Conventional metal recovery technologies do not function adequately with critical metals from effluents containing hydrophilic organic solvents. We investigated dithiocarbamate-functionalized cellulose DPE6 to assess the impacts of organic solvents on its metal sorption capability to establish a new separation/recovery technology applicable to actual effluents. The results show highly efficient critical metal recovery and are expected to contribute to the effective use of finite metal resources and the realization of a sustainable society.
Background
Critical metals *1) are highly important resources to industry and society but carry high supply risks. Critical metals are used in a wide range of fields, including batteries, electronic devices, and renewable energy-related technologies. To secure a stable supply of such resources, there is a need for technologies to recover and reuse metals contained in effluents and waste materials. However, conventional separation technologies such as ion exchange and precipitation mainly target aqueous solutions. Effluents containing organic solvents have proved more challenging since the state of metal ions and the properties of effluents differ from those in an aqueous environment. Thus, it has been difficult for such technologies to achieve sufficient separation performance.
Results
This study was conducted by a team of scientists from the College of Science and Engineering and the Nano Life Science Institute, Kanazawa University, from the Institute of Environmental Radioactivity, Fukushima University, and from Daicel Corporation. In this study, they investigated the recovery performance for lead (Pb) and nickel (Ni) in organic solvents using DPE6 *2) , a functional sorbent based on cellulose modified with dithiocarbamate groups having a structure that readily binds to metals. DPE6 exhibited high sorption performance even in organic solvents, and the sorption reached equilibrium within 10 minutes. DPE6 also exhibited a high maximum sorption capacity in pure methanol and N,N-dimethylformamide (DMF).
Furthermore, they systematically investigated how metal sorption varies with the type and properties of organic solvents and clarified the impact of the type of organic solvent on metal recovery. Analyses using FT-IR, XPS, and XAS revealed that the sulfur atoms of the dithiocarbamate groups of DPE6 strongly capture metal ions. A key feature of this study is that it not only demonstrated the functionality of the novel sorbent but also established the mechanism of metal sorption in organic solvents, translating these insights into a recovery technology applicable to actual organic effluents.
To verify its practicality, the research team applied DPE6 to lead-containing organic effluents generated during the recycling of used perovskite solar cells. As a result, the team succeeded in removing over 99% of the lead from the effluents using methanol, and approximately 91% from the effluents using DMF. Thus, DPE6 demonstrated high lead removal performance even with effluents containing DMF; commercially available sorbents have difficulty in providing sufficient lead removal performance from effluents using DMF.
This study presents a novel technology for recovering critical metals from effluents containing organic solvents. From an academic viewpoint, the significance lies in having systematically elucidated the impact of organic solvent properties on metal sorption by solid phase extraction. It is also expected to lead to applications in technologies for recovering metals remaining in effluents and waste materials thus mobilizing unutilized resources.
Future prospects
The results of this study are expected to be applied to a new recycling technology that recovers critical metals from effluents and waste materials containing organic solvents, enabling their reuse as resources. It is also expected that the study will open the way to the effective use of finite metal resources and the contribution to resource circulation and to the realization of a sustainable society.
It should be noted that Kanazawa University and Daicel Corporation have jointly filed an international patent application (PCT application: PCT/JP2021/34658) regarding the technology related to this study.
Funders
JSPS KAKENHI grants (JP23K04094, JP25K22855, JP25H01197, JP24K15337) and the expenses for the joint research with Daicel Corporation borne by Daicel Corporation.
Glossary
*1) Critical metals
A collective term for metal resources that are highly important to industry and society but carry high supply risks. This study focuses primarily on nickel (Ni) and lead (Pb).
*2) DPE6
A functional sorbent based on cellulose, into which dithiocarbamate groups that readily bind to metals are introduced. DPE6 is designed to adsorb metals stably even in organic solvents.
ACS Applied Materials & Interfaces
Dithiocarbamate-Functionalized Cellulose for High-Efficiency Separation of Critical Metals from Organic Effluents
8-Jul-2026