Decomposition of cyanide in electrolytic cell lining

A method of treating sodium cyanide in spent potlining material from an electrolytic cell for producing aluminum from alumina dissolved in a sodium-containing electrolyte, wherein a cyanide compound forms in the spent potlining material, the method comprising the steps of:

• (a) grinding the spent potlining material containing said cyanide compound to provide particles of spent potlining material;
• (b) adding a reactive compound capable of reacting with said cyanide compound to provide a mixture of reactive compound and spent potlining material, said reactive compound selected from the group consisting of boron oxide, sodium borate, sodium tetraborate, calcium borate, boric acid, calcium oxide and rare earth oxides, said reactive compound present in an amount sufficient to destroy said cyanide compound in said spent potlining material;
• and
• (c) heating said mixture to a temperature effective in reacting said reactive compound with said cyanide compound.

A method of treating sodium cyanide in spent potlining material from an electrolytic cell for producing aluminum from alumina dissolved in a sodium-containing electrolyte, wherein sodium cyanide forms in the spent potlining material, the method comprising the steps of:

• (a) grinding the spent potlining material containing sodium cyanide to provide particles of spent potlining material having a particle size less than 10 mesh (U.S. Sieve Series);
• (b) adding a reactive material comprised of boron oxide capable of reacting with said sodium cyanide to provide a mixture of reactive material and spent potlining material;
• and
• (c) heating said mixture to a temperature in the range of 450.degree. to 750.degree. C. for purposes of reacting said reactive material with said sodium cyanide to destroy said sodium cyanide.

A method of treating sodium cyanide and fluorides in spent potlining material from an electrolytic cell for producing aluminum from alumina dissolved in a sodium- and fluorine-containing electrolyte, wherein sodium cyanide and fluorides form in the spent potlining material during operation of the cell, the method comprising the steps of:

• (a) grinding the spent potlining material containing sodium cyanide and fluorides to provide particles of spent potlining material;
• (b) adding a reactive material selected from the group consisting of carbide, fluoride, carbonate and oxide material capable of reacting with said sodium cyanide and adding lime to react with said fluoride to provide a mixture of reactive material, lime and spent potlining material;
• and
• (c) heating said mixture to a temperature effective in reacting said reactive material with said sodium cyanide to destroy said sodium cyanide and effective in causing said lime to react with said fluorides.