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The present review highlights different types of nanoferrites and their surface-modified composites as alternative adsorbents in waste water treatment.

The present work demonstrates the application of a composite of the zeolite imidazole framework (ZIF-67) and reduced graphene oxide (rGO), synthesized via a simple hydrothermal route for the sensitive sensing of ammonia. The successful synthesis of ZIF-67 and rGO composite was confirmed with structural and spectroscopic characterizations. A porous structure and a high surface area (1080 m 2 g –1 ) of the composite indicate its suitability as a gas sensing material. The composite material was coated as a thin film onto interdigitated gold electrodes. The sensor displays a change in its chemoresistive property (i.e., resistance) in the presence of ammonia (NH 3 ) gas. A sensor response of 1.22 ± 0.02 [standard deviation (sd)] is measured for 20 ppm of NH 3 , while it shows a value of 4.77 ± 0.15 (sd) for 50 ppm of NH 3 . The fabricated sensor is reproducible and offers a stable response, while also providing tolerance against humidity and some other volatile compounds. The average response and recovery times of the sensor, for 50 ppm NH 3 concentration, are found to be 46.5 ± 2.12 (sd) and 66.5 ± 2.12 (sd) s, respectively. The limit of detection of the sensor was found to be 74 ppb.

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