Encapsulation of a powdery spinel-type Li+ ion sieve derived from biogenic manganese oxide in alginate beads

Granulation of Lithium-Ion Sieves Using Biopolymers: A Review

The high demand for lithium (Li) relates to clean, renewable storage devices and the advent of electric vehicles (EVs). The extraction of Li ions from aqueous media calls for efficient adsorbent materials with various characteristics, such as good adsorption capacity, good selectivity, easy isolation of the Li-loaded adsorbents, and good recovery of the adsorbed Li ions. The widespread use of metal-based adsorbent materials for Li ions extraction relates to various factors: (i) the ease of preparation via inexpensive and facile templation techniques, (ii) excellent selectivity for Li ions in a matrix, (iii) high recovery of the adsorbed ions, and (iv) good cycling performance of the adsorbents. However, the use of nano-sized metal-based Lithium-ion sieves (LISs) is limited due to challenges associated with isolating the loaded adsorbent material from the aqueous media. The adsorbent granulation process employing various binding agents (e.g., biopolymers, synthetic polymers, and inorganic materials) affords composite functional particles with modified morphological and surface properties that support easy isolation from the aqueous phase upon adsorption of Li ions. Biomaterials (e.g., chitosan, cellulose, alginate, and agar) are of particular interest because their structural diversity renders them amenable to coordination interactions with metal-based LISs to form three-dimensional bio-composite materials. The current review highlights recent progress in the use of biopolymer binding agents for the granulation of metal-based LISs, along with various crosslinking strategies employed to improve the mechanical stability of the granules. The study reviews the effects of granulation and crosslinking on adsorption capacity, selectivity, isolation, recovery, cycling performance, and the stability of the LISs. Adsorbent granulation using biopolymer binders has been reported to modify the uptake properties of the resulting composite materials to varying degrees in accordance with the surface and textural properties of the binding agent. The review further highlights the importance of granulation and crosslinking for improving the extraction process of Li ions from aqueous media. This review contributes to manifold areas related to industrial application of LISs, as follows: (1) to highlight recent progress in the granulation and crosslinking of metal-based adsorbents for Li ions recovery, (2) to highlight the advantages, challenges, and knowledge gaps of using biopolymer-based binders for granulation of LISs, and finally, (3) to catalyze further research interest into the use of biopolymer binders and various crosslinking strategies to engineer functional composite materials for application in Li extraction industry. Properly engineered extractants for Li ions are expected to offer various cost benefits in terms of capital expenditure, percent Li recovery, and reduced environmental footprint.

Synthesis of Polyporous Ion-Sieve and Its Application for Selective Recovery of Lithium from Geothermal Water

The widespread use of lithium-ion batteries has led to continuously increasing demands for lithium. In order to recover lithium from geothermal water, a novel composite lithium ion-sieve was synthesized and applied in this work. The stability of the material was successfully solved by granulating using acid-alkali resistant polyvinyl chloride as a binder, and its adsorption performances were also improved by using polyethylene glycol (PEG-6000) as a porogen to obtain a polyporous structure. When the developed material was applied for lithium separation from geothermal water, the adsorption capacity reached 12.84 mg/g at 328.15 K with an equilibrium time of about 12 h. The material can be well regenerated using 0.25 mol/L HCl to realize cycle use. The separation factors between Li⁺ and other co-existing ions were within the range of 273.58-521.28, and the attenuation of adsorption capacity after five cycles was no more than 2%. The high selectivity and reusability properties of the polyporous ion-sieve make the material a potential candidate for the selective separation and recovery of a low concentration of lithium from geothermal water.