Static and dynamic adsorption of copper ions on chitosan/polyvinyl alcohol thin adsorptive membranes: Combined effect of polyethylene glycol and aminated multi-walled carbon nanotubes

Polyethylene glycol (PEG) and amino-modified multi-walled carbon nanotubes (MWCNT-NH2) were utilized to modify chitosan/polyvinyl alcohol (CS/PVA) thin adsorptive membranes for copper ion adsorption. SEM, AFM, water affinity and mechanical analysis were performed for membrane characterization. Batch adsorption experiments were conducted to determine the effects of additive, pH, metal concentration and temperature on adsorption. Macroporous membranes were prepared by introducing PEG into the casting dopes; however, the upper limit for PEG loading was 5 wt%. Adsorption capacity of CS/PVA membrane was increased from 11 to 30 mg/g by addition of 5 wt% PEG to the blend. Addition of MWCNT-NH2, especially at optimal concentration of 1 wt%, improved membranes adsorption/transport behavior by creation of nanochannels and supplementary interstices in the compact CS/PVA matrix. Copper ion adsorption on CS/PVA membrane was elevated from 11 to 19 mg/g by introducing 1 wt% MWCNT-NH2. Thermodynamic parameters (Delta H degrees, Delta S degrees and Delta C degrees) revealed endothermic nature, favorability and spontaneity of the adsorption. Moreover, kinetic studies showed that MWCNT-NH2 plays primary role in adsorption rate enhancement. Adsorptive membranes containing combined MWCNT-NH2 and PEG (called 'CPMP'), demonstrated superior sorption capacity (similar to 35 mg/g) and reusability among tested membranes. Finally, thin adsorptive membranes were tested in dynamic mode using a dead-end filtration setup. CPMP showed superior performance as expected. Based on the results, introducing combined MWCNT-NH2-NH2 and PEG can greatly elevate CS/PVA membranes capability for adsorptive removal of copper ions from water. (C) 2012 Elsevier B.V. All rights reserved.