Recycling of red mud in iron-containing catalyst for oxidizing organic impurities in waste water

Red mud is a solid waste of the industrial process of natural bauxite processing in aluminum production by the Bayer method. Currently, there is no effective and profitable technology for industrial red mud processing, and most of it is placed for permanent storage in specialized sludge storage facilities, and therefore development of the recycling technologies for this man-made waste into functional materials for various purposes is extremely relevant, since it will allow both to use its potential raw material resource and to solve environmental problems. This paper presents the results of investigations of the red mud recycling possibility at the Bogoslovsky aluminum plant into an iron- containing catalyst for waste water purification with removal of organic impurities by their oxidizing destruction using hydrogen peroxide. Identification of the initial and obtained samples was carried out by methods of energy dispersive X-ray spectroscopy, scanning electron microscopy, low-temperature nitrogen adsorption, atomic absorption spectroscopy. It is shown that use of hydrochloric acid treatment of red mud with subsequent precipitation of dissolved compounds with ammonium carbonate and calcination of the precipitate allows to obtain the material with the iron content 55.17 wt. %. The sample has a developed specific surface area of 98.4 m2/g 2 /g and porosity of 0.174 cm3/g, 3 /g, and consists of particles having a shape close to spherical with an average size of about 0.2-0.3 mu m. The obtained material showed high catalytic activity and stability in the oxidation reaction of organic substances (on the example of the azo dye carmoisine) in an aqueous solution with hydrogen peroxide. The degree of discoloration of the dye solution during 30 minutes of contact was at least 94 % during 20 cycles of using the catalyst.