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 (Kd) 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.