萃取液相中重金屬之研究

Extraction of Heavy Metals from Aqueous Solution

宋斯偉(Szu W. Sung)

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(1998年)

摘要

本研究是利用萃取法去除廢水中重金屬的污染，其中包括用乳液萃取廢水中的六價鉻，用液液萃取法去除鋅及鎘。探討萃取過程及回收再利用的最佳條件。
液膜分離法是以批式實驗進行各項變因的探討，實驗結果以廢水中六價鉻的去除率為判斷依據。探討的變因包括萃取時間、pH值、製乳轉速、萃取時的擋板及攪拌速度、界面活性劑及載劑的濃度、內水相NaOH的濃度、乳液用量及液膜中油相與內水相的比，另外還有溫度的影響也一併討論。
將乳液分離法以共流多級程序操作，以吸附理論Langmuir及Freundlich等溫式描述乳液萃取的等溫平衡關係曲線，利用此等溫曲線在乳液總量一定的情況下比較一級操作及二極操作的影響。
液液萃取部份是利用D2EHPA萃取含鋅廢水，用McCabe-Thiele圖解法求理論級數，並實際求得中間濃度，印證逆向多級操作的可行性。另一部份是以HEHEHP萃取淋洗土壤後含鎘的酸洗液，實驗探討將酸洗液中重金屬去除的最佳條件，以更經濟的方式處理土壤污染。

關鍵字

萃取 ； 六價鉻 ； 鎘 ； 乳化液膜 ； 鋅 ； 液液萃取 ； 正三辛銨

並列摘要

The objectives of this study are to utilize extraction method for removal of
heavy metals from wastewater. Water/oil/water (W/O/W) emulsion liquid
membrane (ELM) and Liquid-liquid-extraction methods were, respectively,
employed for extracting Cr6+ and zinc and cadmium ions from aqueous
solution.
Batch extractions by liquid membrane were conducted to investigate the
effects of all operating variables on the Cr6+ removal efficiency so as to enable
considered included extraction time, pH, impeller speed of emulsion
preparation, baffles and impeller speed during extraction, surfactant and carrier
concentrations, sodium hydroxide concentration, temperature and the amount
of emulsion relative to the amount of wastewater.
Multistage operation of liquid membrane extraction was performed with an
aim of improving the overall Cr6+ extraction efficiency. Using the Langmuir
and Freundlish isotherm, the Cr6+ removal for the two-stage extraction was
experimentally and theoretically invertigated. The test results indicated that the
two-stage extraction is a more efficient process that the single-stage operation
in terms saving of the amount of extraction emulsion for the same extraction
duty.
D2EHPA (Di-(2-ethyl-hexyl) phosphoric acid) was observed to be a good
extraction agent for zinc removal from wastewater in the liquid-liquid
extraction process. Another extraction agent, HEHEHP (2-ethyl-hexyl
phosphonic acid mono-2-ethyl-hexyl ester), was seen to be good one for
extracting cadmium from wastewater. The McCabe-Thiele method was
employed to determine the number of ideal stage of these liquid-liquid
extraction processes. Both experimental and theoretical investigations were
conducted to compare the efficiency of countercurrent multistage extraction in
comparison with the single-stage operation. Finally, the optimum operating
conditions were determined for effective heavy metal removal removal by the extraction
processes.

並列關鍵字

extraction ； Cr6+ ； Cadmium ； emulsion liquid membrane ； zinc ； liquid-liquid extraction ； TOA

參考文獻

Amanatidou, E., Stefanut, M. N. and Grozav, A. "A Method of Cobalt Ion Concentration from Dilute Aqueous-Solution," Separation Science and Technology, 31, 655-664 (1996)

Bock, J. and Vallnt, P. L. Jr. "Uranium Extraction from Wet Process Phosphoric Acid. A Liquid Membrane Approach," Industrial and Engineering Chemistry Fundamentals, 21, 417 (1982)

Biehl, M. P., Izatt, R. Ming., Lamb, J. D. and Christensen, J. J. "Use of a Macrocyclic Crown Ether in an Emulsion (Liquid Surfactant) Membrane to Effect Rapid Separation of Pb2+ from Vation Mixtures," Separation Science and Technology, 17, 289 (1982)

Beltrame, P. L., and Carniti, P. "Inhibiting Action of Chlorophenol on Biodegradation of Phenol and its Correlation with Structural Properties of Inhibitors," Biotechnology and Bioengineering, 31, 821(1988)

Casamatta, G., Chavarie, C. and Angelino, H. "Hydrocarbon Separation Through a Liquid Water Membrane: Modeling of Permeation in an Emulsion Drop," AIChE Journal, 24, 945 (1978)