Sorption-desorption characteristics and internal mechanism of lead ions on polycarboxylic ion exchange resin

Conventional adsorbents rely on surface active sites (or unsaturated energy) to adsorb heavy metal pollutants by intermolecular force. Its efficient adsorption is limited by the number of active groups. Ion-exchange resins adsorb multiple metal ions in the Coulomb force adsorption mode, which the sorption capacity is generally better than that of traditional adsorbents limited by surface active sites, nevertheless. In this paper, sodium polyacrylate (PAANa) was prepared by solution polymerization. A series of batch sorption and desorption experiments were carried out to investigate the effects of contact time, pH value, temperature and lead ions concentration on PAANa. The structure of PAANa was tested by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). The results show that the maximum sorption capacity of PAANa for lead ions more than 173.6 mg/g, which has a higher sorption upper limit. The mechanism of superior adsorption of lead ions is attributed to the ion-exchange and chelating ability of functional groups (e.g., -COO-) in the PAANa matrix. The sorption/desorption isotherm of PAANa is an exponential curve. The phenomenon indicates that there is osmotic pressure difference between PAANa and the external environment after lead ion adsorption. Furthermore, the SEM analysis shows that PAANa has a loose and porous structure, which increases the specific surface area and sorption efficiency. As an environmentally friendly clean production material, PAANa has great potential in practical application.

Automated summary

This study investigates the enhanced adsorption capacity of sodium polyacrylate (PAANa) on lead ions. It demonstrates that PAANa has a high sorption upper limit and can effectively adsorb lead ions due to its ion-exchange and chelating ability, as well as its loose and porous structure that increases specific surface area and sorption efficiency.