Modeling and Optimization of BT and DBT Photooxidation over Multiwall Carbon Nanotube-Titania Composite by Response Surface Methodology

Molood Barmala,Mohammad Behnood

doi:10.1155/2018/9716383

Abstract

This study investigates optimization of benzothiophene (BT) and dibenzothiophene (DBT) removal via a photocatalytic process by using central composite design (CCD) method. Temperature, pH, and p-25 to MWCNT ratio (g/g) in the composite structure are considered as design factors. According to the results, temperature has the greatest impact on removal rate. In optimal condition, after being exposed to UV lamps (9 W) for 20 min, 59.8% of the solutions’ BT was removed, while DBT was completely removed. Although the generated structure band gap is 3.4, but due to the presence of MWCNTs in the structure, it is capable of absorbing visible light, and this leads to complete removal of DBT and 42% removal of BT under visible light radiation (in similar circumstances). Kinetics analysis of thiophene’s reaction showed that, in the presence of visible light, first order removal rate constants for DBT and BT are 7.98 and 0.953 1/h, respectively.

Highlights

With dramatic growth of petrochemical and automotive industries, air pollution caused by sulfur dioxide has become one of the major global problems
Given that very few research studies are conducted on the use of nanotubes to increase the efficiency of photocatalytic removal of thiophenic compounds based on studies done so far, the aim of this study is to evaluate the effect of important factors on removal of BT and DBT, as sample compounds with low reactivity, by using MWCNT-titania composite
Higher ratios may lead to light scattering in solution; though, they may inversely affect photocatalytic removal rate [5, 7, 16, 19]

Summary

Introduction

With dramatic growth of petrochemical and automotive industries, air pollution caused by sulfur dioxide has become one of the major global problems. Hydrogen desulfurization is considered as a common process for sulfur removal. The process requires large amounts of hydrogen and huge reactors [4,5,6]. Hydrogen process cannot remove thiophene and its derivatives which exist in heavy oil compounds [1, 2, 4, 6, 7]. To save energy and reduce costs, an alternative desulfurization process needs to be developed. In thiophenic compound removal, advanced oxidation processes, which begin with oxygen radicals, may take 3 forms: chemical, bio-, and photooxidation [8,9,10]. The great advantage of photocatalytic removal compared to the previous two processes is that it occurs under ambient temperature and pressure, so after a reasonable time, an acceptable amount of pollutant is eliminated [6, 10]

Objectives

Methods

Results

Conclusion