Kinetics and thermodynamics of the phosphine adsorption on the modified activated carbon

The kinetics and the thermodynamics of phosphine (PH₃) adsorption on the modified activated carbon have been explained for the adsorption process of PH₃. This study investigated the kinetic and thermodynamic properties of PH₃ adsorption on the activated carbon impregnated with 5% HCl solution. The thermodynamic properties including PH₃ adsorption isotherm and adsorption heat were separately investigated at 20°C, 70°C, 90°C. The results showed that the Freundlich-type isotherm equation described the isotherms well. The adsorption capacity increased with increasing temperature between 20°C and 70°C. Between 70°C and 90°C, the adsorption capacity decreased obviously with increasing temperature. The adsorption capacity reached the maximum at 70°C. By analyzing the results of the kinetics and the thermodynamics, we found that the adsorption of PH₃ was dominated by physical adsorption at the lower temperature (20°C). Then with increasing temperature, chemical adsorption gradually dominated in the adsorption process. The adsorption capacity decreased at above 70°C is due to the exothermic effects in the process of adsorption.