ELECTROCHEMICAL ALTERATION OF MAGNETITE

Abstract

Investigations were made in DC current generated by a 6V acid battery. The electrodes were polished magnetite plates placed in electrolytic beakers containing 0.01N NaCl (pH 5) and connected by a salt bridge. One of the plates was positively polarized and the other negatively polarized. The current in the system, the pH in the anode and cathode solutions and the potentials of the electrodes were measured. The magnetite and the products of the electrochemical reactions was studied by X-ray analysis in a DRON-1.5 unit, using Co Kα radiation filtered with iron. The experiments lasted 130 days. Electrochemical treatment causes considerable cathodic alteration of magnetite: an increase in the amount of ferrous iron in it and the generation of a crystal phase consistent of goethite and secondary magnetite that extends deep into the mineral and was deposited with a specific orientation relative to the cathode surface, plus the generation of abundant iron oxide and hydroxide deposits. The anode showed some increase in the unit cell parameter in a very thin surface layer. The experiments indicate that oxidation zones can be generated in an oxide-free situation at great depths, since the model of the decomposition of magnetite presented uses it oxygen reserves. It is therefore logical to assume that the rich oxidized ores represent the cathode pole in a galvanic unit of as yet unknown structure. Additional study results are discussed.