Effect of Oxygen and Solution Composition on the Oxidative Dissolution of Cadmium Microparticles in Water

Cadmium is one of the most hazardous and toxic environmental pollutants. Metallurgical industry, waste incineration, and wide use of cadmium in modern devices have increased the spread of cadmium in the environment and enhanced its impact on human health. The paper discusses the state and transformation of 2–3 μm cadmium particles falling out on water bodies from air. The formation and characteristics of cadmium dispersions in water are studied. The aqueous dispersion is unstable, and microparticles undergo agglomeration, followed by sedimentation. The particle sedimentation velocity is about 1.0 × 10–5 m s–1 (±50%). Cadmium metal microparticles are efficiently oxidized in air to form Cd(OH)2. The thermodynamics and mechanism of the oxidative dissolution of cadmium in water are discussed in relation to the pH, concomitant ions, and other factors. The dissolution appreciably accelerates with increasing acidity and in the presence of the Cl– ions. The dissolution in waters of various compositions and of natural origin was studied. The results of the research establish the patterns of toxic cadmium spreading into the environment during the dissolution of metal microparticles in natural waters.