Reduction of nitrate by NaY zeolite supported Fe, Cu/Fe and Mn/Fe nanoparticles

Nano particles Fe, Cu/Fe and Mn/Fe supported on NaY zeolite (F@Y, CF@Y, and MF@Y) were prepared by two-step processes consisting of ion exchange and liquid-phase reduction. The characterization by XRD, SEM-EDX and BET-N₂ adsorption demonstrated that Fe, Cu/Fe and Mn/Fe nano particles were successfully loaded onto NaY zeolite and exhibited larger BET surface area compared to nano-Fe⁰ (nZVI). Laboratory experiments showed that nitrate removal by metals@Y in unbuffered conditions reached nearly 100% at a dosage of 4 g/L after 6 h of reaction. Moreover, the nitrate removal was not sensitive to the initial solution pH. Even at a high pH of 9.0, metals@Y exhibited nitrate reduction above 94%. CF@Y demonstrated high N₂ selectivity, due to the high content of Cu (20 wt%) and Fe (41 wt%) in CF@Y and the highly active metallic sites on its surface with positive charge. Kinetic data showed a good fit to a first-order kinetic model during early reaction times. A close fit to both a second-order and an nth-order kinetic model was shown for the whole of the reaction period. The data suggest that both liquid phase mass transfer and the intrinsic reaction rate control the process of nitrate reduction by metals@Y.