Fe, N-CQDs triggered the fabrication of alginate encapsulated g-C3N4 hydrogel for efficient photocatalytic activation of PMS and antibiotic degradation.

Carbon dots (CDs) mediated g-C3N4 (CN) is a promising visible-light-driven semiconductor in catalyzing peroxymonosulfate (PMS) for aqueous contaminants remediation. However, the poor dispersibility of powered catalyst and its challenging recyclability impede their broader application. Herein, we embedded FeN bridge within the g-C3N4 framework and immobilized g-C3N4 gel beads (CA/FNCCN) through a 3D cross-linking process with sodium alginate. Alginate can serve as a stabilizing carrier, preserving the crystalline structure of FNCCN through the formation of H bonds between alginate and FNCCN. The resulting beads displayed significantly improved photo-electrochemical performance, along with greatly enhanced adsorption capacity and catalytic activity toward Sulfamethoxazole (SMX). The catalytic efficiency of CA/FNCCN was markedly increased as compared to non-immobilized FNCCN due to reduced photo-carrier recombination and accelerated electron transport. CA/FNCCN-1 can degrade 99.18 % of SMX within 40 mins, with noteworthy reduced Fe leaching. The primary active species in the system were 1O2 and h+, and the direct electron transfer between PMS and SMX mediated by alginate also contributed to the removal of SMX. Additionally, the degradation pathway of SMX was elucidated through LC-MS and DFT calculations. Simultaneously, FNCCN integrated alginate hydrogel can remain active without decay after 10 cycles.