Efficacy of ZnO Adsorbents in Heavy Metal Detection and Removal

Heavy metal contamination poses a serious concern for the environment and health. These are toxic, persistent, and hazardous to human life. This chapter is concerned with zinc oxide nanoparticles (ZnO NPs) as efficient adsorbents which are implemented to remove heavy metal ions such as cadmium (Cd2+), arsenic (As3+/As5+), mercury (Hg2+), lead (Pb2+), and chromium (Cr3+/Cr6+). The high surface area, photocatalytic activity, and eco-friendliness of ZnO make it an efficient candidate for water treatment. Diverse synthesis routes, mainly chemical and biogenic ones, are discussed in the chapter, and these methods of synthesis influence the morphology of ZnO, adsorption efficiency, and consequences in terms of the environment. Adsorption mechanisms mainly include photogenerated redox reactions and physical adsorption processes, alongside kinetic and isotherm models that ensure the optimization of heavy metal ion removal. Biogenic synthesis methods also offer a sustainable and eco-friendly approach that will further open avenues for using ZnO for applications in environmental remediation. ZnO NPs represent an effective, low-cost solution for reducing heavy metal pollution, requiring both environmental sustainability and industrial wastewater challenges to be overcome.