Characterization of Metal Oxide-modified Walnut-shell Activated Carbon and Its Application for Phosphine Adsorption: Equilibrium, Regeneration, and Mechanism Studies

Abstract

We prepared a kind of metal oxide-modified walnut-shell activated carbon (MWAC) by KOH chemical activation method and used for PH₃ adsorption removal. Meanwhile, the PH₃ adsorption equilibrium was investigated experimentally and fitted by the Toth equation, and the isosteric heat of PH₃ adsorption was calculated by the Clausius-Clapeyron Equation. The exhausted MWAC was regenerated by water washing and air drying. Moreover, the properties of five different samples were characterized by N₂ adsorption isotherm, SEM/EDS, XPS, and FTIR. The results showed that the maximum PH₃ equilibrium adsorption capacity was 595.56 mg/g. The MWAC had an energetically heterogeneous surface due to values of isosteric heat of adsorption ranging from 43 to 90 kJ/mol. The regeneration method provided an effective way for both adsorption species recycling and exhausted carbon regeneration. The high removal efficiency and big equilibrium adsorption capacity for PH₃ adsorption on the MWAC were related to its large surface area and high oxidation activity in PH₃ adsorption-oxidation to H₃PO₄ and P₂O₅. Furthermore, a possible PH₃ adsorption mechanism was proposed.

Keywords

phosphine / metal oxide-modified walnut-shell activated carbon / adsorption equilibrium / regeneration / mechanism