Process for the preparation of acicular goethite

摘要

A suspension of an iron(II) compound which is sparingly soluble in water, in an alkaline liquid consisting essentially of water has air, oxygen or another oxidising gas or gas mixture passed through it. The goethite crystals or particles formed are filtered off, washed and dried. Particles more "monoenergetic" from the thermodynamic point of view than those prepared according to known technical processes are produced if the oxidising gas being passed through is interrupted for a while a number of times. This procedure is called "chopped oxidation"; it represents a gradient reversal method, as the concentration of the oxidant in the reaction medium periodically rises and drops again. <IMAGE>