Surface Modification of TiO₂ Nanorods for Dye Removal: Photodegradation vs Adsorption Activity

Area of Science:

• Materials Science
• Environmental Science
• Nanotechnology

Background:

• Colloidal titanium dioxide nanoparticles (NPs) are versatile semiconductors used in wastewater treatment.
• Understanding the relationship between NP surface chemistry, morphology, and dye removal efficiency (adsorption vs. photodegradation) is crucial.

Purpose of the Study:

• To investigate the potential and limitations of surface modification in TiO2 nanorods (NRs) for removing dyes from wastewater.
• To elucidate the mechanisms of dye removal via adsorption and photodegradation pathways based on surface chemistry and NP structure.

Main Methods:

• Synthesis of oleic acid-capped TiO2 nanorods (NR-OA) and their subsequent functionalization with catechol to create NR-Cat.
• Characterization using thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS).
• Evaluation of adsorption and photodegradation efficiencies for various dyes, band gap determination, zeta potential measurements, and scavenging experiments.

Main Results:

• Surface modification of NR-OA to NR-Cat reduced the band gap (2.75 eV to 1.72 eV), enhancing light-harvesting.
• NR-Cat showed high efficiency in adsorption for cationic dyes (methylene blue, rhodamine B) due to increased negative surface charge.
• NR-Cat's photoactivity was limited, primarily activating hydroxyl radicals, while NR-OA demonstrated photocatalytic activity for xanthene-based dyes and methylene blue.

Conclusions:

• Surface modification significantly alters TiO2 NRs' dye removal mechanisms, favoring adsorption or photocatalysis depending on the functionalization.
• A systematic approach correlating NP properties with dye structures is essential for designing effective nanomaterials for wastewater remediation.
• Tailoring semiconductor surface chemistry offers a promising strategy for developing advanced materials to address environmental pollution from industrial dyes.