Whitening of bauxite tailings

The main waste product generated by bauxite flotation in China is aluminosilicate tailings. The dark color caused by high iron content limits the application of bauxite tailings in polymers. We developed a new method for whitening bauxite tailings by adding phosphoric acid. The whiteness of bauxite tailings was considerably improved from 19% to 73% with the addition of 17 g of 85% phosphoric acid and calcination at temperature 550 °C. XRD, EDS and FTIR analyses showed that the particles of the whitened bauxite tailings are coated with a mixture of phosphates and polyphosphates. The amount of the both increased with increasing phosphorus content. N2 adsorption analysis indicated that the surface area of the whitened bauxite tailings gradually decreased, whereas pore size expanded with increasing phosphorus content.