Hollow C, N-TiO2@C surface molecularly imprinted microspheres with visible light photocatalytic regeneration availability for targeted degradation of sulfadiazine

Novel hollow C, N-TiO 2 @C surface molecularly imprinted microspheres (HCNTC-SMIPs) with hydrophilicity, reusability, and selectivity were synthesized. The core–shell hollow structure yields large specific surface areas, high surface-to-volume ratios and effective diffusion rate on both inner and outer exposed surfaces. The C, N-TiO 2 shell possesses high photo-catalytic decomposition capacity toward the specific pollutants. Moreover, TiO 2 acts not only as a photocatalyst but also as a double cross-linker agent of molecularly imprinted to significantly reduce the molar ratio of formaldehyde. The hydrophilic surface imprinted layer provides the recognition sites and specific pore structures. The results showed that HCNTC-SMIPs possessed a high specific surface area of 305.10 m 2 g −1 and a good visible light harvesting property with a bandgap of 1.67 eV. This could efficiently suppress the photoelectron-hole recombination, and thereby heightening the photocatalytic degradation of sulfadiazine (SDZ). The photodegradation efficiency of HCNTC-SMIPs can reach 99.25 % within 140 min and 90.00 % after 6 cycles. The HCNTC-SMIPs had a higher kinetic constant (0.01815 min −1 ) than those of HCNTC (0.00964 min −1 ) and TiO 2 (0.00548 min −1 ). HCNTC-SMIPs can achieve targeted and efficient SDZ removal, as well as in-situ regeneration. The possible degradation pathways of SDZ primarily includes smiles-type rearrangement, SO 2 extrusion, ring hydroxylation, direct oxidation and S N bond cleavage processes based on LC-MS analysis.