Abstract: The invention relates to a method and apparatus for controlling a continuous metal removal in conjunction with a zinc preparation process, in which the metal removal is performed in one or more reactors (11a-c), in conjunction with the reactor, the redox potential (16a-c) and the acidity and/or basicity are measured, and based on the measurement results, the process variables (17a-c) of the metal removal are adjusted towards the desired direction. According to the invention, the redox potential measurements (16a-c) are performed from the sludge produced in the reactor in conjunction with the outlet pipe of the reactor outside the reactor, and the measuring instrument (16a-c) is purified at predetermined intervals.

Abstract: This invention relates to a method for removing thallium from a zinc-containing solution. In particular, the method relates to the purification with metallic zinc powder of a solution going to the electrolytic production of zinc. In this method, thallium is removed by means of a lead compound in the solution purification stage, either during the final purification stage or in a purification stage in which cadmium is precipitated.

Abstract: The invention relates to method for leaching zinc-containing materials in connection with the electrolytic recovery of zinc. According to this method, the feed materials i.e. zinc calcine and zinc sulphide, are leached in three stages, in which he sulphuric acid content of the stages rises in accordance with the direction in which the solids are moving. The solids and solution formed in the leaching stages are routed throughout the process countercurrently in relation to each other.

Abstract: The invention relates to a method for leaching zinc concentrate in atmospheric conditions in the presence of trivalent iron. It is essential that the zinc concentrate is fed into conditions where in addition to trivalent iron, there are also jarosite nuclei. The sulfuric acid content of the leaching step is maintained within the region 10-40 g/l, and the temperature within the region 80° C.—the solution boiling point, and into the leaching step there is fed oxygen, so that the zinc concentrate is dissolved and the iron is precipitated as jarosite.