Sensoring Gaseous Ammonia using Cation Exchanged Faujasite-X Zeolite

Abstract

work presents a method that uses cheap, thermally stable and reusable cation exchanged solid zeolites to detect gaseous ammonia. Here, 24 separately exchanged Cu2+ and Co2+ cations per unit cell of 1.23 Si/Al Faujasite-X (as CuX and CoX, respectively), are used as sensors for the ammonia. Upon exposure of CuX to ≥ 5ppm gaseous ammonia, the CuX showed a Diffuse Reflectance peak at 630 nm and an Infrared (IR) band at 1265 cm-1 that are associated with characteristic interactions of ammonia with CuX framework. Both Diffuse Reflectance (DRS) and Infrared (IR) spectroscopic methods gave a linear detection range of about 25 ppm with attendant R2-value of 0.993 for DRS and 0.986 for IR. A similarly treated CoX upon exposure to ammonia gas showed “fingerprint” Diffuse Reflectance peak and IR band at 527 nm and 1312 cm-1 respectively.