THE INFLUENCE OF PHYSICAL CONFIGURATION ON THE PERFORMANCE OF CHITOSAN-POLY(ACRYLIC ACID) HYDROGEL BEADS AS ADSORBENT FOR LEAD(II)

摘要

Polymer composites of various configurations have been utilized as adsorbent materials to remove heavy metals from the aquatic environment. In this study, the influence of physical configuration on the prevailing adsorption mechanisms and capacity of adsorbents was elucidated by using chitosan-poly(acrylic acid) (CS-PAA) hydrogel beads in the dry and wet states and comparing their ability to remove Pb(ll) from solution. In the production of the beads, crosslinking with glutaraldehyde (GLA) led to the formation of a semi-interpenetrating polymer network (semi-IPN) with enhanced capacity for metal chelation. Meanwhile, the successful integration of CS and PAA was verified by attenuated total reflectance-infrared (ATR-IR) spectroscopy which showed the presence of functional groups contributed by both polymers. Vacuum drying was employed to produce the hard and rigid dry polymer beads. Scanning electron microscopy (SEM) showed that the beads had a convoluted polymer surface covering a homogeneous, compact, and impermeable inner structure. Owing to the non-porous nature of the dry beads, Pb(ll) uptake was limited to 37.85 mg/g. However, the use of the wet configuration enabled the internal polymeric material to contribute to the adsorption process through intraparticle diffusion, thereby increasing lead uptake. Intraparticle diffusion was confirmed to occur in three stages and the lead removal increased by 128.48% to 86.48 mg/g. This significant improvement underscores the influence of physical configuration in dictating the prevailing adsorption mechanisms and how it can be used to maximize the adsorptive capacity of polymer composites for the heavy metals in the environment.