چكيده به لاتين
This study compares the viability of employing volcanic ash (VA) and Portland cement (PC) for solidification/stabilization(S/S) of zinc contaminated soil in different curing conditions and times. Also, the effect of different alkali activators (ratio of sodium silicate to sodium hydroxide) in 10% VA has been investigated. The performance of materials was determined by unconfined compressive strength (UCS) and Toxicity characteristic leaching procedure (TCLP). additionally, X-ray diffraction (XRD), Infrared spectroscopy (IR) and Field Emission Scanning Electron Microscope (FESEM)-Mapping-EDS analysis are performed to elucidate the mechanisms of Zn immobilization in the soil. The compressive results show that geopolymer treatment in contaminated soils is more efficient at the dry curing (DC) while PC has an advantage in wet curing (WC). The TCLP results indicated that the immobilization for both VA and PC were more than 95% in 90 days. However, PC treated samples showed better efficiency than VA samples which were more than 99.98% in all zinc concentration. Moreover, the highest UCS result in the presence of sodium silicate in the 2500mg/Kg Zinc was achieved at the ratio of 1 which was 19.27 MPa after 28 days of curing. Although the results were not significantly different from those containing sodium hydroxide. Also, the samples containing sodium hydroxide alone has a better performance in TCLP tests. The microstructure results indicate that Clayey soil has a potential for immobilization of contamination and formation of Albite and C-S-H in VA and PC, respectively, are the primary mechanisms for the S/S of zinc in contaminated soil.
