Toxicity Leaching Characteristics of Cement Based Stabilized / Solidified sands Contaminated with Heavy Metals

Abstract

EPA Toxicity Leaching Procedure TCLP method 1313 was carried out to test the effectiveness , performance and efficiency of the solidification / stabilization treatment of five different heavy metals contaminated sands using   ordinary locally produced Portland Cement type A . Three mix designs were performed on the contaminated sands at three different pollution loads and concentrations . Results showed that using ( 3: 1: 0.5) Sand-Cement-Water Mix ratio is very effective in retaining heavy metal contamination . Effective retention percentages of ( 95 , 94.1 , 97.7 , 93.3 and 94 ) for Cr , Cd , Cu , Ni and Pb ions respectively was obtained even when the inertial contamination load with those ions exceeded 3000 mg / kg . Particle size had a significant influence on the amount of metals leached during the extraction process. Particles with sizes above 9.5 mm showed a better effectiveness in holding and retaining metals within the Solidified / stabilized matrix. Samples with low cement mix treatments were not able to maintain the required TCLP regulatory limits for samples contaminated with Chromium, Cadmium and lead . Although the inertial extraction fluid was at pH 4.9 the final leached extractions recorded pH values above 9.5 which demonstrates the alkanet   and stabilization effect of the cement matrix