Adsorption of Cadmium (II) Ions from Aqueous Solutions using Poly(Amidoamine)/Multi-Walled Carbon Nanotubes Doped Poly(Vinylidene Fluoride-Co-Hexafluoropropene) Composite Membrane

Document Type : Research Paper

Authors

1 Cnr R71; University Road University of Limpopo, N-Block, Office No. 1020

2 Cnr R71; University Road University of Limpopo

3 Chemistry, Science and Agriculture, University of Limpopo, South Africa

Abstract

Composite membranes consisting of Poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP) blended with functionalised multi-walled carbon nanotubes (MWCNTs) and poly-amidoamine (PAMAM) were prepared using a phase inversion technique for adsorptive elimination of Cd (II) ions from contaminated water samples. Upon the addition of PAMAM-MWCNTs on PVDF-HFP, a stable, microporous structure with enhanced surface area and hydrophilic composite membranes were obtained; as confirmed by Focused Ion Beam Scanning Electron Microscopy (FIB-SEM), Fourier transform infrared (FTIR), Thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) analysis and contact angle measurements. The pH, adsorption isotherm, thermodynamic parameters and reusability of the composite membranes were investigated in batch experiments. The maximum adsorption capacity of 1 wt.% PAMAM-MWCNTs/PVDF-HFP composite membrane calculated by Langmuir model was 167 mg/g at 25°C and pH 6.5. All composite membranes demonstrated that the Cd(II) ions adsorption conformed to Freundlich model (R2 = 0.999), which suggests that the adsorption process is multilayer. In addition, the thermodynamic parameters indicated that the adsorption process is spontaneous and endothermic in nature. The adsorption capacity of 1 wt.% PAMAM-MWCNTs/PVDF-HFP composite membrane remained above 90% after four reusability cycles, as confirmed by Inductively coupled plasma-optical emission spectrometry (ICP-OES) analysis. The 1 wt.% PAMAM-MWCNTs/ PVDF-HFP composite membrane exhibited higher selectivity coefficients towards Cd(II) in Cu(II), Zn(II) and Ni(II) binary metal solutions.

Highlights

• Thermally stable, hydrophilic composite membranes with high surface area

• 1 wt.% PAMAM-MWCNTs/PVDF-HFP showed maximum adsorption ability of 167 mg/g at 25°C

• Cd(II) adsorption conformed to Freundlich model

• Adsorption remained above 90% after four reusability cycles

Keywords

Main Subjects



Articles in Press, Corrected Proof
Available Online from 15 July 2020
  • Receive Date: 01 March 2020
  • Revise Date: 19 June 2020
  • Accept Date: 15 July 2020