本文選題：氟硅酸　切入點(diǎn)：氨化沉淀法　出處：《北京化工大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：本課題致力于解決工業(yè)冶煉稀土過程中產(chǎn)生的氟硅酸廢水處理問題,并充分回收利用氟和硅資源,在低成本的條件下制備經(jīng)濟(jì)效益較高的產(chǎn)品。課題中主要研究以氟硅酸為原料,氨化沉淀法制備納米級(jí)高比表面積二氧化硅的工藝技術(shù)。即以氨水為氨解劑,通過單因素試驗(yàn)、正交試驗(yàn)、定-轉(zhuǎn)子反應(yīng)器實(shí)驗(yàn),制備出產(chǎn)率高、分散性好、高比表面積納米級(jí)二氧化硅。課題中考察了各工藝參數(shù)對(duì)產(chǎn)品二氧化硅產(chǎn)率及比表面積的影響,研究了制備過程中不同的工藝條件；通過BET、XRD、SEM等測(cè)試手段對(duì)產(chǎn)品進(jìn)行表征,并結(jié)合理論對(duì)氟硅酸氨化沉淀法生成二氧化硅的反應(yīng)進(jìn)行探究。研究結(jié)果表明：氟硅酸氨化沉淀法的正加方式(底液：氟硅酸,添加液：氨水)和反加方式(底液：氨水,添加液：氟硅酸)對(duì)產(chǎn)品二氧化硅的團(tuán)聚方式、比表面積及分散度影響并不相同。正加方式制備二氧化硅以小顆粒團(tuán)聚成無規(guī)則的空間網(wǎng)狀結(jié)構(gòu),孔率高、比表面積較大。反加方式制備的二氧化硅以小顆粒聚集為球狀,分散度較好,比表面比正加方式所制備二氧化硅小。通過實(shí)驗(yàn)研究獲得氟硅酸氨化沉淀法制備二氧化硅的最佳工藝條件如下：①正加最優(yōu)條件為：氨水滴加速率10mL/min、氨水質(zhì)量分?jǐn)?shù)5%,氨水用量與理論比值1：0.8、氟硅酸質(zhì)量分?jǐn)?shù)35%、打漿水洗兩次,制備出比表面積高達(dá)768.3m2/g的納米二氧化硅。②反加最優(yōu)條件為：氟硅酸滴加速率23 mL/min、氟硅酸質(zhì)量分?jǐn)?shù)35%,氟硅酸用量與理論比值1：1.2、氨水質(zhì)量分?jǐn)?shù)10%,制備出比表面積高達(dá)548 m2/g的納米二氧化硅。在使用定-轉(zhuǎn)子反應(yīng)器進(jìn)行氟硅酸氨化沉淀制備二氧化硅的實(shí)驗(yàn)中,研究表明定-轉(zhuǎn)子反應(yīng)器可強(qiáng)化液-液相間微觀混合,使二氧化硅粒徑更均勻,分散性更好,比表面積更高。通過實(shí)驗(yàn)獲得了適宜的定-轉(zhuǎn)子反應(yīng)器操作條件,即定-轉(zhuǎn)子反應(yīng)器轉(zhuǎn)速為2800r/min,循環(huán)量為600 mL/min,加料速度35 mL/min,在此條件下可以制備出分散性好,比表面積達(dá)到573m2/g的納米二氧化硅。本課題創(chuàng)新點(diǎn)在于：首次使用定-轉(zhuǎn)子反應(yīng)器進(jìn)行氟硅酸氨化沉淀反應(yīng),利用其強(qiáng)化傳質(zhì)及微觀混合特點(diǎn),在生產(chǎn)氟化銨產(chǎn)品的同時(shí),制備出高比表面積二氧化硅。
[Abstract]:This project is devoted to solve the problem of wastewater treatment of fluorosilicic acid produced in the process of industrial smelting rare earth, and fully recover and utilize fluorine and silicon resources. The technology of preparing nanometer silica with high specific surface area by ammoniation precipitation method with fluorosilicic acid as raw material was studied in this paper, that is, ammonia water was used as ammonolytic agent, and single factor test was carried out. Orthogonal experiments and stator rotor reactor experiments were conducted to prepare nano-sized silica with high yield, good dispersion and high specific surface area. The effects of various process parameters on the yield and specific surface area of silica were investigated. The different process conditions in the preparation process were studied, and the products were characterized by means of BET-XRDX SEM. The results show that the positive adding method (substrate: fluorosilicic acid, additive solution: ammonia water) and reverse adding method (bottom liquid: ammonia water) of fluorosilicic acid ammoniation precipitation method are used to study the reaction of producing silica by ammoniation precipitation method of fluorosilicic acid. The additive solution: fluorosilicic acid) has different effects on the agglomeration mode, specific surface area and dispersion of silica. The specific surface area is large. The silica prepared by reverse addition method is spherical with small particles, and the dispersion is better. The optimum technological conditions for the preparation of silica by ammoniation and precipitation of fluorosilicic acid were obtained as follows: the optimum conditions of positive addition of ammonia water were as follows: the adding rate of ammonia water was 10ml / min, the mass fraction of ammonia water was 10mL / min, and the optimum conditions were as follows: the addition rate of ammonia water was 10ml / min. The ratio of ammonia to theory is 1: 0.8, the mass fraction of fluorosilicic acid is 35 and the water is washed twice. The optimum conditions for preparation of nano-silica with a specific surface area of 768.3 m2 / g are as follows: dropping rate of fluorosilicic acid 23 mL / min, mass fraction of fluorosilicic acid 35, ratio of fluorosilicic acid to theoretical value 1: 1.2, mass fraction of ammonia water 10, and the specific surface area as high as 10. 548 m2 / g nanocrystalline silica. In the experiment of preparing silica by ammoniation of fluorosilicic acid in a stator rotor reactor, The results show that the liquid-liquid phase micromixing can be enhanced in the stator rotor reactor, and the particle size of silica is more uniform, the dispersion is better and the specific surface area is higher. That is, the speed of the stator / rotor reactor is 2800r / min, the circulation is 600 mL / min, and the feed rate is 35 mL / min, and under these conditions the dispersion can be very good. Nano-silica with a specific surface area of 573m2 / g. The innovation of this project lies in the first use of a stator rotor reactor for the ammoniation of fluorosilicic acid, and the use of its enhanced mass transfer and microcosmic mixing characteristics to produce ammonium fluoride at the same time. Silica with high specific surface area was prepared.
【學(xué)位授予單位】：北京化工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TQ127.2;TB383.1

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