Design of recoverable biochar/alginate gel and its removal performance for Pb(II) in water: Simulation and experiment

In this paper, activated biochar and alginate are combined to form gel for the removal of Pb(II) in water. This composite not only improves the adsorption performance of biochar for Pb(II), avoiding the drawback of difficult recovery of biochar but also enhances the structural stability of alginate gel in the recycling process by utilizing biochar. The adsorption mechanism of Pb(II) on functional group-modified carbon and alginate structures, as well as the structural stability of the adsorbent, were observed using density functional theory (DFT) and molecular dynamics (MD) simulations. The results indicate that the adsorption of carboxyl groups to Pb(II) is stronger than that of hydroxyl groups, and the adsorption performance of alginate is stronger than that of carbon. Carbon improves the stability of the composite adsorbent. The biochar/alginate composite gel was synthesized by compounding activated platanus acerifolia leaf charcoal with alginate and was used in the experiment of removing Pb(II) from water. The experimental results achieved the expectations of the simulation. The adsorption isotherms and kinetic data were analyzed and fitted. The results indicate that the adsorption isotherms conform to the Langmuir model, and the adsorption kinetics follow pseudo-second-order adsorption.