Novel chitosan/poly(vinyl) alcohol thin adsorptive membranes modified with amino functionalized multi-walled carbon nanotubes for Cu(II) removal from water: Preparation, characterization, adsorption kinetics and thermodynamics
2012
Salehi, E. | Madaeni, S.S. | Rajabi, L. | Vatanpour, V. | Derakhshan, A.A. | Zinadini, S. | Ghorabi, Sh | Ahmadi Monfared, H.
In the current study, amino functionalized multi-walled carbon nanotubes (MWCNT-NH₂) were synthesized from raw MWCNTs and utilized to prepare novel chitosan/PVA thin adsorptive membranes for copper ion removal from water. Various weights of the CNTs were embedded in the membranes to obtain the optimum MWCNTs content. Finger-like nanochannels appeared in the compact structure of the CS/PVA membrane by addition of 0.5 wt.% of the MWCNTs; however, fibril-shape and dense structures were generated at higher percent weights i.e. 1 and 2 wt.%, respectively. Adsorption capacity of the membrane containing 2 wt.% MWCNTs (20.1mg/g at 40°C) was almost twice as large as that of the plain membrane (11.1mg/g); however, capacity enlargement was not significant (<3mg/g), when MWCNTs content raised from 1 to 2 wt.%. This indicates that the optimum CNT loading is 1 wt.%. Freundlich isotherm could, thus, superiorly describe the adsorption equilibria. Thermodynamic studies revealed spontaneous (ΔG°<0) and endothermic (ΔH°>0) adsorption together with entropy generation (ΔS°>0) at the solid/liquid interface. Additionally, kinetic studies showed that membranes with higher MWCNTs content could support faster adsorption rate. No significant adsorption capacity loss (∼3%) was observed for the membrane containing MWCNT-NH₂ in comparison to the capacity loss of the plain membrane (∼10%) after four successive adsorption/regeneration cycles. The results suggested that the novel CS/PVA/MWCNT-NH₂ composite membranes can be effectively applied for the adsorptive removal of copper ions from aqueous solutions.
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