Adsorption Capacity of Expansion Graphite for Xylenol Orange

Abstract

Expansion graphite (EG) processing of an expanded volume of 400 mL/g was prepared with 50 mesh crude graphite after chemical oxidation intercalation of potassium permanganate and vitriol, and its adsorption kinetics and thermodynamics characteristics for xylenol orange (XO) was investigated. In thermodynamic study, adsorption isotherm and free energy change (⊿G°) were detected and calculated, respectively. Influence of ionic strength on adsorbance was investigated. Kinetic studies were carried out with a series of XO concentration under different temperatures, and the data were simulated with pseudo first-order and second-order kinetic model, respectively. Results illustrate: adsorption of EG for XO is a spontaneous process, and adsorption isotherm is type II; equilibrium adsorbance increases with the increase of ionic strength. Kinetic studies show that the kinetic data can be delineated by pseudo second-order kinetic model. Initial adsorption rate increases with the increase of temperature. Adsorption activation energy is less than 20 kJ/mol; physical adsorption is the major mode of the overall adsorption process.