Source water in China contains in general pollutants of trace heavy metals. In this paper it is suggested that use of hydrous manganese dioxide enhance removal of cadmium in source water without changing the conventional treatment technique. Hydrous manganese dioxide prepared with thiosulfate and potassium permanganate by oxidation-reduction reaction was used as a new type of purifying agent. The parameters such as pH

turbidity and humic acid

which affect its purifying efficiency

were also studied. The properties of new purifying agent

such as morphology

surface composition and structure are characterized by X-ray diffraction(XRD)

X-ray photoelectron spectroscopy (XPS) and transmission electron microscope (TEM) to establish links between them and coagulation phenomenon

and the characteristics of flocculation process are monitored by transmitted light fluctuation technique in order to reveal possible mechanism of cadmium removal by hydrous manganese dioxide. The results show that hydrous manganese dioxide is a kind of colloid with large specific surface

which exhibits strong adsorption characteristic thus excellent removal efficiency for dissolved and adsorbed cadmium. The mechanism of cadmium removal by hydrous manganese dioxide is probably that it is a combination result of specific adsorption

electrostatic-adsorption and entrapping-settling. So

it should be concluded that hydrous manganese dioxide can remove cadmium ions effectively from source water and can make effluent meet the national criteria for drinking water.