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.