Kaolinite can be used as in-furnace adsorbent to capture gaseous semi-volatile metals during combustion, incineration, or gasification processes for the purposes of toxic metals emission control, ash deposition/slagging/corrosion inhibition, ultrafine particulate matter emission control, and so on. In this work, the adsorptions of typical heavy metals (Pb and Cd) and typical alkali metals (Na and K) by meta-kaolinite were investigated by the DFT calculation. The adsorption energies followed the sequence of NaOH-Si surface > KOH-Si surface > PbO-Al surface ≈ CdO-Al surface ≈ NaOH-Al surface > KOH-Al surface > NaCl-Al surface ≈ Na-Si surface > Na-Al surface > KCl-Al surface > Pb-Al surface > PbCl₂-Al surface > CdCl₂-Al surface ≈ K-Si surface ≈ PbCl-Al surface > K-Al surface > CdCl-Al surface > NaCl-Si surface > KCl-Si surface > Cd-Al surface. Si surface was found available to the adsorptions of Na, K, and their compounds, although it was invalid to the adsorptions of Pb, Cd, and their compounds. The interactions between adsorbates and surfaces were revealed. Furthermore, the discussion of combining with the experimental data was applied to the subject validity of calculation results and the effect of chlorine on adsorption and the effect of reducing atmosphere on adsorption.
Keywords: adsorption; cadmium; kaolinite; lead; potassium; sodium.