Indium (III) porphyrins immobilized on carbon-based supports for the remediation of organic contaminants and bactericidal activity in water

Abstract

This thesis investigates the removal of organic contaminants and the deactivation of E. coli, a common bacterium in waterborne diseases, using indium (III) porphyrins immobilized on carbon-based supports. Various carbon-based support materials, including activated carbon-related supports, granular activated carbon (GAC), oxygen-functionalized activated carbon (ACO), and polyacrylonitrile/activated carbon (PAN/AC) composites, were evaluated, along with indium-metalated porphyrin-loaded samples (1a and 2a). The study found that the physicochemical nature of these materials significantly influences their efficiency in dye removal through adsorption and combined adsorption-photodegradation processes. The addition of porphyrins improved the photoactivity of the composites without significantly affecting their surface area. Hydrogen peroxide enhanced the photodegradation of methylene blue (MB) and the deactivation of E. coli, especially with colloidal activated carbon (CAC) and porphyrin-loaded CAC samples (1a, 2a, and 3a). Higher activities were realized with the porphyrin samples, although porphyrin aggregation, as seen with porphyrin 3a, can interfere with these activities. The study also found that natural sunlight was more effective than a Xe lamp for degrading ciprofloxacin. The effect of porphyrin charge on antimicrobial photodynamic therapy (aPDT) activities was significant, with positively charged porphyrins showing higher antimicrobial efficacy compared to neutral porphyrins. Additionally, the study highlighted the importance of porphyrin functional groups and symmetry in enhancing performance in photodegradation and antimicrobial applications. The antimicrobial potential of the indium metalated pyridinyl-based trans-A2B2 porphyrin complexes (4a, 4b, 5a, and 5b) was investigated. The dicationic porphyrins, 4b and 5b, exhibited remarkable aPDT efficacy against both S. aureus E. coli and planktonic forms and biofilms. Further experiments focused on the photodegradation of MB and methyl orange (MO) using porphyrins 1a, 2a, 3a, and 5b loaded on PAN/nitrogen-doped carbon quantum dot (NCQD) fibers. Overall, the porphyrin-loaded PAN/NCQD composites were effective, especially those loaded with cationic indium porphyrin 5b, which exhibited higher aPDT effects for E. coli and in MB degradation experiments. The unsymmetrical indium porphyrin 3a showed good activity in both MO and MB, making it the overall better performer during the degradation experiments. The findings reveal that the symmetry of porphyrins can significantly influence their effectiveness in photodegradation and antimicrobial applications.