Immobilization of As, Cd, Cr and PB-containing soils by using cement or pozzolanic fixing agents

The present work reports leaching data for a soil contaminated with four inorganic model wastes, Cd (II) and Pb (II) nitrates, sodium arsenite, and sodium chromate, at concentrations in the range of 10,000 to 12,200 ppm. Various combinations of Type I portland cement (OPC), Type F fly-ash, blast furnace slag, lime, and silica fume have been used to treat the contaminated soils, which are then leached using a slightly modified EP Tox1 leaching procedure. In no case does fly ash improve performance when mixed with other binding agents. Slag offers superior performance compared to fly ash in any combination tested and has some potential for general utility in practice. In particular, several mixtures including slag are effective in immobilizing lead, which sometimes given problems in solidification with cement. Type I portland is a very versatile and dependable reagent compared to the other agents used. In the cases of As and Cr, the performance of portland alone is superior to that of any other reagent or combination, when comparisons were made at the same dosage level. Cement alone was not among the fixing agents tested for Cd and Pb, but several combinations with cement were included. In every case, inclusion of OPC results in leachate concentrations as low as or lower than the corresponding mixture without OPC. © 1990