Method for dissolution and stabilization of silica-rich fibers
AssigneeUnited States Department of Energy
InventorCarol M. Jantzen
Life of this patent
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Abstract
A method for dissolving silica-rich fibers such as borosilicate fibers, fiberglass and asbestos to stabilize them for disposal. The method comprises (1) immersing the fibers in hot, five-weight-percent sodium hydroxide solution until the concentration of dissolved silica reaches equilibrium and a only a residue is left (about 48 hours), then immersing the residue in hot, five-weight-percent nitric acid until the residue dissolves (about 96 hours). After adjusting the pH of the dissolved fibers to be caustic, the solution can then be added to a waste vitrification stream for safe disposal. The method is useful in disposing contaminated HEME and HEPA filters.
Claims20
A method for dissolving silica-rich fibers, said method comprising the steps of:
- making a first mixture of sodium hydroxide and water;
- immersing said fibers in said first mixture;
- maintaining said fibers in said first mixture until the concentration of silica in said first mixture approaches equilibrium and a residue of said fibers remains;
- removing said residue from said first mixture;
- making a second mixture of nitric acid and water;
- immersing said residue in said second mixture;
- and
- maintaining said residue in said second mixture until said residue dissolves.
A method for dissolving silica-rich fibers, said method comprising the steps of:
- making a first mixture of sodium hydroxide and water;
- immersing said fibers in said first mixture;
- heating said first mixture to a first temperature;
- maintaining said fibers in said first mixture at said first temperature until the concentration of silica in said first mixture approaches equilibrium and a residue of said fibers remains;
- removing said residue from said first mixture;
- making a second mixture of nitric acid and water;
- immersing said residue in said second mixture;
- heating said second mixture to a second temperature;
- and
- maintaining said residue in said second mixture at said second temperature until said residue dissolves.
A method for preparing a filter containing silica-rich fibers for disposal, said method comprising the steps of:
- making a first mixture of sodium hydroxide and water;
- immersing said filter in said first mixture;
- heating said first mixture to approximately at least the boiling temperature of said first mixture;
- maintaining said filter in said first mixture at said boiling temperature until the concentration of silica in said first mixture approaches equilibrium and a residue of said fibers remains;
- removing said residue from said first mixture;
- making a second mixture of nitric acid and water;
- immersing said residue in said second mixture;
- heating said second mixture to approximately at least the boiling temperature of said second mixture;
- and
- maintaining said residue in said second mixture at said second temperature until said residue dissolves.
Dependencies are inferred from the claim text.