Study On The Mg²⁺/Li⁺ Separation In Salt Lake Brine By Nanofiltration

Lithium is an important energy metal element and is rich in China, which mainly distribute in the provinces of Qinghai and Tibet. Currently, most lithium production research has emphasized recovery from brine sources. However, the salt lake brine in Qinghai exhibits characteristically high Mg2+/Li+ ratio, which renders difficult the efficient extraction of Li.The membrane separation technique is a new separation method blooming in the 21 th century. It have been widely applied to the water treatment field, such as sea water desalination and wastewater purification. The nanofiltration membrane is able to make monovalent ions pass through and divalent ions rejected, and owns high permeation flux under low pressure. These features will contribute to solving the gordiantechnology of Mg2+/Li+ separation in the salt lake brine owning high Mg2+/Li+ ratio.This paper aims at the key issues of Mg2+/Li+separation for salt lake brine’s comprehensive exploitation. The craftwork of extraction of lithium from brine by nanofiltration was researched. The outcomes as follows:(1) The experimental data of nanofiltration by different commercial membrane elements was obtained, and the suitable membrane element for brines’ nanofiltration was selected.(2) The nanofiltration of brine owning different compositions was operated. The feasibility of separating Mg2+/Li+ by nanofiltration was proved, and the suitable raw material for nanofiltration was found.(3) The affecting factors of nanofiltration was investigated, and the optimum operating conditions were acquired.(4) The mechanism of Mg2+/Li+separation in nanofiltration was described on the base of current theory and experimental data.The craftwork researched was applied to experiment of extraction of lithium from salt lake brine. The lithium-riched permeate could be basically satisfied with the economic requirements. Based on brief flow, easy operating and non-pollution, the craftwork will provide important references for comprehensive exploitation of salt lake brine.