Facile and Efficient Removal of Tungsten Anions Using Lysine-Promoted Precipitation for Recycling High-Purity Tungsten

We present a facile method for tungsten ion removal using lysine for the development of an environmentally friendly and sustainable recycling technique. Lysine addition to the tungsten solution achieved 100% tungsten removal within 5 min, as a white lysine tungsten precipitate. Electrospray ionization mass spectrometry analyses of the tungsten and lysine mixed solutions showed that lysine promoted dehydration condensation reactions of anionic tungsten species such as HWO4- and W6O192- through the electrostatic interactions between positively charged lysine and negatively charged tungsten ions. Calcination of the lysine tungsten precipitate produced tungsten oxide powder of high purity (99.6%) because the lysine is completely decomposed. This facile and useful metal removal method can be used for polyoxometalates of other metals such as molybdenum, tantalum, and niobium.