GB676854A - Method of separating solid substances or colloids from liquids - Google Patents

Abstract

676,854. Purifying liquids electrolytically. METALLGES. AKT.-GES. Oct. 10, 1950 [Oct. 28, 1949; June 9, 1950], No. 24771/50. Class 41. A method of separating from liquids solid substances dispersed therein comprises causing these substances to flocculate in a clarifying vessel provided with electrodes connected to a source of electric current, the cathode being disposed substantially horizontally at the lower end of the vessel and being supplied with current at a density of about 1 to 20 amps. per square dcm., and the solid substances being transported to the surface of the liquid simultaneously or subsequently by gas bubbles produced in or introduced into the liquid. The bubbles may be produced by electrical decomposition at the cathode. The anode may be disposed at a small distance, for example 2 to 0.5 cm. above the cathode. The method may be carried out in two stages in the first of which the floes are formed by using a high current density, and in the second of which the current is reduced to form fine gas bubbles which transport the floes to the surface of the liquid. The electrodes may be perforated to allow escape of the gas bubbles. The metals which are most electropositive, for example aluminium, are more suitable as electrodes than metals, for example copper or iron, which are more electronegative. It is also advantageous to use metals which yield to the liquid to be clarified constituents similar to those which are to be separated. The method of separating, particularly where aluminium electrodes are employed, may be carried out with alternating current, in one or both stages. Air or other gases may be introduced into the clarifying vessel through a dividing device, for example a clay cell, to form very fine gas bubbles. Gases produced at the anode such as chlorine, which are not desired in the clarified liquid, may be removed from the space between the anode and surrounding diaphragm. A magnetic field may be applied to the clarifying vessel to accelerate clarification.