Microwave-assisted synthesis of biodegradable interpenetrating polymer network of aloe vera–poly(acrylic acid-co-acrylamide) for removal of malachite green dye: equilibrium, kinetics and thermodynamic studies

The present work deals with the synthesis of a biodegradable interpenetrating polymer network (IPN) consisting of natural polysaccharide aloe vera, acrylamide and acrylic acid. Biodegradability of the synthesized IPN was studied through soil burial and composting methods. The synthesized IPN was completely degraded within 70 days through the composting method and showed 91% degradation within 77 days through the soil burial method. Evidence of biodegradation of the synthesized IPN was studied by different techniques, for instance Fourier infrared spectroscopy and scanning electron microscopy. The synthesized IPN was used as a device for the removal of malachite green dye. The effect of different reaction parameters on IPN synthesis and dye removal was investigated. The maximum dye adsorption occurred at pH 4.5, because at this pH methylene green dye molecules are present in monomeric state. The result of Weber–Morris intra-particle diffusion showed that the rate-limiting step was not the intra-particle diffusion. The adsorption isotherm models, i.e., Langmuir, Freundlich, Dubinin–Radushkevich, Temkin, Redlich–Peterson and Sips, were studied and it was found that the Langmuir was the best-fitting model for the experimental data. An increase in temperature resulted in a decrease in malachite green dye removal, suggesting that the adsorption process was exothermic in nature. This synthesis is important from industrial viewpoints.