Kinetics, Thermodynamics, and Equilibrium Studies on Adsorption of Reactive Red 198 from Textile Wastewater by Coral Limestone as a Natural Sorbent

Abstract Introduction: Dyes are among the most hazardous chemicals in industrial wastes due to their toxicity for aquaculture, reduction of light permeability, and in turn development of disorders in photosynthesis process. The current study aimed to investigate the efficiency of coral in removing red reactive 198 from textile dye wastewater was investigated. Materials & Methods: In this experimental study, the adsorption process was completed performed on a synthetic sample in a batch system Optimal conditions was also performed on the real wastewater of Yazdbaf textile factory. The effects of such parameters as the pH, dyeʹs concentration, contact time, sorbentʹs dose, and temperature were investigated, following this, adsorption isotherms were determined and then the process was examined kinetically and thermodynamically. Next, the study data was analyzed by SPSS (ver, 21), EXCEL 2007, applying Pearson correlation coefficient. Results: The optimal conditions in removing the dye included pH=3, an equilibrium contact time of 120 min, 25 mg/L of the dyeʹs concentration, and 3g/100mg of the sorbentʹs initial value. Under the optimal conditions, the dyeʹs removal efficiency and the maximum adsorption capacity in the synthetic and real wastewater sample of Yazdbaf Company were 97.63%, 8.14 mg/g and 67.78%, 5mg/g respectively. The equilibrium data followed the Langmuir adsorption isotherm with a correlation coefficient of R2=0.96 and the adsorptionʹs kinetics followed pseudo-second-order model with a correlation coefficient of 1 (R2=1). The thermodynamic investigations also indicated that the adsorption is of physical process and endothermic. Conclusion: As the results revealed, the good performance of the coral sorbent in removing dyes in aquatic environments, enjoying suitable density, having quick precipitation properties, not needing activation, and environmental safety of the process can encourage the efficiency of this adsorbent in treatment of dye-containing wastewaters.