CN101570346A

CN101570346A - Method for preparing ammonium paratungstate from sodium tungstate solution

Info

Publication number: CN101570346A
Application number: CNA2009100436698A
Authority: CN
Inventors: 赵中伟; 陈星宇; 李洪桂; 霍广生; 陈爱良
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2009-06-11
Filing date: 2009-06-11
Publication date: 2009-11-04

Abstract

The invention provides a method for preparing pure ammonium paratungstate (APT) from crude Na2WO4 solution containing NaOH, P, As, Si, Sn and other impurities. The method comprises the following steps of crystallizing tungsten into Na2WO4 crystals through concentration, separating NaOH from impurities, redissolving and acidifying the Na2WO4 crystals till the pH of the crystals is between 2.0 and 6.0, adsorbing the crystals by use of macroporous weak alkaline anion exchange resin, desorbing the crystals by use of NH4OH, obtaining (NH4)2WO4 solution, performing evaporation crystallization and obtaining the APT. Under the condition that the crystallization rate is between 88 and 90 percent, the P, the As and the Si contained in the APT are all less than 10*10<-6>. The method has the outstanding advantage of small amount of discharged wastewater (mainly liquid after exchange), namely the volume of the discharged liquid after the exchange is one third to one twenty-fifth of that of liquid before the exchange; in addition, the discharged liquid after the exchange contains no detrimental impurities and is easy to control.

Description

Produce the method for ammonium paratungstate from sodium tungstate solution

Technical field

The present invention relates to tungsten metallurgy and tungsten chemical field, particularly from coarse sodium tungstate, produce the method for ammonium paratungstate (APT).

Background technology

Ammonium paratungstate (APT) is the important tungsten metallurgy and the intermediates of tungsten chemical industry.Be the preparation ammonium paratungstate, its raw material is mainly the coarse sodium tungstate of handling tungsten raw material (containing raw mineral materials and secondary raw material) gained, wherein removes to contain Na ₂WO ₄Also contain superfluous NaOH and P, As, impurity such as Si, Sn outward.Therefore should finish two tasks for therefrom producing ammonium paratungstate: one is a purification and impurity removal, and it promptly is converted into ammonium salt by sodium salt two for making the transition.For finishing above-mentioned task, main technique has strongly basic anion exchange resin absorbing process and magnesium salts method removal of impurities-abstraction and type-reverting technology under alkaline condition both at home and abroad.And most advanced, widespread use is the strongly basic anion exchange process.

The flow process of strongly basic anion exchange process such as accompanying drawing 1 contain the Na of free NaOH and impurity ₂WO ₄Solution dilution is to containing WO ₃Behind 10-20g/L, at first adsorb with strongly basic anion exchange resin.This moment the WO in the solution ₄ ^2-With resin Cl mutually ^-Permutoid reaction takes place and enter the resin phase.Impurity P, As, Si, Sn and NaOH are retained in and hand in the liquid of back load WO ₄ ^2-Resin NH ₄The Cl solution stripping promptly gets (NH ₄) ₂WO ₄Solution, thereby process is adsorbed, two processes of desorb have just been finished the task of purification and impurity removal and transition, the revaporization crystallization obtains the ammonium paratungstate product.

Contain free NaOH and P, As, impurity such as Si, Sn after the friendship after the above-mentioned absorption in the liquid.

The main drawback of strongly basic anion exchange process is:

1. wastewater discharge is big, and is difficult to administer.Because the WO that liquid allows before handing over ₃Concentration low (only 10-20g/L), thereby have to big water gaging stoste be diluted.It causes waste water (handing over back liquid) amount big on the one hand, and the concentration of detrimental impurity such as P, As, Si, Sn is diluted in the solution on the other hand, is difficult to handle.

2.NaOH be important chemical material.Not only fail in the strongly basic anion exchange process to recycle, and also want consumption acids that it is neutralized when liquid is handled after friendship.No matter thereby consider it all is inappropriate from the angle of the comprehensive utilization of valuable material or environmental protection.

Summary of the invention

In order to address the above problem, the invention provides and a kind ofly produce the method for ammonium paratungstate from sodium tungstate solution, this method wastewater displacement is few, and valuable material NaOH can fully reclaim and utilize.

Ultimate principle: (1) adopts the condensing crystal method from Na ₂WO ₄Reclaim NaOH in the solution, impurity A s, P, Si, Sn stay alkali liquor with the overwhelming majority and and Na ₂WO ₄Crystal separation.Thereby employing condensing crystal Na ₂WO ₄Process will be received the effect of double gain, promptly on the one hand can effective recycling Na ₂WO ₄NaOH in the solution is turned waste into wealth and is reduced the discharging of chemical reagent, can remove Na on the other hand ₂WO ₄In impurity P, As, Si, Sn.(2) adopt macroporous weakly basic anion exchange resin can from the sodium tungstate solution of high density (30-500g/L), adsorb tungsten effectively and and then use NH ₄The OH desorb gets (NH ₄) ₂WO ₄Solution.Because the strength of solution height, correspondingly wastewater volume significantly reduces, and does not wherein contain objectionable impurities such as As.These have created favourable condition for reclaim valuable material (being mainly sodium salt) from waste water again.

