REPROCESSING HYDROFLUORIC ACID ETCHING SOLUTIONS BY REVERSE OSMOSIS

Abstract

Reverse osmosis has been applied in this study for reprocessing HF present in etching solutions. Experimental results show a very high degree of permeation of HF and rejection of ionic impurities by certain membranes. An ion exclusion model has been developed to estimate the degree of HF permeation and shows the same trends as the experimental data.

To check the chemical stability of the membranes, when exposed to different concentrations of HF and Fluosilicic acid (the major impurity present in the HF etching solutions) for extended periods of time, ion rejection and water permeability properties of fresh and exposed membranes were determined. No significant change in the rejection properties was observed even after prolonged periods of exposure. The results of this work indicate that several commercially available thin film composite membranes can be used to reprocess HF by removing ionic and particulate impurities.

KEYWORDS:

• Etching solutions
• Membrane separations
• Ultrapurification Recycling