Task-Specific Ionic Liquids as Extractants for the Solvent Extraction of Molybdenum(VI) from Aqueous Solution Using Different Commercial Ionic Liquids as Diluents

Abstract

In this work, the recovery of molybdenum­(VI) (Mo) from aqueous solutions was carried out by solvent extraction (SX) using ammonium and phosphonium-based task-specific ionic liquids (TSILs) as extractants diluted in kerosene and two other hydrophobic room-temperature ionic liquids (RTILs). Four different TSILs were used as extractants: trioctylmethylammonium bis­(2-ethylhexyl) phosphate [TOMA]­[D2EHP]; trioctylmethylammonium benzoate [TOMA]­[BA]; trihexyltetradecylphosphonium bis­(2-ethylhexyl) phosphate [P6,6,6,14]­[D2EHP]; and trihexyltetradecylphosphonium benzoate [P6,6,6,14]­[BA]. These TSILs were synthesized to assess the effect of the cation and anion on the SX of Mo­(VI). Experimental results indicated that high extraction percentages of Mo­(VI) were obtained with all the synthesized TSILs. Besides that, the best cation was [TOMA]+ for all the diluents and [BA]− was the best anion when kerosene and 1-octyl-3-methylimidazolium bis­(trifluoromethylsulfonyl)­imide, [omim]­[Tf2N], were the diluents. Furthermore, the SX process using these ionic liquids followed an anion-exchange mechanism for kerosene and [omim]­[Tf2N] as diluents. Finally, the stripping was successfully performed with a solution of ammonium carbonate, and the extent of stripping depended on the selected diluent.

Ionic Liquids as Components of Systems for Metal Extraction

“…Furthermore, a problem associated with the use of ILs as extractants is their high viscosity; therefore, they are dissolved in molecular solvents. This approach allows for producing highly efficient extraction systems for the recovery of indium(III) and gold(III) from electronic waste [21,22] and Mo(VI) in high (more than 99%) yields [23].…”

Rhenium(VII) extraction from sulfuric aqueous solutions using ionic liquids as diluent and extractant: insights on the extraction stoichiometry and process parameters

“…Recent works have proposed ILs as extractants, where the most important achievement is that high extraction percentages were reported with only a small concentration of them in a diluent, 14,15 when compared to conventional extractants. In this sense, in previous works, the IL trioctylmethylammonium benzoate [TOMA][BA] has been introduced as an extractant, for Mo(VI) extraction, showing high extraction percentages (90–100%) at low pH values and with a small amount of this extractant (1% v/v) 14 . A recent work showed that the IL tricaprylmethylammonium nitrate ([A336][NO 3 ]) extracted negatively charged vanadium, V(V), species ( or ) from acid solutions 16 .…”

“…In this sense, in previous works, the IL trioctylmethylammonium benzoate [TOMA][BA] has been introduced as an extractant, for Mo(VI) extraction, showing high extraction percentages (90-100%) at low pH values and with a small amount of this extractant (1% v/v). 14 A recent work showed that the IL tricaprylmethylammonium nitrate ([A336][NO 3 ]) extracted negatively charged vanadium, V(V), species (V 4 O −4 12 or V 3 O −3 9 ) from acid solutions. 16 This latter IL contains a similar cation to the proposed in this work, which allows extraction of the V(V) species, demonstrating that [TOMA] − could extract anionic species of Re(VII) present in a wide range of pH values in a sulfuric acid medium.…”

Environmentally Friendly Extraction and Recovery of Cobalt from Simulated Solution of Spent Ternary Lithium Batteries Using the Novel Ionic Liquids of [C8H17NH2][Cyanex 272]

“…The above research can realize the selective separation of Co 2+ and the recovery of Co 2+ products by stripping, 18 but there are two problems in the extraction process: (1) the extraction system composed of kerosene and organic extractant is easy to volatilize due to its relatively high saturated vapor pressure, 40 which is easy to cause damage to the operator's body and environment. 41 (2) The extraction system easily accumulates static electricity due to low conductivity, and a large number of volatile solvents is used in the separation process.…”