HYDROFLUORIC ACID HYDROGEN FLUORIDE DEIONIZATION EDI ION EXCHANGE MATERIALS RECOVERY SEMICONDUCTORS WASTEWATER

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Abstract

Editor’s note: Welcome to a technical article from our library of more than 2,100 technical and water business articles published since 1984. This article by Chris Jones, Adrienne Pierce, and Ben Roberts, PhD, was published in the July/August 2006 issue of Ultrapure Water Journal. This article examines the use of EDI technology for removal of hydrofluoric acid wastes in high-purity wastewaters.

Electrodeionization (EDI) is one of the unit operations used to produce high-purity water.  EDI can remove ionic contaminants from selected wastewater streams, so water can be recycled for reuse.  This technology combines ion exchange (IX) and electrodialysis in a single cell.  The mixed-bed IX deionizes solutions passing through the EDI cells.  The electrodialytic components move the ions from the resin to a concentrate stream, thereby achieving a continuous IX process without the need for periodic regeneration or regenerant chemicals.

Point-of-use (POU) scrubbers, including those incorporated into thermal processing units, often use significant amounts of water to scrub acid exhaust gases.  A modified EDI process can be used to effectively concentrate these acids while accomplishing the following:  

• Recycling water local to its POU.
• Mitigating corrosion by reducing the concentrations of acids in the scrubber water.
• Lowering the final wastewater volume to reduce the burden on back-pad precipitation systems. 
• Operating without additional chemicals or frequent operator intervention.

This article will review how a particular EDI technology may be used to recover water for reuse in POU wet scrubbers. 

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