Liquid–liquid extraction of neodymium using a mixture of D2EHPA and TBP from acidic sulfate solutions

Liquid–liquid extraction of neodymium from sulfate solutions has been studied. The effect of different parameters on the extraction recovery such as type of extraction, extractant concentration, diluent type, pH, time and aqueous/organic phase ratio has been investigated. A mixture of di(2-ethylhexyl) phosphoric acid (D2EHPA) and tri-n-butyl phosphate (TBP) in kerosene achieved a neodymium extraction recovery of over 80%. pH has a great influence on the extraction recovery of neodymium in sulfate solutions. At a pH below 1, the mixture of D2EHPA and TBP exhibited very low efficiency for the extraction of neodymium from sulfate solutions.The optimum extraction conditions as follow: extraction solvent type and concentration: D2EHPA (15%) + TBP (5%) + 80% kerosene; pH 3.5; extraction time 10 min and at an aqueous to organic phase ratio of 0.75.Furthermore, the stripping experiments indicated that a 3.0 M nitric acid (HNO₃) solution provided the optimum conditions for neodymium recovery, achieving complete stripping within 10 minutes.