PNNL

Abstract

Among the most common amendments added to groundwater during site remediation are compounds used to adjust or maintain pH. This research describes an approach to encapsulate mineral particles (MgO and CaCO3) within oil droplets suspended within an aqueous phase for the purpose of delivery to the subsurface environment. A series of batch experiments was combined with mathematical modeling to illustrate encapsulation and understand the influence of particle encapsulation on rates and extents of alkalinity release. Encapsulation of the alkalinity releasing particles resulted in slower rates of amendment release as compared to rates obtained using suspensions of bare mineral particles, allowing for the possibility of control as a function of pH. Results indicate that alkalinity release from particle suspensions follows a mineral dissolution mechanism that could not explain the rate of alkalinity release of encapsulated particles. The reduction in mineral dissolution rates observed with the encapsulated particles was found to result from a mass transfer limitation. This limitation was well described using a linear driving force expression to account for the resistance of mass transfer at the oil-water interface.