China Nonferrous Metallurgy

A large amount of red mud is produced in the process of alumina smelting. The high alkalinity of red mud restricts its large-scale consumption and application. In this paper, the alkali removal test of red mud was carried out with waste acid of activated clay. The effects of leaching temperature, leaching time, solid-liquid ratio and stirring speed on the removal rate of sodium oxide from red mud were investigated, and the composition, particle size and phase of red mud before and after acid leaching were analyzed. The following conclusions were drawn: the better conditions for alkali removal of red mud are temperature 55℃, time 2h, solid-liquid ratio 150g/L, stirring speed 260r/min, addition of waste acid of activated clay per unit of red mud 00022mol. Under this condition, the removal rate of sodium oxide in red mud is more than 90%, the content of sodium oxide in red mud after leaching is 046%, and the scale consumption of composite red mud is required; after acid leaching, the red mud has coarsened particle size, smooth surface, reduced voids, disappeared sodium silicon slag phase, and clavicular gypsum crystals are formed when the acid is excessive. The dealkalized red mud can be used to prepare cement, silicon calcium sulfur magnesium fertilizer, soil improver, etc. The process simultaneously treats two kinds of hazardous wastes, namely waste acid of activated clay and red mud, and achieves the goal of treating wastes with wastes.