Efficacy of Fe3O4/Starch Nanoparticles on Sporosarcina pasteurii Performance in MICP Process

Abstract

The microbial induced calcite precipitation (MICP) has been explored using well-known urease producer bacterium Sporosarcina pasteurii for many applications including soil stabilization. Urease enzyme hydrolyzes urea and in the presence of calcium chloride causes calcium carbonate precipitation between sand particles increasing sand stiffness and strength. In this study, the liquefied soil samples from Anzali coast were positioned inside injection columns by standard positioning technique. The columns were treated by injecting S. pasteurii suspension and cementation solution (CaCl2 and urea). The effect of different conditions consisting of number of injections, injection intervals, flow rate, and ratio of injection solution on unconfined compression strength (USC) of sands formed inside the columns were evaluated. The results indicated that soil strength was increased when ratio of reactant solutions and injection time were elevated. Moreover, the maximum Ca-precipitation in MICP reaction in liquid medium was obtained while Fe3O4/starch concentration and time of addition of nanoparticle to culture medium were 10.8 mg/L and 1.4 h, respectively. The USC results showed that the columns injected by bacterial suspension treated by Fe3O4/starch under optimized conditions improved the soil strength up to 1200 kPa in comparison to the control column as 220 kPa.