Experimental Study Of Preparation Of Silica From Corn Straw Ash

Currently, effective utilization of corn straw is not high, and the straw ash after combustion has not been utilized. This is a remendous waste of resources, and has caused serious environmental pollution. Containing high amorphous silica, while less heavy metal impurities, corn straw ash is ideal for preparation of silica materials. With the precipitation method, preparation of silica from corn straw ash was studied.During the study of the processes of preparing water glass from corn straw ash, the module of water glass and the dissolution rate of silica were taken for indexes. The influence of single factors, including the molar concentration of NaOH, material ratio, reaction time and reaction temperature on the indexes were studied. Through orthogonal experiment, the influence of four correlative parameters were studied.The level difference, square difference and effects analysis were applied to the orthogonal experimental, and results of three analytical methods were broadly identical. The optimal conditions were determined: the molar concentration of NaOH was 2mol/L, material ratio was 1:4 g /mL, reaction time was 6h and reaction temperature was 115℃. It was vertified that the optimal experiment results were the modulus 3.31, and the dissolution rate of silica 68.01%. Overall status of the current study, the influence of the concentration of water glass, reaction temperature, terminal PH of reaction, the type of acid, the concentration and the addition speed of acid, aging time to the quality of silica were discussed respectively, and the rang of these parameters were determined . The conditions of preparing silica with the sulfuric acid precipitation method were studied using water glass prepared in the optimum conditions. The purity of silica was taken for index. And the concentration of sodium silicate, sulfuric acid and reaction temperature were taken as parameters. Through part of the orthogonal polynomial regression design, experimental results were analized. It showed that the concentration of sodium silicate, sulfuric acid and reaction temperature had effects to the quality of silica in different degree. The optimal conditions were determined: the concentration of silica was 13 Baume degrees, the concentration of sulfuric acid was 15%, and reaction temperature was 78℃. The purity of silica prepared under the optimum conditions was 97.68%.The quality of the prepared silica was over the national standards. The refractive index, transmittance, absorption value and the content of Na of the products were determined.