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

膨润土是工业化世界中使用最广泛的粘土。目前，全世界每年使用2000万吨膨润土，每年耗资40亿美元。大多数人每天都会接触到含有膨润土或由膨润土制造的材料。铸造厂在铸造汽车零部件时使用膨润土，涂料中包括膨润土作为流变剂和颜料悬浮剂，造纸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，制药依靠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其行为。由于膨润土在有水的情况下会膨胀，膨润土具有“紧密”多孔结构的特点，在稳定的条件下往往会阻碍液体的迁移。由于这个原因，膨润土也经常用于控制流体流动和含水污染物在地球环境应用中的运输，例如地下水截流墙，废物密封屏障（例如，垃圾填埋场，废水池，核储存等），储罐场的二次密封，以及监测和供水井的密封。这些应用程序在美国无处不在；几乎每个社区都有一个废物控制设施、一个石油储存设施、一个地下水修复或处理项目，或密封的监测或供水井。然而，在许多这些应用中，膨润土暴露在可能导致不稳定和性能差的条件下。因此，对常规膨润土进行改性以克服这种不稳定倾向是一个重要的研究领域。因此，本研究的重点是在纳米尺度上对膨润土进行改性，以提高其在各种地球环境应用中的稳定性和可持续性能。改性将涉及在由纳米级膨润土组成的结晶蒙脱土层之间插入大的有机分子，然后在插入后将这些分子聚合。这个过程将产生一个更刚性的结构，保留大的有机分子，从而提供持久性。这种被称为膨润土-聚合物纳米复合材料（BPN）的改性材料预计将保留传统膨润土的有用优点，同时更能抵抗地质环境应用中常见因素造成的长期不稳定性。除了产生卓越的屏障、密封和吸附剂，可以大大降低对人类健康和环境的风险外，bpn还可以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工业合作伙伴（CETCO，或胶体环境技术公司）之间的跨学科合作努力，并将促进工业研究人员、教师和学生之间的交叉受精。计划还将努力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.