Photocatalytic Activity of Carbon Nanotubes and Zinc Oxide Composite Catalyst on Methylene Blue under Ultraviolet and Visible Light Irradiation

Authors

  • Remmus Roi L. Banzuela

Keywords:

Photocatalytic degradation, carbon nanotubes, zinc oxide, ultraviolet, visible light, irradiation

Abstract

INTRODUCTION

Water pollution caused by plastics, heavy metals, and dyes is a main source of diseases. Dyes are used by different industries to produce textile, plastics, and clothes. Fifteen percent of over 70,000 tons of commercially available dyes is lost during dyeing process and this leaching can affect both aquatic and human life. in this study, Methylene blue, a heterocyclic dye, will serve as an indicator of the photocatalytic activity of carbon nanotubes and zinc oxide composite catalyst under ultraviolet, visible, and without light irradiation.

METHODS

Multi-walled carbon nanotubes (MWCNTs) and zinc oxide (ZnO) composite catalyst were prepared with the following CNT-ZnO ratios: 0-100, 25-75, 50-50, 75-25, and 100-0 through heterogeneous mixing method. Methylene blue solution made from dissolving 60 mg of methylene blue powder into 2 L of distilled water was mixed with the composite catalyst, ultrasonicated for 5 mins, and then exposed to ultraviolet, visible, and without light irradiation for 30 mins with constant magnetic stirring. After irradiation, 4 mL was gathered and centrifuged, transferred into test tubes and the mean transmitted intensity (lux) was measured from each of the samples using a light sensor connected to a LabQuestTM spectrometer. The percent degradation was obtained using the formula [(P0 -Pi)/P0] x 100 where P0 and Pi are the sample and pure methylene blue solution transmittance, respectively.

RESULTS

Ratio 75-25 of CNT-ZnO yielded the highest percent degradation on methylene blue under ultraviolet, visible, and without light irradiation having 65.39%, 59.12%, and 56.59%, respectively. Meanwhile, lowest percent degradation was yielded by the ratio 0-100 having 45.01%, 10.85% and 10.09%, respectively. Statistical analysis showed that there is a significant interaction between the ratios of CNT-ZnO and light source irradiation on the percent degradation on methylene blue.

DISCUSSIONS

The ratio 75-25 of CNT-ZnO under ultraviolet, visible, and without light irradiation degraded methylene blue better implying that CNT-ZnO can be effectively used for water treatment and remediation. In congruence, the study conducted by Byrappa, et al. (2008) and Qu, Luo and Cong (2012) yielded similar results showing that the combination of CNT-ZnO has higher degradation efficiency compared to pure CNT and pure ZnO. Other composite catalysts and methods of fabricating it were recommended to establish better percent degradation.

Published

2019-01-18