Chitosan-metalloporphyrin as a green catalyst for methylene blue degradation: Performance insights

5, 10, 15, 20-tetrakis(4-methoxyphenyl)porphyrin (TMPP) was synthesized and subsequently metallized with cobalt(II) to form Co(II)TMPP. This complex was then immobilized onto a chitosan (CTS) support, resulting in the composite Co(II)TMPP@CTS, which was utilized for the degradation of methylene blue (MB) in aqueous solutions. Fourier-transform infrared spectroscopy (FT-IR) confirmed strong coordination between cobalt metal and nitrogen atoms within the chitosan matrix. The X-ray diffraction (XRD) patterns indicated a decrease in crystallinity for the Co(II)TMPP@CTS composite. Scanning electron microscopy (SEM) imaging displayed elongated crystal structures, while EDX analysis validated the elemental composition of the catalyst. The catalytic performance was evaluated for the oxidative degradation of MB, employing hydrogen peroxide in a bicarbonate medium. The degradation process adhered to first-order kinetics, achieving a remarkable removal efficiency of 94.7 % within 31 min. Studies on operational parameters-including catalyst dosage, hydrogen peroxide concentration, bicarbonate concentration, initial dye concentration, and temperature-revealed that increased catalyst and bicarbonate concentrations significantly enhanced degradation rates by facilitating the generation of peroxocarbonate, a more potent oxidant. Hydroxyl radicals (^.OH) have been identified as key players in the degradation process, as evidenced by radical scavenging experiments. Notably, the Co(II)TMPP@CTS complex demonstrated remarkable reusability across several cycles, highlighting its promising application in wastewater treatment for effectively removing hazardous dyes.