Developing montmorillonite/PVDF/PEO microporous membranes for removal of malachite green: adsorption, isotherms, and kinetics

Montmorillonite clay nanoparticles (0, 10, 20, and 30 wt.% MMT) were hybridized with Poly(vinylidene fluoride)/polyethylene oxide (PVDF/PEO) polymer matrix for the removal of malachite green (MG) dye for the first time. Clay was chosen because it is a naturally occurring material, abundant, low cost, environmentally friendly, and has high surface area, good adsorption properties, and microporous layered structure. The cross section field-emission scanning electron microscope (FESEM) images proved the absence of interface between PVDF and PEO, which indicating good compatibility between two polymers. Additionally, the incorporation of MMT in the polymer matrix induced the formation of microporous structure. X-ray diffraction (XRD) and Attenuated Total Reflection Fourier Transformer Infrared (ATR-FTIR) analyses confirmed the good interaction between membrane components. The results revealed that the optimum composite membrane is more thermally stable compared to pure PVDF/PEO and acheived 95.4% removal and 33.4 mg/g adsorption capacity. The sorption data at equilibrium obeyed the Langmuir model (R-2 = 0.9961) rather than Freundlich, Dubinin-Radushkevich, and Temkin isotherm models, proving a monolayer adsorption of MG. The adsorption kinetics were studied and according to R-2, the pseudo second order is the best to fit the experimental results indicating that the chemisorption is the rate-limiting step for MG sorption onto MMT/PVDF/PEO membranes.