Efficient Regeneration of Waste Styrene Adsorption Carbon Catalyzed by Spinel NiCo2O4 Active Sites and Cyclic VOC Adsorption and Desorption Performance

During thermal regeneration of styrene-saturated activated carbon (AC), styrene’s C=C bonds are prone to polycondensation. It forms fixed carbon species that deposit as carbonaceous residues within AC pores, significantly decreasing the adsorption performance. To address this challenge for efficient AC regeneration and recycling, Ni and Co transition metal components were loaded onto AC and subsequently pyrolyzed to generate NiCo2O4 active species. The optimal Ni–Co loading amount was determined to be 5 wt %. Under these conditions, the adsorbent exhibited optimal cyclic adsorption performance, maintaining 75% of its initial capacity after four consecutive adsorption–regeneration cycles. Comprehensive characterization revealed that the 2.5Ni-2.5Co-AC formulation maximized AC recyclability, and this enhanced performance is attributed to the well-dispersed NiCo2O4 species and the formation of carbon defect sites within the adsorbent. This study presents a novel strategy and provides a scientific basis for solving the regeneration problem of styrene-adsorbed activated carbon.