Kinetics And Isotherm Studies For Adsorption Of Gentian Violet Dye From Aqueous Solutions Using Synthesized Hydroxyapatite

Document Type

Article

Publication Date

Spring 4-2023

Abstract

Water is the most important resource for life but it has been greatly exhausted over the past century as a result of the human population and environmentally harmful activities. The excessive quantity of dyes exits in the wastewater produced from the textile industries is the main reason for serious human health and environmental problems. There are many dye removal techniques and it is found that the most promising one is the adsorption technique. The novelty of this research is using of an unmodified synthesized Hydroxyapatite (HAp) as an adsorbent for removal of Gentian Violet (GV) dye from aqueous solutions as there is no sufficient data in literature about using it in the adsorption of GV dye from aqueous solutions. Un modified HAp was synthesized by a combined precipitation microwave method. The prepared adsorbent was characterized by Scanning Electron Microscope (SEM), Energy Dispersive X-Ray (EDX), X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Zeta Potential analysis. The kinetic study showed that the Pseudo Second Order (PSO) model was the best fitted model with the experimental data. Analysis of adsorption isotherms using different models represented that this adsorption system was better described by Halsey isotherm with a maximum adsorption capacity of (qmax) = 1.035 mg/g. The effects of Initial solution pH, initial dye concentration, adsorbent dose and contact time experimental factors were studied during investigation of (GV) dye removal efficiency. The experimental results indicated that the maximum adsorption efficiency of GV dye using HAp adsorbent (99.32 %) was achieved at the following conditions; contact time = 90 min, pH = 12, initial GV dye concentration = 3 mg/L and adsorbent dose = 1 g/L. The adsorption mechanism of GV using HAp might be explained by the electrostatic interaction between the negatively charged surface of the HAp and the positively charged group of the GV dye. Thermodynamics study was performed on the adsorption process of GV dye from aqueous solutions using the synthesized HAp which revealed that this process was endothermic and spontaneous due to positive values of ΔH and ΔS and negative values of ΔG.

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