Abstract: The invention relates to a method for recovering nickel in one and the same process from two pyrometallurgically produced nickel mattes, one of which contains a remarkable percentage or iron. The leaching of iron-bearing nickel matte is carried out in one step by conducting solution from the leaching cycle of a less iron containing matte into the leaching of a more iron containing matte at a stage where the iron of the less iron containing matte is in soluble form. The iron contained in the mattes is advantageously precipitated as jarosite and the solution created in the leaching of the more iron containing matte is conducted back into the leaching cycle of the less iron containing matte.

Abstract: A process for purifying aqueous solutions, of metal ions precipitating as arsenides, antimonides, tellurides, selenides, and tin and mercury alloys, wherein arsenic, antimony, tellurium, selenium, tin, mercury and/or compounds of the same are added to the aqueous solution as auxiliary agents, whereafter the impurities are cemented under reducing conditions by means of the auxiliary agent, and the cementation is catalyzed by means of the formed cementate by contacting the aqueous solution with the cementate, the quantity of which is substantially greater than that primarily cemented from the aqueous solution.

Abstract: A hydrometallurgical method of recovering zinc, copper and cadmium from their ferrites so that the ferrites are treated under atmospheric conditions in sulphuric acid bearing solution in the presence of potassium-, sodium- or ammonium-ions, is disclosed, in which the treatment takes place in one stage under such conditions that the non-ferrous metals, zinc, copper and cadmium, contained in the ferrites are transferred as sulphates to the solution and the iron is converted in the same stage to a solid basic iron salt by adjusting the sulphuric acid or ferric sulphate addition to be equivalent with regard to the ferrite amount fed into this stage and by adjusting the temperature to 80.degree. - 105.degree.C, preferably to 95.degree. - 105.degree.

Abstract: Materials dissolved in water are separated from each other by means of a cementation agent. The materials treated are those having a greater hydrogen overpotential than the potential difference between the cementation agent and hydrogen gas. A water solution of material to be cemented is fed upwards to a reaction zone through a bed containing the cementation agent, and agglomerates produced sink from the bed to be crushed in a zone below the bed.The addition of a flocculation agent to the reaction zone causes the material to cement as smooth-surfaced particles which do not adhere to each other or allow large gas bubbles to grow attached to the particles.