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

Abstract

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 W6O19 2– 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.

Simple, Rapid, and Environmentally Friendly Method for Selectively Recovering Tantalum by Guanidine-Assisted Precipitation

“…As the guanidine concentration increased, the final Ta ion concentration decreased and a larger quantity of white precipitate formed (Figure a,b), indicating that the decrease in the Ta ion concentration was directly related to the Ta recovery. Similar results were found in our previous study of W recovery . The Ta formed a stable hexatantalate anion [Ta 6 O 19 ] 8– in a highly basic solution, similar to what was found for W. This suggests that [Ta 6 O 19 ] 8– is highly deprotonated. , Guanidine is very basic (p K a of 13.6) and was present as [H 2 NC­(NH 2 ) 2 ] + . , The acidity of [Ta 6 O 19 ] 8– and basicity of [H 2 NC­(NH 2 ) 2 ] + will mean that [Ta 6 O 19 ] 8– and [H 2 NC­(NH 2 ) 2 ] + mainly interact electrostatically.…”

“…W can form stable hexametalate ions, [W 6 O 19 ] 8– , in the presence of other metal ions . The formation of such polyanions will be preceded by the formation of HWO 4 – ions . However, the formation of these ions would not be promoted at pH 13.2, which was the pH used in this experiment.…”

Effects of cerium and tungsten substitution on antiviral and antibacterial properties of lanthanum molybdate

“…Several reports have described adsorption or interaction between Mo or W ion (strictly speaking, poly type anions of molybdate (MoO 4 2− ) or tungstate (WO 4 2− ) ions) and lysine under different pH [ [41] , [42] , [43] ]. The adsorption amount of Mo and W polyacids to lysine depends on the lysine–metal ratio.…”

“…The adsorption amount of Mo and W polyacids to lysine depends on the lysine–metal ratio. The adsorption amount of W exceeds that of Mo when the ratio becomes higher than a certain value [ 43 ]. This ratio might engender antiviral activity difference between WO 3 and MoO 3 in dissolved ion contact method.…”

Controllable Synthesis of h-WO3 Nanoflakes by L-lysine Assisted Hydrothermal Route and Electrochemical Characterization of Nanoflakes Modified Glassy Carbon Electrode

“…Prior to the hydrothermal treatment, when the pH of the reaction solution was reduced to ~1.0, tungstate ion undergoes dehydration by H + ions, followed by condensation to form [W10O32] 4polytungstate ions [31,32] as shown in equation (1). At this pH, L-lysine is positively charged in the reaction solution because its acid dissociation constant (pKa COOH) is 2.2 [33] . L-lysine therefore serves as a counter cation to [W10O32] 4ion in the reaction solution.…”