Application of ESEM to environmental colloids.

Environmental colloids are toxic or radioactive particles suspended in ground or surface water. These hazardous particles can facilitate and accelerate the transport of toxicants and enhance the threat to humans by exposure to pathogenic substances. The chemical and physical properties of hazardous colloids have not been well characterized nor are there standard colloid remediation technologies to prevent their deleterious effects. Colloid characterization requires measurement of their size distribution, zeta potential, chemical composition, adsorption capacity, and morphology. The environmental scanning electron microscope (ESEM) by ElectroScan, Inc., analyzes particle sizes, composition, and morphology. It is also used in this study to identify the attachment of colloids onto packing or rock surfaces in our development of a colloid remediation process. The ESEM has confirmed the composition of groundwater colloids in our studies to be generally the same material as the surrounding rock. The morphology studies have generally shown that colloids are simply small pieces of the rock surface that has exfoliated into the surrounding water. However, in general, the source and chemical composition of groundwater colloids is site dependent. We have found that an ESEM works best as a valuable analysis tool within a suite of colloid characterization instruments.