium. It effectively exchanges inorganic acids and can adsorb impurities with large molecular size and use in non-aqueous solutions. It has the advantages of high regeneration efficiency, large exchange capacity, strong anti-pollution ability and good mechanical strength.

Ion exchange column: φ 2 cm × 100 cm.

(2) Analytical method of vanadium in solution

Determination of mass concentration of vanadium in sulfuric acid solution of ferrous ammonium sulfate volumetric method.

(3) Test methods

1, static adsorption

5 mL of the wet resin was placed in a 100 ml flask, 50 mL of the vanadium-containing raffinate was added each time, and the mixture was shaken at room temperature (26 ° C) for a certain period of time, and then the amount of adsorption was measured to calculate the adsorption rate.

Adsorption rate = ×100%,

In the formula: The mass concentration of vanadium before and after adsorption, g/L.

2, column adsorption (dynamic adsorption)

A self-made ion exchange column was used, and the column was filled with a certain amount of wet resin. The vanadium-containing raffinate is passed through the ion exchange column at a flow rate. The effluent was taken at intervals to analyze the vanadium mass concentration, and the volume of the solution passing through the ion exchange column was recorded. After the adsorption is completed, the resin in the exchange column is washed with deionized water, and then the resin in the exchange column is desorbed with a certain amount of a certain concentration of desorbent. The solution flows through the ion exchange column from top to bottom during adsorption and desorption.

Second, the test results and discussion

(1) Static adsorption

In the static test, there are two kinds of adsorption stock solutions, which are vanadium mass concentration 1.99 g/L, pH=2.1 and vanadium mass concentration 1.67 g/L, pH=5.1. The test was carried out 14 times for 30 minutes each time, the first solution was used for the first 8 times, and the second solution was used after the ninth time. The results of 14 tests are shown in Figure 1.

Figure 1 The relationship between the cumulative concentration of vanadium in D301 resin and the number of tests

It can be seen from Figure 1 that the mass concentration of vanadium in the solution decreased from 1.99 g/L after the first 30 min ion exchange treatment. 0.191g / L, vanadium adsorption rate of 90.4%; with the increase of the number of tests, the concentration of vanadium in the resin increased, gradually approaching the adsorption of the original solution, the vanadium adsorption rate decreased in a single test; in the 14th test, the cumulative mass concentration of vanadium in the resin It tends to be stable at 112.4 mg/mL. It can be seen that the saturated capacity of the resin adsorbing vanadium is 112.4 mg/mL wet resin.

(2) Influence of adsorption time

Adsorption stock solution: Vanadium mass concentration 1.67g / L, pH = 5.1. The static adsorption method was used to sample every 10 minutes until 60 min. The mass concentration of vanadium in the solution after ion exchange was analyzed, and the vanadium adsorption rate was calculated to obtain the optimum adsorption time. The test results are shown in Table 1.

Table 1 Effect of adsorption time on vanadium adsorption rate

It can be seen from Table 2 that the adsorption rate of vanadium increases gradually with the extension of adsorption time; after 40 min adsorption, the vanadium adsorption rate remains basically stable, further prolonging the adsorption time, and the adsorption rate does not change significantly. It can be seen that the adsorption of vanadium by the resin is already saturated. Therefore, the optimum time for D301 resin to adsorb vanadium is 40 min.

(III) Column adsorption test

In addition of the ion exchange column HSO ₄ ^- D301-type resin 260mL, liquid adsorption vanadium concentration 1.59 g / L, pH = 7.0 . The solution flow rate was set to 500 mL/h, and the column adsorption test was performed at room temperature. The test set the effluent vanadium mass concentration through the ion exchange column to be greater than 5 mg/L as the breakthrough point, and the effluent volume is in multiples of the bed volume. The relationship between the amount of adsorbed raw liquid and the mass concentration of vanadium is shown in Fig. 2.

Fig. 2 Relationship between the amount of adsorbent solution and the mass concentration of vanadium

It can be seen from Fig. 2 that under the test conditions, the breakthrough volume of vanadium adsorbed by D301 resin is 48 times bed volume, and when the amount of adsorbed raw liquid is within 48 times of bed volume, the mass concentration of vanadium after treatment is less than 5 mg/L, adsorption The rate is greater than 99%; the saturated volume of vanadium adsorbed by D301 resin is 88 times bed volume, and the resin can no longer be adsorbed after the treatment volume exceeds 88 bed volume.

The D301 resin penetrating capacity was 76.32 mg/mL wet resin, and the saturated capacity was 108.7 mg/mL wet resin, which was basically consistent with the saturated capacity of 112.4 mg/mL wet resin measured by static test.

(4) Desorption test

After the column adsorption test, the supported resin in the column was desorbed with a desorbent. The desorbent was a 1 mol/L NaOH solution, the flow rate was controlled at 260 mL/h, and the desorption was carried out at room temperature (26 ° C). The desorption of the vanadium-bearing resin in the ion exchange column is shown in Fig. 3. It can be seen that the vanadium can be effectively desorbed from the resin by using 1mol/L NaOH solution. When the desorbent volume is 2 times the bed volume, the vanadium mass concentration in the desorbing solution is the highest (up to 56.2g/L), and the desorption rate is obtained. It is 76%; when the desorbent volume is 3.6 times bed volume, the vanadium desorption rate is 99%; when the desorbent is 4 times bed volume, all vanadium can be desorbed and desorbed without tailing.

Figure 3 Desorption curve of vanadium-loaded ion exchange resin

Third, the conclusion

(1) Vanadium can be enriched from the vanadium-containing raffinate using D301 macroporous weakly basic anion exchange resin. The vanadium-containing solution has a mass concentration of 1.67 g/L and a pH of 5.1. At room temperature, the adsorption capacity of the vanadium is 112.4 mg/mL wet resin.

(2) When the volume of the vanadium-containing raffinate treated by D301 resin is 48 times bed volume, the mass concentration of the tailings vanadium after adsorption does not exceed 5 mg/L.

(3) The 1 mol/L NaOH solution can effectively desorb the vanadium from the resin, and the desorption liquid vanadium has a high mass concentration and can be returned to extract vanadium.

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