Study On The Key Technology Of Separating And Extracting Oxide From Chrysotile Asbestos Tailings In Akesai

Based on the chemical compositions of chrysotile asbestos tailings were SiO₂ and MgO, resource utilization tailings from three mines in Akesai ore distract by extracting mental oxide function in this paper Mineralogical characteristics of different mines and pretreatment technology were studied. Short chrysotile fibers were separated from chrysotile asbestos tailings and efficient utilization, respectively. Fibri-form porous silica was prepared with short chrysotile fibers via separating oxide by acid leaching method or mix-roasting method; Porous silica was prepared with chrysotile asbestos tailings powders （electing short fibers） via separating oxide by a mix-roasting method. Magnesium hydroxide crystal was synthesized with remained purified magnesium sulfate by hydrothermal, xonotlite thermal insulation material was hydrothermal synthesized by porous silica as silicon sourece.The results show that:①Chenical compostions of chrysotile asbestos tailings are SiO₂ and MgO, the main mineral compositions of chrysotile asbestos tailings are serpentine, together with small amounts of talc, magnetite; After pretreatment, purified short chrysotile fibers are separed from chrysotile asbestos tailings, but also have talc;②The optimum efficiency of an acid leaching method is obtained at the concentration of sulfuric acid mass fraction of 35%, the leaching temperature of 90℃, the leaching time of 2.00h, and the ratio of liquid-solid of 10:1. Compositions of SiO₂ are 98.30%; The fiber morphology is remained, The S_BET and BJH pore volume are 369.2m²/g, 0.43cc/g, respectively, and pore width is 3.78nm. The optimum efficiency of short chrysotile fibers mix-roasting with ammonium bisulfate is obtained by NH₄HSO₄:MgO molar ratio of 2.5, the roasting temperature of 500℃, the roasting time of 1.5h. The fibri-form silica are steady for structure and performance. Magnesia octahedral sheets ire removed by H⁺ in the process of extracting mental oxide function, which can remained and modify the Si-O tetrahedral sheets in chrysotile fiber. ③ The optimum efficiency of tailings mix-roasting with ammonium bisulfate is obtained by NH₄HSO₄:MgO molar ratio of 4, the roasting temperature of 500℃, the roasting time of 2h, and the particle size of 120 mesh. Compositions of SiO₂ for porous silica is 72.17%, Loss on ignition is 21.15%; The morphology of porous silica are fibers mixture with non-fibers, The S_bet, BJH pore volume and pore width of porous silica are estimated to be 80.56m²/g,0.193cc/g and 3.818nm, respectively. Which are good for structure but have no phases change from 20 to 1000℃. Ammonium bisulfate are reacted with serpentine, brucite in molten condition, magnesia octahedral sheets are dissolved, crystal structure of serpentine and brucite are collapsed, the porous silica by the recombined of remained SiO₄ tetrahedra;④The optimum efficiency of mgnesium hydroxide hydrothermal synthesis by purfied magnesium sulfate is reaction temperature of 180℃, reaction time of 8.Oh, n_Mgso4:nNaOH=0.995, crystal shape control agent are Sodium dodecylbenzene sulfonate, cetyl trimethyl ammonium bromide, ethylene glycol, glycerol and diethanol amine;⑤Xonotlite is hydrothermal synthesized by porous silica as silicon source in n_siO2:n_CaO=1:1, reaction temperature 220℃, reaction time 18h, the ratio of liquid-solid 30:1. Complex anion [H₂Si0]^4- is ionized by porous silica and reacted with Ca（H₂O）₅（OH）²⁺ionized by Ca（OH）2. Firstly, C-S-H（Ⅱ） is formed, but C-S-H（Ⅱ） transforms into C-S-H（Ⅰ） gel. With further rise in reaction temperature, C-S-H（Ⅰ）gel with more [H₂SiO]^4- to form tobermorite. Finally, Xonotlite is formed with rises temperature or continues reaction time.The research will provide a new research orientation for chrysotile asbestos tailings. The results are not only resolved the social issues and environment problems by stacked tailings, but also can efficient atilization the tailings and create a higher economic value.