Synthesis of functionalized carbon nanotubes by floating catalytic chemical vapor deposition method and their sorption behavior toward arsenic

• Floating catalyst CNTs (FCNT) prepared without substrate using Ferrocene at lower temperature.
• Ferrocene serves the dual purpose as catalyst for CNT and sorption of arsenic.
• Functionalized by physical and chemical methods.
• Studies on the removal of As(III) and As(V) for the first time.
• Mechanism proposed by XPS studies.

In this work carbon nanotubes (CNT) were prepared by floating catalytic chemical vapor deposition method using Ferrocene and Benzene as hydrocarbon source. Use of ferrocene serves the dual purpose as the floating catalyst for the CNT formation and as well as to facilitate arsenic sorption. CNTs were further activated by two ways (1) chemical treatment of CNTs using nitric acid which oxidized CNTs (FCNT-OX), (2) heat treatment at 1000 °C in N2 atmosphere and further oxidized with nitric acid to obtain FCNT-HOX. The energy dispersive X-ray spectroscopy of FCNT, FCNT-OX and FCNT-HOX revealed the presence of iron in the CNTs. The specific surface area of FCNT, FCNT-OX and FCNT-HOX were found to be the prepared 74, 129 and 169 m2/g respectively. The adsorption properties of As(III)/As(V) as a function of pH, contact time and initial metal concentration were evaluated. The adsorption kinetics fitted the Pseudo Second Order Kinetics with correlation coefficients >0.99. The equilibrium data were modeled with Langmuir and Freundlich isotherms and various isotherm parameters were evaluated. The maximum adsorption capacity of FCNT-HOX towards As(III) and As(V) were found to be 5.99 and 6.37 mg/g respectively. It was found that the As(III)/As(V) adsorption capacity for the prepared adsorbents were in the order of FCNT-HOX > FCNT-OX > F CNT. Using XPS studies suitable mechanism for sorption of As(III) and As(V) has been postulated.

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