Separation of Magnesium and Lithium from Brine Water and Bittern Using Sodium Silicate Precipitation Agent

Potential natural resources of lithium in Indonesia from brine water and bittern generally have low lithium and high magnesium levels, which need to be separated before further extraction. This research investigates the separation process of magnesium from brine water and bittern using a sodium silicate solution. The experimental results showed that the magnesium precipitation efficiency using sodium silicate was better in brine water than in bittern. A separation selectivity ratio of magnesium to lithium (Mg/Li) below 1 was obtained in brine water of 0.59 and bittern of 0.11 with the addition of a 1.25 mole fraction of sodium silicate solution to magnesium ions. After the precipitation at optimum addition of sodium silicate and water leaching process using distilled water, lithium’s recovery in the brine water and bittern filtrate was 84% and 35%, respectively. In brine water, water leaching increased lithium and magnesium ions in the filtrate. However, in bittern, the water leaching increased lithium recovery without dissolving magnesium ions into the filtrate. The precipitation products from the bittern were identified as complex lithium compounds in the forms of Li₂MgO₄SiLi₂(MgSiO₄) and LiMg₄Na₃O₃₀Si₁₂ phases, while the precipitation products in brine water mostly had a phase of CaO·MgO·Si₂O₅ (Diopside) and LiCl.