Flocculation of Coal and Mineral Particles with a Polyanionic Biopolymer

Abstract

A polyanionic biopolymer known as alpha-emulsan was found to flocculate fine particle suspensions of pyrite quite readily, but other materials including silica (quartz), kaolin, and a particular bituminous coal required activation in order to respond in large measure. Activation of these materials was achieved with small amounts of ferric iron which is known to hydrolyze to form ferric hydroxy complexes and colloidal particles of ferric hydroxide. When the positively charged hydrolyzed species of iron(III) were adsorbed by the negatively charged particles, the latter experienced a charge reversal which made them more receptive to adsorption of the polymeric anions. Larger amounts of ferric iron interfered with the flocculation of all the materials except pyrite, and the interference seemed due to the formation of ferric iron complexes with emulsan. Since high concentrations of ferric iron and low pH favored the flocculation of pyrite with emulsan but not the flocculation of the other materials, these conditions were applied to the selective flocculation of binary mixtures of pyrite and either silica, kaolin, or coal. Partial separation of the mixtures was achieved.