Using Titanium Dioxide/carbon Nanotubes To Remove Humic Acids In Water

Dept. of Civil Engineering, National Chi Nan University, 1, University Rd., PuLi, NanTou, Taiwan

Adv. Mater. Lett., 2016, 7 (2), pp 95-97

DOI: 10.5185/amlett.2016.6100

Publication Date (Web): Jan 04, 2016

Copyright © IAAM-VBRI Press

E-mail: yptsai@ncnu.edu.tw, chi813@gmail.com

Abstract

This study used multi-walled carbon nanotubes (MWCNTs), TiO₂ and their mixture (TiO₂/CNT) to remove humic acids (HA) in water. The thermodynamic parameters with respect to the adsorption of MWCNTs, including free energy of adsorption (ΔG⁰), enthalpy (ΔH⁰), and entropy (ΔS⁰) changes, are further calculated in the study. The ΔH⁰ data showed the adsorption of HA onto MWCNTs is an endothermic physisorption. The ΔG⁰ data indicates the adsorption of HA onto MWCNTs was spontaneous and thermodynamically favorable. Photocatalytic experiments showed 60 mgl^-1 of HAs were completely degraded and mineralized as CO₂ after 5 h UV irradiation by 0.8 gl^-1 of TiO₂, indicating the efficiency of TiO₂ for the removal of HA is better than CNTs. The experiments of TiO₂/CNT indicated the photocatalytic efficiency of TiO₂ in the presence of CNTs was not improved, even worse than TiO₂ alone. However, the photocatalytic efficiency of TiO₂/CNT mixture became better than TiO₂ alone due to the supply of oxygen by aeration, ascribing to the reason that the provided oxygen might be adsorbed on the surface of CNTs and accept e- as well as form •O₂^-, which also leads to the formation of •OH^- in the system. 

Keywords

Carbon nanotubes, humic acid, adsorption, titanium dioxide, photocatalyst.