摘要:
以偏铝酸钠为铝源,在不同pH值下水解沉淀得到氧化铝水合物;用XRD、SEM表征其晶型和形貌,结合水溶液中各种单体铝存在的优势区分析不同氧化铝水合物产生的水解历程。以偏铝酸钠为改性剂在不同pH值下对钛白粉进行表面包覆,研究改性后钛白粉水分散性和稳定性的变化。结果表明:空白试验在pH=4~5下沉淀得到无定形水合氧化铝,形貌为颗粒粒径为数拾纳米的团聚体;在pH=6~10下沉淀得到勃姆石型水合氧化铝,结构疏松,呈絮状;在pH>10下沉淀得到三水铝石,呈片状或棱镜形状。不同pH值下包覆的钛白粉具有不同的表面zeta电位,包覆后钛白粉其等电点均比未包覆钛白粉高。在pH=10的水溶液中,pH=4和5下包覆的钛白粉水分散性和稳定性较差,而在pH=9、10、10.5下包覆的钛白粉其水分散性和稳定性比未包覆的钛白粉提高明显。
关键词:
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钛白粉 /
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包膜 /
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氧化铝 /
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分散性 /
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zeta电位
Abstract:
The alumina hydrates were obtained by hydrolysis at different pH with sodium metaaluminate as raw materials.The structure and morphology of the obtained alumina hydrates were characterized by XRD and SEM,and their hydrolysis processes were analyzed by combination with the advantage zones of various monomer aluminum ions existing in aqueous solution.Surface modification of titanium dioxide was carried out by coating sodium metaaluminate at different pH,and the water dispersibility and stability of the modified titanium dioxide were investigated.The results show that amorphous hydrated alumina is obtained at pH=4~5,which exists as aggregate structure with tens of nanometers.Boehmite hydrated alumina is precipitated at pH=6~10 with loose and flocculent morphology.Gibbsite with platy and prismlike structure is formed at pH > 10.Zeta potential on the surface of titanium dioxide varies with the pH value for coating,and the isoelectric point of the coated titanium dioxide is higher than that of the uncoated ones.In the aqueous solution of pH=10,the titanium dioxide modified at pH=4 and 5 has a poor water dispersibility and stability,while the water dispersibility and stability of the titanium dioxide coated at pH=9,10 and 10.5 are significantly improved with comparison to those of the uncoated ones.
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