石棉尾矿加碱焙烧去非金属氧化物作用研究

以石棉尾矿为原料,将其与氢氧化钠经混合焙烧、水浸得到焙烧水浸产物。考察主要工艺条件NaOH与SiO2摩尔比、焙烧反应温度和焙烧反应时间等对焙烧产物及焙烧水浸产物的影响,结合物相、结构变化等探讨去非金属氧化物作用过程和作用机制。结果表明,加碱焙烧的优化工艺条件为:n(NaOH)∶n(SiO₂)摩尔比为4.0,反应温度为600℃,反应时间为2 h,此条件下加碱焙烧去非金属氧化物作用明显,水浸渣中主晶相均为氧化镁。当焙烧温度大于255℃时,随焙烧温度的升高,镁氧八面体片发生脱水,硅氧四面体结构破坏,形成可溶的硅酸镁钠;当焙烧温度为830℃时,硅酸镁钠由可溶物质转变为难溶物质。

Study on Removing Non-Metal Oxides from Asbestos Tailings Roasting with Alkali

Asbestos tailings were used as raw materials,mixed and roasted with sodium hydroxide,and then leached in water to obtain a roasted water leaching product.The effects of main process conditions,such as the molar ratio of NaOH to SiO2,calcination reaction temperature and calcination reaction time on calcination products and calcination water leaching products were researched,and the process and mechanism of removing non-metal oxides in combination with phase and structure changes.The result shows that the optimized process conditions for alkali roasting are n(NaOH)∶n(SiO2)of 4.0,reaction temperature of 600℃,reaction time of 2 h,and the effect of adding alkali roasting to remove non-metal oxides was obvious,and the main crystal phase in the water-leaching slag was all magnesium oxide under this condition.When the calcination temperature was higher than 255℃,with the increase of the calcination temperature,the magnesium oxygen octahedron sheet was gradually dehydrated,the silicon oxygen tetrahedron structure was destroyed,and the soluble sodium magnesium silicate was formed.When the calcination temperature was 830℃,sodium magnesium silicate changes from a soluble substance to a poorly soluble substance.