UTILIZING MODIFIED KAOLINITE FOR PHENAZOPYRIDINE REMOVAL THROUGH ADSORPTION AND SUBSEQUENT THERMOLYSIS DECOMPOSITION
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Date
2024-11-21
Authors
Salman, Sahar
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Publisher
An-Najah National University
Abstract
In this study, modified kaolinite was utilized as an adsorbent for the elimination of phenazopyridine hydrochloride (PhPy) and methyl orange (MO) dyes from aqueous solutions. Various parameters, such as the effects of different concentrations of adsorbate, the amount of adsorbent, the solution pH, and the temperature, have been studied and analyzed using UV-Vis. When the concentration decreased, the adsorption increased and was affected by the amount of modified kaolinite until the equilibrium level was reached. The ideal pH value for PhPy adsorption was 5, but for MO, it was 2, and equilibrium adsorption was established within the first fifteen minutes. Additionally, the adsorbed PhPy and MO clearly decreased when the temperature increased, suggesting exothermic adsorption. Kinetic models were used to analyze the experimental data to illustrate the kinetic adsorption process. The PhPy and MO adsorption processes followed pseudo second-order kinetics. The data were resolved via the most common adsorption isotherms, i.e., the Langmuir and Freundlich isotherms, and the adsorption process fit well with the Langmuir isotherm model for both dyes. The activation energy of PhPy and MO adsorption on the modified kaolinite was estimated. The results confirmed that the process was followed physical adsorption.
Characterization of the modified kaolinite was essential in perception its adsorption properties. X-ray diffraction (XRD) analysis was used to determine the crystalline structure and emphasize the successful modification of kaolinite. XRD patterns provided insights into changes in the interlayer spacing, indicating interactions between the kaolinite and ZnCl2. Scanning electron microscopy (SEM) was utilized to analyze the surface morphology and observe the textural changes caused by the modification process. SEM images revealed an increase in surface roughness and porosity. Thermogravimetric analysis (TGA) was utilized to evaluate the thermal stability and decomposition behavior of the modified kaolinite. TGA curves demonstrated the material's resistance to thermal degradation up to specific temperatures, confirming its suitability for regeneration for four cycles through thermal decomposition at 600 °C for PhPy and MO without impacting adsorption efficiency.
Fourier transform infrared (FT-IR) spectroscopy was utilized to further confirm the adsorption process and assess the interaction between the dyes and the modified kaolinite. The FT-IR spectra revealed shifts or changes in specific functional group vibrations, indicating the adsorption of PhPy and MO onto the kaolinite surface. FT-IR also provided evidence of the thermal decomposition process by identifying changes in the functional groups of the adsorbed dyes after thermal treatment at 600 °C. The disappearance of peaks associated with organic functional groups from PhPy and MO in the post-regeneration FT-IR spectra validated the successful decomposition of the adsorbed dyes and the regeneration of the modified kaolinite surface for reuse.