Optimization of Nitrate Removal from Aqueous Solutions with ZSM Hierarchical Zeolite Modified with Amine Using Response Surface Method

In this study, the ZSM hierarchical zeolite was prepared and modified by tetraethylenepentamine to be used to remove nitrate ions. The features of synthesized adsorbents were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR)and nitrogen adsorption–desorption isotherms. The results showed that the modified  hierarchical zeolite with the tetraethylenepentamine had a higher adsorption capacity than that of the unmodified hierarchical zeolite in the removal of nitrate ion. The higher adsorption capacity of the amine modified zeolite is due to the presence of amine groups of tetraethylenepentamine, which leads to an increase in the active sites of adsorbent and an electrostatic interaction between the adsorbent surface and nitrate anions. The effect of four parameters including concentration, adsorbent dose, pH and contact time on the nitrate removal using Central composite design approach-based response surface methodology (RSM-CCD) and was investigated and optimized in 22 experiments and 5 levels. Optimal values for a maximum adsorption capacity were 50 milligrams per liter of nitrate, 0.005 g of adsorbent, 25 min and pH = 4.