Peat Water Treatment using Chitosan-Silica Composite as an Adsorbent

Abstract

The objective of this study is synthesis and characterization of the chitosan-silica composite (CSC) and use them as an adsorbent material for peat water treatment. The resulting composite was characterized<br />by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM), X-ray diffraction<br />(XRD), N2 adsorption-desorption isotherm and zeta potential. The sorption experiments were carried out in<br />batch mode to optimize various parameters such as contact time, dose of CSC, pH and temperature. In<br />addition, adsorption isotherms of humic acid onto the CSC were also evaluated with the Langmuir, Freundlich<br />and Sips approximations. Kinetic data were tested using the pseudo-first-order, pseudo-second-order kinetic<br />models and intra-particle equations. The results from this work showed that the adsorption of humic acid was<br />found to increase with increase in contact time and temperature while acidic pH was more favorable for the<br />adsorption of humic acid from peat water. The optimum dosage of CSC was 5 g. Equilibrium data were best<br />described by the Langmuir isotherm model, with maximum monolayer adsorption capacity of 120.2 mg/g at 25 oC and pH 4.12. The kinetics of the adsorption process was found to follow the pseudo-second-order kinetic model, with a rate constant in the range of 0.034 - 0.105 g/mg/min, while intra-particle-diffusion were the main rate determining step in the humic acid adsorption process. Thermodynamic parameters data indicated that the humic acid sorption process was non-spontaneous and endothermic under the experimental conditions, with the Gibbs free energy (“Go) in the range of 1.05-3.89 kJ/mol, enthalpy (“Ho) and entropy (“So) of 24.69 kJ/ mol and 69.62 J/mol, respectively and the activation energy was 23.23 kJ/mol. The CSC investigated in this study thus exhibited as a high potential adsorbent for the peat water treatment.