Optimization of Aluminium Oxide/Acid‐Treated Palygorskite by Response Surface Methodology and its Application in Adsorptive Separation of the Methanol‐Dimethyl Carbonate Azeotrope

Abstract

A low-cost composite adsorbent aluminium oxide/acid-treated palygorskite (Al 2 O 3 /HPal) was prepared by the total incipient wetness method and succesfully applied for the separation of methanol-dimethyl carbonate (MeOH-DMC) azeotrope for the first time. Major synthetic factors influencing the final separation performance were explored by the response surface methodology (RSM) based on Box-Behnken design (BBD). Adsorbents under optimized synthesis conditions were characterized by XRD, FT-IR, SEM, TEM and BET analysis. Adsorptive separation performance of Al 2 O 3 /HPal were investigated by both static and dynamic experiments. The adsorption capacities for MeOH and DMC were 335.52 mg g À 1 and 23.92 mg g À 1 , respectively, while the selectivity S and the separation factor α towards MeOH equaled to 14.03 and 6.1. Kinetic curves fitted the pseudo-second-order model. Isotherm study results indicated two different adsorption behaviors for this azeotrope where heterogeneous multi-layer adsorption was observed for DMC but monolayer adsorption occurred for MeOH with surface inhomogeneity. Moreover, thermodynamic study suggested that the driving force of the MeOH-DMC system on Al 2 O 3 /HPal included both enthalpy and entropy effects.