Comparison between carbon nanotubes and molybdenum trioxide nanoparticles embedded in polymeric membrane for environmental remediation

In this study, a comparison was conducted involving novel chitosan/polyvinyl alcohol-based membranes comprising carbon nanotubes and molybdenum trioxide nanoparticles. This comparison's primary focus was to assess synthesized membranes' effectiveness in removing methyl red from aqueous solutions. The Fourier transform infrared spectroscopy and scanning electron microscopy confirmed the presence of specific functional groups and homogeneous dispersion of carbon nanotubes and molybdenum trioxide nanoparticles within the membranes, respectively. The membranes underwent additional characterization using various swelling parameters to assess mechanical strength and cross-linking. These parameters included swelling over time in water, swelling in electrolyte solutions, and different pH solutions and gel fraction analysis. Furthermore, the diffusion of water adhered Fickian diffusion principle. Various adsorption parameters were employed, including batch studies, isotherm studies at different pH levels, and temperature studies. The results of the batch study highlighted that chitosan/polyvinyl alcohol/carbon nanotubes membrane exhibited the highest adsorption, reaching approximately 9.7 mM/g (98%) and achieving equilibrium within 60 min. The maximum adsorption of methyl red was observed at pH 7 and decreased with increasing temperature. Moreover, the experimental data were simulated using kinetic models (pseudo-first-order, pseudo-second-order, Elovich model, and diffusion model) and isothermal models (Freundlich, Langmuir, and Langmuir Freundlich). Data indicated that pseudo-first order was the best-fitted model, which confirms physisorption. Among the isothermal models, Langmuir exhibited the most suitable fit, confirming that single-layer adsorption had taken place on the adsorbent surface. Thermodynamic parameters were studied, ensuring the adsorption process was exothermic and spontaneous.