Modeling and investigation of adsorption isotherms of 2,4,6-Trinitrophenol from aqueous medium using modified Portunus segnis crab shell bio-composite

Trinitrophenol is one of the major pollutants present in the effluents of petrochemical, oil, pharmaceutical and plastic industries, as well as in smaller amounts in municipal and agricultural wastewater. The aim of this study is to remove Trinitrophenol from aqueous solution using a modified Portunus segnis crab shell magnetic bio-composite. In order to optimize the adsorption process of Trinitrophenol, Design-Expert software and surface response method are used in the central composite design. The adsorption is evaluated by parameters of adsorbent dosage contact time (10 to 120 mins), pH (2-7), initial concentration of Trinitrophenol (10 to 60 mg / L) and adsorbent dosage (10 to 50mg). The equilibrium adsorption isotherms are analyzed using Langmuir, Freundlich and Tamkin isotherm models. The results show that under optimal conditions, the maximum removal efficiency of Trinitrophenol is attained 52% with an optimum value of pH = 3.25, the amount of adsorbent dosage is 40mg, the initial concentration of Trinitrophenol is 22.5mg per liter and the time is 92.5 minutes. Also, the study of the isotherm model show that the adsorption of Trinitrophenol on the adsorbent follows the Langmuir model with a correlation coefficient of (R2 = 86) and the maximum adsorption capacity based on the Langmuir model is 59.88mg per gr. The results of this study show that the modified Portunus segnis crab skin magnetic bio-composite has a good efficiency in removing Trinitrophenol, and at the same time its cheap price and easy access make this bio-composite to be considered a desirable biosorbent.