Regenerating spent aluminium@-contg. nitric acid soln. - from chemical surface treatments of aluminium@ parts, with redn. of effluent nitrate content and recovery of free and combined acid

摘要

Regenerating process for spent aluminium containing nitric acid solution from chemical surface treatments of aluminium and aluminium alloy parts, whereby proportion of the spent nitric acid solution is drained from the treatment bath and mixed with 3 to 5% (vol.) sulphuric acid, 240% (vol.) organic solvents and 60% (vol.) organic thinners; the dispersion is separated by extraction into an aluminium sulphate containing aqueous phase substantially free of nitrates and a nitrate containing organic phase; the aqueous aluminium sulphate containing phase is neutralised, the nitrate containing organic phase is mixed with water and the free and combined nitric acid is thereby converted to the aqueous phase and separated from the organic phase; the regenerated nitric acid solution is returned to the treatment bath and the organic phase is returned to the drained spent nitric acid solution. USE/ADVANTAGE - Used for the recovery of spent aluminium containing nitric acid solution from chemical surface treatments of aluminium parts, substantially reducing the effluent nitrate content, recovering free and combined acid and prolonging the life of the treatment solution.