The Process Research Of Lithium Absorption From Brineand Production Of Lithium Carbonate

Abstract:Because of the rapid development of lithium ion battery, nuclear energy and Mg-Li alloys, the demand of lithium as raw material and fuel of these industries is increasing. With the shortage of high grade lithium containing minerals, the exploitation of lithiumin brine has become a focused topic. China is one of the most rich country in salt lake resources and the recoverable reserve of lithium is very huge. At present, the separation of magnesium and lithium in salt lake containing high magnesium-lithium ratio is a key technical problem in the development of salt lake brine. A new process was proposed to extract lithium from Xinjiang Lop Norsalt lake brine including absorption of lithium ions using granular-type lithium ion-sieve adsorbent and manufacture of lithium carbonate using sodium carbonate.The adsorption of lithium in solution was studied by static adsorption experiments. There are the effects we considered including the initial lithium concentration, pH, temperature, reaction time, cycle time and other ions. The results showed that pH had a great impact on adsorption. After3hours, the absorption capacity reached to5.8mg/g at the conditions of initial lithium concentration260mg/L, pH=12. The value declined to5.4mg/g after20loops. Based on the standpoints of thermodynamics and kinetics, the sorption of lithium ions involves a number of mechanisms:film and intraparticle transport both are controlling steps of the sorption behavior. And the sorption of lithium on CSU-200is chemical adsorption.The dynamic adsorption process of lithium in brine on fixed bed was studied. The optimum process conditions were obtained as follows: temperature was above25℃, dilution ratio of brine was1.25, adsorption time was9h.The absorption capacity in brine was3.8mg/g. The volume of hydrochloric acid in pickling experiment was determined by lithium absorption capacity. The extractability of lithium was up to98%and manganese loss in CSU-200was less than0.2%in the first2h.The concentration of Mg2+in pickling solution was between 0.7-0.9g/L, which should be removed before producing lithium carbonate. The depositing magnesium with sodium hydroxide was optimized by single-factor and orthogonal experiments. The optimum process conditions were obtained as follows:concentration of NaOH was10mol/L, feeding speed lOmL/min, reaction temperature60℃,reacting time40min, and the amount of water for washing equal to the weight of wet filter cake. Under such conditions, magnesium was removed completely and the lithium loss was less than0.5%.The optimum process conditions for producing lithium carbonate were obtained by single-factor and orthogonal experiments. In solution with Li+concentration above20g/L, reaction temperature was90℃, balance time60min, sodium carbonate consumption0.1times more than the theoretical value, aging time8h, the amount of water for washing was twice the weight of wet filter cake. Under such conditions, lithium recovery rate was90%, and the purity of product was up to the first level of national industrial standard.The pilot scale experiment was achieved on the basis of lab experiment. The technical and economical feasibility of lithium adsorption onto CSU-200in brine has been approved by the results of a pilot plant experiment, although the adsorption properties of CSU-200manufactured by larger scale were poorer than that of lab experiment. This paper has50figures,23tables and82references.