GB746615A - Process for producing chlorine dioxide and for disinfecting and purifying water - Google Patents

Abstract

Chlorine dioxide is produced by reacting a chlorite or chlorous acid with ozone in the presence of water. Chlorites may be sodium, potassium, magnesium, calcium, ammonium, or aluminium chlorites. The reaction may be effected by adding ozone-containing water to, or introducing ozone-containing gases into aqueous solutions or suspensions of chlorites or chlorous acid. Thus, a solution of 50-150 parts sodium chlorite in 200 parts water flows down a tower at not more than 30 DEG C., e.g. 15-25 DEG C., countercurrent to ozonized air. Alternatively, a paste, prepared by mixing a chlorite or chlorous acid, water, and an inert solid carrier, e.g. asbestos kieselguhr, silica gel, earthenware, aluminium oxide or sand, may be spread in thin layers on stoneware plates, and treated with ozonized air at not more than 28 DEG C. The reaction may be used in the disinfecting and purifying of water (see Groups I, VI).ALSO:The preparation of chlorine dioxide by reacting a chlorite or chlorous acid with ozone in the presence of water (see Group III) is applied to the disinfecting and purifying of water. Thus, water, which is being subjected, while flowing down a tower, to a countercurrent of ozonized air, e.g. 1-3 per cent ozone, has continuously added thereto a dilute or concentrated solution of a chlorite, e.g. sodium chlorite 0.05-5 per cent solution. The ozone destroys organic material and nitrite, and precipitates iron and manganese as oxides in the lower part of the tower. Unabsorbed ozone reacts in the upper part of the tower with the chlorite, which should be in amount stoichiometrically equivalent to the unabsorbed ozone so that no chlorite remains, to form chlorine dioxide. Alternatively, chlorine dioxide may be produced in a minor stream of water, e.g. ground or well water, by adding chlorite solution thereto and reacting with ozone, and the resulting chlorine dioxide-containing stream added to the bulk of the water, e.g. surface water.ALSO:The preparation of chlorine dioxide by reacting a chlorite or chlorous acid with ozone in the presence of water (see Group III) is applied to the disinfecting and purifying of water. Thus, water, which is being subjected, while flowing down a tower, to a countercurrent of ozonised air, e.g. 1-3 per cent ozone, has continuously added thereto a dilute or concentrated solution of a chlorite, e.g. sodium chlorite 0,05-5 per cent solution. The ozone destroys organic material and nitrite, and precipitates iron and manganese as oxides in the lower part of the tower. Unabsorbed ozone reacts in the upper part of the tower with the chlorite, which should be in amount stoichiometrically equivalent to the unabsorbed ozone so that no chlorite remains, to form chlorine dioxide. Alternatively, chlorine dioxide may be produced in a minor stream of water, e.g. ground or well water, by adding chlorite solution thereto and reacting with ozone, and the resulting chlorine dioxide-containing stream added to the bulk of the water, e.g. surface water.