title: Enhanced removal of Cr(VI) from aqueous solutions using polypyrrole wrapped oxidized MWCNTs nanocomposites adsorbent.
abstract: Polypyrrole wrapped oxidized multiwalled carbon nanotubes nanocomposites (PPy/OMWCNTs NCs) were prepared via in situ chemical polymerization of pyrrole (Py) monomer in the presence of OMWCNTs using FeCl3 as oxidant for the effective removal of hexavalent chromium [Cr(VI)]. The as-prepared PPy/OMWCNTs NCs were characterized by FE-SEM, HR-TEM, ATR-FTIR, XRD, XPS and BET method. Characterization results suggested that PPy was uniformly covered on the OMWCNTs surface and resulted in enhanced specific surface area. Adsorption experiments were carried out in batch sorption mode to investigate the effect of pH, dose of adsorbent, contact time, concentration of Cr(VI) and temperature. The adsorption of Cr(VI) on the nanocomposite surface was highly pH dependent and the kinetics of the adsorption followed the pseudo-second-order model. The adsorption isotherm data were in good conformity with the Langmuir isothermal model. The maximum adsorption capacity of the PPy/OMWCNTs NCs for Cr(VI) was 294mg/g at 25°C. The calculated values of the thermodynamic parameters such as ΔG(0) (-0.237kJ/mol), ΔH(0) (13.237kJ/mol) and ΔS(0) (0.0452kJ/mol/K) revealed that the adsorption process is spontaneous, endothermic and marked with an increase in randomness at the solid-liquid interface. The presence of co-existing ions slightly affected the Cr(VI) removal efficiency of the PPy/OMWCNTs.
authors.affiliation: Department of Applied Chemistry, University of Johannesburg, Johannesburg, South Africa.
authors.forename: Madhumita
authors.initials: M
authors.lastname: Bhaumik
authors.affiliation: Department of Applied Chemistry, University of Johannesburg, Johannesburg, South Africa.
authors.forename: Shilpi
authors.initials: S
authors.lastname: Agarwal
authors.affiliation: Department of Applied Chemistry, University of Johannesburg, Johannesburg, South Africa. Electronic address: vinodfcy@gmail.com.
authors.forename: Vinod Kumar
authors.initials: VK
authors.lastname: Gupta
authors.affiliation: Department of Applied Chemistry, University of Johannesburg, Johannesburg, South Africa; DST/CSIR National Centre for Nanostructured Materials, Materials Science and Manufacturing, Council for Scientific and Industrial Research (CSIR), Pretoria, South Africa. Electronic address: amaity@csir.co.za.
authors.forename: Arjun
authors.initials: A
authors.lastname: Maity
keywords: Adsorption; Isotherms; Kinetics; Nanocomposites; OMWCNTs; Polypyrrole