Extraction of Fe3+ from sodium dihydrogen phosphate with colloidal liquid aphrons

The preparation of fine phosphoric products, for example sodium dihydrogen phosphate (NaH2PO4) from wet-process phosphoric acid (WPA), has been gaining interest in recent years. However, there are some undesirable impurities (Fe3+, Al3+ and Mg2+) in WPA, which will degrade the quality of the phosphoric products. Enhancing the pH of the solution, often to 4-4.5, can remove most of the metal ions, but the presence of some metal ions such as Fe3+ has great impact on the crystallization of the NaH2PO4. Therefore, in order to get industrial grade NaH2PO4 products, the neutralized NaH2PO4 solution should be purified. The extraction of Fe3+ from NaH2PO4 solution with colloidal liquid aphrons (CLAs) was investigated. The good extraction efficiency of Fe3+ with CLAs was verified. Meanwhile, to study the advantages of the CLAs process, the major influencing factors on the extraction efficiency for Fe3+ were investigated, and the optimal influencing factors for removal of Fe3+ with CLAs were presented. The results of the extraction experiments from practical NaH2PO4 solution: show that superior grade NaH2PO4 can be obtained by three cross-flow extractions under the appropriate conditions.