您目前所在的位置:首页 - 期刊简介 - 详细页面

铁道科学与工程学报

JOURNAL OF RAILWAY SCIENCE AND ENGINEERING

Vol. 13    No. 4    August 2003

[PDF Download]    [Flash Online]

    

Transformation of monomer aluminate ions from tetrahedron to octaheron
CHEN Qi-yuan(陈启元), ZHOU Jun(周 俊),
LI Jie(李 洁), YIN Zhou-lan(尹周澜)

College of Chemistry and Chemical Engineering,
Central South University, Changsha 410083, China

Abstract:During the precipitation of gibbsite from supersaturated sodium aluminate solution, the main aluminum containing species in solution will transform from tetrahedral [Al(OH)4- to sixfold octahedral [(H2O)2Al-(OH)4-. In order to elucidate the mechanisms responsible for above transformation, the formation Gibbs free energy as well as frontier orbits of a wide range of aluminum species are studied by ab initio method at B3LYP/6-31G** level. Based on theoretical calculation results, thermodynamic possibility and coordination possibility for aluminate ion transforming from [Al(OH)4- to [(H2O)2Al(OH)4- are analyzed and thermodynamic permitted reaction pathways are extracted. It is found that [Al(OH)4- can not react directly with H2O to carry out the variation of coordination number. Transformation of tetrahedral [Al(OH)4- to octahedral [(H2O)2Al(OH)4- is involved in two reaction pathways, one is realized by neutral [Na(H2O)+4·Al(OH)-4] acting mediator, the other is carried by neutral [(H2O)Al(OH)3]. Though there is a strong thermodynamic trend for the transformation of [Al(OH)4- to[(H2O)2Al(OH)4-,the practical transformation is very slow. Thus, it can be concluded that there is a great kinetic resistance during the transformation from [Al(OH)4- to [(H2O)2Al(OH)4-.

 

Key words:  ab initio calculation; aluminate ion; Gibbs free energy;frontier orbital theory

ISSN 1672-7029
CN 43-1423/U

主管:中华人民共和国教育部 主办:中南大学 中国铁道学会 承办:中南大学
湘ICP备09001153号 版权所有:《铁道科学与工程学报》编辑部
------------------------------------------------------------------------------------------
地 址:湖南省长沙市韶山南路22号 邮编:410075
电 话:0731-82655133,82656174   传真:0731-82655133   电子邮箱:jrse@mail.csu.edu.cn