逆滲透與化學沈澱法處理半導體氫氟酸廢水之研究

Reverse Osmosis and Chemical Precipitation Treatments of Waste Hydrofluoric Acid Solution from Semiconductor Fabrication

廖崢(Jeng Liau)

指導教授 ： 林勝雄

元智大學/工程學院/化學工程與材料科學學系/碩士(2003年)

摘要

無資料

關鍵字

氫氟酸 ； 逆滲透法 ； 化學沈澱法

並列摘要

Hydrofluoric acid has been commonly used in the semiconductor industries for wafer ething and tool cleaning. Those processes lead to generation of a large quantity of waste acid solution which comprises primarily the hydrofluoric (HF) and hydrofluorosilicic (FSA) acids. Conventional method of waste HF acid disposal is conversion of HF to invert calcium fluoride (CaF), leading to a generation of a large amount of CaF sludge. Due to its low CaF content (20~40 %) and existence of other impurities, the CaF sludge creates a new round environmental problem. To overcome this difficulty, the present study is to utilize the reverse osmosis (RO) in an attempt to recover HF from the waste HF acid solution for possible reuse. The present experimental work was to investigate the treatment performance characteristics of the RO system using both the simulated and real wastewater acid solution.
In addition to HF, the waste acid solution also contains a certain amount of hydrofluorosilicic acid (FSA). Therefore, the experimental RO tests were conducted to determine the effects of many important operating transmenbrane pressure and recycle ratio on the HF recovery, HF concentration and FSA rejection. Test results indicate that the permeate HF concentration is rather close to that in the inlet feed and is independent of the inlet waste acid composition. The FSA rejection was found to be quite, exceeding 93.8 % in all instances. For a recycle ratio of 20, the HF recovery was seen to be excellent, being over 98.8 %.
Due to low initial HF Concentration in the real plant waste acid solution, the HF acid recovered by the RO process was rather low also. Hence chemical conversion of the RO purified HF acid to CaF might offer a good alternative. In the chemical conversion tests, calcium chloride (CaCl2) was adopted as a primary reactant. Experimental tests were conducted to explore the effects of initial pH and HF concentration on the conversion efficiency. The test results show that adjustment of initial pH improves the settability of the CaF sludge. In the events that the CaF sludge is very difficult to settle out, centrifugation was found to offer significant advantages. The CaF content in the sludge obtained from the RO purified solution by chemical conversion was found to exceed 80 %, even can up to 99.5 %. Such a high CaF-content sludge can be readily used as flux for steeling making or even better used for HF manufacturing.

並列關鍵字

HASH(0xb8f3128)

參考文獻

Castel, C., Schweizer, M., Simonnot, M. O. and Sardin M.,“ Selective Removal of Fluoride Ions by a Two-way Ion-exchange Cyclic Process ”, Chemical Engineering Science, 55, 3341 (2000)

Chai, X., Chen, G., Yue, P. and Mi, Y.,“ Pilot Scale Membrane of Electroplating Waste Water by Reverse Osmosis ”, Journal of Membrane Science, 123, 235 (1997)

Chuang, T. C., Huang, C. J. and Liu, J. C.,“ Treatment of Semiconductor Wastewater by Dissolved Air Flotation ”, Journal of Environmental Engineering, ASCE, 128, 974-980 (2002)

Feng, D., Aldrich, C. and TAN, H.,“ Treatment of Acid Mine Water by Use of Heavy Metal Precipitation and Ion Exchange ”, Minerals Engineering, 13, 623 (2000)

Gagliardo, P., Adham, S., Trussell R. and Olivieri A.,“ Water Repurification via Reverse Osmosis ”, Desalination, 117, 73 (1998)