Crown-Ether Functionalized Graphene Oxide Membrane for Lithium Recovery from Water

Abstract

The massive worldwide transition of the transport sector to electric vehicles has dramatically increased the demand for lithium. Lithium recovery by means of ion sieves or supramolecular chemistry has been extensively studied in recent years as a viable alternative approach to the most common extraction processes. Graphene oxide (GO) has also already been proven to be an excellent candidate for water treatment and other membrane related applications. Herein, a nanocomposite 12-crown-4-ether functionalized GO membrane for lithium recovery by means of pressure filtration is proposed. GO flakes were via carbodiimide esterification, then a polymeric binder was added to improve the mechanical properties. The membrane was then obtained and tested on a polymeric support in a dead-end pressure setup under nitrogen gas to speed up the lithium recovery. Morphological and physico-chemical characterizations were carried out using pristine GO and functionalized GO membranes for comparison with the nanocomposite. The lithium selectivity was proven by both the conductance and ICP mass measurements on different sets of feed and stripping solutions filtrated (LiCl/HCl and other chloride salts/HCl). The membrane proposed showed promising properties in low concentrated solutions (7 mgLi/L) with an average lithium uptake of 5 mgLi/g in under half an hour of filtration time.

Tailoring Monovalent Ion Sieving in Graphene-Oxide Membranes with High Flux by Rationally Intercalating Crown Ethers

“…As shown in Figure a, we introduce various types of CEs as an intercalator into the GO laminates to acquire precise recognition of a certain monovalent ion and at the same time to enhance water/ion flux. Three types of CEs were chosen, including 12-C-4, 15-C-5, and 18-C-6, which selectively bind Li + , Na + , and K + , respectively. − Based on the host–guest coordination chemistry, , when the size of ions and CE are matched, the CEs open the most and hold the metal ions at the center of the ether ring, and the binding effect is strong and therefore has good stereoselectivity, manifested by size-matching rule. ,− …”

“…Due to the strong complexation of crown ethers (CEs) to metal ions, they are widely used for ion adsorption or separation. Although CE-functionalized GO has been previously reported, it is mainly used in a nanoporous manner and rarely in stacked morphology. , Furthermore, in a stacked membrane, it is more often used as an absorbent for solvent–solute (such as water-solute) separation and Li/Mg extraction, , while the solute–solute selectivity, especially between monovalent ions by the dual regulation of membrane structure and affinity, was ignored.…”

The “How” and “Where” Behind the Functionalization of Graphene Oxide by Thiol‐ene “Click” Chemistry

“…Hence, the simplest approach consists of performing the reaction by heating while combining GO and the respective amine, and as consequence the amidation proceeds by condensation reaction with a water molecule as a second product. Alternatively, the activation of carboxylic acids can be assisted by carbodiimides at room temperature as illustrated in Figure 2, III [8,20,32b] . Here, the functionalization of carboxylic acids is enhanced under mild conditions, but the orthogonality can still be questioned due to possible nucleophilic attack towards epoxides (Figure 2, IV).…”

“…Indeed, in recent years some efforts have been paid in order to develop orthogonal functionalizations. Some attempts involving Williamson reaction, [16] amine‐Michael addition, [17] thiol‐ene Michael addition, [18] carboxylation on hydroxyl groups, [19] and carbodiimide chemistry, [20] resulted in significant advancements in the selective functionalization of GO. Nonetheless, the functionalized GO can still be questioned since the reaction conditions, type of catalyst and the molecules used can conduct to more than one product, especially when polymers are used to functionalize GO.…”

Recent Advances in the Lithium Recovery from Water Resources: From Passive to Electrochemical Methods

“…In the first case, its use is mostly motivated by its ionic and molecular ion sieve properties related to its porosity and layered structure. [210] Its use as additive is instead generally used to improve antifouling properties, hydrophilicity and mechanical properties of the matrix. [211,212] The most common polymers added to GO to form membranes are PVDF, polyethersulfone, and PVA.…”