Sustainable remediation of Pb(II) from wastewater using gel bead of sodium alginate-living Chlorella sorokiniana FK-montmorillonite.

This study presents a novel adsorbent of sodium alginate (SA)-living Chlorella sorokiniana FK-montmorillonite (MMT) gel beads (SA-CHL-MMT gel beads) for Pb(II) removal from wastewater. The Chlorella sorokiniana FK-MMT composite was encapsulated within the sodium alginate-Ca (II) network. The structure protected the inner Chlorella from Pb(II) toxicity, resulting in a 2.83-fold increase in its survival rate. The Pb(II) adsorption behavior was well described by the pseudo-second-order kinetic model and Langmuir isotherm model, suggesting monolayer surface adsorption with intra-particle diffusion as the rate-limiting step. The SA-CHL-MMT gel beads achieved a maximum Pb(II) adsorption capacity of 134.9 mg/g at 308.15 K. Thermodynamic analysis demonstrated that Pb(II) adsorption was spontaneous and exothermic. The gel beads after Pb(II) adsorption were characterized by Zeta potential, SEM, FT-IR, XRD, and XPS. The results demonstrate that Pb(II) was initially adsorbed onto MMT and SA throough electrostatic attraction, pore filling, surface complexation, and cation exchange, followed by the formation of Pb(II)-containing minerals induced by living Chlorella. The gel beads exhibited excellent regeneration performance, swelling stability, and high selectivity for Pb(II) removal from real wastewater. Overall, this study represents the first attempt to prepare gel materials with living Chlorella, and to develop a useful and sustainable strategy for Pb(II) remediation in complex wastewater.