Problems with the environment have recently gotten worse as a result of crude hydrocarbons, microbial contamination, heavy metal pollution in water, and the price of pricey antioxidants. It motivated scientists to investigate the possibility of certain metal oxide nanoparticles for the treatment of water contaminants Ca(OH)2 was used as a wet chemically generated precursor using the direct thermal breakdown technique to create CaONPs (calcium oxide nanoparticles). The samples were analyzed using TEM, IR, XRD, SEM, and Zetasizer. The particle size was in the 49.8 to 75.8 nm range. There is an evidence that CaONPs have antimicrobial properties. The removal process of heavy metals by CaONPs was dependent on temperature and pH. CaONPs have a less expensive alternative to expensive sorbents for the elimination of metal ions. The effectiveness of the prepared calcium oxide nanoparticles was achieved as an effective and inexpensive adsorbent for the removal of various heavy metal ions (iron, lead, manganese, chromium, and copper(II)) from aqueous solutions, with a good opportunity to soon be integrated into technologies for treating polluted water and wastewater. CaONPs are a low-cost, versatile material utilized in a variety of environmental treatments.