Development of Selective Recovery System of Lithium from Deep Ocean Water Using A Novel MnO_2 Type Adsorbent

为了从深海中高效、选择性地分离和回收锂，我们开展了：(1)对锂对钠具有高选择性的新型λ型二氧化锰（λ- mno_2）吸附剂的研制；(2)对λ- mno_2吸附剂的吸附和分离性能进行评价；(3)开发适用于λ- mno_2吸附剂的制粒方法，防止吸附柱压降过大；(4)利用柱模块对海水中锂的选择性回收系统进行研究。研究结果如下：(1)利用盐酸洗脱尖晶石型二氧化锰锂中的锂，研制出高选择性识别锂离子的λ-MnO_2吸附剂。该结果已申请日本专利（专利申请2002-46288），并在期刊和国际会议上发表。(2)利用λ-MnO_2吸附剂对锂离子和钠离子进行了分离。在批量法中，锂/钠的选择性超过800倍，在柱分离法中，选择性达到2300倍。这种选择性是世界上最好的。(3)用甲壳素粘结剂制备了毫米级颗粒吸附剂。用扫描电镜观察了颗粒状吸附剂的结构，并用x射线衍射仪分析了颗粒状吸附剂的晶体结构。(4)详细考察了一些实验条件对人工深海和真实海水中锂钠选择性回收的影响。在该柱式模块系统的吸附-解吸操作下，从海水中获得了高浓度的锂溶液。该结果已应用于期刊和国际会议的发表。

For the purpose of efficient and selective separation and recovery of lithium from deep ocean water, we have carried out: (1)Development of novel λ type manganese dioxide (λ-MnO_2) adsorbents having high selectivity of lithium against sodium, (2)Evaluation of adsorption and separation performance of the λ-MnO_2 adsorbents, (3)Development of granulation method suitable for the λ-MnO_2 adsorbent preventing large pressure drop in the adsorption column of, and (4)Investigation of selective recovery system of lithium from the seawater using the column module. As a result of this research, the followings were obtained.(1)We have successfully developed λ-MnO_2 adsorbent which high-selectively recognizes lithium ion by eluting lithium from spinel type lithium manganese dioxide with aqueous hydrochloric acid. This result was applied to a Japanese patent (Patent pending 2002-46288), as, well as to the publication to journal and international conference.(2)We have carried out the separation of lithium ion from sodium ion using the λ-MnO_2 adsorbent. We have obtained the selectivity of lithium/sodium of over 800 times in case of batchwise method, while 2300 times selectivity in case of column separation method. This selectivity is the best all over the world.(3)We have prepared the granular adsorbents with some millimeter order using with chitin binder. We have observed the structures of granulated adsorbents with a scanning electron microscope as well as elucidated the crystal structure with X-ray diffractometer.(4)We have examined the influence of some experimental conditions on the selective recovery of lithium and sodium in artificial deep ocean water and real seawater in detail. We have obtained highly concentrated lithium solution from seawater under the adsorption-desorption operation of this column module system. This result was applied to the publication to journal and international conference.