Removing Cationic Dye from Aqueous Solutions Using as-grown and Modified Multi-Walled Carbon Nanotubes
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Department of Environmental Protection, Maritime University of Szczecin, Szczecin, Poland
Institute of Chemical and Environment Engineering, West Pomeranian University of Technology, Szczecin, Poland
Submission date: 2017-10-12
Final revision date: 2017-12-10
Acceptance date: 2018-02-05
Online publication date: 2018-10-26
Publication date: 2018-12-20
Corresponding author
Wojciech Konicki   

Department of Integrated Transport Technology and Environmental Protection, Maritime University of Szczecin, Szczecin, Poland, H. Pobożnego St. 11, 70-507 Szczecin, Poland
Pol. J. Environ. Stud. 2019;28(2):717-727
In this research we studied the adsorption process of Basic Red 46 (BR46) cationic dye onto as-grown (MWCNTs) and modified multi-walled carbon nanotubes (MWCNTs-MOD). MWCNTs were synthesized by the chemical vapor deposition method using ethylene as a carbon source and nanocrystalline iron as catalyst, and oxidized by concentrated nitric acid to give MWCNTs-MOD. The adsorbents were characterized by XRD, TGA, HRTEM, FTIR, BET, and zeta potential measurements. The effects of initial dye concentration (5 to 40 mg L-1), pH (4.0 to 11.5), and temperature (20, 40, and 60°C) on BR46 adsorption onto MWCNTs and MWCNTs-MOD were studied. The isotherm data were analyzed using Langmuir and Freundlich equations. The equilibrium data fit well the Langmuir isotherm for both MWCNTs and MWCNTs-MOD. The maximum adsorption capacities of BR46 onto MWCNTs and MWCNTs-MOD were 19.5 and 51.8 mg g-1, respectively. The pseudo first-order and pseudo second-order kinetic models and the intraparticle diffusion model were used to describe the kinetic data. Kinetic studies showed that the kinetic data were well described by the pseudo second-order kinetic model. The experimental results indicated that the maximum BR46 removal could be attained at a solution pH of 11.5 and the adsorption capacity obtained was 23.5 and 57.2 mg g-1 for MWCNTs and MWCNTs-MOD, respectively. Thermodynamic parameters (ΔGO, ΔHO, ΔSO) were obtained and it was found that the adsorption of BR46 onto MWCNTs and MWCNTs-MOD was an endothermic and spontaneous process.
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