Synthesis of polyacrylonitrile-co-sodium methallyl sulfonate copolymer (AN69) and polyacrylic acid (PAA) membranes for the removal of methylene blue from water

Abstract

The scope of this work is focused on the removal of methylene blue (MB) from aqueous solution by adsorption (bach method) on polyacrylonitrile-co-sodium methallyl sulfonate copolymer (AN69) and polyacrylic acid (PAA) synthetic membranes which were prepared specifically for this purpose. Investigations have covered membrane properties and the determination of adsorption parameters. The immobilization of PAA chains into AN69 matrix was revealed by FTIR analysis, whereas the presence of small superficial microcavities was demonstrated by AFM scanning. Otherwise, the increase in PAA fraction (0 to 10%), in membrane composition, induces an increase in swelling ratio (12–22%) and ionic exchange capacity (0.8–1.2 meq/g). Moreover, the equilibrium adsorption capacity improves with the increase in alkalinity of initial adsorbate solution (pH = 2–11) and with the concentration (C = 20–80 mg/L). The results of kinetic adsorption show that the mechanism of adsorption is perfectly fitted by pseudo-second order (R2 = 0.999) and the isotherm adsorption follows the Freundlich isotherm (R2 = 0.98). From the different applied adsorption models, it was found that the maximum Langmuir adsorption capacity Qm was 116 mg/g and the Freundlich index of adsorption n was 2.2.