Efficient Pb(II) removal using sodium alginate–carboxymethyl cellulose gel beads: Preparation, characterization, and adsorption mechanism

• Synthesis of SA–CMC–Ca–Fe gel beads through cross-linking beading of SA and CMC in CaCl2 and FeCl3 solutions.
• SA–CMC gel bead shows larger specific surface area and porosity due to the internal network structure.
• The lead ions’ removal rate by SA–CMC is significantly better than the conventional adsorbents.
• The high Pb2+ adsorption capacity of SA–CMC was discussed by different adsorption isotherms.
• Based on different kinetic study, chemical adsorption is the main adsorption process of Pb2+ adsorption of SA–CMC gel beads.

Alginate–carboxymethyl cellulose (CMC) gel beads were prepared in this study using sodium alginate (SA) and sodium CMC through blending and cross-linking. The specific surface area and aperture of the prepared SA–CMC gel beads were tested. The SA–CMC structure was characterized and analyzed via infrared spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Static adsorption experiment demonstrated that Pb(II) adsorption of SA–CMC exceeded 99% under the optimized conditions. In addition, experiments conducted under the same experimental conditions showed that the lead ion removal efficiency of SA–CMC was significantly higher than that of conventional adsorbents. The Pb(II) adsorption process of SA–CMC followed the Langmuir adsorption isotherm, and the dynamic adsorption model could be described through a pseudo-second-order rate equation. Pb(II) removal mechanisms of SA–CMC, including physical, chemical, and electrostatic adsorptions, were discussed based on microstructure analysis and adsorption kinetics. Chemical adsorption was the main adsorption method among these mechanisms.