| 摘要 |
<p>The present invention provides a process for processing silicon-dioxide-containing air-borne waste fines from the production of metallic silicon or silicon alloys to a crystalline zeolitic type-Y molecular sieve, in which in step I the air-borne waste fines are dissolved in alkali-metal-hydroxide solution at temperatures in the interval from 60 to 110.degree.C while alkalimetal-silicate solution having a modulus (SiO2 : MeI2O) in the range from 4.0 : 1 to 5.0 : 1 is formed, in step II the alkalimetal-silicate solution thus obtained is freed from organic components by treatment with at least one of active carbon and oxidizing agents and that the non-decomposable residue is separated from the solution, and in step III the alkali-metal-aluminate solution is reacted at room temperature with the dilute purified alkali-metal silicate solution obtained according to the steps I and II and having a modulus (SiO2 : Na2O) from 4.0:1 to 5.0:1, whereupon the reaction mixture (SiO2 : Al2O3 = 4-7, Na2O : SiO2 = 0.4 - 0.7, H2O : Na2O = 30-50) is crystallized at temperatures from 75 to 100.degree.C for 8 to 48 hours while stirring, followed by filtering, washing and drying in order to obtain a zeolitic type-Y molecular sieve having a faujasite structure and a whiteness degree according to BERGER ranging from 90 -to 94% at 460 m.mu..</p> |
