Synthesis and characterization of modified UZM-5 as adsorbent for nitrate removal from aqueous solution

• Surface modification by HDTMA mainly changed the lattice structure of UZM-5 zeolite.
• Structure of alkyl chains of surfactant loaded on UZM-5 consist of large number of ordered trans conformers.
• Equilibrium and thermodynamic adsorption of nitrate on the SMU were studied.
• Equilibrium data were fitted well in the Frendlich model and the adsorption capacity of nitrate was determined as 18.62 mg/g at 298 K.
• Nitrate sorption on SMU is strongly affected by pH, initial ion content and rival anions.

This article introduces synthesis and characterization of UZM-5 and its surfactant modification by using solutions of hexadecyltrimethylammonium bromide (CH3(CH2)15N(Br)(CH3)3, HDTMABr). Potential application of produced surfactant modified UZM-5 (SMU) as adsorbent for nitrate removal from aqueous solution were investigated. The effect of HDTMABr concentration on its adsorption on UZM-5 was studied by FTIR, TGA, N2 adsorption–desorption, and XRD techniques. Intense reduction in surface area, total pore volume of the UZM-5 sample upon alkyl chain attachment was observed by the BET method. From the TGA results, the electrostatic interactions were proved to be the main mechanisms that govern the adsorption of HDTMA cation on UZM-5. Adsorption isotherms of nitrate on SMU were measured at aqueous concentration range of 30–100 mg L−1. The adsorption data was fitted by the Langmuir, Freundlich and Dubinin–Redushkevich (D–R) isotherms. The maximum monolayer sorption capacity of SMU for nitrate removal was found to be 18.62 mg g−1 at 298 K. Thermodynamic study of nitrate sorption on SMU was performed based on ΔHo, ΔGo and ΔSo. The results showed that nitrate sorption on SMU were strongly affected by pH, initial ion content and rival anions.