Improvement of photocatalytic decomposition of methyl orange by modified MWCNTs, prediction of degradation rate using statistical models

Sedigheh Abbasi

doi:10.1007/s10854-021-05707-x

Abstract

Multi-walled carbon nanotubes (MWCNTs) have been successfully modified with TiO2 nanoparticles via a two-step hydrolysis technique. Firstly, the pristine MWCNTs are functionalized in nitric acid (HNO3) to creation of oxygen containing groups. Secondly, TiO2 nanoparticles are synthesized on the surface of functionalized MWCNTs through hydrolysis method. The synthesized samples have been used as photocatalyst for decomposition of methyl orange (MO) as dye organic pollutant. The characterization of samples using X-ray diffraction pattern (XRD) confirm the presence of TiO2 nanoparticles with mixture of anatase and rutile phases. Regarding the photocatalytic performance of TiO2 nanoparticles and modified MWCNTs with TiO2 nanoparticles, it observed that the degradation rate of MO increases by increasing the irradiation time from 5 to 35 min. The variation of degradation rate upon pH of suspension reveals that the maximum and minimum degradation rate are in acidic (pH = 3) and neutral condition (pH = 7). Meanwhile, the results show that the presence of MWCNTs leads to the enhancement of degradation rate. The analysis of variance (ANOVA) results confirm that both of main factors (irradiation time and pH) and their interaction have a significant influence on the degradation rate of MO. However, the effect of irradiation time is more than that of pH and their interaction. The graphical methods verify the quality and adequacy of the statistical models for prediction of the degradation rate.

Highlights

The elimination of organic contaminates from wastewater of industries is a major problem in the recent decades
The results show that the presence of Multi-walled carbon nanotubes (MWCNTs) leads to the enhancement of degradation rate
The correlation between experimental data and predicted values that are obtained by statistical model of TiO2 nanoparticles and modified MWCNTs with TiO2 nanoparticles are presented in Fig. 13 and Fig. 14, respectively. Regarding these Figures, it can be observed that there is a good consistency among actuals and predicted degradation rate of methyl orange (MO)

Summary

Introduction

The elimination of organic contaminates from wastewater of industries is a major problem in the recent decades. The application of semiconductor photocatalysts is a new approach for decomposition of organic pollutants [1, 2]. In this technique, a light source with energy higher than the band gap of used semiconductors is applied [3]. The other technique for decreasing the recombination rate of electrons and holes is application of a specific support with high surface area such as multi-walled carbon nanotubes (MWCNTs) and graphene oxide (GO) [10]. The coupling of semiconductor oxides to the carbon supports can decrease the recombination of electrons and holes It has a synergistic effect on the enhancement of energy range that stimulates electrons [13]

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Conclusion