Pure silica gels and silicate solns. prodn. - by treating gel particles with hydrochloric acid then washing to remove iron, aluminium, arsenic and lead

摘要

Prodn. of silicic acid gel, xerogels and silicate solns. of very low Fe, Al, As and Pb contents comprises washing conventionally-prepd. gel particles with HCl, then washing with water and opt. dissolving in an alkaline soln. The HCl may include an agent for chemically binding the impurities. Pref. particles have diam. 0.1-5 (0.5-3)mm and concn. of HCl is 8-38 (20-37)wt.%. Esp. 1-5(1-2) vol. HCl are used per vol. gel and treatment is at 10-70 (20-60) degrees C. Treatment with HCl can be carried out 1-5 (2-4) times with each step lasting 0.25-24 (0.5-5)hrs. Prods. are useful e.g. as catalyst (carriers), drying agents, fillers, additives to cleaning compsns. and in mfr. of molecular sieves. Simple process gives very high degree of impurity removal. The liq. and solid phases are easily sepd. by decanting and the HCl can be recovered.