Poly(lactic acid)-poly(ethylene glycol)/Magnesium Silicate Membrane for Methylene Blue Removal: Adsorption Behavior, Mechanism, Ionic Strength and Reusability Studies

In this work, the effect of magnesium silicate (MgSiO3) as a filler on poly(lactic acid)-poly(ethylene glycol) (PLA-PEG) membrane was investigated towards the enhancement of adsorption capacity for removal of cationic dye. The preparation and fabrication of membranes were performed through copolymerization and phase inversion techniques. Analysis of functional groups, tensile strength, morphology and surface wettability were employed in the characterization of the membranes. After the addition of MgSiO3, it was found that the PLA-PEG/MgSiO3 membrane presented a higher hydrophilic property with improved mechanical strength. Next, the adsorption of methylene blue (MB) was optimized using response surface methodology (RSM) with the parameters mass of membrane and initial concentration of MB solution. The effects of pH and ionic strength were also examined to determine the mechanism involved during adsorption processes, which later were found to be electrostatic interaction and ion-exchange mechanism. From the isotherms and kinetics studies, the PLA-PEG/MgSiO3 membrane was well fitted by the Freundlich model and pseudo second order model, respectively. This membrane also demonstrated reusable character of up to six cycles.