Eco-friendly ceramsite from dredged sediment/biomass for Pb(II) removal: Process optimization and adsorption mechanistic insights

The disposal of dredged sediment (DS) is a challenge because of its output and ecotoxicity. Highly toxic Pb(II) enriched in aquatic environment has become a severe global issue. In this study, we developed a new type of ceramsite by co-utilizing of DS and rice husk (RH) to remove Pb(II) from aquatic environments from the viewpoint of "using waste to treat waste." Optimized ceramsite (D9R1-C) sintered at 1120 degrees C with 10% RH additive, exhibited excellent adsorption potential and environmental friendliness. RH addition was an essential component in obtaining ceramsite with richer pore structures, higher polymerization degree and more zeolite serials contents. D9R1-C had selective adsorption to Pb(II), with a maximum adsorption capacity of 18.53 mg/g. The incorporation of adsorption kinetics, isotherms, and thermodynamics, it indicated that adsorption behavior of D9R1-C was codetermined by physisorption and chemisorption. Between the two, physisorption was uppermost. The detailed adsorption mechanism was summarized as follows: (1) physisorption occurred in the intersurface and pore structure of the sorbent; (2) Si-O-T or -OH bond from gismondine or gismondine-like phases combined with Pb(II) to form a stable Si-O-Pb bond; (3) Pb(II) disintegrated the skeleton structure of zeolite serials and then reacted with decomposed units to form Pb-containing minerals such as alamosite.