Research on the removal process and mechanism of aluminum/iron impurities from wet phosphoric acid through deep extraction
The presence of impurities in phosphoric acid hinders its application in downstream processes.The development of wet-process phosphoric acid deep purification technology enables the direct preparation of phosphate-based new energy materials through a simplified process,which represents the mainstream direction for industry advancement.The solvent extraction method was employed for the extraction and separation of Al and Fe impurities in wet-process phosphoric acid.The effects of different extractants,temperature,O/A ratio,time,and extractant content on the separation efficiency of Al and Fe impurities were investigated.Optimal conditions were determined as follows:N,N-N-octyl amine di(methylene phenylphosphonic acid)(OADMPPA)extractant,extractant content of 20wt％,time of 3 min,temperature at 25℃,O/A ratio of 1∶1 and 3-stage cross-flow extraction.Under these conditions,the extraction rates for Al and Fe reached 54.5％and 99.6％.Consequently,the contents of Al and Fe impurities in phosphoric acid decreased from 0.857wt％and 0.175wt％to 0.717wt％and 0.015wt％.Additionally,the MER value reduced from 9.037％to 7.227％.Further optimization of stripping process of OADMPPA extractant loaded with Al and Fe was carried out,ammonium oxalate was identified as the optimal stripping agent.The optimized stripping conditions were as follows:25℃,5-stage cross-flow stripping,O/A ratio of 2∶1,time of 15 min,and concentration of the stripping agent at 0.2 mol/L;the stripping efficiencies for loaded extractant Al and Fe reached 96.4％and 88.3％,effectively achieving their separation from the extractant phase.Finally,the mechanism behind Al or Fe extractants was investigated by stoichiometric calculation and Fourier infrared analysis during the extraction process.It was found that during this process,one molecule of Al combined with one-and-a-half molecules of OADMPPA extractant while one molecule of Fe combined with two molecules of OADMPPA extractant;functional groups involved in these interactions included P=O and P-O-H bonds.A competitive mechanism exists in the extraction process between Al and Fe,where Fe is more easily extracted.
wet-process phosphoric acidaluminum and iron impuritiesextractionstrippingmechanism
万方数据
维普
