EFFECT OF ENVIRONMENTAL RELEVANT ORGANIC COMPLEXANTS ON THE SURFACE CHARGE AND THE INTERACTION OF CLAY MINERAL AND METAL OXIDE PARTICLES

摘要

There is a tremendous variety of dissolved small and macromolecular organic compounds rich in anionic functional groups (e.g., phenolic compounds, humic and fulvic acids) in most aquatic environments, which are able to form various complexes on the surface active sites of inorganic mineral particles present in surface waters, soils. Clay mineral and metal oxide particles are the most abundant inorganic colloid components of these natural systems. The solution composition influenced surface properties of colloidal clay and metal oxide particles play the major role in the particle-particle interactions resulting in either dispersing or aggregation of particles. Particle aggregation is of great importance in environmental point view considering such fields as soil erosion, particle transport, sediment formation, etc. In aquatic systems the surface of mineral particles is coated by a polyanionic organic layer formed Spontaneously in the presence of natural complexants such as humic and fulvic acids. This surface modification inherently influences particle interactions. The colloidal stability of an organic rich composite system can improve to such a degree that even a humate-assisted transport of mineral particles becomes probable. Considering the role of the solution composition in the colloidal stability of composite aqueous dispersions in environment, the presence of multifunctional organic complexants is of crucial importance besides the well-known master variables, the pH and ionic strength, as well as the muitivalent inorganic ions dissolved generally in soil solutions, surface, ground and subsurface waters.