講演情報
[P092C]リチウムイオン電池酸浸出液に対する膜分離回収プロセスにおけるリチウム損失の抑制手法
○趙 耕賢1、鳥海 渓1、所 千晴2,1、宮本 竜馬3,2、峯岸 進一3、高谷 雄太郎 (1. 東京大学、2. 早稲田大学、3. 東レ株式会社)
キーワード：
リチウムイオン回収、ナノろ過膜、酸浸出液、イオン交換樹脂
As global warming becomes increasingly urgent, lithium-ion batteries (LiBs) have become essential for supporting sustainable energy systems, leading to a surge in lithium (Li) demand. Natural lithium resources are limited, and the expansion of mining operations poses serious environmental concerns. Therefore, efficient Li recycling technologies have been intensively studied. The present LiBs recycling process involves the acid treatment of black mass followed by solvent extraction to recover valuable metals such as cobalt (Co) and nickel (Ni), with lithium typically recovered last via precipitation. However, this conventional method often results in low lithium recovery rates. To address this limitation, our study explored a novel approach that prioritizes lithium recovery earlier in the process using nanofiltration membranes. These membranes selectively allow lithium ions to pass through while retaining other metals. Simultaneously, hydron and sulfate ions also permeate the membrane, causing a localized increase in pH. This change in pH leads to pH-driven secondary precipitation on the membrane surface, which can compromise the membrane performance and trap lithium in the resulting precipitates, causing significant loss. The mechanism of this precipitation is not yet fully understood. To investigate this phenomenon, we used an anion-exchange resin to remove sulfate ions from the black mass leachates. Various solutions were tested: the real industrial process containing mainly lithium, aluminum, manganese, sulfur, and trace amounts of valuable metals; and several simplified model solutions containing lithium, sulfur, and combinations of aluminum, manganese, or both. The results indicated that lithium tends to co-precipitate with aluminum or manganese when the pH exceeds approximately 3.0. Aluminum and manganese account for most of the co-precipitated lithium. Our findings suggest two key strategies to minimize lithium loss: maintaining the leachate pH below 3.0 or preventing impurities such as aluminum from entering the solution prior to the acid treatment stage.