Efficient decontamination of tetracycline via fenton-like process mediated by chitosan-based Fe-MOFs under wide pH range

Fe-MOF is one of the highly-promising Fenton-like catalysts. However, the shape of powder and low Fe(II)/Fe(III) cycle efficiencies restrict its applications. In this research, MIL-101(Fe) was incorporated into a chitosan (CS) matrix to obtain easy-recyclable MIL-101(Fe)@CS beads as Fenton-like catalysts for tetracycline (TC) degradation. The CS partially wrapped the octahedral MIL-101(Fe) particles for protection and dispersion. The MIL-101(Fe)@CS/H2O2 system demonstrated better TC removal efficiency (similar to 90.00 % within 140 min), with a pseudo-first-order kinetic constant 3.5 times higher than that of the MIL-101(Fe)/H2O2 system. In addition, the reaction system exhibited a wider pH application range (5.12 - 12.96), higher H2O2 utilization rate (70 %), better interference resistance of the common anions in water, excellent reusability (94.10 % degradation efficiency retained over five cycles), and lower risk of secondary pollution with Fe ions (1.47 mg/L). Furthermore, theoretical evaluations and antibacterial tests revealed that the MIL-101(Fe)@CS/H2O2 system effectively reduced the potential risk of TC in the ecosystem. A mechanistic study showed that hydroxyl radicals (center dot OH) were the main reactive species involved in the reaction and that the presence of CS accelerated the Fe(II)/Fe(III) cycle. This study offers an immobilization strategy to optimize the catalytic performance of Fe-MOFs and improve their practical application, providing theoretical and technical support for refractory organic degradation in wastewater by Fenton-like processes.