Effects of pH and ions on the morphological evolution of boehmite prepared by hydrothermal treatment of ultrafine Bayer gibbsite

The desired morphology can improve the application and performance of boehmite and its subsequent products. Boehmite with various morphologies obtained by hydrothermal treatment of ultrafine Bayer gibbsite is systematically studied in aqueous solutions with pH of 3-13.5. Needle-like/long hexagonal,...

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Veröffentlicht in:CrystEngComm 2020-11, Vol.22 (42), p.6983-6992
Hauptverfasser: Huang, Wenqiang, Liu, Guihua, Qi, Tiangui, Li, Xiaobin, Zhou, Qiusheng, Peng, Zhihong
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Sprache:eng
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Zusammenfassung:The desired morphology can improve the application and performance of boehmite and its subsequent products. Boehmite with various morphologies obtained by hydrothermal treatment of ultrafine Bayer gibbsite is systematically studied in aqueous solutions with pH of 3-13.5. Needle-like/long hexagonal, rhombic, and hexagonal boehmite with different crystallite sizes were formed in acidic, near-neutral, and alkaline solutions, respectively, which is mainly determined by the pH of the solution. Furthermore, ionic adsorption caused the differences in the exposed surface by reducing the surface energy, regulating the zeta potentials and altering the growth habits of boehmite. At pH of approximately 3, absorption of SO 4 2− and Cl − anions on the (100) and (001) surfaces generated a fine needle-like shape, while absorption of NO 3 − on the (101), (100) and (010) surfaces formed a long hexagonal shape. At pH of approximately 8, SO 4 2− and Cl − anions slightly enlarged the (010) area of rhombic boehmite with (101) and (010) exposed surfaces, and Na + adsorption reduced the thickness of the (010) surface. In the pH range of 10 to 13.5, adsorption of SO 3 2− , CO 3 2− , and S 2− anions formed hexagonal boehmite with (010), (101), and (100) exposed surfaces and affected the area of the (010) surface. Therefore, understanding the morphological evolution mechanism of boehmite can provide guidance for large-scale production of boehmite with desired morphology. Boehmite morphology depended on the pH and ions of the solution by hydrothermal treatment of gibbsite owing to the difference in nucleation and growth of boehmite from Al 3+ , Al(OH) 4 − or the Al(OH) 4 − Na + ion pair.
ISSN:1466-8033
1466-8033
DOI:10.1039/d0ce00808g