化工进展 ›› 2017, Vol. 36 ›› Issue (03): 1120-1125.DOI: 10.16085/j.issn.1000-6613.2017.03.047

• 资源与环境化工 • 上一篇    下一篇

碳酸钠沉淀法制备氢氧化铝及其形成机理探讨

黄静, 夏举佩, 罗中秋   

  1. 昆明理工大学化学工程学院, 云南 昆明 650500
  • 收稿日期:2016-08-18 修回日期:2016-11-01 出版日期:2017-03-05 发布日期:2017-03-05
  • 通讯作者: 夏举佩,副教授,从事固体废弃物共伴生资源利用方面的研究。
  • 作者简介:黄静(1991-),女,硕士研究生,从事固体废弃物共伴生资源利用方面的研究。E-mail:HuangJing513401@163.com。

Preparation and growth mechanism of aluminium hydroxide by precipitation method with sodium carbonate

HUANG Jing, XIA Jupei, LUO Zhongqiu   

  1. Faculty of Chemical Engineering, Kunming University of Science and Technology, Kunming 650500, Yunnan, China
  • Received:2016-08-18 Revised:2016-11-01 Online:2017-03-05 Published:2017-03-05

摘要:

以十八水硫酸铝[Al2(SO43·18H2O]为沉淀前驱剂,碳酸钠(Na2CO3)为沉淀剂制备氢氧化铝,采用X射线衍射(XRD)、傅里叶变换红外光谱(FTIR)、热重分析(TGA)和扫描电子显微镜(SEM)探究硫酸铝水解反应机理。研究结果表明,75℃下0.02 mol/L的硫酸铝溶液在pH=2.50时水解率为1.98%,pH=3.80时水解率为100%。XRD、FTIR、TG-DTG和SEM结果表明,在Al2(SO43溶液中滴加Na2CO3沉淀剂制备氢氧化铝的过程中,pH起着重要作用。当溶液pH<3时,Al3+以[Al(OH26]3+形式存在,随着溶液pH的增加,[Al(OH26]3+水解生成[Al(OH)4(OH22]-,[Al(OH)4(OH22]-在水化作用下脱水缩合为[Al2(OH)8(OH22]2-,碱性增强,[Al2(OH)8(OH22]2-转化为[Al2O(OH)6]2-,最终形成氢氧化铝沉淀。pH=3、5、7时,Al2(SO43水解所得产物为无规则团聚的非晶态氢氧化铝;pH=9、11时,氢氧化铝从非晶态转变为晶态的勃姆石(γ-AlOOH)及少量拜尔石[α-Al(OH)3],且pH=11时硫酸铝水解所得氢氧化铝结晶晶型较pH=9时好。

关键词: 氢氧化铝, 沉淀法, 勃姆石, 拜尔石

Abstract:

Aluminum hydroxide was synthesized by one-pot precipitation method using sodium carbonate (Na2CO3) and aluminum sulfate[Al2(SO4)3·18H2O] as precipitator and precipitate precursor agents, respectively. Simultaneously,the growth mechanism was investigated by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),thermo gravimetric analysis(TGA) and scanning electron microscopy(SEM). The results showed that the hydrolysis ratio of aluminum sulfate solution(0.02mol/L) was 1.98% and 100% under pH=2.50 and 3.80 at 75℃,respectively. The results of XRD,FTIR,TG-DTG and SEM showed that pH played an important role in the preparation of aluminum hydroxide by the dropwise addition of Na2CO3 in Al2(SO4)3. When pH was less than 3,Al3+ kept a stable state as[Al(OH2)6]3+. With the gradual increase of pH,[Al(OH)4(OH2)2]- was generated hydrolyzed from[Al(OH2)6]3+ and subsequently dehydrated-condensed into[Al2(OH)8(OH2)2]2- under the effect of hydration. Then,[Al2(OH)8(OH2)2]2- transformed into[Al2O(OH)6]2-with the increase of alkalinity. Finally,aluminum hydroxide was generated. Aggregated and amorphous aluminum hydroxide could be obtained when pH was 3,5 and 7. Under the pH of 9 and 11,amorphous aluminum hydroxide transformed into crystalline state of boehmite(γ-AlOOH) and a little bayerite[α-Al(OH)3]. Meanwhile,the crystal form of aluminum hydroxide at pH=11 was better than pH=9.

Key words: aluminum hydroxide, precipitation method, boehmite, bayerite

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