Abstract: A process is described for the treatment of spent pot lining material from electrolyte reduction cells, this spent material having a substantial content of cryolite. The spent material is first leached with water at a dilution and a time sufficient to dissolve substantially all water soluble fluorides, after which the solid residue is separated from the liquid. The solid residue obtained is then subjected to a caustic leach with an aqueous sodium hydroxide solution containing about 20 to 50 g/L of NaOH and thereafter the solid residue is separated from the liquid.

Abstract: A process is described for the treatment of spent pot lining material from electrolyte reduction cells, this spent material having a substantial content of cryolite. The spent material is first leached with water at a dilution and a time sufficient to dissolve substantially all water soluble fluorides, after which the solid residue is separated from the liquid. The solid residue obtained is then subjected to a caustic leach with an aqueous sodium hydroxide solution containing about 20 to 50 g/L of NaOH and thereafter the solid residue is separated from the liquid.

Abstract: The invention relates to a reactor for the treatment of wastewater solutions containing cyanide and other dissolved organic material, having an elongated tube having an entrance (28) and an exit (32), and an energy source (22) for the tube, preferably positioned adjacent the exit. The energy source generates intense energy such that a cyanide/organic material-containing solution can be treated by passing it through the tube to expose it to said energy so that the solution absorbs sufficient energy from the energy source to degrade the cyanide and/or dissolved organic material contained therein. The source of intense energy is preferably a plasma, e.g. a plasma generated by a plasma torch or a DC electric arc. The invention also relates to a process of treatment of such a wastewater solution by passing it through such a reactor.

Abstract: A process for recycling spent potlining material from aluminum reduction cells contaminated with fluoride and aluminum values. The process comprises first reducing the average particle size of the spent potlining material to smaller than 28 Tyler mesh to form a powder. The powder is then treated with an aqueous sodium hydroxide solution containing about 10 to 60 g/L of sodium hydroxide at a temperature in the range of between 60.degree. and 90.degree. C. to form a solution containing fluoride and sodium aluminate and a residual solid. The solution is removed from the residual solid and the content of NaOH is adjusted in the solution to the range of about 10 to 60 g/L of NaOH, if the content differs from this range, to produce a solution suitable for cyanide destruction. This solution is then heated to a temperature in the range of about 160.degree. to 220.degree. C. at a pressure in the range of about 150 to 350 p.s.i. for a time of between about 1/2 and 3 hours to destroy cyanide values in the solution.

Abstract: A process for using nitride-containing aluminum dross residues to produce refractory products. The process involves mixing a dross residue which contains AlN, without prior conversion of the aluminum nitride in the dross to aluminum oxide or hydroxide, with a material comprising a metal oxide or a metal oxide precursor, and calcining the resulting mixture at a temperature suitable to produce a refractory product. During the calcination step, the AlN reacts with other components of the mixture. Since the reaction is exothermic, less heat is required for the calcination step than if a dross residue containing no AlN were used. The AlN can also reduce various contaminants (e.g. Fe.sub.2 O.sub.3, silicon and titanium) present in the metal oxide refractories, and so the invention can be used to produce conventional refractory products of improved purity and appearance. The process enables dross residues to be used for useful purposes rather than being discarded.

Abstract: The invention relates to a chrysotile asbestos fiber substantially coated on its exterior surface with hydrated titanium dioxide, the titanium dioxide content being from 0.5 to 35% by weight, part of the titanium dioxide being chemically bonded to the asbestos fiber and the remaining titanium dioxide being retained by electrostatic bond, said modified fiber having an Mg:Si ratio of from less than 3:2 to 2:2 when calculated on an atomic number ratio, a Ti:Si ratio of from more than 0:2 to less than 1:2 and said modified fiber being also characterized by an infrared spectrum wherein the relative peaks at 1082, 1025 and 957 cm.sup.-1 have been substantially altered in their intensity and as shown in curves C and D of FIG. 1 , said fiber resisting leaching of the Mg ions by strong acids 3 to 6 times better than natural asbestos fibers and resisting leaching of SiO.sub.2 groups in strong alkali media 1.5 to 3 times better than unmodified chrysotile fibers.