Preparation and Characterization of Acrylamide-2-Methyl Propane Sulfonic Acid (AMPS) and Acrylamide (AAm) Hydrogel, and Its Applications in Removal of Heavy Metals (Cu2+, Pb2+)

The current research aimed to absorb heavy metal ions (Cu2+ and Pb2+) from wastewater. The hydrogel of acrylamide (AAm) and acrylamide-2-methylpropanesulfonic acid (AMPS) was prepared in different molar ratios of feed compositions (1:1, 1:2 and 1:0.25) by the free radical polymerization method. Potassium persulfate (KPS) was used as an initiator, and N, N’methylene-bis-acrylamide was used as a crosslinking agent at 70°C for seven hours.  AAm is a neutral monomer, and AMPS is a solid acidic monomer. Strong complexes were obtained when two monomers with different molar ratios of feed composition were mixed. The complex was analyzed by UV-Vis spectroscopy. The swelling properties of the prepared hydrogels were investigated at different pH values, temperatures, and ionic strengths. Fourier transform infrared (FT-IR) and thermogravimetric analysis (TGA) were used to study the hydrogels’ structural behavior and thermal stability. The diffusion phenomenon was investigated for the prepared hydrogels at a pH of 7, considering the non-Fickian state. The Cu+2 and Pb+2 adsorption from wastewater by the prepared hydrogels at different mole ratios of a feed composition was investigated by Atomic Absorption Spectrometry (AAS). Moreover, the morphology of the hydrogel was evaluated by Scanning Electron Microscopy (SEM). The surface adsorption fitting results indicated a higher correlation coefficient of 0.9588 for hydrogel in 1:2 [or M4(Cu2+)] mole ratio of feed composition adsorption in both Langmuir and Freundlich isotherms. The evaluation of adsorption kinetics indicated a strong fit of the pseudo-first-order Elovich model, evidenced by correlation coefficients of 0.9685 and 0.9186 for Cu2+ and Pb2+ adsorption, respectively.