Recovery of lithium from Urmia Lake by a nanostructure MnO2 ion sieve

The ion exchange process was employed to recover lithium from brine collected from Urmia Lake Iran, which contains saturated levels of Na, Mg, K and low Li (2.45 mmol·L^{- 1} or 17 mg·L^{- 1}). The high levels of these impurities in Urmia Lake would create difficulties during lithium processing if conventional techniques were used. To this end, the spinel-type MnO₂ nanorod, with the size about 40-90 nm in diameter and 150-900 nm in length, was first synthesized as a lithium ion sieve via a hydrothermal method. The lithium uptake capacity of this synthesized ion sieve reached to 9 mmol·g^{- 1}, which is the maximum value among the adsorbents studied to date. The crystalline structure, property and size of all products involving oxidizer, precursor and ion sieve are examined via powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Also the lithium selective adsorption property was investigated by measuring the distribution coefficients (K_d) of a series of alkaline and alkaline-earth metal ions, which is significant for lithium extraction from aqueous solutions with very low lithium content. Furthermore, the results show that the synthesized MnO₂ nanorods could be utilized in lithium extraction from Urmia Lake brine and other environments including sea water and waste water.