Study On The Preparation Of Precipitated Silica And The Coproduction Of Potassium Sulfate From Quartz Tail-sand

In this dissertation, precipitated silica was prepared through calcination, extraction and precipitation using purified quartz tail-sand and sodium carbonate as raw materials,sulfuric acid as precipitant; and then potassium sulfate was prepared via the "two steps"method using the above by-product sodium sulfate as raw materials. The main research work includes:(1) Taking the extraction rate of silica in quartz tail-sand as the main indexes, the optimum condition was obtained through single-factor experiments and orthogonal experiments as following: molar ratio 1:1.1, calcination temperature 1250?, calcination 2.0h, extraction temperature 100?, and extraction time 50min. The repeated experiments under the optimum condition showed that the average extraction rate of silica in quartz tail-sand reached 96.07%.(2) Taking the yield of silica as the main indexes, the optimum condition was obtained through single-factor experiments as following: the concentration of sodium silicate 5%, the concentration of sulfuric acid 15%, reaction temperature 80?, and aging time 2h. The repeated experiments under the optimum condition showed that the average yield of precipitated silica reached 99.45%. The as-prepared precipitated silica sample can meet the technical requirements of the standard (HG/T3061-2009).(3) Taking the content of K2O and Cl- in the sample prepared as the main indexes, the optimum preparation conditions of aphthitalite and potassium sulfate were investigated and determined through single-factor experiments and orthogonal experiments.The preparation process of aphthitalite as following: the amount of potassium chloride is 1.10 times of the theoretical value, the amount of water added is 3 times of the theoretical value,reaction time 3.5h. The repeated experiments under the optimum condition showed that the average content of K2O and Cl- in aphthitalite sample reached 39.93% and 1.906%, respectively.The preparation process of potassium sulfate as following: the amount of potassium chloride is0.95 times of the theoretical value, the amount of water added is 1.6 times of the theoretical value, reaction time 3.5h. The repeated experiments under the optimum condition showed that the average content of K2O, Cl- and H2O in potassium sulfate sample reached 53.10%, 1.08% and 1.58%, respectively. The prepared potassium sulfate samples can meet the technical requirements of the high-class product in the standard (GB20406-2006).(4) Aphthitalite was prepared with sodium sulfate and mother liquid from the "two-step" process, and potassium sulfate was prepared from the as-prepared aphthitalite.Sample test results showed that the average content of K2O, CI- and H2O in potassium sulfate sample reached 53.08%?1.093% and 1.61%,respectively, which can also meet the technical requirements of the high-class product in the standard (GB20406-2006). All the above results showed good feasibility of the as-designed circulation process route.