C - Chemistry – Metallurgy – 01 – G
Patent
C - Chemistry, Metallurgy
01
G
C01G 28/00 (2006.01) C01B 17/90 (2006.01)
Patent
CA 2155949
The present invention provides a process for recovering arsenic acid from a starting mixture comprising sulfuric and arsenic acids and water. In step (a), the starting mixture is treated with a sulfur (IV) compound which will reduce the arsenic acid to arsenic (III) compound under conditions sufficient to substantially convert the arsenic acid to arsenic (II) wherein the resulting mixture comprises arsenic (III) compound, the sulfur (IV) compound, sulfuric acid, and water. In step (b), the resulting mixture is purged with inert gas to substantially remove the sulfur (IV) compound from the mixture wherein the purged mixture comprises the arsenic (III) compounds, sulfuric acid, and water. In step (c), the purged mixture is treated under conditions sufficient to substantially separate the arsenic (III) compounds from the purged mixture. In step (d), the separated arsenic (III) compound is reacted with an oxidizing agent to substantially convert arsenic (III) compound to arsenic acid wherein the final mixture comprises arsenic acid, unreacted oxidizing agent, and water. In step (e), impurities are removed from the final mixture to provide substantially pure aqueous arsenic acid. The recovered arsenic acid may be used for example as a raw material for the production of CCA wood preservative. The purged mixture which is sulfuric acid may be reused for example in the process of commonly assigned U.S. Patent 5,089,241.
Redmon Charles Lewis
Smith Robert Andrew
Subbanna Somanahalli Naranappa
Allied-Signal Inc.
Gowling Lafleur Henderson Llp
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