A rapid and efficient lithium-ion recovery from seawater with tripropyl-monoacetic acid calix[4]arene derivative employing droplet-based microreactor system

Abstract A rapid and efficient lithium-ion recovery from seawater established by employing calix[4]arene derivatives as extraction reagents in a microreactor system. A tripropyl-monoacetic acid derivative of calix[4]arene (1Ac) exhibited a very high extraction ability for lithium-ion within 2.00 s by using a microreactor system. The complete stripping of the lithium ions achieved with 1.0 M HCl as a stripping reagent. In a competitive metal system containing lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium and barium ions; lithium-ion selectively loaded on 1Ac. Further, lithium recovery from seawater was carried out without any pretreatment or pH adjustment in the three-step process. In the first step of the process, 1Ac extracted 100% lithium and 2.56% sodium ions from the seawater. Both lithium and sodium ions stripped with HCl in the second step and then sodium in the stripped solution selectively re-extracted with monopropyl-triacetic acid calix[4]arene derivative (3Ac) thus yielding pure lithium chloride in the aqueous phase. Both 1Ac and 3Ac calix[4]arene derivatives regenerated after the stripping process.