Preparation Of Lithium Ion Sieve Membrane And Study Of Its Application Preparation In Brine

Lithium is an extremely important energy metal element.The lithium resources of brine is rich in China.However,the many salt lake brine in China exhibits characteristically high Mg²⁺/Li+ ratio,which obstacle the efficient extraction of Li+.The H_1.6Mn_1.6O₄ is considered to be the most promising material for adsorbing Li+ from lithium containing brines.The ion-sieve adsorbent as the adsorption material shows high lithium adsorption capacity,good selectivity and stability properties.It is one of the most promising way from high Mg²⁺/Li+ ratio salt lake brine and seawater recover lithium.Its also has disadvantages,such as small particle size and easily lost in the actual operation.Therefore,it is necessary in ensuring its excellent adsorption performance of the premise,by forming means to widen the scope of the use.A new lithium ion sieve precursor Li_1.6Mn_1.6O₄ synthesized via hydrothermal-low temperature solidphase,after hydrochloric acid to elution afford lithium ion sieve H_1.6Mn_1.6O₄.The products were characterized,study of the adsorption and desorption performance by scanning electron microscopy?SEM?,x-ray powder diffraction?XRD?and atomic absorption spectroscopy?AAS?.The results showed that: lithium ion sieve precursor in hydrochloric acid concentration was 0.5 mol·L^-1,elution temperature was 30 ?,solid-liquid ratio was 500:1?mL/g?,elution time was 12 h,the lithium elution rate was more than 92% and manganese loss rate was <2.0%,the loss rate of Mn is lower.Lithium ion sieve lithium adsorpt Li+ in the first adsorption to reach 26.0 mg·g^-1 in 12 h,and maximum adsorption capacity up to 34.56 mg·g^-1.Five cycles adsorption–desorption test indicates that the lithium ion sieve adsorption capacity only loss 4.0%,the performance of a good stability.PAN-H_1.6Mn_1.6O₄ lithium ion-sieve membrane were prepared by blend of lithium ion sieve(H_1.6Mn_1.6O₄)with hydrophilic polymer poly?acrylonitrile??PAN?.The effects of adding amount of lithium ion sieve for PAN-H_1.6Mn_1.6O₄ membranes structure and Li+ adsorption-desorption properties were investigated by SEM,Li+ static adsorption experiments,?NH₄?₂S₂O₈ elution experiments and adsorption experiments in brine.Results showed that the adsorption capacity of PAN-H_1.6Mn_1.6O₄ membrane(17.45 mg·g^-1)achieves to 88.0% of H_1.6Mn_1.6O₄ powder when the concentration of PAN was 10 wt% and the amount of loading of H_1.6Mn_1.6O₄ was 50 wt%.In addition,?NH₄?₂S₂O₈ solution was used as eluent,the amount of lithium ion elution was 17.23 mg·g^-1 and the manganese loss of ratio was only 1.14% when the eluent concentration,liquid-solid ratio and time were 0.3 mol·L^-1,600: 1 and 12 h,respectively.The PAN-H_1.6Mn_1.6O₄ membrane show good selectivity for Li+ in Lop Nor brine which contain a lot of cations such as Na+,K+,Mg²⁺ and Ca²⁺.After ten time adsorption–desorption cycle experiments were investigated in brine,the adsorption capacity of lithium ion was lost only 6.0%(from 1_1.64 mg·g^-1 decrease to 10.94 mg·g^-1).Overall results demonstrate that use hydrophilic PAN carrier material has little effect on the adsorption capacity of H_1.6Mn_1.6O₄ for lithium ion,and mild eluent is conducive to chemical stability of lithium-ion sieve membrane.The spherical,hollow fiber membrane,electrostatic spinning membrane,and film-like plate PAN-H_1.6Mn_1.6O₄ adsorbent were prepared.By adsorption tests in different concentrations lithium solution,different temperatures,different time and five cycles.Results showed that PAN-H_1.6Mn_1.6O₄ hollow fiber membrane adsorbent has a maximum adsorption capacity.In homemade dynamic adsorption-desorption apparatus for dynamic experiments,when pressure is 0.05 MPa and the feed flow rate is 10 L·h^-1,the adsorption rates of hollow fiber membrane adsorber in lithium solution and artifical brine were 91.8% and 87.6%,respectively.In artificial brine,the single-stage lithium recovery rate was 86.2%,and the recovery tate of other ions is less than 0.5%,its can be well separate lithium from brine.