Desilication Of High-silica Bauxite Alkali Leaching Desilication Solution And Utilization Of Silicon Slag

The roasting-alkali leaching desilication-high pressure leaching treatment of low-grade bauxite is one of the current research hotspots.In this paper,for the silicon-containing alkaline solution produced by the desilication of ore,the solution is desiliconized by adding lime,red mud,silicon slag and its mixture.The important parameters of the amount of desilication agent,temperature,time and other important parameters are systematically studied.The effect of the desiliconization liquid was used to cyclically desiliconize the ore,and combined with XRD,XRF,SEM,TEM,FTIR and other characterization methods,the desilication kinetics and mechanism were analyzed.The main conclusions are as follows:The addition amount and time of lime have a significant effect on the desilication effect,but the initial alkali concentration and temperature have no obvious effect.After the desilication time exceeds 2h,the desilication rate of the solution tends to be gentle;when the initial concentration of Si O₂ in the solution is 9g/L When the amount of lime added is1.2 based on C/S?the molar ratio of effective Ca in lime/Si in solution,ie C/S?,the preferred desilication conditions are:caustic concentration 110 g/L,temperature 95^oC,reaction time 2h,stirring rate 300r/min,the desiliconization rate is 87.51%,the silicon slag produced is mainly CSH?I?,Ca₄Si₅Al O₁₅?OH?₂·5H₂O and a small amount of Ca?OH?₂,the crystallinity is more low;under this preferred condition,the roasted ore is subjected to five cycles of desilication,and the A/S of the desiliconized concentrate can be increased from 4.01 in the original ore to more than 7.2,and the effect is better.When the added C/S of lime is 1.0,the desilication rate is 63.68%,and the desilication rate of 30 g/L red mud alone is 34.35%.Mix the above red mud and lime to increase the desilication rate to 87.55%;the desilication rate of adding 30g/L silicon slag is 53.22%.After the silicon slag is roasted at 600 ^oC,the desilication rate is increased to 67.46%.The silicon slag before and after roasting is mixed with lime with C/S 1.0 The desiliconization rate of silicon is about 94%,and the desilication effect of silicon slag is obviously better than that of red mud.The kinetic equation of lime desilication is 1-2/3X_B-?1-X_B?2/3=15.80exp[-29350/?RT?]·t,the apparent activation energy is 29.35 k J/mol,and the internal diffusion is the control In the step,the reaction between Ca?OH?₂ and Si O₂?OH?₂^2-occurs mainly;red mud is used as the seed crystal,and the sodalite in which the dissolution-recrystallization reaction takes place during the desilication process,and desilication in cooperation with lime.To further enhance the desilication effect;the silicon slag is ball-milled for desilication before roasting,and the internal unreacted Ca O plays the role of desilication,and the crystallization of calcium silicate product and lime produce a synergistic desilication effect,which significantly improves the desilication rate.After roasting,the crystallinity of silicon slag is high,which is conducive to heterogeneous nucleation.In solution,dicalcium silicate and tricalcium silicate are oriented first,and synergistic desilication occurs with lime.