Abstract:

PAN-H_1.6Mn_1.6O₄ lithium ion-sieve membrane was 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 membrane structure and Li⁺ adsorption-desorption properties were investigated by SEM, Li⁺ static adsorption, (NH₄)₂S₂O₈ elution and adsorption experiments in brine. The results showed that the adsorption capacity of PAN-H_1.6Mn_1.6O₄ membrane (17.45 mg·g^-1) achieved to 88.0% of H_1.6Mn_1.6O₄ powder when the concentration of PAN was 10% (mass) and the amount of loading of H_1.6Mn_1.6O₄ was 50% (mass). In addition, when (NH₄)₂S₂O₈ solution was used as eluent with the eluent concentration, liquid-solid ratio and time of 0.3 mol·L^-1, 600:1 and 12 h, respectively, the amount of lithium ion elution was 17.23 mg·g^-1 and the manganese loss of ratio was only 1.14%. The PAN-H_1.6Mn_1.6O₄ membrane showed good selectivity for Li⁺ in Lop Nor brine containing other cations such as Na⁺, K⁺, Mg²⁺ and Ca²⁺. After ten times adsorption-desorption cycles in brine, the adsorption capacity of lithium ion was lost only 6.0% (from 11.64 mg·g^-1 to 10.94 mg·g^-1). Overall results demonstrated that using hydrophilic PAN carrier material had little effect on the adsorption capacity of H_1.6Mn_1.6O₄ for lithium ion, and the mild eluent was favorable to chemical stability of lithium-ion sieve membrane.

Key words: lithium ion-sieve, adsorption, poly(acrylonitrile), porous membrane, separation, recovery

摘要：

采用亲水的PAN为成膜材料，制备了掺杂H_1.6Mn_1.6O₄的PAN-H_1.6Mn_1.6O₄锂离子筛膜。通过SEM、Li⁺静态吸附实验、（NH₄）₂S₂O₈对锂的洗脱实验和卤水中吸附实验，研究了锂离子筛的添加量对PAN-H_1.6Mn_1.6O₄锂离子筛膜结构、Li⁺吸附-洗脱性能的影响。结果表明，PAN浓度为10%（质量），H_1.6Mn_1.6O₄的添加量为50%（质量）时，PAN-H_1.6Mn_1.6O₄离子筛膜的吸附量为17.45 mg·g^-1，达到粉末状吸附量的88.0%。以（NH₄）₂S₂O₈为洗脱剂，当浓度为0.3 mol·L^-1、液固比为600:1、时间为12 h时，锂洗脱量为17.23 mg·g^-1，锰溶损率仅为1.14%。在含有Na⁺、K⁺、Mg²⁺和Ca²⁺的罗布泊老卤卤水中，锂离子筛膜对Li⁺有很高的选择性。在卤水中进行10次吸附与解吸循环，吸附量从11.64 mg·g^-1下降到10.94 mg·g^-1，吸附容量仅损失6.0%。总体结果表明亲水性载体对H_1.6Mn_1.6O₄吸附容量影响较小，温和的洗脱剂对锂离子筛膜的化学稳定性有利。

关键词: 锂离子筛, 吸附, 聚丙烯腈, 多孔膜, 分离, 回收