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
Wojciech Konicki   

Department of Integrated Transport Technology and Environmental Protection, Maritime University of Szczecin, Szczecin, Poland, H. Pobożnego St. 11, 70-507 Szczecin, Poland
Online publication date: 2018-10-26
Publication date: 2018-12-20
Submission date: 2017-10-12
Final revision date: 2017-12-10
Acceptance date: 2018-02-05
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.