ABSTRACT
I. INTRODUCTION Most phosphate fertilizers currently produced worldwide contain P20 5 in a highly water-soluble form. These fertilizers are often derived from phosphoric acid. The phosphoric acid is obtained from the reaction of rock phosphate with sulfuric acid. After initial acidulation of rock phosphate, the unwanted solid reaction products, mainly phosphogypsum and silica, are separated off. The resulting dilute phosphoric acid is processed further into water-soluble phosphate salts. Roughly 40 million metric tons of P20 5 are consumed annually worldwide [1]. As a result, about 150 million tons of contaminated phosphogypsum are produced and washed and must be discharged annually [1].
