Synthesis of Modified 12-Crown-4-Ether Moieties Grafted on Asphalt Derived Mesoporous Carbons for the Selective Adsorption of Lithium ions from Brine.

Lithium is a very important metal, which has broad applications and one of the most extensively used in batteries. The main resources of Li are salt lake brine, geothermal brines, seawater, and pegmatite. According to existing literature, around 70% of lithium resources are abundant in salt brine and the rest are other alkaline metals such Na, K, Mg, and Ca ions. Therefore, developing an efficient, effective, fast, and low-cost method is the need of the hour for the selective adsorption and removal of lithium ions from other ions present in brine. Numerous techniques have been reported to isolated lithium ions from brine, namely precipitation, ion exchange, solvent extraction, membrane separation, and adsorption. Among these methods, adsorption was found to be an effective, efficient, low-cost, and environmental-friendly technique for the selective removal of lithium ions from an aqueous solution. Several metallic, non-metallic, metal-nonmetal composites and membranes have been reported and used for the separation of lithium ions. However, our focus of the study is to use Crown ethers (CEs) for the selective removal of lithium ions from the brine. CEs are series of macrocyclic ligands containing repeated units of an ethylene oxide (CH2CH2O)n ring. The size of CEs have special binding abilities for the specific alkali metals ions such as 18-crown-6 ether has a high affinity for K+, 15-crown-5 ether for Na+, and 12- crown-4 ether for Li+. However, free crown ethers are hazardous and difficult to be extracted. Therefore, our study will explore chemical route(s) to graft 12- crown-4 ether on mesoporous carbons derived from asphalt for the selective removal of Li+ from brine water