Abstract
Several leaching tests were carried out for the stabilized/solidified sludge to evaluate the release of inorganic contaminants. The main objective is to examine the effect of seawater attack on the heavy metal leaching from the monolithic materials stabilized/solidified with the Portland or slag cement. Batch leaching tests were used to determine the basic leaching characteristics of contaminated sludge and cement-based materials. Dynamic tank leaching tests on monolithic materials (with and without crushing) were conducted to determine the rate of heavy metal release as a function of leaching time with the different solvents (distilled water and seawater). The concentrations of zinc released from the contaminated sludge during the tank leaching test were significantly influenced by pH of solutions. The use of seawater as the solvent reduced the alkali leaching from the cement-based materials and influenced the pH of leaching solutions (pH 8-9). In response to decreasing pH, the amount of released Zn decreased, since the solubility of Zn under pH 8-9 is lower than under the strong alkaline condition. However, in the cases with seawater as the leaching solvent, Zn release was gradually increased as a function of leaching time. In addition, stabilization/solidification (S/S) with the Portland cement achieved the immobilization of Zn more effectively than the S/S with the slag cement.
