Stability of copper smelter slag in sea water

The long-term stability of the slag in sea water is an essential requirement for its use in marine environment. Because no specific standards exist for studying the leachability of slag in sea water, its long-term stability was assessed through four types of indigenously designed extraction tests: (i) extraction tests on the slag similar to that specified in the multiple extraction procedure USEPA 1320, however, using sea water as the leachant; (ii) mechanical activation of the slag followed by extraction test using sea water as leachant; (iii) pressure leaching of the slag (at 1000 psi) in N2 and O2 for 4 h at different temperatures up to 120 degrees C; and (iv) mechanical activation of slag followed by pressure leaching of the slag in the temperature range of 40120 degrees C. In all these four tests, the leachability of the copper smelter slag was found to be higher in sea water compared to that in the Toxicity Characteristic Leaching Procedure medium and in acids. However, the highest concentration of all the relevant elements in the leachate was below the prescribed limits in USEPA method 1311. (C) 2010 American Institute of Chemical Engineers Environ Prog, 201