Chemistry of phosphomolybdate adsorption on alumina surfaces. 1. The molybdate/alumina system
Chemistry of phosphomolybdate adsorption on alumina surfaces. 1. The molybdate/alumina system
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DOI：
10.1021/j100376a021
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发表时间：
1990-06
期刊：
影响因子：
--
通讯作者：
J. Veen;P. Hendriks;E. Romers;R. R. Andréa-R.
中科院分区：
文献类型：
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作者：
J. Veen;P. Hendriks;E. Romers;R. R. Andréa-R.
The adsorption of ammonium heptamolybdate (AHM) on {gamma}-Al{sub 2}O{sub 3} and {alpha}-AlOOH has been studied by using FTIR and Raman spectroscopies, TPR, and EXAFS. It is shown that molybdate adsorption on alumina cannot be explained in terms of electrostatic binding to protonated surface hydroxyls but can be rationalized by assuming (i) a reaction between the molybdate and basic surface OH groups, leading to the decomposition of the adsorbing molecule/ion, and (ii) physisorption on coordinatively unsaturated (cus) Al{sup 3+} sites. In the AHM/{alpha}-AlOOH case, surface precipitation, presumably of (NH{sub 4}){sub 2}Mo{sub 3}O{sub 10}, takes place at surprisingly low initial AHM concentrations. The presence of (divalent) cations can influence the shape of the AHM/{gamma}-Al{sub 2}O{sub 3} isotherm but does not affect the ultimate loadings that can be achieved through processes (i) and (ii).
The adsorption of ammonium heptamolybdate (AHM) on {gamma}-Al{sub 2}O{sub 3} and {alpha}-AlOOH has been studied by using FTIR and Raman spectroscopies, TPR, and EXAFS. It is shown that molybdate adsorption on alumina cannot be explained in terms of electrostatic binding to protonated surface hydroxyls but can be rationalized by assuming (i) a reaction between the molybdate and basic surface OH groups, leading to the decomposition of the adsorbing molecule/ion, and (ii) physisorption on coordinatively unsaturated (cus) Al{sup 3+} sites. In the AHM/{alpha}-AlOOH case, surface precipitation, presumably of (NH{sub 4}){sub 2}Mo{sub 3}O{sub 10}, takes place at surprisingly low initial AHM concentrations. The presence of (divalent) cations can influence the shape of the AHM/{gamma}-Al{sub 2}O{sub 3} isotherm but does not affect the ultimate loadings that can be achieved through processes (i) and (ii).