擔體對於不同結晶物之半穩帶影響探討

機構典藏 > College of Engineering > Graduate Institute & Department of Water Resources and Environmental Engineering > Thesis > Item 987654321/74756

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Title:	擔體對於不同結晶物之半穩帶影響探討
Other Titles:	Investigation of the effects of substrate on metastable zone during crystallization process for various crystals
Authors:	林晨鈺;Lin, Chen-Yu
Contributors:	淡江大學水資源及環境工程學系碩士班李奇旺;Li, Chi-Wang
Keywords:	半穩帶;擔體;結晶;碳酸鈣;磷酸銨鎂;Metastable zone;seed;Crystallization;calcium carbonate;Magnesium ammonium phosphate
Date:	2011
Issue Date:	2011-12-28 19:25:25 (UTC+8)
Abstract:	結晶操作成功關鍵，在於將溶液的過飽和度控制在半穩定帶區域內，且於半穩定帶範圍內加入擔體使得結晶析出成長在擔體上。以往多數文獻皆著重於劃定純粹只有溶液時的半穩定帶，並沒有針對加入擔體後半穩定帶是否產生變化來研究，因此本研究將探討加入擔體後原有純溶液時所劃定的半穩定帶會有何變化，並分別探討不同擔體表面性質及同相與異相結晶的影響。本研究利用兩種不同的結晶物 – 磷酸銨鎂及碳酸鈣來討論擔體對於不同結晶物之半穩帶影響。先利用異相材質石英砂為擔體，討論石英砂對於原劃定的磷酸銨鎂和碳酸鈣半穩帶有何影響。再用與結晶物擁有相同表面性質的同相材質擔體 – 自製的MAP擔體及覆有碳酸鈣結晶的石英砂擔體，分別討論這兩種同相擔體對於原劃定的磷酸銨鎂和碳酸鈣半穩帶有何影響。並同時改變各種擔體的量，討論各種擔體可提供有效結晶表面積多寡對於原劃定的半穩帶之影響。經由實驗結果可以發現，在10分鐘內，pH=9時，異相材質的石英砂擔體對於磷酸銨鎂和碳酸鈣原劃定的半穩帶都沒有顯著的影響。而同相材質的自製MAP擔體和預先覆有碳酸鈣結晶的石英砂擔體，分別對於磷酸銨鎂和碳酸鈣原劃定的半穩帶有擴大的作用。這是因為同相材質的擔體比異相材質的擔體更容易使得結晶物附著到擔體上，進而促進結晶成長，降低了溶液的飽和度，延遲初成核出現的時機，因此使得半穩帶擴大。而擔體量增加後提高了有效結晶表面積，會讓結晶的效果更好。 To be successful on the crystallization technology, the supersaturation of solution should be controlled in the metastable zone. In the metastable zone of solution, seed can be added to disturb the stable condition causing crystallization. Most of the earlier references mainly focused on defining the metastable zone of the solution without seed. In this study, seed is added into the solution and effect of seed on metastable zone is investigated. The effects of seeds with or without the same properties as the crystal, i.e., homogenous or heterogenous seeds, are discussed during crystallization process. Two kind of crystal, namely MAP and CaCO3, are studied in this study. First, the heterogenous SiO2 is used as seed, and the impact of heterogenous seed to the metastable zone of magnesium ammonium phosphate and calcium carbonate are investigated. Then, the homogenous MAP and CaCO3 precoated SiO2 are used as seeds, and the impact of homogenous seed to the metastable zone of magnesium ammonium phosphate and calcium carbonate are discussed, respectively. In the meanwhile, the effective surface area of seed which may affect the metastable zone is also investigated. According to the result, the metastable zone of magnesium ammonium phosphate and calcium carbonate are not affected by heterogenous SiO2 seed at pH 9 in 10 min. But, the homogenous MAP seed and CaCO3 precoated SiO2 seed enlarged the metastable zone of magnesium ammonium phosphate and calcium carbonate, respectively. The homogenous seed is more effective than heterogenous seed to make crystal grow on seed which will reduce the saturation of solution and delay the opportunity of occurrence of primary nucleation. Furthermore, the effective crystal surface area will increase by raising the amount of seed which make the effect of crystallization better.
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