Resource utilization of chemical excess sludge to produce metal-organic framework with outstanding Fenton-like performance for sulfamethoxazole removal

The safe disposal of excess sludge has emerged as a pressing concern due to its high toxicity, stemming from a diverse array of components such as viruses, heavy metals, and polycyclic aromatic hydrocarbons. Herein, this study explored the feasibility of using extracted Fe from the excess sludge to produce metal-organic frameworks (MOFs). Specifically, MIL-100 and MIL-88A were successfully synthesized by coordinating 1,3,5-benzene tricarboxylic acid and fumaric acid with excess sludge-retained iron under wide reaction conditions. The purity of the resulting MOFs was ascertained through elemental analysis. Moreover, the synthesized MOFs demonstrated outstanding electrocatalytic performance in the degradation of sulfamethoxazole (SMX). Compared to the control group without catalysts, the addition of MIL-100-170-6 (30 mg) led to a remarkable enhancement in SMX removal efficiency, increasing it to 99.9 % from 58.3 %. This enhancement was accompanied by a substantial increase in the corresponding kinetic constant (kobs) values, reaching 0.1137 min(-1), representing an 8.1-fold improvement over the blank group. The catalytic mechanism was further evaluated via quenching experiments and electron paramagnetic resonance (EPR) spectroscopy, suggesting that the center dot OH and O-2(center dot-) radicals were responsible for SMX degradation. Economic analysis of MOF materials preparation revealed that the use of excess sludge-retained Fe can significantly reduce the cost of MOFs. Thus, it is believed that our work provides a low-cost and sustainable approach for converting excess sludge into functional MOFs, which not merely facilitates the recycling of excess sludge-retained Fe, but also provides functional materials with outstanding performance for the degradation of SMX.