Technical scheme of the present invention is: produce the method for ammonium paratungstate from sodium tungstate solution, mainly be made up of following operation:

1. thick Na ₂WO ₄The condensing crystal of solution

Make Na ₂WO ₄Supersaturation forms the sodium wolframate crystal and separates out, and impurity such as P, As, Si, Sn are retained in the alkaline solution, return raw mineral materials alkali decomposition process.In the alkali decomposition course impurity such as these P, As, Si, Sn will with sheelite (or Ca (OH) ₂) reaction generates insoluble calcium salts and solidify and enter the alkali decompose slag.

2. dissolving of sodium wolframate crystalline and acidifying

Above-mentioned sodium wolframate dissolution of crystals must be contained WO ₃The solution of 30-500g/L is acidified with acid simultaneously to pH2.0-6.0.This moment the WO in the solution ₄ ^2-Aggregate into metatungstic acid radical ion H ₂W ₁₂O ₄₀ ^6-Acidifying Na ₂WO ₄The used acid of solution is mineral acids such as sulfuric acid, hydrochloric acid or nitric acid.

3. anionite-exchange resin absorption

Adopt macroporous weakly basic anion exchange resin to adsorb, make H ₂W ₁₂O ₄₀ ^6-With resin SO mutually ₄ ^2-(or Cl ^-Or NO ₃ ^-) permutoid reaction takes place and enter the resin phase.For example, when adopting the tertiary amine groups resin, react and be:

3(R ₃NH) ₂SO ₄+H ₂W ₁₂O ₄₀ ^6-＝(R ₃NH) ₆H ₂W ₁₂O ₄₀+3SO ₄ ^2-

4. desorb

Load tungsten resin NH ₄The OH desorb, the H of resin phase ₂W ₁₂O ₄₀ ^6-Become (NH ₄) ₂WO ₄Form enters solution, reacts to be:

(R ₃NH) ₆H ₂W ₁₂O ₄₀+24NH ₄OH＝4R ₃N+12(NH ₄) ₂WO ₄+16H ₂O

5. evaporative crystallization

Gained (NH ₄) ₂WO ₄Solution carries out evaporative crystallization and gets APT after removing molybdenum.Evaporative crystallization under normal pressure or negative pressure be to carry out under the condition of 50Kpa.

6. transition of resin (or regeneration)

Return absorption with acid after with ion exchange resin conversion.

2R ₃N+H ₂SO ₄＝(R ₃NH) ₂SO ₄

Compared with prior art, the present invention has the following advantages:

Na ₂WO ₄The strength of solution height, correspondingly its outstanding advantage of bringing is that waste water (mainly being to hand over back liquid) quantity discharged is few, and easily administers.Owing to adopt macroporous weakly basic anion exchange resin among the present invention, strong with the anionic affinity of tungsten, the 3-25 that the preceding liquid concentration of the friendship of permission is strongly basic anion exchange process under alkaline condition doubly.Therefore after the friendship of discharging liquid long-pending also only be its 1/3-1/25.Simultaneously wherein be substantially free of harmful impurity, so easily administer.Use H in particularly working as with in the process ₂SO ₄Or HNO ₃When making neutralizing agent, then hand over the Na that mainly contains valency in the liquid of back ₂SO ₄Or NaNO ₃Available evaporative crystallization method reclaims, and hands over this moment back liquid discharging near zero.This extracellular concentration height also causes all dwindling at double of equipment volume workshop area.Valuable material NaOH is recycled, and turns waste into wealth.

Description of drawings

Fig. 1: the strongly basic anion exchange process is handled Na ₂WO ₄Produce the schematic flow sheet of APT;

Fig. 2: process flow diagram of the present invention.

Embodiment

Embodiment 1

The thick Na of NaOH decomposition of tungsten mineral raw material gained ₂WO ₄Solution contains WO ₃147g/L, free NaOH 50g/L, P 0.275g/L, As 0.3g/L, Si 0.7g/L get 2L and carry out condensing crystal under the ebullient conditions, get Na ₂WO ₄Crystal 4 10g wherein contains WO ₃65.5%, NaOH 2.1%.Get Na after the crystal water dissolving ₂WO ₄Solution contains WO ₃503g/L, free NaOH 16.1g/L, Si 0.09g/L, As 0.1g/L, P 0.1g/L.Thick Na ₂WO ₄In P, As more than 95% and 98% Si all enter alkali liquor after the crystallization, alkali liquor contains NaOH 310g/L.

Embodiment 2

Embodiment 1 described thick Na ₂WO ₄Solution 2L carries out condensing crystal under the condition of 50Kpa to get Na ₂WO ₄Crystal 4 25g wherein contains WO ₃63.8%, NaOH 2.6%, and dissolution of crystals gets Na ₂WO ₄Solution contains WO ₃490g/L, NaOH 18.2g/L, Si 0.10g/L, As 0.11g/L, P 0.1g/L, thick Na ₂WO ₄In about 95% P, As and 97% above Si all enter alkali liquor, alkali liquor contains NaOH 300g/L.

