Leaching and concentration of P and K from P-K associated ore by using a sequential leaching process with leachate recycling

The concentrations of P and K in leaching solution are relatively low and the consumption of acid is relatively large, which are the existing problems in the leaching of P and K from P-K associated ore by using the low-temperature acid leaching process. In this work, a sequential leaching process with leachate recycling was developed, in which P and K were sequentially leached out from P-K associated ore and the obtained P- and K-containing leachates were recycled into the next leaching process. In this sequential process with leachate recycled two times the concentrations of K and P2O5 in leachate were increased from 20.18 and 15.79 g/L to 53.26 and 45.97 g/L, respectively. In comparison, in the simultaneous leaching process with leachate recycling both the leaching efficiencies of K and P and the concentrations of K and P2O5 were significantly lower than those in the sequential leaching process, which can be mainly attributed to the fact that Ca in the ore, which could react with PO43- to generate Ca-containing sediments, was precipitated first in the sequential leaching process. The sequential leaching process with leachate recycling will provide an efficient method for leaching and concentrating P and K from P-K associated ore.