Improved Pb(II) removal in aqueous solution by sulfide@biochar and polysaccharose-FeS@ biochar composites: Efficiencies and mechanisms

Novel biochars, namely nano iron [email protected] walnut shell biochar ([email protected]), [email protected] and [email protected], were prepared by WNS loaded with nano FeS and starch (or chitosan). Nano FeS can be effectively improved lead ions (Pb(II)) removal and starch (or chitosan) improved the stability of FeS and the defect of easy agglomeration. The materials were characterized by SEM, EDS, FTIR and XRD, and the preparation was successful. The adsorption capacity of Pb(II) reached 63.5, 80.0, 84.7 mg g−1 under 0.5 g L−1 of [email protected], [email protected] and [email protected] The adsorption of Pb(II) on the materials was more consistent with the pseudo-second-order kinetic model (K2 = 0.001–0.005 g (mg·min)−1, R2 = 0.980–0.999) and Langmuir model (R2 = 0.974–1.00), indicating that the adsorption of Pb(II) was mainly monolayer adsorption dominated by chemical adsorption. △G < 0 (-3.7~-6.97) and △H > 0 (1.56–20.49) indicated that the reaction was a spontaneous endothermic process. The mechanisms of Pb(II) removal from aqueous solutions involved electrostatic attraction, hydrogen bonding, physical adsorption, ion exchange and oxidoreduction. Additionally, stability and reusability of [email protected], [email protected] and [email protected] was good. The novel sorbents of [email protected] and [email protected] can be used in Pb(II) wastewater treatment.