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Effect of aging time and Al substitution on the morphology of aluminous goethite

Liu, Haibo, Chen, Tianhu, Frost, Ray L., Chang, Dongyin, Qing, Chengsong, Xie, Qiaoqin
Journal of colloid and interface science 2012 v.385 no.1 pp. 81-86
X-ray diffraction, aluminum, chemical composition, coprecipitation, energy-dispersive X-ray analysis, goethite, potassium hydroxide, transmission electron microscopy
Goethite and Al-substituted goethite were synthesized from the reaction between ferric nitrate and/or aluminum nitrate and potassium hydroxide. XRF, XRD, TEM with EDS were used to characterize the chemical composition, phase and lattice parameters, and morphology of the synthesized products. The results show that d(020) decreases from 4.953 to 4.949Å and the b dimension decreases from 9.951Å to 9.906Å when the aging time increases from 6days to 42days for 9.09mol% Al-substituted goethite. A sample with 9.09mol% Al substitution in Al-substituted goethite was prepared by a rapid co-precipitation method. In the sample, 13.45mol%, 12.31mol% and 5.85mol% Al substitution with a crystal size of 163, 131, and 45nm are observed as shown in the TEM images and EDS. The crystal size of goethite is positively related to the degree of Al substitution according to the TEM images and EDS results. Thus, this methodology is proved to be effective to distinguish the morphology of goethite and Al substituted goethite.