[Reading Science] Metal "Grows" from Wastewater...KIST Develops World's Highest-Performance Copper Recovery Capsule

Selective Recovery and Recycling of Copper from Industrial Wastewater
Simultaneous Achievement of Resource Security and Environmental Protection Expected

A technology that transforms copper, previously treated as hazardous wastewater in industrial settings, back into high-purity metal has been developed by a domestic research team.

A research team from the Korea Institute of Science and Technology (KIST) has attracted attention in the fields of securing strategic metals and eco-friendly resource circulation by developing an innovative recovery material that adsorbs copper ions from wastewater and directly grows them into metal crystals inside capsules.

Controlled crystallization mechanism according to the curvature of the internal pore structure of 3D high-density amine millicapsules (DMC). It was confirmed that the density of introduced amine functional groups varies depending on the curvature of various pores formed inside the high-density amine millicapsules. Based on this, crystallization-inducing functional groups were introduced. After copper adsorption, micro-CT images confirmed that the internal multi-stage pore structure is filled with high-density crystals, and high selectivity for copper was observed even under coexistence conditions with other cationic metal ions. Compared to copper recovery reported in previous literature, the copper recovery capacity was found to be more than twice as high as that of nanosized adsorbents. Illustration and provision: Jaewoo Choi, Principal Researcher at Korea Institute of Science and Technology; Youngkyun Jung, Postdoctoral Researcher; Yoon Lee, Student Researcher.

From Wastewater to Metal Resource...A Clue to Solving the Copper Supply Shortage

On November 20, the National Research Foundation of Korea announced that Dr. Jaewoo Choi’s KIST research team developed a high-capacity, high-durability “three-dimensional amine millicapsule” and published their findings in the international journal Advanced Composites and Hybrid Materials.

Copper is an essential metal for semiconductors, power grids, secondary batteries, and renewable infrastructure. While demand is rapidly increasing, the high reliance on overseas sources has heightened the need for stable recovery technologies.

Conventional methods such as electrolysis or membrane separation are limited in practical application due to high costs, and adsorbents based on planar structures are difficult to apply immediately in industrial settings because of reduced capacity and selectivity. Nanoparticle-based materials offer excellent performance but pose challenges in separation processes and handling in large-scale operations.

To overcome these limitations, the research team implemented an “adsorption-crystallization mechanism” in which copper ions enter the capsule’s internal space and grow directly into crystals within the three-dimensional structure. Inside the rice grain-sized millicapsules, a radial skeleton and multilayer pore structure are formed, and high-density amine functional groups introduced on the surface rapidly capture copper. The subsequent process, in which the copper combines with anions and grows into metal crystals, occurs inside the capsule, ensuring both structural stability and high recovery efficiency.

World’s Highest Capacity...Stable Even After 50 Days of Continuous Operation

This material achieved a maximum adsorption capacity of 1,602.3 mg/g, which is more than twice as high as existing materials and is the highest level worldwide. After seven cycles of reuse, the performance decrease was limited to within 6.4%, and no structural damage was observed even after 50 days of continuous operation.

Even in industrial wastewater containing a mixture of various metals, the material exhibited very high selectivity for copper, making it suitable for application in actual semiconductor, plating, and metalworking wastewater. Because the capsules are millimeter-sized polymer structures, solid-liquid separation is easy and pressure loss is minimal, allowing for immediate integration into existing continuous column processes-an industrial advantage.

Another notable feature of this technology is the use of acrylic fiber, a common component in everyday clothing, in the production of the material. This allows for the conversion of waste clothing into high-value-added recovery materials, greatly expanding its potential as an eco-friendly circular economy technology.

Dr. Jaewoo Choi explained, “The high-purity copper crystals grown inside the capsules can be recycled into high-value-added materials such as catalysts or electrodes, laying the foundation for a ‘wastewater-to-metal production’ structure rather than just a simple treatment technology.” Co-researcher Dr. Youngkyun Jung added, “We plan to further enhance industrial applicability by conducting additional demonstrations with actual industrial wastewater from semiconductors and plating processes.”

The demand for copper is expected to surge further due to the expansion of AI data centers, the adoption of electric vehicles, and the strengthening of power transmission and distribution networks. As the importance of utilizing urban waste, electronic waste, and industrial wastewater as new “urban mines” grows, this technology is anticipated to serve as a platform that simultaneously targets domestic resource security, environmental pollution reduction, and industrial competitiveness enhancement.

The paper published in ACHM is titled “Controlled in-situ crystallization in amine-rich millicapsules for hyper-efficient copper recovery.” This research was supported by the “Sejong Science Fellowship” from the Ministry of Science and ICT and the National Research Foundation of Korea.