Abstract: Spherical Li₄Mn₅O₁₂ ion-sieve precusor with particle diameter about 2—3 mm was prepared with the Li₄Mn₅O₁₂ ultrafine powder synthesized by the authors' lab and the agarose granulation process. Agarose was dissolved in deionized water at 90℃. The Li₄Mn₅O₁₂ ultrafine powder was added to agarose solution and mixed uniformly. Then the mixture was dropped into cold liquid paraffin. Spherical adsorbents were obtained at the bottom of the reactor, which were filtered and cleaned by ethyl acetate, ethanol and deioned water separately. The particles were cross-linked with epichlorohydrin, and then treated with 1 mol·L^-1 HCl to obtain the spherical ion-sieve. The effects of concentration of agarose, granulation temperature, concentration of cross-link agent, and cross-link time were studied. It was found that 5% agarose solution, 90℃, epichlorohydrin concentration of 2 ml·g^-1, and cross-link time of 6 h were the best condition to prepare the spherical ion-sieve. The lithium ion adsorption capacity of the spherical ion-sieve can reach 4.25 mmol·g^-1, which is 75.6% of that of lithium ion sieve powder. The adsorption rate of the spherical ion-sieve is 1.77×10^-5 s^-1, decreasing one order magnitude compared with that of the powder (3.29×10^-4 s^-1). The equilibrium lithium adsorption capacity increases apparently with pH value, reaching 5.5 mmol·g^-1 at pH 12. The selectivity experiment shows that the prepared lithium ion-sieve presents a highly selectivity for lithium ions. The results show that the spherical ion-sieve is an attractive adsorbent for lithium extraction from brine or seawater.

Key words: ion sieve, granulation, cross-link, adsorption, powders, particulate processes

摘要： 利用琼脂糖溶液的溶胶凝胶性质，通过锐孔凝固浴法，对实验室合成的Li₄Mn₅O₁₂粉体进行成型，制备了粒径2～3 mm的球形颗粒，对球形颗粒进行交联后，用1 mol·L^-1的盐酸对球形颗粒进行酸洗脱锂，最终制得球形锂离子筛吸附剂。考察球形吸附剂制备和交联的影响因素，结果表明：5%的琼脂糖浓度和90 ℃的温度为最佳制备条件，2 ml·g^-1的交联剂用量和6 h的交联时间为最佳交联条件。对球形离子筛吸附剂进行静态评价实验，结果表明锂吸附容量为4.25 mmol·g^-1，吸附速率为1.77×10^-5 s^-1，成型后离子筛吸附量是离子筛粉末的75.6%，吸附速率较粉体（3.29×10^-4 s^-1）下降一个数量级。Li⁺平衡吸附容量随平衡pH值的升高而增加，在pH>12时吸附容量高达5.5 mmol·g^-1。共存离子选择性实验表明，交联球形离子筛吸附剂对Li⁺具有高选择性，成型后离子筛可以用于盐湖卤水或者海水提锂。

关键词: 离子筛, 造粒, 交联, 吸附, 粉体, 颗粒过程