Sorption of Acid Orange 3 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 3 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 (50 and 140). The concentration of dye in the synthetic wastewater was 25 mg/L. In this study, increasing adsorbent dose from 2 to 5 g/100 mL led to an increase in the adsorption efficiency from 36.6% to 55.36% and by decreasing the size of eggshell particles from 50 to 140 mesh, the adsorption efficiency increased. The maximum adsorption took place in the first 90 minutes of the reaction. By increasing pH from 5 to 9, the process efficiency increased from 78 to 82%; however, at pH higher than 9, the adsorption efficiency decreased. Additionally, the adsorption characteristics of this pollutant on eggshell fitted Freundlich isotherm (R2 >0.989). Due to the characteristics of textile wastewater such as alkaline pH, eggshells can be used as a natural adsorbent in textile wastewater treatment.