Polymer/silicate composites: new materials for subsurface permeable reactive barriers

Investigations were performed into the suitability of novel composites to serve as materials for subsurface permeable reactive barriers (PRBs). These new materials are Type I composites—they are preformed organic polymers embedded in an inorganic matrix without significant covalent bonding between the components. The required properties for these materials to function efficiently are: (1) a tunable water passing rate to approximate the hydraulic conductivity of the subsurface environment where the PRB will be placed, (2) sufficient mechanical strength (both wet and dry) to maintain barrier integrity, (3) the ability to incorporate selective metal sequestration agents so that they remain active—yet do not leach from the barrier, and (4) to be deployable through direct injection methods such that trenching is not needed. Additionally, there is a need to keep the technology as low cost as possible, while remaining reliable. Results recently obtained in our laboratory show that our materials, remarkably, exhibit all of these properties and show great promise as vadose zone deployable PRBs.