A novel anion exchanger was prepared by modifying poplar sawdust (PSD) with 3-chloro propyl trimethoxysilane and (1,4-diazabicyclo[2.2.2]octane) (Dabco). After characterizing the physicochemical properties of PSD and modified PSD (MPSD), the effects of various operational conditions on nitrate adsorption by MPSD were examined. The results indicated that the MPSD removed over 98% of nitrate from water at optimum operation conditions, i.e. Ci =20 mg L-1; pHi=7; T= 25 ± 1 °C; adsorbent dosage=2 g L-1 and contact time=30 min. Kinetic studies showed that the adsorption process followed the pseudo-second-order (PSO) model and was a three-step process. Among the equilibrium isotherms, Freundlich model provided the best fit to the experimental data, which demonstrated multilayer adsorption of nitrate on heterogeneous surfaces. According to thermodynamic studies, the nitrate adsorption by MPSD was exothermic ( <0) and spontaneous ( <0) in nature. Among the studied competing anions, sulfate had the maximum inhibition effect on the nitrate adsorption by MPSD, while phosphate had the minimum effect. In a nutshell, it can be concluded from the experimental results that the MPSD was an efficient and economical adsorbent for nitrate removal from water.
