Patents by Inventor Hans F. T. Haraldsen

Hans F. T. Haraldsen has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Method for removal of heavy metals, especially cadmium, from phosphoric acid containing solutions
    Patent number: 4986970
    Abstract: The present invention relates to a method for removal of heavy metals, especially cadmium, from phosphoric acid containing solutions, primarily such solutions made by digestion of rock phosphate by nitric acid and subsequent removal of the main part of calcium from the mother liquor. The phosphoric acid solution is pre-purified for removal of sludge and insolubles and then partly neutralized with ammonia to pH 1.4-2 and cooled to 5.degree.-40.degree. C. Metal salts of dithio carbonic acid-O-esters are added for precipitating the heavy metals which then are separated from the solution. The solution is preferably neutralized to pH 1.6-1.8 and cooled to 10.degree.-20.degree. C. before precipitation of the heavy metals which then can be removed from the phosphoric acid solution by flotation and subsequent filtration.
    Type: Grant
    Filed: November 3, 1989
    Date of Patent: January 22, 1991
    Assignee: Norsk Hydro a.s.
    Inventor: Hans F. T. Haraldsen