不同合成與老化溫度對鋁物種生成轉變之影響

Abstract

本研究利用Ferron比色法、硫酸根沉澱法、鋁-27核磁共振光譜法 (27Al NMR)以及X光繞射分析等方法，研究不同合成與老化溫度下之過氯酸鋁溶液，在水解反應過程中物種型態的生成與轉變。根據Ferron法的分析結果，隨著OH/Al莫耳比的增加，單體鋁的部份會因鹼溶液的加入促使聚合反應的進行而減少，造成聚合鋁的增加；在27Al NMR中所測定到的Al13也與Ferron法之聚合鋁部分有相同的變化趨勢；而硫酸根沉澱法的結果也顯示出無法沉澱的單體或低聚合態部分的含量會隨著OH/Al莫耳比的增加而減低，可以被沉澱的高聚合態鋁則增加。另外，藉由改變合成與老化的溫度，觀察不同條件下鋁水解過程可能發生的變化，結果顯示低溫合成的樣品隨著老化的進行會有較高的濁度，而粒徑分析與硫酸根沉澱後固體的SEM結果顯示，在低溫下合成的樣品較高溫合成樣品會生成較大的結晶核，隨著老化的進行會較快生成三水鋁石 (gibbsite)沉澱，有較短的靜止期(Induction period)，高溫合成下的樣品則因生成的結晶核粒子小，水解過程較緩慢，有較長的Induction period，須在較高的老化溫度或高的OH/Al莫耳比才會有gibbsite沉澱生成；因此合成溫度會影響溶液中鋁物種的結晶生成，而升高老化溫度或增加OH/Al莫耳比則可加速三水鋁石的結晶成長。

The effect of synthesized and aged temperatures on the formation and transformation of hydrolytic Al species were investigated. The Al speciation in Al(ClO4)3 solution was determined using ferron colorimetric, sulfate precipitation, 27Al nuclear magnetic resonance spectroscopy (27Al NMR), and X-ray diffraction methods. In ferron assay, upon increasing the OH/Al molar ratio, the content of monomeric Al were decreased while that of polymeric Al increased, the formation of Al13 were also increased by 27Al NMR, with sulfate precipitation method, the content of monomeric Al or small polymeric species can not be precipitate by sulfate were decreased, and the high polymeric or colloidal Al can be precipitated by sulfate ion were increased. The comparison of Al hydrolysis at different synthesized and aged temperature, particle size distribution and scanning electron micrographs (SEM) were indicated sample synthesized at low temperature with larger nuclei, upon aged, there had faster production rate of gibbsite, with shorter induction period, but synthesis at high temperature resulted in smaller nuclei formation, with lower degree hydrolysis and longer induction period, in order to production of gibbsite, have to increase aged temperature or OH/Al molar ratio. Thus, the temperature of synthesized was greatly influenced on the nuclei growth of Al species, increasing aged temperature and OH/Al molar ratio could enhance the growth of gibbsite.