Abstract: The invention relates to a process and device for the production of highly concentrated spinning solutions from acrylonitrile polymers, where the dissolving is carried out in one step in a stirred mixing vessel, which has a disc-shaped stirrer rotating in a horizontal plane, the polymeric material to be dissolved and the solvent are metered in separately at room temperature into the stirring vortex which is formed, and the temperature of the solution being formed is maintained at a constant preset value in the range from 60.degree. to 120.degree. C. by controlling the peripheral velocity of the stirrer.

Abstract: Effluent containing organic impurities which are difficult to degrade is purified by oxidation in the aqueous phase at temperatures of 100.degree. to 310.degree. C. and under elevated pressure. This is effected by initially treating the effluent in a first stage with gases containing oxygen, but without the addition of catalysts, until the C.O.D. value has been reduced by 50 to 98%. The effluent which has received preliminary treatment in this way is subsequently treated, in a second stage, with an oxidizing agent stronger than oxygen, in the liquid phase and at the same, or at a higher, temperature, until the C.O.D. value has fallen to approximately 0 g/l.