Peat Water Treatment using Chitosan-Silica Composite as an Adsorbent

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 by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM), X ray diffraction (XRD), N2 adsorption-desorption isotherm and zeta potential. The sorption experiments were carried out in batch mode to optimize various parameters such as contact time, dose of CSC, pH and temperature. In addition, adsorption isotherms of humic acid onto the CSC were also evaluated with the Langmuir, Freundlich and Sips approximations. Kinetic data were tested using the pseudo-first-order, pseudo second-order kinetic models and intra-particle equations. The results from this work showed that the adsorption of humic acid was found to increase with increase in contact time and temperature while acidic pH was more favorable for the adsorption of humic acid from peat water. The optimum dosage of CSC was 5 g. Equilibrium data were best 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.