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ECN publication
Leaching of ferrochrome slag in the marine environment
Published by: Publication date:
ECN 1998
ECN report number: Document type:
ECN-C--98-012 ECN publication
Number of pages: Full text:
26 Download PDF  

The leaching of Ferrochrome slag was investigated using seawater asleaching medium. Compared to the natural concentration of different elements apparent in seawater, the contribution of ferrochrome stag leaching is minimal. Exact determination of the leaching is difficult certainly if the leached concentrations are lower than the concentration already apparent in the seawater. This implies that the impact from the slag leaching to the marine environment is small. An exception is the leaching of Mn. The enhanced leaching of Mn can be explained by the execution of the test. In order to test the leaching properties the slag is size reduced with a top size of 4 min. Due to the size-reduction, fresh leaching surface is generated. The oxidation of liberated Mn to MnO2 is a slow process which is slower than the surface oxidation of the slag. Within the time frame of the test the surface oxidation is still continuing. In practice the slag will not be size reduced, no fresh surface will be generated and Mn leaching will not be of great importance. In addition, Mn is not an element specified in existing regulations. The Cr-content in the slag is high (1.3 %) but it is very important to consider that the potential for leaching (in seawater) is small (0.6 mg/kg). Studying the actual leaching under seawater conditions the exposure is marginal because the leached concentrations are not exceeding the natural seawater concentrations. The measurement of Pb in seawater using the ICP-AES technique is difficult and not very accurate. Upon request these can be analyzed using another more accurate technique. However, based on the experience with steeIslag, materials which posses the same features (low Pb content together with a relatively high Pb availability) the leachability is also low in the pH region of interest. 4 refs.

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