Oxidation treatment of a sulphide-bearing scrubber dust from the Mansfeld Region, Germany: Organic and inorganic phase changes and multi-element partition coefficients between liquid and solid phases

A low temperature oxidation process has been developed to separate Pb from Zn in a complexly contaminated scrubber dust. The material consists of appr ox. 50% galena (PbS) and sphalerite/wurtzite (ZnS), and also an amorphous c omponent, a variety of different silicate and carbonate phases as well as n aturally-occurring radionuclides and oil and grease. The two-stage process consists of a grinding stage followed by placing this material into a hydro gen peroxide solution. The resultant oxidation reaction is violently exothe rmic - the temperature rises spontaneously to approx. 96 degrees C. The amo unt of solid phases remaining after completion of the reaction was reduced by approx. 40% and consisted largely of insoluble lead sulphate which retai ned the bulk of the radionuclides. Almost all of the zinc was placed into s olution by this process as was the Cd, Re and Cu. The total PAH content of the original Theisenschlamm (468 ppm) was reduced to 11.25 ppm in the resid ual sediment and the PCDD/PCDF concentrations were reduced by approx. 40%. The radionuclides are almost totally concentrated in the solid phase. The m ethod shows considerable promise as a separation technique for very fine-gr ained sulphide-bearing residues. (C) 1998 Elsevier Science B.V. All rights reserved.