GOALI/Collaborative Research: Benentonite-Polymer Nanocomposites for Geoenvironmental Applications

膨润土是工业化世界中应用最广泛的粘土。目前，全球每年使用2000万吨膨润土，年成本为40亿美元。大多数人每天都会接触到含有膨润土或用膨润土制造的材料。铸造厂在铸造汽车零件时使用膨润土，涂料包括膨润土作为流变剂和颜料悬浮剂，纸张依靠膨润土提供不透明度，水处理厂使用膨润土作为催化剂，制药厂使用膨润土作为载体和中和剂，塑料工业使用膨润土来增强聚合物的性能。膨润土的其他应用包括化肥、农药、动物饲料、食品(填充剂)和饮料(过滤)、洗涤剂、蜡、石油勘探和粉尘控制。在每一种应用中，膨润土中的纳米级现象都会影响行为。由于膨润土在水的存在下会发生广泛的膨胀，膨润土具有一种特有的“紧密”的多孔结构，这种结构在稳定条件下往往会阻碍液体的迁移。为此，膨润土还经常用于控制地质环境应用中的液体流动和水污染物传输，如地下水防渗墙、废物封堵屏障(例如，垃圾填埋场、废水池塘、核储存等)、油罐区的二次封堵以及监测和供水井的密封。这些应用在美国无处不在；几乎每个社区都有废物遏制设施、石油储存设施、地下水修复或处理项目，或者密封的监测或供水井。然而，在许多这样的应用中，膨润土暴露在可能导致不稳定和性能差的条件下。因此，对传统膨润土进行改性以克服这种不稳定的倾向是一个重要的研究领域。因此，本研究的重点在于对膨润土进行纳米尺度的改性，以提高其稳定性，使其在各种地质环境应用中具有可持续的性能。改性将涉及将大的有机分子插入组成纳米级膨润土的结晶蒙脱石层之间，然后在插入后聚合这些分子。这一过程将产生更坚硬的结构，保留大的有机分子，从而提供持久性。这种改性材料被称为膨润土-聚合物纳米复合材料(BPN)，预计将保留传统膨润土的有用优势，同时更能抵抗由于地质环境应用中常见因素造成的长期不稳定。BPN除了可以产生卓越的屏障、密封剂和吸附剂，大幅降低对人类健康和环境的风险外，还可能彻底改变全球膨润土的使用方式，并影响广泛的行业。该研究项目还代表了三所大学的研究人员和一个行业合作伙伴(CETCO或胶体环境技术公司)之间的跨学科合作努力，并将促进行业研究人员、教师和学生之间的交叉培养。还计划让本科生以及妇女和少数民族参与研究。

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.