Studying On The Preparation Of Aluminum Fluoride Trihydrate And Nano-silica Fluorinea From Fluosilicic Acid Waste

In this dissertation, aluminum fluoride trihydrate and nano-silica fluorinea were produced using fluosilicic acid acid waste as raw material and the optimized conditions were studied. The main research work includes:(1) Taking the yields of silica and aluminum fluoride trihydrate as the main indexs, the optimum conditions was obtained through single-factor experiments and orthogonal experiments as following:the reaction temperature 95℃, the initial concentration of fluorosilicic acid solution 20%, the reaction time 30 min, the stirring speed 400 rpm and the molar ratio 1:0.85. The repeated experiments under the optimum conditions showed that the average yield of silica and aluminum fluoride trihydrate reached 95.10% and 70.09% respectively. The circulating experiments results showed that the average yield reached 95.40% and 76.65% respectively.(2) In aqueous system, taking the activation grade of silica as the main index, sodium laurate was chosen as the more appropriate modifier and the modification conditions were investigated via single-factor experiments as following:the modifier dosage 2.5%, the modification time 40 min, the modification temperature 70℃, the ratio of silica to solvent 5:100 and the stirring speed 300 rpm. The repeated experiments under the optimum conditions showed that the average activation grade of silica reached 99.55%.(3) The structure, morphology and surface property of both non-modified and modified silica were characterized by Fourier transform infrared spectrometer (FT-IR), X-ray diffraction analyzer (XRD), field emission scanning/transmission electron microscope (FESEM/TEM) and laser particle size analyzer, etal.. The results showed that the particle surface was successfully coated by sodium laurate. Both non-modified and modified silica have the same crystal type, but the modified silica has pretty higher lipophilicity. The modification enhances the dispersity and stability of modified silica while weakening the aggregation.(4) The wetting contact angle, average particle size, the specific surface area value (BET) and the oil absorbed value (DBP) of both no-modified and modified silica was studied and the conclusions were obtained as follows:comparing to the no-modified silica, the contact angel of modified silica increases from 0° to 132.5°, the average particle size (D50) reducing from 32.4 μm to 790 nm, the specific surface area value (BET) increasing from 75 m2·g-1 to 165 m2·g-1, the oil absorbed value (DBP) increasing from 2.25 mL·g-1 to 3.12 mL·g-1, dry reduction reducing from 4.65% to 0.47%, the methanol value of silica increasing from 0% to 72.31%.