Process for Reducing the Concentration of Arsenic in an Aqueous Solution Comprising a Fluoroacid

Patent metadata

Field	Value
Publication number	US-2019270656-A1
Application number	US-201716348242-A
Country	US
Kind code	A1
Filing date	Nov 9, 2017
Priority date	Nov 10, 2016
Publication date	Sep 5, 2019
Grant date	—

Abstract

A process for reducing the concentration of one or more arsenic-containing compounds in an aqueous solution comprising at least one fluoroacid, which process comprises: (i) contacting the aqueous solution with an oxidising agent to produce one or more Asv-containing compounds; and (ii) removal of precipitated arsenic-containing compounds; wherein the process comprises a step (iii) the addition of an aqueous alkali solution or slurry, which may take place after step (i) and before step (ii) or after step (ii).

First claim

1 . A process for reducing the concentration of one or more arsenic-containing compounds in an aqueous solution comprising at least one fluoroacid, which process comprises:
(i) contacting the aqueous solution with an oxidising agent to produce one or more As V -containing compounds; and (ii) removal of precipitated arsenic-containing compounds;
wherein the process comprises a step (iii) the addition of an aqueous alkali solution or slurry, which may take place after step (i) and before step (ii) or after step (ii).

2 . A process according to claim 1 , wherein the aqueous solution comprises fluorosilicic acid.

3 . A process according to claim 1 or 2 , wherein the fluoroacid is present in an amount of from about 1 to about 50% by weight based on the total weight of the aqueous solution.

4 . A process according to any of the preceding claims, wherein the one or more arsenic-containing compounds comprise AsF 3 or a hydrolysed form of AsF 3 .

5 . A process according to any of the preceding claims, wherein the oxidising agent is selected from chlorine (Cl 2 ), hypochlorite salts (M + ClO − ), hypochlorous acid (HClO), hydrogen peroxide (H 2 O 2 ) and permanganate salts (M + MnO 4 − ) and mixtures thereof.

6 . A process according to any of the preceding claims, wherein the removal of the precipitated arsenic-containing compounds comprises gravity-settling, filtration, anion-exchange resin or a combination thereof.

7 . A process according to any of claims 1 to 6 , wherein step (ii) is preceded by the addition of an aqueous alkali solution or slurry.

8 . A process according to any of claims 1 to 6 , wherein step (ii) is followed by the addition of an aqueous alkali solution or slurry.

9 . A process according to any of the preceding claims, wherein the alkali is calcium hydroxide (Ca(OH) 2 ) or calcium oxide (CaO).

10 . A process according to claim 9 , wherein the calcium hydroxide or calcium oxide is present in an amount of from about 15 to about 20% by weight of the solution or slurry.

11 . A process according to any of the preceding claims, further comprising dilution of the solution prior to the addition of the alkali solution or slurry.

12 . A process according to claims 8 to 11 comprising a subsequent step (iv) of removal of the resulting precipitate.

13 . A process according to any of the preceding claims, wherein the addition of the oxidising agent is carried out at a temperature of from about 0 to about 35° C.

14 . A process according to any of the preceding claims, wherein step (i) is carried out in a time period of from about 1 to about 30 minutes.

15 . A process according to claim 14 , wherein step (i) is carried out in a time period of from 2 to 5 minutes.

16 . A process according to any preceding claim, wherein in step (i) the oxidising agent is used in a stoichiometric excess relative to the quantity of oxidisable arsenic-containing compounds.

17 . A process according to claim 16 , wherein the stoichiometric excess is 4 to 60 times the quantity of oxidisable arsenic-containing compounds.

18 . A process according to claim 17 , wherein the stoichiometric excess is 20 to 40 times the quantity of oxidisable arsenic-containing compounds.

19 . A process according to any of the preceding claims, wherein step (iii) is carried out at a temperature of from about 0 to about 35° C.

20 . A process according to claim 18 or 19 , wherein step (iii) is carried out at a temperature of from about 15 to about 30° C.

21 . A process according to any of the preceding claims comprising subsequently recycling all or part of the treated aqueous solution and repeating a process as defined in any one of claims 1 to 20 .

22 . A process according to any of the preceding claims, wherein from about 50 to about 100% by weight of the arsenic-containing compounds is removed from the solution.

23 . A process according to any of the preceding claims, wherein the treated solution contains about 5 ppm or less of arsenic-containing compounds.

24 . A process according to any of the preceding claims, wherein the treated solution contains about 1 ppm or less of arsenic-containing compounds.

25 . A process for the production of fluorosilicic acid comprising a process as defined in any of the preceding claims.

26 . A process for the purification of fluorosilicic acid comprising a process as defined in any of the preceding claims.

27 . A process for the production of HF comprising a process as defined in any of the preceding claims.

28 . A process for the production of aluminium trifluoride (AlF 3 ) comprising a process as defined in any of the preceding claims.

Assignees

• Mexichem Fluor Sa De Cv

Inventors

• Garcia Juan Alberto Juarez
• Castillo Iris Samantha Duran
• Robles Nilo Martinez

Classifications

• C02F1/5245 Primary

  using basic salts, e.g. of aluminium and iron · CPC title

• C02F2103/34

  from industrial activities not provided for in groups C02F2103/12 - C02F2103/32 · CPC title

• C02F1/66

  by neutralisation; pH adjustment (for degassing C02F1/20; using ion-exchange C02F1/42; for flocculation or precipitation of suspended impurities C02F1/52; for removing dissolved compounds C02F1/58) · CPC title

• C02F2101/103

  Arsenic compounds · CPC title

• C02F1/76

  with halogens or compounds of halogens {(C02F1/4674 takes precedence)} · CPC title