Recycling of waste sulfuric acid
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United States of America Patent
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Jun 4, 1996
Grant Date -
N/A
app pub date -
Dec 15, 1993
filing date -
Dec 16, 1992
priority date (Note) -
Expired
status (Latency Note)
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Abstract
Sulfuric acid used in the process of fabricating semiconductor devices, etc., can be recycled to reduce the amount of sulfuric acid to be discarded. A sulfuric acid effluent is fed to an anode chamber of a sulfuric acid-concentrating electrolyzer partitioned by at least one cation exchange membrane to concentrate sulfuric acid and generate oxidizing substances, so that the sulfuric acid can be used at the step of using sulfuric acid, and, when the concentration of impurities built up in the system exceeds a certain level, a part of sulfuric acid in the system is fed to a unit for refining sulfuric acid, where the sulfuric acid is refined and whence the refined sulfuric acid is fed back to the system. According to this recycling process, it is possible to obtain sulfuric acid having high oxidizing power with no addition of an oxidizing substance such as hydrogen peroxide thereto.
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