| Summary: | 碩士 === 元智大學 === 化學工程學系 === 91 === Hydrofluoric acid has been commonly used in tile semiconductor industries for wafer etching and tool cleaning. Those processes lead to generation of large quantity of waste acid solution which comprises primarily the hydrofluoric (HF) and hydrofluorosilicic (FSA) acids. The objective of this study is to utilize ion exchange resins to recover both
acids from waste solution. The present investigation focuses on the batch equilibrium and column ion exchange experimental tests and the related theoretical modeling using the appropriate ion exchange models.
Two types of ion exchange resins were used in the present study. The strong basic OH-type resin was to capture HF and FSA from the waste acid solution in the first step while the strong acid H-type resin served to convert NaF and Na2SiF6, obtained from the OH-type resin to HF and FSA in the second step. Batch experimental tests were carried out to determine the equilibrium ion exchange capacities of both resins under competitive ion exchange conditions of the two-component (HF/FSA) system. Various isotherms, including Langmuir, extended Langmuir and Freundlich types, were adopted and tested to model the equilibrium ion exchange of the two-component system. The verified isotherms permit easy estimation of the equilibrium ion exchange capacities of both resins.
Column tests were performed primarily to determine the ion exchange characteristics under continuous flow conditions. The two operating variables were the feed flow rate and the inlet HF arid FSA concentrations in the feed. Breakthrough data of the column tests were collected. Different breakthrough models, like the simplified logistic, Richards and Hill models, were adopted to simulate the breakthrough characteristics. Using the observed data, statistic best model fit am obtained by proper identification of the model parameters.
In addition to batch equilibrium and column ion exchange tests, regeneration of the exhausted resins was also conducted. Experimental tests were to determine the type of regenerant to be used and the regeneration conditions. The test variables consisted of feed flow rate and inlet concentration of regenerant and operating temperature. The observed
batch and column data allowed determination of optimum operating conditions of the regeneration process.
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