イオン液体は従来の分子性液体とは大きく異なる特殊な性質を有することから，新たな機能性媒体としてさまざまな分野で注目されている。溶媒抽出における抽出媒体としてイオン液体を用いた場合は，“液状イオン交換体”としても働くため，従来の有機溶媒系よりも優れた抽出分離能を示すことが期待される。著者らは，このようなイオン液体の特性に着目し，高性能溶媒抽出系の開発を目指して，イオン液体を抽出媒体とした金属イオンの抽出分離に関する研究を行ってきた。本稿では，金属イオン抽出におけるイオン液体の溶媒特性評価，イオン液体系での協同効果による希土類金属の分離，大環状抽出剤の開発とイオン液体に抽出された金属錯体の構造解析について紹介する。

A frequency of cyanobacterial blooms appearance in lakes has been increasing as a consequence of eutrophication together with global warming. Although cyanobacterial blooms have been removed/collected by a suction method, there are few ways to effectively use the cyanobacterial biomass. If added values such as adsorptive function for pollutants in aqueous solution can be provided to the cyanobacterial biomass, it would be contributed to solve problems on cyanobacterial blooms and water pollution. This study aimed to prepare adsorbent from cyanobacterial bloom sample collected in a eutrophic lake for the removal of pollutants, and attempted to remove Cd²⁺ by cyanobacterial blooms-originated adsorbent (CBA) prepared via dehydration treatment using a concentrated sulfuric acid. As a result, CBA possessed smaller specific surface area (13.1 m²/g) and higher amount of total acidic functional groups (8.29 mmol/g), and the maximum amount of Cd²⁺ adsorption was 1.43 mmol/g, which was higher than oxidized activated carbons. From these values, the number of carboxy groups per unit surface area was calculated to be 1.51 × 10²⁰ number/m², and the distance between carboxy groups was estimated to be 8.14 × 10⁻² nm, which would be one of the major reasons of higher amount of Cd²⁺ adsorption. Furthermore, adsorption/desorption experiments were repeatedly conducted 3 times, and the results showed that the adsorption amount and recovery rate were not largely varied, indicating that CBA can be reused for the Cd²⁺ adsorption. These results suggest that the preparation of adsorbent for the removal of Cd²⁺ would be one of the effective ways for the effective utilization of cyanobacterial biomass.