Lithium salt solution purification is a very important link in the production of lithium carbonate / lithium hydroxide (to ensure that the impurity content meets the quality standard). It is usually necessary to remove impurities such as calcium, magnesium, silicon, boron and aluminum. At present, it is difficult to ensure effective and stable product quality by using the traditional precipitation method; With the development of membrane technology, membrane technology can solve the purification of the following products.