Removal of Cationic Dye from Aqueous Solution by a Macroporous Hydrophobically Modified Poly(acrylic Acid-acrylamide) Hydrogel with Enhanced Swelling and Adsorption Properties

A macroporous, hydrophobically modified poly(acrylic acid-acrylamide) hydrogel was prepared. The fourier transform infrared (FTIR) spectrum and field emission scanning electron microscopy (FE-SEM) results showed that the hydrogel had a macroporous structure. The dynamic swelling and removal of cationic dyes, crystal violet (CV) and basic magenta (BM), by this macroporous hydrophobically modified poly(acrylic acid-acrylamide) hydrogel were studied. The adsorption capacity and kinetic and isotherm studies of the cationic dyes into the hydrogels have been evaluated. It was found that the macroporous hydrophobically modified hydrogel (M) exhibited improved swelling and adsorption capacity compared with the non-macroporous hydrophobically modified hydrogel (NM). The adsorption process agreed very well with the Langmuir model and the adsorption of the cationic dyes depended on the pH of the solution via a mechanism combining swelling, electrostatic, and hydrophobic interactions. Moreover, adsorption kinetic studies showed that the adsorption followed a pseudo-second-order kinetic model, indicating that chemical adsorption was the rate-limiting step.