Performance and Microscopic Influence Mechanism of Solidified Cadmium Contaminated Soil by Rice Husk Ash Based Geopolymer

Abstract

In order to realize the comprehensive utilization of industrial solid waste rice husk ash and heavy metal cadmium contaminated soil, rice husk ash-based geopolymer prepared by alkaline activator was used to modify cadmium contaminated soil. The main physical and chemical properties of rice husk ash were clarified by SEM, XRF and X-ray diffraction. The unconfined compressive strength test and toxicity leaching test were carried out on the modified soil. Combined with FTIR and TG micro-level, the solidification mechanism of rice husk ash-based geopolymer solidified cadmium contaminated soil was discussed. The results show that the strength of geopolymer modified soil is significantly higher than that of plain soil, and the unconfined compressive strength at 7 d age is 4.2 times that of plain soil. The strength of modified soil with different dosage of geopolymer at 28 d age is about 36% to 40% higher than that of modified soil at 7 d age. Geopolymer has a significant effect on the leaching of heavy metals in contaminated soil. When the cadmium content is 100 mg/kg, it meets the standard limit. In the process of complex depolymerization-condensation reaction, on the one hand, geopolymers are cemented and agglomerated to form a complex spatial structure, which affects the macro and micro characteristics of soil. On the other hand, it has significant adsorption, precipitation and replacement effects on heavy metal ions in soil, showing good strength and low heavy metal leaching toxicity.

Keywords

rice husk ash / alkali excitation / heavy metals / curing mechanism

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