Design, synthesis, and characterization of glyoxime-functionalized hydroxypropyl methylcellulose/acrylic acid hydrogel for efficient removal of lead (II) ions from aqueous media

The present work describes the fabrication of a functionalized hydroxypropyl methylcellulose/acrylic acid hydrogel with glyoxime (OXIM-HPMC/AAC) through the free radical approach for the effective removal of Pb (II). Hydrogel characterization has been performed using FTIR, SEM, and EDX techniques. SEM showed the presence of porous three-dimensional structures that improve diffusion of metal ions in the hydrogel, but pores were partially blocked following adsorption because of the neutralization of charges. EDX results validated the Pb (II) adsorption by the presence of characteristic peaks. The gel fraction varied depending on the composition and ranged from 86.3% at OXIM-HPMC/AAC (70/30) to 77.6% at (30/70). The swelling capacity improved with increasing HPMC content to reach its maximum value of 219.6% after 5 h. Pb (II) removal efficiency was investigated under different experimental conditions, and the optimum values were determined to be pH 3.0, 45 min contact time, and a V/m ratio of 0.1 L/g. Adsorption kinetics followed the pseudo-second-order rate model with adsorption capacity (q e = 9.42 mg/g) and R 2 = 0.94, whereas equilibrium data followed the Langmuir isotherm model with monolayer adsorption of 20.4 mg/g and correlation coefficient of 0.95. Thermodynamic analysis showed the process to be spontaneous and exothermic.