Valorization of waste plastics to a novel metal-organic framework derived cobalt/carbon nanocatalyst as peroxymonosulfate activator for antibiotics degradation

Abstract

Metal-organic frameworks (MOFs), with excellent structural properties, exhibit unique advantages as promising catalysts in the degradation of emerging organic contaminants (EOCs) by PS-AOPs. Herein, Co-MOF-71 was prepared by hydrothermal method using terephthalic acid (TPA) obtained from the hydrolysis of waste PET plastics as an organic ligand, and the derived cobalt/carbon composite (PETC) was prepared by carbonizing Co-MOF-71 under N₂ atmosphere. Characterizations revealed that PETC800 carbonized at 800 °C possessed a loose and porous layered morphology with a surface area of 148 cm²/g, and had a porous structure rich in active sites that are effective in peroxymonosulfate (PMS) activation and tetracycline (TC) degradation. Degradation experiments revealed that the maximum degradation rate of TC by PETC800 could reach 90.94% within 20 min, with a maximum rate constant of 0.2700 min^-1 and activation energy of 19.50 kJ/mol, which was lower than that of previous reports. Additional studies confirmed high effectiveness also towards other pharmaceuticals degradation such as metronidazole, levofloxacin and doxorubicin. More importantly, PETC800 could degrade TC efficiently in a broad pH region (3.0-9.0). The degradation performance of TC could be 72.18% after four cycles, demonstrating good reusability. Both radical (•OH, SO₄^•−, and O₂^•−) and nonradical pathways (singlet oxygen (¹O₂) and electron transfer) contributed to the TC degradation process, with the non-radical pathway dominating. LC-MS and toxicity analyses have postulated the degradation of TC into intermediates with lower levels of toxicity. The preparation of MOFs-derived catalysts from waste plastics allows resourceful utilization of waste plastics as well as enhances the catalytic performance of MOFs-derived cobalt/carbon-based catalysis for efficient degradation of emerging organic contaminants.