Embodiment 3

Na described in the embodiment 1 ₂WO ₄Na after the crystal water dissolving ₂WO ₄Solution 0.5L contains WO ₃503g/L adds H ₂SO ₄Being neutralized to pH is about 6, makes it and H ₂SO ₄The macroporous weakly basic anion exchange resin D301 of transition carries out ion-exchange, and the result hands over back liquid (absorption back liquid) to contain WO ₃0.02g/L.Load tungsten resin NH ₄OH solution (contains NH ₃About 28%) desorb, must contain WO ₃208g/L (NH4) ₂WO ₄Solution 1.20L, the latter gets APT through evaporative crystallization, is under about 88% the condition at percent crystallization in massecuite, APT through the impure P of spectroscopic analysis, As, Si all less than 10 * 10 ^-6, Sn is less than 1 * 10 ^-6

Embodiment 4

Embodiment 1 described Na ₂WO ₄Na after the crystal water dissolving ₂WO ₄Solution 0.5L (contains WO ₃503g/L) be diluted to WO ₃Concentration is 30g/L, and being neutralized to pH with hydrochloric acid is about 2, adopts the macroporous weakly basic anion exchange resin D312 that makes the transition through hcl acidifying to carry out ion-exchange, hands over back liquid to contain WO ₃0.02g/L, load tungsten resin NH ₄OH solution (contains NH ₃About 28%) carry out desorb, must contain WO ₃Concentration is the (NH of 190g/L ₄) ₂WO ₄Solution 1.30L, the latter gets APT through evaporative crystallization, when percent crystallization in massecuite is 88% left and right sides, gained APT through the impure P of spectroscopic analysis, As, Si all less than 10 * 10 ^-6, Sn is less than 1 * 10 ^-6

Embodiment 5

Embodiment 1 described Na ₂WO ₄Na after the crystal water dissolving ₂WO ₄Solution 0.5L contains WO ₃503g/L uses HNO ₃Being neutralized to pH is about 2, with process HNO ₃Macroporous weakly basic anion exchange resin D363 absorption after acidifying makes the transition hands over back liquid to contain WO ₃0.03g/L, load tungsten resin NH ₄OH solution (contains NH ₃About 28%) carry out desorb, must contain WO ₃Concentration is the (NH of 202g/L ₄) ₂WO ₄Solution 1.2L, the latter gets APT through evaporative crystallization, is under about 90% the condition at percent crystallization in massecuite, gained APT through the impure P of spectroscopic analysis, As, Si all less than 10 * 10 ^-6, Sn is less than 1 * 10 ^-6

Embodiment 6

Embodiment 1 described Na ₂WO ₄Na after the crystal water dissolving ₂WO ₄Solution 0.5L (contains WO ₃503g/L) be diluted to WO ₃Concentration is 250g/L, uses H ₂SO ₄Being neutralized to pH is about 5, with process H ₂SO ₄Macroporous weakly basic anion exchange resin D314 absorption after acidifying makes the transition hands over back liquid to contain WO ₃0.03g/L, load tungsten resin NH ₄OH solution (contains NH ₃About 28%) carry out desorb, must contain WO ₃Concentration is the (NH of 204g/L ₄) ₂WO4 solution 1.22L, the latter gets APT through evaporative crystallization, is under about 90% the condition at percent crystallization in massecuite, gained APT through the impure P of spectroscopic analysis, As, Si all less than 10 * 10 ^-6, Sn is less than 1 * 10 ^-6

Embodiment 7

Liquid contains Na after the friendship of embodiment 3 gained ₂SO ₄290g/L, pH=6 gets the 0.5L evaporating, concentrating and crystallizing and gets Na ₂SO ₄131g.

Claims

1. produce the method for ammonium paratungstate from sodium tungstate solution, it is characterized in that: mainly form by following operation:

1) thick Na ₂WO ₄The condensing crystal of solution

Make Na ₂WO ₄Supersaturation forms the sodium wolframate crystal and separates out;

2) dissolving of sodium wolframate crystalline and acidifying

With above-mentioned sodium wolframate dissolution of crystals to containing WO ₃The solution of 30-500g/L is acidified with acid simultaneously to pH2.0-6.0;

3) anionite-exchange resin absorption

Adopt macroporous weakly basic anion exchange resin to adsorb;

4) desorb

Load tungsten resin NH ₄The OH desorb;

5) evaporative crystallization

Resolve gained (NH ₄) ₂WO ₄Solution carries out evaporative crystallization and gets APT after removing molybdenum.

2. method according to claim 1 is characterized in that: the alkaline solution that contains P, As, Si, Sn impurity behind the condensing crystal returns raw mineral materials alkali decomposition process.

3. method according to claim 1 is characterized in that: the used acid of described sodium tungstate solution acidifying is sulfuric acid, hydrochloric acid or nitric acid.

4. method according to claim 1 is characterized in that: described evaporative crystallization under normal pressure or negative pressure be to carry out under the condition of 50Kpa.

5. method according to claim 1 is characterized in that: return absorption after the resin after the desorb makes the transition with acid.