Extraction of Al and K salts from associated alunite tailings by an acid calcination-water leaching method

An acid calcination-water leaching method was developed to treat associated alunite tailings due to their high mass fraction of potassium and aluminum and simple crystalline phase composition. When the tailings first are calcined at 300 °C by 30% H2SO4 solution with the liquid-solid ratio of 2:1 and then leached at 80 °C aqueous solution with the liquid-solid ratio of 10:1, the leaching efficiency of aluminum and potassium is 87.2% and 85.3%, respectively. Based on the crystallochemistry principle, a multi-step crystallization method was devised to separate potassium and aluminum salts preliminarily, and aluminum sulfate and alum crystal with high purity were obtained.