▎ 摘　　要

NOVELTY - Preparing composite catalyst comprises (i) preparing graphene oxide (GO) by Hummer method, (ii) using iron source, cobalt source, dopamine and graphene oxide (GO) prepared in the step (i) as raw materials, using hydrothermal method to prepare cobalt ferrite-loaded, polydopamine-coated reduced graphene oxide hydrogel, marking as cobalt ferrite/polydopamine (PDA)-reduced graphene oxide (rGO), reacting, and heat preserving for 10-14 hours, (iii) using cobalt ferrite/PDA-rGO prepared in the step (ii) as a raw material, using freeze-drying method to prepare the reduced graphene oxide airgel with three-dimensional (3D) structure, loaded with cobalt ferrite and coated with polydopamine, and marking as 3D cobalt ferrite/PDA-rGA, and (iv) using 3D cobalt ferrite/PDA-rGA as raw material, using high-temperature annealing method to prepare 3D structure, cobalt ferrite-loaded and N-doped reduced graphene oxide airgel, marking as 3D cobalt ferrite/N-rGA. USE - The composite catalyst and peroxymonosulfate (PMS) are useful for forming synergistic system in degrading tetracyclines (claimed). ADVANTAGE - The method: prepares composite catalyst through simple operations; and has strong operability, low loss of active components and low cost of raw materials. The catalyst: can quickly and efficiently activate PMS to generate free radicals to catalyze the degradation of tetracycline; is easy to recycle; and can be recycled for multiple times. DETAILED DESCRIPTION - Preparing composite catalyst comprises (i) preparing graphene oxide (GO) by Hummer method, (ii) using iron source, cobalt source, dopamine and graphene oxide (GO) prepared in the step (i) as raw materials, where the amount ratio of cobalt and iron is 1:2, using hydrothermal method to prepare cobalt ferrite-loaded, polydopamine-coated reduced graphene oxide hydrogel, marking as cobalt ferrite/polydopamine (PDA)-reduced graphene oxide (rGO), reacting at 160-200°C, and heat preserving for 10-14 hours, (iii) using cobalt ferrite/PDA-rGO prepared in the step (ii) as a raw material, using freeze-drying method to prepare the reduced graphene oxide airgel with three-dimensional (3D) structure, loaded with cobalt ferrite and coated with polydopamine, and marking as 3D cobalt ferrite/PDA-rGA, and (iv) using 3D cobalt ferrite/PDA-rGA as raw material, using high-temperature annealing method to prepare 3D structure, cobalt ferrite-loaded and N-doped reduced graphene oxide airgel, marking as 3D cobalt ferrite/N-rGA, reacting at 500-700°C, and heat-preserving for 3-5 hours, where the composite catalyst is 3D, loaded cobalt ferrite, N-doped reduced graphene oxide airgel, which is marked as 3D cobalt ferrite/N-rGA. An INDEPENDENT CLAIM is also included for a composite catalyst which is a cobalt ferrite-loaded, N-doped reduced graphene oxide aerogel with 3D structure prepared by the above-mentioned method.