Sorption of Acid Orange ۳ From Aqueous Solution Using Eggshell

Dyes are used extensively in textile industries. The wastewater of these industries contains high amounts of pollutants which can be toxic, carcinogenic, and mutagenic and needs to be treated before being discharged into the environment. The aim of this study was to evaluate the application of eggshell as a sorbent for the removal of Acid Orange ۳ from synthetic wastewater. This study is applied experimental research which was performed on a laboratory scale. Eggshell as a sorbent was prepared at laboratory temperature and pulverized by standard ASTM sieves in two sizes (۵۰ and ۱۴۰). The concentration of dye in the synthetic wastewater was ۲۵ mg/L. In this study, increasing adsorbent dose from ۲ to ۵ g/۱۰۰ mL led to an increase in the adsorption efficiency from ۳۶.۶% to ۵۵.۳۶% and by decreasing the size of eggshell particles from ۵۰ to ۱۴۰ mesh, the adsorption efficiency increased. The maximum adsorption took place in the first ۹۰ minutes of the reaction. By increasing pH from ۵ to ۹, the process efficiency increased from ۷۸ to ۸۲%; however, at pH higher than ۹, the adsorption efficiency decreased. Additionally, the adsorption characteristics of this pollutant on eggshell fitted Freundlich isotherm (R۲>۰.۹۸۹). Due to the characteristics of textile wastewater such as alkaline pH, eggshells can be used as a natural adsorbent in textile wastewater treatment.