Multiwalled carbon nanotubes / Titanium dioxide for water treatment: Synthesis, characterization, and application

Abstract

Multiwalled carbon nanotubes (MWNTs), titanium dioxide (TiO₂), and their composites (MWNT-TiO₂) have been widely studied for a broad range of applications in water treatment, catalysis, photonics, carbon capture, hydrogen storage, and solar energy harvesting, owing to their uncommon characteristics. This study is focused on the investigation of one-pot synthesis process of MWNT-TiO₂ composite, its characterization and application for adsorption removal of organics from water. MWNTs were selected as a support material (for TiO₂ in the composite) because they are reported to enhance the photocatalytic activity of TiO₂, possess a high surface area, and exhibit exceptional mechanical strength and chemical resistivity in various applications. The synthesis of MWNT-TiO₂ composite was brought about by sonication using response surface methodology approach for experimental design. Prior to composite fabrication, the sonication energy was calibrated, quantified, modeled, and optimized. Dispersion of MWNTs in water was identified as an important parameter controlling the attachment of TiO₂ onto MWNTs and was therefore studied in detail. Each step of the composite fabrication process was modeled, analyzed, validated, and optimized. This comprehensive methodology is expected to make the process to be reproducible, making it broadly applicable to the fabrication of other types of carbon/metal oxide composites such as graphene-titania, fullerene-zinc oxide, and activated carbon-alumina. The composite and its parent materials were characterized by electron microscopy, nitrogen adsorption/desorption, zeta potential, dynamic light scattering, x-ray diffraction, thermogravimetric analysis, and inductively coupled plasma-optical emission spectrometry to assess change in physical and chemical characteristics of MWNTs and TiO₂ when brought together in a composite by sonication energy input. Finally, the MWNT-TiO₂ composite was utilized to remove an ionizable organic compound, ibuprofen, from water and compared to its removal with the composite's constituent materials. The adsorption mechanism was evaluated by fitting the experimental data to established models for ionized and neutral species of ibuprofen. An empirical model was developed to describe adsorption of ibuprofen and similar organic acids in an aquatic system.

Date of Award	Dec 2016
Original language	American English
Supervisor	Farrukh Ahmad (Supervisor)