Urchin-like CO2-responsive magnetic microspheres for highly efficient organic dye removal

Abstract

CO₂-responsive materials have emerged as promising adsorbents for the remediation of refractory organic dyes-contaminated wastewater without the formation of byproducts or causing secondary pollution. However, realizing the simultaneous adsorption-separation or complete removal of both anionic and cationic dyes, as well as achieving deeper insights into their adsorption mechanism, still remains a challenge for most reported CO₂-responsive materials. Herein, a novel type of urchin-like CO₂-responsive Fe₃O₄ microspheres (U-Fe₃O₄ @P) has been successfully fabricated to enable ultrafast, selective, and reversible adsorption of anionic dyes by utilizing CO₂ as a triggering gas. Meanwhile, the CO₂-responsive U-Fe₃O₄ @P microspheres exhibit the capability to initiate Fenton degradation of non-adsorbable cationic dyes. Our findings reveal exceptionally rapid adsorption equilibrium, achieved within a mere 5 min, and an outstanding maximum adsorption capacity of 561.2 mg g^-1 for anionic dye methyl orange upon CO₂ stimulation. Moreover, 99.8% of cationic dye methylene blue can be effectively degraded through the Fenton reaction. Furthermore, the long-term unresolved interaction mechanism of organic dyes with CO₂-responsive materials is deciphered through a comprehensive experimental and theoretical study by density functional theory. This work provides a novel paradigm and guidance for designing next-generation eco-friendly CO₂-responsive materials for highly efficient purification of complex dye-contaminated wastewater in environmental engineering.