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Precipitated silicon dioxide white is generally a silicate (usually in the form of sodium silicate) and inorganic acid (usually use sulfuric acid) and precipitation reaction way of preparing, after generating hydrated silica precipitation, according to the product requirements, the roller press filter or in plate filter press, filtering, washing to remove excess water and reaction by-products, get silica white cake, then through dry (usually the spray drying) for finished products. By controlling the reaction process of the proportion of material, flow rate and reaction temperature, time, after filtering, washing and drying processing, can get different specific surface area, particle size, purity, morphology, structure and porosity of the products. Silica white different production technology, its physical chemical properties are different, its just can meet the requirements of different USES and performance.

Precipitation conditions such as acidity, temperature, time and other factors had a great influence on the nature of the product. Quality is bad in sodium silicate solution, often contain complex silicate polymer, the polymerization in the process of acidification experience expanded rapidly, forming clots, silicate some mechanical impurities such as Fe3 +, Al3 +, Ca2 + can promote the formation of the clot electrolytes such as, affect the quality of the products. Especially the high iron content causes the silica white product with red, transparency is low. The concentration of a solution of sodium silicate can seriously influence the dispersion and the structure of the products. Improve the acidification temperature (95 ~ 95 ℃ under curing 30 min ideal) boost cohesion of silicate, accelerate silicic acid dehydration condensation, so as to promote the formation of the particles, is advantageous to the silica white quality improvement. But due to high temperature will soon precipitation and form massive particles, reduce silicon dioxide white quality.

Will create seed sodium silicate and hydrochloric acid, then the seed, sodium silicate and hydrochloric acid join reaction pot, maturation. This method is the preparation of highly active silica white, the key is to prevent silicate gathered into silica gel. Therefore in the process of the preparation of silicon dioxide sol, should strictly control the pH, choose as far as possible close to the gel point pH as the best control values; Second in the precipitation reaction process, the choice of pH 6.0 ~ 8.0, the reaction temperature is 50 ~ 80 ℃ is more ideal. Adding appropriate NaC1 when necessary, to make the silicon dioxide(SiO2), gathered into secondary particles settle, and adding suitable amount of surfactant, improve product of oil absorption value and color brightness.

 

 

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