Pollution Research Paper

USING GEOPOLYMERS MATERIALS FOR REMEDIATION OF LEAD-CONTAMINATED SOIL

HASSAN JAWAD KADHIM, KHITAM ABDULHUSSEIN SAEED AND NAGAM OBAID KARIEM

Abstract

(Solidification and Stabilization) is an economic and effective technology in the treatment of contaminated soil by heavy metals, as well as in the sludge and sediment. The main purpose of the study was to investigate the effect of geopolymers materials for the remediation of contaminated soil by S/S technique. In this study, soil was polluted by 2000 ppm of lead by using lead nitrate Pb(NO3)2. The Pb- impacted soil was treated using three rich silicon materials of (Silica fume, Rice husk ash and fly ash ) as an alternative cementitious material, and replaced with contaminated soil at (10, 15 and 20%) respectively. The three rich silicon material was activated with 9.5 and 11.5 molal of NaOH concentrations along with 5 molar Na2SiO3 solution, by keeping the ratio of (NaOH/Na2SiO3) mixtures at 2. The binder performance was analysed by used unconfined compressive strength ( UCS) to the solidified soil at three curing time which 7, 14 and 28 day. Leaching Procedure (TCLP) was also applied to investigate the Treatment degree of solidified soil for the specimens within 28 day. Furthermore, micro-structural analysis with (X-Ray diffraction and Scanning electron microscopes) were used for samples which gained maximum strength to demonstrate the development in strength, as well as the lead immobilization. The result of (UCS) indicated development in strength with curing day for all binders, and proved that all mix ratio exceed the Minimum Criteria of landfill disposal which is 340 kPa (0.34 N/mm2). It also showed increasing in strength with using sodium hydroxide solution of 11.5 than 9.5 molal except with fly ash binder, which caused drop in strength with 11.5 molal. The result of TCLP test for the stabilized soil after 28 day of curing, showed reduction in lead leaching rate for all binder, below leachability limit of 5 mg/L. It also found the sodium hydroxide solution caused reduction in lead concentration when used 11.5 than 9.5 molal for all mix ratio. It was also observed that the higher strength of the solidified sample lower the leaching rate of lead in the TCLP. Microstructural analysis indicated the formation of cementitious compounds within solidified soil which is responsible for development in strength and lead immobilizations. It also showed the variation in strength and leaching rate through each binders, was related to the density and homogeneity of cementitious compound that is formed.