Adsorption kinetics of p-nitrophenol (PNP) on coal-based activated carbon: experimental and simulation

The adsorption kinetics of p-nitrophenol (PNP) on coal-based activated carbon (CBAC) inside a finite stirred batch adsorber has been investigated using different initial concentrations of PNP solution and different adsorbent dosages. The mathematical models including homogeneous surface diffusion model (HSDM) and pore surface diffusion model (PSDM) have also been applied to predict the adsorption kinetics of PNP on CBAC. The mathematical models were solved numerically by finite element method, and film mass transfer coefficient (kf), surface diffusivity (Ds), and pore diffusivity (Dp) were obtained using nonlinear least square method. The results deduce that the effects of initial concentrations of PNP and adsorbent dosages on the values of kf and Ds are very little. It has been also demonstrated that the intraparticle diffusion is the main controlling step through the adsorption process. Sensitivity analysis of HSDM and PSDM has been also studied using the error sum of squares (ESS) method. The results prove that all the models are sensitive to kf and Ds, but the PSDM is insensitive to Dp.