Method for the processing of potassium containing materials

A method for the processing of potassium containing materials, the method comprising the steps of:

• (i) passing a potassium containing material to a first separation step in which a potassium containing mineral is separated from gangue minerals present;
• (ii) leaching the potassium containing mineral in acid in a leach step whereby substantially all potassium, iron, aluminium and magnesium present is solubilised and a mixed potassium/iron double salt formed;
• (iii) selectively crystallising the mixed potassium/iron double salt formed in the leach of step (ii) in a crystallisation step;
• (iv) passing a liquor from the crystallising step (iii) to a second separation step to separate the mixed potassium/iron double salt formed in step (iii);
• (v) passing the double salt to a thermal decomposition step to produce an iron oxide, a potassium salt and one or more phosphates;
• (vi) leaching the product of the thermal decomposition step;
• (vii) passing a leach liquor from step (vi) to a third separation step to separate the iron oxide and phosphates from the potassium salt;
• (viii) recovering the potassium salt by crystallisation;
• (ix) separating the iron oxide and phosphate of step (vii) by leaching and subsequent solid liquid separation;
• and
• (x) precipitating phosphate from a liquor produced in step (ix) through the addition of a base thereto.