Bentonite is the most widely used clay soil in the industrialized world. Currently, 20 million tons of bentonite are used worldwide each year, at an annual cost of $4 billion. Most people come into contact with materials containing or manufactured with bentonite on a daily basis. Foundries employ bentonite when casting automobile parts, paints include bentonite as a rheological agent and for pigment suspension, paper relies on bentonite to provide opacity, water treatment plants use bentonite as a catalyst, pharmaceuticals rely on bentonite as a carrier and neutralization agent, and the plastics industry uses bentonite to enhance the properties of polymers. Other applications for bentonite include fertilizers, pesticides, animal feeds, foods (extenders) and beverages (filtration), detergents, waxes, petroleum exploration, and dust control. In each of these applications, nanoscale phenomena in the bentonite affect behavior.
Because bentonite swells extensively in the presence of water, bentonite has a characteristic "tight" porous structure that tends to impede liquid migration when in a stable condition. For this reason, bentonite also is often used to control liquid flow and aqueous contaminant transport in geoenvironmental applications, such as in groundwater cutoff walls, barriers for waste containment (e.g., landfills, wastewater ponds, nuclear storage, etc.), secondary containment in tank farms, and seals in monitoring and water supply wells. These applications are ubiquitous in the United States; nearly every community has a waste containment facility, a petroleum storage facility, a groundwater remediation or treatment project, or sealed monitoring or water supply wells. However, in many of these applications, bentonite is exposed to conditions that can lead to instability and poor performance. Thus, modification of conventional bentonite to overcome such tendencies towards instability represents an important area of research.
Accordingly, this research focuses on modifying bentonite at the nanoscale to improve its stability for sustainable performance in a variety of geoenvironmental applications. Modification will involve inserting large organic molecules between crystalline montmorillonite layers comprising the bentonite at the nanoscale, and then polymerizing these molecules after insertion. This process will yield a more rigid structure that retains the large organic molecules thereby providing permanence. The modified material, known as a bentonite-polymer nanocomposite (BPN), is expected to retain the useful advantages of conventional bentonites, while being more resistant to long-term instability due to factors commonly encountered in geoenvironmental applications. Aside from resulting in superior barriers, seals, and sorbents that can provide considerable reduction in the risk to human health and the environment, BPNs also could revolutionize the way bentonite is used worldwide and impact a wide range of industries. The research project also represents an interdisciplinary, collaborative effort among researchers at three universities and an industrial partner (CETCO, or Colloidal Environmental Technologies Corporation), and will stimulate cross-fertilization among industry researchers, faculty, and students. Efforts also are planned to involve undergraduate students in the research as well as women and minorities.
