چكيده به لاتين
Heavy metals pollution in soil poses a severe threat to human health, so solving the problems caused by heavy metals has received a lot of attention. Solidification/stabilization of heavy metals is recently introduced as a promising approach for the reduction of contamination leaching. Geopolymers as environmentally-friendly binders can trap heavy metal ions in their three-dimensional structural network, as well as the ability to low-solubility chemical bonds with heavy metal. In this study, the potential of volcanic-ash (VA) based geopolymer incorporating ground granulated blast furnace slag (GGBFS) inimmobilization of lead contaminated soil was investigated. In this line, the effect of VA content, GGBS/VA content, curing time, and curing condition on mechanical and leaching characteristics were investigated. Unconfined compressive strength (UCS), Toxicity characteristic leaching procedure (TCLP) and Synthetic Precipitation Leaching Procedure (SPLP) were used to determine the mechanical and leaching properties of treated and untreated samples, respectively. Mechanical strength of specimens showed that VA-based geopolymer treated specimens cured at dry condition (oven curing at 50˚C) gained more strength than wet curing condition (room temperature with a relative humidity of 80%). Although lead has a detrimental effect on the mechanical strength of VA treated samples, replacing VA with GGBFS resulted in strength development at both curing conditions. Leaching test results showed excellent immobilization efficiency of VA-based geopolymer to the extent that lead leaching decreased by 92%. The results were also verified by the microstructural analysis, FESEM, EDS, Map and XRD, which indicate better compacted and dense microstructure of geopolymer treated samples, Lead was also found to reduce the formation of geopolymer networks.
