The heavy metal adsorption characteristics on metakaolin-based geopolymer

Since porous materials often function as adsorbents, this study chose to investigate the adsorption of heavy metals by geopolymers. The geopolymer was made by condensing a mixture of metakaolin and alkali solution at a fixed ratio at room temperature and then pre-crashed to a fixed-radius size. This paper examined the adsorption efficiency of the geopolymer for different heavy metals (i.e., Pb2+, Cu2+, Cr3+, and Cd2+) in aqueous solutions under discrete experimental parameters. The experimental results verified that the geopolymer could adsorb heavy metals. Of the metals tested, optimal adsorption with the implementation of the geopolymer occurred with Pb2+. The data fit both the pseudo-second-order and the Langmuir equations. This discovery may facilitate the development of optimized procedures for wastewater treatment, thus providing an alternative solution to environmental damages caused by heavy metal pollutants.

► The adsorption efficiency of the geopolymer for different heavy metals.
► Geopolymer could adsorb heavy metals, having the best adsorption for Pb2+.
► Adsorption dynamics fit the pseudo-second-order kinetic model well.
► Both physical adsorption and chemical bonding are containing the adsorption mechanism.