Purification of Silica Micro Powder and Application in Building Structural Adhesive

Abstract

Silica powder is by-products from the ferrosilicon smelting industry. The material contains some of trace amounts of iron oxide and carbon and other impurities, so its application scope has been blocked. Hydrochloric acid pickling can remove the original iron oxide powder effectively. It was found that iron removal ratio increased with increasing of the amount of hydrochloric acid, when hydrochloric acid was more than original powder 10 g/150 mL (20 % hydrochloric acid), removal iron reaction was basic balance. The carbon can be effectively removed by calcinations and carbon removal ratio increased with increasing of calcinations temperature, the sample colour turned from dark gray to light gray and until white. When the temperature was higher than 400 ºC, the calcinations time was greater than 3 h, carbon combustion reaction was basic balance, which can achieve satisfactory bleaching effect. It was found that particle diameter increased with increasing of calcinations temperature, because in the calcinations process particles occurred fusion and copolymerization phenomenon. It was found that the adding amount of silicon powder appropriately can improve the tensile and bending strength of structural adhesive. The optimum calcinations temperature range was between 400 and 500 ºC, the optimum addition of silicon powder was 6 %.