Upcycling Microplastic-Laden Spent Adsorbents to Mitigate Secondary Pollution: Insights into the Drivers, Pressures, State, Impacts, Responses (DPSIR) Framework

The Driver, Pressure, State, Impact, Response (DPSIR) framework was applied to assess microplastic pollution and the risk of secondary contamination from microplastic-laden spent adsorbents. Key driving forces include increasing plastic production, widespread polymer consumption, and growing reliance on adsorption technologies for microplastic remediation. These drivers impose pressures through the continuous release of polystyrene microplastics (PS-MPs) into aquatic systems and the accumulation of spent adsorbents after treatment. The resulting state is characterized by microplastic-contaminated water and spent adsorbents that pose secondary pollution risks if unmanaged. Circular carbon material (CCM), produced via pyrolysis of spent adsorbents at 600 °C for 2 h, achieved approximately 60% PS-MP removal and exhibited a surface area of 108–137 m2/g and showed a Type II isotherm. The associated impacts include limited recovery efficiency and potential microplastic remobilization. As a response, CCM was upcycled into magnetic circular carbon (MCC) via co-precipitation of iron oxide nanoparticles, improving removal efficiency to ~89%, enhancing mesoporosity and producing a Type IV–H3 isotherm (enhanced mesoporosity), and enabling easy magnetic separation. Overall, DPSIR analysis demonstrates that spent-adsorbent upcycling offers a stabilization and risk-mitigation pathway for microplastic-laden residues, reducing their environmental mobility and supporting circular-economy-based microplastic remediation, while highlighting the need for future emissions characterization to fully quantify net environmental benefits.