Removal of Fe3+ and Al3+ ions from phosphoric acid–nitric acid solutions with chelating resins

Abstract

Fe3+ and Al3+ ions existed in phosphoric acid–nitric acid solutions are very troublesome for the neutralization process of nitrophosphate (NP) fertilizer. This paper studied the performances of three chelating resins (S957, S950 and S930) on the removal of Fe3+ and Al3+ ions from phosphoric acid–nitric acid solutions, and one strong acid cation resin (001×7) was also studied for comparison. The batch adsorption equilibrium of Fe3+ ion and Al3+ ion on four resins and the effects of phosphoric acid and nitric acid concentrations on the separation characteristics of four resins were firstly investigated. After that, the dynamic adsorption and elution processes through the fixed bed column were carried out. The batch adsorption results reveal that S957 and 001×7 resins present the higher adsorption ability to Fe3+ ion and Al3+ ion in pure water. But in phosphoric acid–nitric acid solutions, the adsorption ability of S957 and S950 resins is better for the removal of Fe3+ ion and Al3+ ion, whereas 001×7 and S930 resins present very low or even no adsorption ability. The dynamic adsorption and elution processes show that S957 resin is more suitable for the further dynamic operation in view of the recyclability of separation process, while S950 resin expresses poor regeneration performance. Moreover, the coexistent Ca2+ and Mg2+ ions in phosphoric acid–nitric acid solutions have little influence on the removal of Fe3+ and Al3+ ions through the fixed bed S957 resin column. All results demonstrate that S957 resin is capable of removing the Fe3+ and Al3+ ions from phosphoric acid–nitric acid solutions.