Treatment of pit waste containing chromated copper arsenate
Number of patents in Portfolio can not be more than 2000
United States of America Patent
Stats
-
May 16, 1995
Grant Date -
N/A
app pub date -
Jun 22, 1993
filing date -
Jun 22, 1993
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A chemical process for treating pit waste contaminated with chromated copper arsenate (i.e. CCA). CCA is recovered for recycling, and remaining solids are decontaminated for safe disposal. Pit wastes are pulverized and reacted with concentrate sulfuric or phosphoric acid. Wood particles are partially decomposed and approximately 60% to 70% of the CCA is leached out. The acid-treated mixture is centrifuged or filtered to separate liquids from solids. Liquids are recycled for reuse in the CCA process. CCA-bearing solids enter a heated digester equipped with an air or water cooled condenser. Concentrated nitric and sulfuric acids are inputted into the digester and the ratio of nitric acid to sulfuric acid to solids is approximately six to two to one by volume. Nitric acid completely oxidizes all organic matter in the solids. Sulfuric acid serves as a dehydrating agent and liquid media for CCA. The initial oxidation is carried out at a temperature greater than 70.degree. C. and less than 100.degree. C. In the final stage of oxidation nitric acid is reacted and passed off as lower nitrogen oxides between 100.degree. C. and 110.degree. C. Recovered nitric acid may be recycled to the instant process.
First Claim
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