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Regeneration and Recycling of Waste Chromic Acid-sulfuric Acid Etchants.

Authors
Soboroff-DM; Troyer-JD; Cochran-AA
Source
NTIS: PB 80-111693 :13 pages
Link
NIOSHTIC No.
10007963
Abstract
Etchants containing hexavalent chromium and sulfuric acid are used in a variety of surface-finishing operations. When the resultant spent solutions are discarded, substantial quantities of chromium are lost and pollution problems are created. To minimize the undesirable environmental effects while improving metal and minerals recycling technology, the Bureau of Mines is conducting research on a method for the economic inplant recycling of these waste etchants. Trivalent chromium, produced when the etchant reacts with a substrate, is oxidized in the anode chamber of a diaphragm cell; other metals, dissolved during the etching operation, are transferred to the catholyte. When waste brass etchants are treated in this manner, all of the trivalent chromium is oxidized and more than 40 percent of the copper and zinc is removed. Similar copper removal and chromium oxidation are achieved with waste printed circuit board etchants and rinse waters from plastic etching operations. The electrical energy needed to regenerate 1 kg sodium dichromate is less than 9 kwhr. Regenerated brass etchants evaluated by two companies equaled or exceeded the performance of fresh etchants.
Publication Date
19790101
Document Type
IH; Report of Investigation;
Fiscal Year
1979
NTIS Accession No.
PB80-111693
NTIS Price
A03
Identifying No.
RI 8377
NIOSH Division
RORC;
Source Name
NTIS: PB 80-111693
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