A Recyclable Co-Fe Bimetallic Immobilized Cellulose Hydrogel Bead (CoFeO@CHB) to Boost Singlet Oxygen Evolution for Tetracycline Degradation

In the current work, a novel Co-Fe bimetallic immobilized cellulose hydrogel bead (CoFeO@CHB) was prepared via in situ chemical precipitation followed by heat treatment and applied for tetracycline (TC) degradation in the presence of peroxymonosulfate (PMS). The characterization results indicated that the Co-Fe particles were evenly distributed within the porous cellulose hydrogel beads, without affecting their morphologies or crystal structures. During the TC degradation, the CoFeO@CHB/PMS system showed a high resistance and stability to different water bodies, and the common anions and natural organic matters showed a limited effect on TC degradation. The chemical quenching experiments (using chemicals to react with specific reactive species) as well as electron paramagnetic resonance (EPR) results showed that CoFeO@CHB can effectively active PMS to generate multiple reactive oxygen species (ROS, such as SO4•−, •OH and 1O2), in which the 1O2-dominated non-radical pathway played a vital role in TC degradation. Both Co and Fe were proposed as the active sites for PMS activation, and the CoFeO@CHB/PMS system showed a high potential in practical application due to its high selectivity and robustness with much less toxic intermediate products. Furthermore, a long-term continuous home-made dead-end filtration device was constructed to evaluate the stability and application potential of the CoFeO@CHB/PMS system, in which a >70% removal was maintained in a continuous 800 min filtration. These results showed the promising potential for cellulose hydrogel beads utilized as a metal-based nanomaterial substrate for organic degradation via PMS activation.