Method of making and a slow release composition for abating acid water

Abstract

Various chemolithotrophic bacteria such as Thiobacillus ferrooxidans by direct or indirect mechanisms catalyze the oxidation of metal sulfides and produce acid, i.e. sulfuric acid and soluble metal salts at a much faster rate than chemical oxidation. Elimination of such bacteria would inhibit the formation of the acid. The natural production of such acids is particularly troublesome in mines e.g. coal mines, since acid water is produced which is damaging to the environment. An effective method of abating or eliminating such acid water production is to apply a bactericide such as a biodegradable organic surfactant which at low pH values are bactericides and hence inhibit the bacteria from catalyzing the metal sulfides. The affected acid water site can thus be treated with the surfactant which provides a temporary or short term result usually for a few months. A long term solution, that is 1 year to several years, is provided through the use of a slow release composition of the present invention in which a heterogeneous matrix contains a thermoplastic domain and an organic surfactant domain. A suitable porosity is created when proper amounts of surfactant are utilized so that a long term slow release composition is formed. A method of making the heterogeneous matrix or slow release composition involves the dry blending of a thermoplastic compound and various processing aids, subsequently adding a bactericide thereto and mixing under shear and heat the resulting molten composition. A suitable slow release article can be formed such as pellets.