Adsorptive removal of organic dyes from aqueous solutions using acrylic acid-acrylonitrile-N-isopropylacrylamide polymeric gels as adsorbents: linear and non linear isotherms

The polymeric gels, acrylic acid-acrylonitrile-N-isopropylacrylamide with varying contents of N-isopropylacrylamide (NS1, NS2, NS3, and NS4), were prepared via free radical polymerization. Adsorption studies of methylene blue and bromophenol blue were carried out on the synthesized gels at 298 and 308K. Among all the adsorbents, the gel NS4 showed better adsorption percent for the removal of methylene blue from aqueous solutions. This gel was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy before and after adsorption of methylene blue. The equilibrium data were fitted to both linear and nonlinear models in an urge to find the accurate results. It was found that the adsorption of methylene blue on the adsorbent NS4 was well described by the Langmuir adsorption isotherm in both linear and nonlinear analyses. The adsorption capacity calculated from the Langmuir model was 2.79mg/g for the adsorption of methylene blue dye on the adsorbent NS4. The kinetic data followed pseudo-second-order model revealing that both the internal and external mass transfers were taking place. Keeping in view the higher value of adsorption capacity, it is suggested that the synthesized adsorbent NS4 can be effectively used for the removal of methylene blue dye from aqueous solutions.