Removal of p-Nitrophenol from Aqueous Solution Using Brazilian Peat: Kinetic and Thermodynamic Studies

Removal of p-nitrophenol (PNP) from aqueous solutions using fibrous peat has been investigated in this study by batch adsorption experiments. Factors that can affect the adsorption process, such as pH, temperature, initial PNP concentration and contact time, have been investigated. Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA) measurements have also been obtained in order to study the adsorption mechanism of PNP by peat. The Langmuir and Freundlich equations have been applied to investigate the equilibrium. The data fitted the Langmuir isotherm well, with the maximum adsorption capacity decreasing with temperature from 23.4 to 16.1 mg g(-1). In general, the adsorption equilibrium was attained within 100 min. For the kinetics study, the best fit was obtained by the pseudo-second-order model instead of the pseudo-first-order model, both of which applied to the experimental data, whereas the results of intraparticle diffusion show a two-step adsorption process. The activation energy value of 70.31 kJ mol(-1), calculated from the Arrhenius equation, indicated a predominantly chemical adsorption, whereas the thermodynamic parameters, obtained by the van't Hoff equation, were exothermic and spontaneous in nature.