Rheological Properties of Aqueous Colloidal Silica Suspensions Related to Amendment Delivery for Subsurface Remediation

Aqueous colloidal silica suspensions as non-Newtonian fluids have been reported as carriers for remedial amendment delivery in subsurface. The knowledge of the rheological behavior of the silica suspensions is essential for the field injection and subsurface application. This contribution is focused on the rheological characteristics of colloidal silica suspensions under various environmental conditions relevant to amendment delivery for subsurface remediation. We systemically studied the influence of silica particle concentration, ionic strength, pH, aging, amendment type and concentration, and subsurface sediment on the rheological behavior of the suspensions. Results indicated the suspensions maintained shear thinning in a number of varieties. Higher colloidal suspensions concentration raised the absolute suspensions viscosity and increased the degree of shear thinning. Addition of salts (e.g., Na+ and K+) to increase the solution ionic strength also increased the viscosity of suspensions and the degree of shear thinning. The silica suspensions exhibited controllable viscosity at acidic and alkaline pH. Meanwhile, the viscosity of suspensions increased with aging and eventually became gels under favorable conditions. The gelation rate is related to silica particle concentration, ionic strength and addition of sediments.