Treatment of degraded oxime metal extractants in process organic solutions
The invention relates to a method for regenerating the extractive potential of an organic hydroxyoxime-based extraction solution used in the recovery of metals by liquid-liquid extraction. The method is two-stage, in which a solid hydroxylamine is used in the reaction stage, and the removal of the undesirable compounds generated in the reaction occurs in the second stage by adsorption purification. The method of the invention is suitable for treatment of degraded oxime metal extractants in various process organic solutions both in aldehyde and ketoxime extractant solutions. The method can also be used to treat a mixture of degraded oxime extractants.
1. A method of regenerating ketone and aldehyde oxime degradation products of a degraded hydroxyoxime based organic extraction solution used in the recovery of metals by liquid-liquid extraction, comprising the step of (a) contacting the degraded hydroxyoxime based organic extraction solution comprising the ketone and aldehyde oxime degradation products with a wetted hydroxylamine or salt thereof in solid form in the presence of a solid alkaline salt to obtain a solid-organic mixture and thereafter removing any solid particles from the degraded hydroxyoxime based organic extraction solution, and the step of (b) purifying the organic extraction solution by adsorption purification by bringing said degraded hydroxyoxime based organic extraction solution into contact with an adsorption material in solid form,
wherein the method is performed without the use of a phase transfer catalyst.
2. The method according to claim 1 , wherein in step (a) the solid-organic mixture is stirred and solid particles are dispersed into the degraded hydroxyoxime based organic extraction solution.
3. The method according to claim 1 , wherein the solid hydroxylamine or salt thereof is at least one selected from the group consisting of: hydroxylamine sulphate, hydroxylamine halide, hydroxylamine phosphate, or hydroxylamine sulphonate.
4. The method according to claim 1 , wherein the quantity of hydroxylamine used in step (a) is at least the stoichiometric equivalent of the total quantity of aldehyde and/or ketone formed in the extraction solution as hydroxyoxime degradation products.
5. The method according to claim 1 , wherein the solid alkaline salt is selected from the group consisting of: alkali metal hydroxide, earth alkali metal hydroxide, alkali metal carbonate, alkali earth metal carbonate, and ammonia.
6. The method according to claim 1 , wherein the solid alkaline salt is sodium carbonate.
7. The method according to claim 1 , wherein any solid particles are removed from the organic extraction solution by a decanter or filter.
8. The method according to claim 1 , wherein after contacting the organic extraction solution with the wetted hydroxylamine or salt thereof in solid form in the presence of the solid alkaline salt and prior to the removal of the solid particles, the organic extraction solution is washed with an aqueous solution.
9. The method according to claim 8 , wherein the washing is done at a pH of 2-5 and temperature of about 25-40° C.
10. The method according to claim 8 , wherein the washing is carried out using a one stage mixer-settler unit or with only a mixer and the aqueous solution and the organic extraction solution are separated with a centrifuge or decanter.
11. The method according to claim 8 , wherein the hydroxylamine or its salt is recycled after the washing.
12. The method according to claim 1 , wherein the adsorption material in a solid form is at least one selected from the group consisting of: bentonite, diatomite, aluminium silicate, metal oxide, activated carbon, polymeric adsorbent, and polymeric ion exchange resin.
13. The method according to claim 1 , wherein the quantity of adsorption material is 0.01-10 weight % based on the degraded hydroxyoxime based organic extraction solution.
14. The method according to claim 1 , wherein the quantity of adsorption material is 0.5-3 weight % based on the degraded hydroxyoxime based organic extraction solution.
15. The method according to claim 1 , wherein the adsorption material is separated from the degraded hydroxyoxime based organic extraction solution by settling, filtration or centrifugation.
16. The method according to claim 1 , wherein the adsorption material is in ground form.
17. The method according to claim 1 , wherein the adsorption material is a powder, spheres or filaments.
18. The method according to claim 1 , wherein the step (a) and the step (b) take place as a batch operation.
19. The method according to claim 1 , wherein the step (a) and the step (b) take place as a continuous operation.
20. The method according to claim 1 , wherein the step (a) takes place as a batch operation and the step (b) takes place as a continuous operation.
21. The method according to claim 1 , wherein the step (a) takes place as a continuous operation and the step (b) takes place as a batch operation.