Preparation of porous sustainable adsorbent and its adsorption behavior for Pb²

Using granulated blast furnace slag as raw material, chitosan and NaCl as modifier, chitosan modified granulated blast furnace slag based porous geopolymer (PCG) was prepared under the activation conditions of NaOH and sodium silicate. It was used to wrap different types of lightweight aggregates to obtain PCG-lightweight aggregate shell-core structure (PCG-L). PCG-L was used for the adsorption of Pb²⁺. Firstly, the influencing factors on the adsorption performance of the main component materials (PCG, lightweight aggregates) of PCG-L were studied. Then, the static adsorption properties and sustainable adsorption properties of Pb²⁺ by different shell-core structures were investigated. The relationship between the water absorption characteristics of the paste and the aggregate and the adsorption characteristics of PCG-L towards Pb²⁺ was established. The adsorption kinetics, adsorption isotherms and adsorption thermodynamics were analyzed. Finally, the adsorption mechanism of PCG-L was discussed by Zeta analyzer, FT-IR, EDS, XPS and MIP. The results indicate that as chitosan (0-2 wt%) and NaCl (0-60 wt%) increase, the saturated adsorption capacity of PCG for Pb²⁺ rises (98.57-159.93 mg/g). The Pb²⁺ adsorption capacity of lightweight aggregate (0.34-1.21 g/dm³) increases with its water absorption (0.2-15.0%). Under the premise that the water absorption rate of aggregate is greater than that of PCG, the higher the water absorption rate of the two, the stronger the adsorption capacity of the matching PCG-L, the maximum adsorption capacity of A2N30-H is 5.12 g/dm³ and it can still maintain a high removal rate after 40 cycles of adsorption. PCG-L adsorption via ion exchange, electrostatic attraction, surface complexation, and pore fixation.