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Zhong, L., B.D. Lee, and S. Yang.
Vadose Zone Journal 17(1):170175(2018) PNNL-SA-129486

Aqueous colloidal silica suspension has characteristics that potentially can be used for nutrient delivery and slow-release carbon source setup for subsurface remediation. Research was conducted to (i) demonstrate delayed gelation of colloidal silica suspensions with the presence of nutrients; (ii) prove that gelation takes place in sediment and the gel slowly releases nutrients; and (iii) show that silica suspensions are injectable for vadose zone emplacement. The nutrient-laden colloidal silica suspensions showed low initial viscosity and then increased in viscosity with time until reaching gelation, allowing for slow release of nutrients into the environment. Higher salt and silica concentrations increased the rate of viscosity climbing and the rate of gelation, whereas higher silica concentrations resulted in stronger gels. Gels released nutrients slowly in both batch and column experiments. The rheological and injection behavior of the silica suspensions revealed the injectability of these fluids. Results demonstrated that colloidal silica suspension could be used as a carrier to distribute nutrients to the vadose zone and establish slow-release nutrient sources. https://dl.sciencesocieties.org/publications/vzj/pdfs/17/1/170175

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