硅铝包覆钛白粉水悬浮液pH值调控规律

研究了钛白粉经过氧化硅、氧化铝包膜后的水悬浮液pH值和颗粒表面电位特性的变化。实验获得连续、均匀、致密的无机氧化物膜状包覆,膜层厚度随包覆量增加而增加。根据国家标准GB/T1706—2006中的测定方法,将包膜后钛白粉制成质量分数为10%的悬浮液,检测悬浮液pH值随包覆量的变化。结果表明:钛白粉经氧化硅和氧化铝表面包膜处理后,水悬浮液pH值偏离中性;包氧化硅后钛白粉悬浮液呈碱性,随包覆量增加,pH值增高直至pH9.7;包氧化铝后钛白粉悬浮液呈酸性,随包覆量增加,pH值降低直至pH4.4。颗粒表面包覆量对颗粒表面的ζ电位的影响与pH值相似。通过对包硅产品进行微量包铝、或对包铝产品进行微量包硅能够有效调控最终包覆产品水悬浮液的pH值。

pH control of suspensions of titania coated with silica and alumina

pH control of suspensions of titania coated with silica and alumina has been investigated. The experimental results show that SiO₂and Al₂O₃can form a dense film coating on the titania particle surfaces, and the film became thicker as the amount of coating material was increased. According to GB/T 1706—2006, the samples were formed into aqueous suspensions at a concentration of 10% by weight. pH measurements showed that the suspension of titania coated with SiO₂ is alkaline, and the pH increases with coating amount up to pH 9.7. In contrast, the suspension of titania coated with Al₂O₃ is acid, and the pH decreases with coating amount down to pH 4.4. The zeta potential was also affected by the surface coating in a similar way to the pH. The pH of the suspension can be controlled effectively by a thin coating of alumina on silica-coated particles, and a thin coating of silica on alumina-coated particles.