Enhanced dye degradation using MIL-53(Fe)-Modified kraft lignin as a heterogeneous Fenton catalyst

MIL-53(Fe), a metal–organic framework (MOF), is capable of degrading harmful organic contaminants, but it has relatively low Fenton catalytic efficiency. To enhance the degradation performance of MIL-53(Fe), we synthesized MIL-53(Fe)-MKL by incorporating modified kraft lignin (MKL) into pristine MIL-53(Fe). The as-prepared composite demonstrated Fenton activity, degrading 97 % of methylene blue (MB) within 50 min. Compared to pristine MIL-53(Fe) (which achieved 62.4 % MB degradation), the MIL-53(Fe)-MKL composite showed a 34.6 % improvement in MB degradation under identical reaction conditions. The incorporated MKL promotes Fe²⁺ regeneration from Fe³⁺ in the Fenton process, activating H₂O₂ to produce [rad]OH radicals, which were identified through scavenging experiments and chemical dosimetry with ESR analysis. The MIL-53(Fe)-MKL composite was reused for at least five cycles without a significant decrease in catalytic efficiency. This reported catalyst takes advantage of both MKL and MIL-53(Fe) to enhance catalytic activity, providing a basis for developing innovative catalysts for organic pollutant degradation.