Sodium “Activation” of Silano‐Phosphonate Modified Mesoporous TiO₂ Leading to Improved Rare‐Earth Element Extraction

Abstract

Due to their presence in most modern electronic devices and as waste products in the nuclear cycle, a great deal of interest has been generated in the acquisition and/or recycling/removal of rare-earth elements (REE). Here, we present a simple one-pot route for the preparation of dimethylphosphatoethyltriethoxysilane (SiP) functionalised mesoporous TiO 2 particles. The resistance of TiO 2 to strong bases allowed for the use of NaOH to "activate" the phosphonate head group of [a] 2268 the functionality, significantly improving its efficiency. Levels of 92.6 mg/g Ce 3+ were extracted from water, which is double the previously reported value for the extraction of REEs with this type of extractant. SiP-TiO 2 (Na) was also used to separate completely the Ce 3+ from aqueous solutions containing Sr 2+ and Cs + . Finally, the nanocomposite separated Ce 3+ from other homovalent REEs, for example, Yb 3+ (1:1.4 separation ratio).

Functionalization of mesoporous materials for lanthanide and actinide extraction

“…These moieties have been anchored through ( postsynthesis) grafting strategies onto several solid-phase supports, such as ordered mesoporous silica materials (e.g., KIT-6, SBA-15, MCM-41), 16a,38,42,126,148-152 silica microspheres, 44 silica nanoparticles, 149,153 monoliths 45 or metal oxide particles (e.g., Fe 3 O 4 , TiO 2 ). 154,155 Fewer attempts have been performed on carbon-based supports, such as mesoporous carbon 156 or graphene oxide. 157,158 Some researchers have also studied the application of simple un-functionalized or oxidized-only supports; however, both types of sorbents usually lack the required selectivity for REE separation/purification or showed insufficient analyte uptake.…”

“…Although phosphorus-based ligands are mostly used for Ac extraction as described previously, their role as efficient chelates for REEs has also been widely explored. 42,151,154,159,160 These ligands are used principally in the final purification step, where the individual metals are isolated from a mixture of elements. Several organophosphorus ligands were reported in the literature and demonstrated good sorption behavior.…”

Gd3+ Adsorption over Carboxylic- and Amino-Group Dual-Functionalized UiO-66

“…This method also allows recovery from low-concentration sources of REEs . To this end, different kinds of adsorbents have been tested for separation of REEs, including porous silica-based materials, , carbons, , metal oxides, , polymers, and metal–organic frameworks (MOFs). − Among these, MOFs composed of metal or metal oxide clusters linked by organic ligands are promising for a broad range of adsorption applications, owing to their high porosity and tunable surface functionality. − …”

Efficient adsorption and separation of dysprosium from NdFeB magnets in an acidic system by ion imprinted mesoporous silica sealed in a dialysis bag

“…Up to now, several approaches have been reported for separation and recovery of REEs from NdFeB leaching aqueous media including coprecipitation (co-ppt), 8,9 liquid-liquid extraction (LLE), [10][11][12][13][14] and solid-liquid extraction (SLE). 15,16 LLE strategies have already been used for industrial separation and recovery in hydrometallurgy widely as they achieve acceptable enrichment needed by multiple extraction steps. With the recent development of the area of ionic liquids, solvent extraction has received extensive attention.…”