Rhodamine B Photodegradation in Aqueous Solutions Containing Nitrogen Doped TiO2 and Carbon Nanotubes Composites.

Adelina Udrescu,Ionel Mercioniu,Stefania Florica,Madalina Chivu,Elena Matei,Mihaela Baibarac

doi:10.3390/molecules26237237

Adelina Udrescu, Ionel Mercioniu + Show 4 more

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https://doi.org/10.3390/molecules26237237

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Abstract

In this work, new results concerning the potential of mixtures based on nitrogen doped titanium dioxide (TiO2:N) and carbon nanotubes (CNTs) as possible catalyst candidates for the rhodamine B (RhB) UV photodegradation are reported. The RhB photodegradation was evaluated by UV–VIS absorption spectroscopy using samples of TiO2:N and CNTs of the type of single-walled carbon nanotubes (SWNTs), double-wall carbon nanotubes (DWNTs), multi-wall carbon nanotubes (MWNTs), and single-walled carbon nanotubes functionalized with carboxyl groups (SWNT-COOH) having various concentrations of CNTs. The best photocatalytic performance was obtained for sample containing TiO2:N and 2.5 wt.% SWNTs-COOH, when approx. 85% of dye removal was achieved after 300 min. of UV irradiation. The reaction kinetics of RhB aqueous solutions containing TiO2:N/CNT mixtures followed a complex first-order kinetic model. The TiO2:N/CNTs catalyst induced higher photodegradation efficiency of RhB than TiO2:N due to the presence of CNTs, which act as adsorbent and dispersing agent and capture the photogenerated electrons of TiO2:N hindering the electron–hole recombination.

Highlights

Titanium dioxide (TiO2) is a wide bandgap semiconducting material (3.0, 3.2, and 3.5 eV for rutile, anatase, and brookite phases, respectively) that has gained special attention due to its nontoxicity, and chemical and physical stability [1,2]
The rhodamine B (RhB) photodegradation was evaluated by UV–VIS absorption spectroscopy using samples of TiO2:N and CNTs of the type of single-walled carbon nanotubes (SWNTs), double-wall carbon nanotubes (DWNTs), multi-wall carbon nanotubes (MWNTs), and single-walled carbon nanotubes functionalized with carboxyl groups (SWNT-COOH) having various concentrations of CNTs
This study is focused on the following important aspects regarding the photodegradation of RhB in aqueous solutions containing TiO2:N/CNT composites: (i) the determination of the optimal single-walled carbon nanotube (SWNT) concentration in TiO2:N/SWNT composites to obtain the best photocatalytic activity; (ii) the influence of CNTs, including double-wall carbon nanotubes (DWNTs), multi-wall carbon nanotubes (MWNTs), and single-walled carbon nanotubes functionalized with carboxyl groups (SWNTs-COOH), on the photocatalytic efficiency of composites based on TiO2:N/CNTs; and (iii) the explanation of the rate kinetic mechanism of RhB aqueous solutions in the presence of TiO2:N/SWNTsCOOH mixtures

Summary

Introduction

Titanium dioxide (TiO2) is a wide bandgap semiconducting material (3.0, 3.2, and 3.5 eV for rutile, anatase, and brookite phases, respectively) that has gained special attention due to its nontoxicity, and chemical and physical stability [1,2].

Results

Conclusion