基材亲疏水性能对EVOH/LIS复合吸附剂成型结构及提锂性能的影响

Effects of Hydrophilic/Hydrophobic Properties of Substrate on Molding Structure and Lithium Extraction Performance of EVOH/LIS Composite Adsorbent

以锂离子筛H_(1.6)Mn_(1.6)O_(4)(LIS)为吸附剂,乙烯-乙烯醇共聚物(EVOH)为成型基材,制备乙烯-乙烯醇/锂离子筛(LIS)中空纤维膜状复合吸附剂(EVOH/LIS)。改变EVOH中乙烯基的含量调控成型材料的亲疏水性,研究基材亲疏水性对复合吸附剂成型结构、LIS负载量和吸附提锂性能的影响。结果表明,成型材料亲水性越强,复合吸附剂具有越高的孔隙率,LIS分散越均匀。另外,成型材料亲水性对LIS的添加量也具有一定的影响,EVOH-32为成型基材时,LIS的最大添加量为30%(质量分数);EVOH-38和EVOH-44为成型基材时,LIS的最大添加量则为50%(质量分数)。此外,成型材料亲水性显著提高了复合吸附剂对Li^(+)的吸附能力、吸附速率和吸附-解吸循环稳定性,其中EVOH-32/LIS-30在循环吸附五次后,吸附容量仍保持为初始吸附量的95.8%,具有良好的吸附稳定性。以适宜亲水性的EVOH-38为基材制备EVOH-38/LIS-50中空纤维膜状复合吸附剂,其对Li+的吸附量为29.6 mg·g^(-1)(为粉体LIS的93.9%),在锂镁比高于400的模拟卤水中αLi Mg高达559.5,表明该复合吸附剂能够用于高镁锂比卤水中提锂。

The lithium ion sieve H_(1.6)Mn_(1.6)O_(4)(LIS) was used as the adsorbent and the ethylene-vinyl alcohol copolymer(EVOH)was used as the molding substrate to prepare the ethylene-vinyl alcohol/lithium ion sieve(LIS)hollow fiber membrane composite adsorbent.The content of vinyl in EVOH was changed to control the hydrophilicity of the molding material.The effect of the hydrophilicity of the substrate on the molding structure,LIS loading and lithium extraction performance was studied.The results showed that the stronger the hydrophilicity of the molding material,the higher the porosity of the composite adsorbent and the more uniform dispersion of LIS.On the other hand,the hydrophilicity of molding material also had a certain influence on the addition amount of LIS.The maximum content of LIS in composite adsorbent was 30wt%when EVOH-32 is molding material.However,the maximum content of LIS in composite adsorbent was 50wt%when EVOH-38 and EVOH-44 were molding material.In addition,the hydrophilicity of the molding material significantly improved the Li^(+)adsorption capacity,adsorption rate and adsorption-desorption cycle stability of composite adsorbent.Among them,the adsorption capacity of EVOH-32/LIS-30 composite adsorbent remained at 95.8%of the initial Li+adsorption capacity after cyclic adsorption for 5 times,showing good adsorption stability.Finally,the suitable hydrophilic EVOH-38 was selected as molding material to prepare the EVOH-38/LIS-50 hollow fiber membrane composite adsorbent,whose adsorption capacity for Li+was 29.6 mg·g^(-1)(93.9%of the adsorption capacity of LIS powder).In the simulated brine with a lithium magnesium ratio higher than 400,theαLi Mg was as high as 559.5,indicating that the composite adsorbent could be used to extract lithium in the brine with a high magnesium lithium ratio.