UV–vis spectroscopic method for detection and removal of heavy metal ions in water using Ag doped ZnO nanoparticles

The primary source of heavy metal discharge into the water is human activity and urbanization near water bodies. Contamination of drinking water sources with heavy metals has a harmful impact on the environment and human health. The most commonly used heavy metals are Zinc (Zn), Copper (Cu), Nickel (Ni), Lead (Pb), Cadmium (Cd), Chromium (Cr), Arsenic (As), Mercury (Hg), etc. The heavy metal ions are easily absorbed by living things via water and spread throughout the food chain, posing a threat to humans, plants, and animals (Zhang et al., 2018; Lu et al., 2019; Ma et al., 2020; Gao et al., 2018; Wen et al., 2018; Saranya et al., 2021). Colorimetric sensing is a simple and cost-effective method for the detection of heavy metal ions. Moreover, the results can be analysed with naked eye. In this work, Ag doped ZnO nanoparticles synthesized via co-precipitation method are used for the colorimetric detection of heavy metal ions. The nanoparticles are characterized for their morphology, structural, and chemical analysis using XRD, SEM, EDS, and XPS techniques. The synthesized nanoparticles are used for the colorimetric detection of heavy metal ions. The heavy metal ions such as Ni2+, Cu2+, Cr3+, Cr6+, Fe2+, and Fe3+ are successfully detected and the color change is visible from the naked eye. The minimum concentration detected is found to be 100 μM. The results are analysed via UV-vis spectroscopy. In addition to detection, the nanoparticles are further used as catalyst during the degradation of above detected heavy metal ions using NaBH4. All the heavy metal ions are degraded with in the duration of 30 min. Thus, the Ag doped ZnO nanoparticles successfully detected the heavy metal ions in aqueous solution and also acted as a catalyst during their degradation.