CLEAN ION-EXCHANGE TECHNOLOGIES - I - SYNTHESIS OF CHLORINE-FREE POTASSIUM FERTILIZERS BY AN ION-EXCHANGE ISOTHERMAL SUPERSATURATION TECHNIQUE

This paper reports the results of studying ion-exchange synthesis of c hlorine-free potassium sulfate from KCl and Na2SO4 on strong acid cati on-exchange and strong base anion-exchange resins using an ion-exchang e isothermal supersaturation (MISS) effect. This effect is observed fo r a number of ion-exchange systems, where the ion-exchange process is accompanied by the formation of a stable supersaturated solution of sl ightly or sparingly soluble substances in the interstitial space of io n-exchange columns. The formation of stable K2SO4 solutions in the col umns has been observed by the displacement of either K+ or SO42- ions from a cation or anion exchanger with concentrated Na2SO4 or KCl solut ions, respectively. After leaving the column, a supersaturated solutio n crystallizes spontaneously, which allows for the design of a practic ally ideal ion-exchange process where a crystalline chlorine-free pota ssium sulfate is obtained right after the ion-exchange conversion cycl e. The process is practically wasteless and ecologically clean; hence, it can be considered as a competitive alternative to existing K2SO4 p roduction technologies based on, e.g., the Mannheim process. The flow sheet of a proposed process is presented and discussed.