Carbon nanotubes: Mechanism, Langmuir Hinshelwood growth kinetics and it application for the removal of Chromium (VI)

Abstract

In this study, kinetic model for decomposition of acetylene for the production of carbon nanotubes (CNTs) have been explored. The kinetics model described the CNTs growth in the chemical vapour deposition (CVD) reactor while Arrhenius equation was employed for the determination of the activation energy. The result of the analysis shows activation energy of 237.2483 kJmol-1 which is an indication that the reaction that leads to the production of CNTs is adsorption inclined. The observed frequency factor shows that the reactants’ particles collide at faster rate which enhances CNTs growth. The prepared CNTs were characterized using high resolution scanning electron microscope/high resolution transmission electron microscope (HRSEM/HRTEM), selected area electron diffraction (SAED), energy dispersive spectroscope (EDS) and Brunauer Emmett Teller (BET) method for morphology, crystallinity, elemental composition and surface area. CNT with best physiochemical properties was used to investigate effect of CNTs dosage, pH, contact time and temperature on percentage removal of chromium (VI). The pseudo first and second order rate equations were tested on kinetic data and the pseudo fist order rate kinetics best described the adsorption process. The equilibrium data shows satisfactorily fitted the Langmuir isotherm (R2= 0.9914) than the Freundlich isotherms (R2= 0.09758), Dubinin-Radushkevich isotherms (R2= 0.9092) and Temkin isotherm (R2= 0.9355)