Abstract
ABSTRACT
This study deals with the neutralization and detoxification of a spent ferric chloride etching solution from the manufacture of nickel alloy heating elements. In the manufacture of these elements some surface metal is removed by means of a ferric chloride solution that gradually loses its effectiveness due to an excessive build up of nickel and chromium salts. Although the etching waste is not a hazardous waste according to the United States EPA criteria, the state of Missouri includes all etching solutions as hazardous waste. In order to change this spent ferric chloride etching solution from a hazardous waste to an industrial solid waste classification, neutralization tests were performed using three alkaline sources; sodium hydroxide, calcium hydroxide, and sludge from a municipal water treatment plant. Neutralization of the liquid etching waste solution precipitates relatively insoluble metal hydroxide sludges. These sludges were tested according to the EPA Extraction Procedure (EP) toxicity test. Passage of the EP toxicity test allows a waste generator to petition the regulatory agencies for a delisting of the hazardous waste. Results indicate that calcium hydroxide is the most effective and economic means of neutralizing the spent ferric chloride etching solution. A calcium hydroxide addition of the 0.7 kg per liter of waste will neutralize the acidic waste, allow passage of the EP toxicity test for hazardous waste delisting, and produce a solid with a suitable solids content to permit it to be landfilled.
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