Abstract: A method and apparatus for converting an iron-bearing residue generated in a hydrometallurgical process that contains small amounts of soluble heavy metals into a stable form by means of a neutralizing agent. The residue is elutriated and the elutriated residue is fed into at least one stabilization or homogenization reactor, into which a neutralizing agent is also routed, and the homogenous mixing together of the residue and neutralizing agent takes place by means of a helix mixer, where the ratio of the diameter of the mixer to the diameter of the reactor is 0.75-0.99.

Abstract: A method and apparatus for converting an iron-bearing residue generated in a hydrometallurgical process that contains small amounts of soluble heavy metals into a stable form by means of a neutralising agent. The residue is elutriated and the elutriated residue is fed into at least one stabilisation or homogenisation reactor, into which a neutralising agent is also routed, and the homogenous mixing together of the residue and neutralising agent takes place by means of a helix mixer, where the ratio of the diameter of the mixer to the diameter of the reactor is 0.75-0.99.

Abstract: The purpose of the invention is to remove copper selectively from a concentrated zinc sulphate solution by ion exchange. The method enables a significant reduction in the use of zinc powder during the solution purification of zinc sulphate solution and makes possible to avoid usage of arsenic or antimony trioxides as a precipitation chemical. The method is to be combined with the chloride removal that occurs as a sub-stage of solution purification.

Abstract: This invention relates to a method for the removal of iron as hematite from a zinc sulphate solution in atmospheric conditions during the electrolytic preparation of zinc. According to the method, the pH of the iron-containing solution is adjusted to a value of at least 2.7, oxygen-containing gas is fed into the solution and part of the hematite thus formed is recirculated to the precipitation stage.

Abstract: The purpose of the invention is to remove copper selectively from a concentrated zinc sulphate solution by ion exchange. The method enables a significant reduction in the use of zinc powder during the solution purification of zinc sulphate solution and makes possible to avoid usage of arsenic or antimony trioxides as a precipitation chemical. The method is to be combined with the chloride removal that occurs as a sub-stage of solution purification.

Abstract: The invention relates to a method for improving the filterability and washing result of fine-grained waste material generated in the metallurgical industry. According to the method some of other fine-grained solid is added to the first waste precipitate before filtration, which is also removed from the process, and which remains stable in the same conditions as the first waste precipitate.

Abstract: This invention relates to a method for the removal of iron as hematite from a zinc sulphate solution in atmospheric conditions during the electrolytic preparation of zinc. According to the method, the pH of the iron-containing solution is adjusted to a value of at least 2.7, oxygen-containing gas is fed into the solution and part of the hematite thus formed is recirculated to the precipitation stage.