Urchin-Like CO2-Responsive Magnetic Microspheres for Highly Efficient Organic Dye Removal

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 5minutes, and an outstanding maximum adsorption capacity of 561.2mgg−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. Environmental implication Massive discharge of organic dyes contaminated wastewater into the ecosystem threatens human health and the aquatic environment, ascribed to the hazardous and toxic natures of dyes. Thus, designing advanced materials for the highly efficient removal of organic dyes from wastewater is extremely promising. Herein, novel urchin-like CO2-responsive magnetic microspheres were devised to enable highly efficient selective adsorption−separation of anionic dyes and simultaneous removal of anionic/cationic dyes, even in the complex synthetic dye effluent by combining CO2-triggered adsorption and Fenton degradation. This work provides insights for developing 'smart' materials for the purification of complex dye-contaminated wastewater in environmental engineering.