Process for converting silicon dioxide containing waste flue dust to crystalline zeolitic molecular sieves of type A
Silicon dioxide containing waste flue dust from the production of silicon metal and silicon alloys is converted to crystalline zeolite molecular sieves of type A. The process involves: (1) dissolving the flue dust in alkali metal hydroxide solution with the formation of alkali metal silicate solution having a module (SiO/sub 2/:Me/sub 2/IO) in the range of 2.0:1 to 3.5:1 at a temperature of 60/sup 0/-100/sup 0/ C; (2) purifying the thus obtained alkali metal silicate solution from organic constituents by treatment with activated carbon and/or an oxidizing agent and separating the non-decomposable residue from the solution; and, (3) reacting alkali metal aluminate solution present at room temperature with the diluted, purified alkali metal silicate solution with a module (SiO2:Na2O) of 2.0:1 to 5:1 obtained by steps (1) and (2) and subsequent crystallizing the reaction mixture ((2.0-4.4)Na/sub 2/O:Al/sub 2/O/sub 3/; (1.3-1.8)SiO/sub 2/:(90-120)H/sub 2/O) at a temperature of 90/sup 0/-95/sup 0/ C for a period of 6-12 hours, subsequently filtering, washing to ph of about 10-11 and drying to recover a crystalline, zeolitic molecular sieve of type a having a degree of whiteness according to berger (A. Berger, die farbe 8 nr. 4/6 (1959) pages 187-202) at 460 mu in the range of 90-95%.
- Assignee:
- Degussa (Germany, Federal Republic Of)
- Patent Number(s):
- US 4310496
- OSTI ID:
- 5605814
- Country of Publication:
- United States
- Language:
- English
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ACTIVATED CARBON
ADSORBENTS
AEROSOL WASTES
ALKALI METAL COMPOUNDS
ALLOYS
ALUMINATES
ALUMINIUM COMPOUNDS
ASHES
CARBON
CHALCOGENIDES
CHEMICAL PREPARATION
CLEANING
DRYING
DUSTS
ELEMENTS
FILTRATION
FLUE GAS
FLY ASH
GASEOUS WASTES
HYDROGEN COMPOUNDS
HYDROXIDES
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MATERIALS
MINERALS
MOLECULAR SIEVES
NONMETALS
OXIDES
OXIDIZERS
OXYGEN COMPOUNDS
PH VALUE
RESIDUES
SEPARATION PROCESSES
SILICATES
SILICON ALLOYS
SILICON COMPOUNDS
SILICON OXIDES
SYNTHESIS
WASHING
WASTE PRODUCT UTILIZATION
WASTES
ZEOLITES