Immobilization of Cadmium in a Cd-Spiked Soil by Different Kinds of Amendments

Chemical stabilization of heavy metals is one of the soil remediation methods based on the application amendments to reduce mobility of heavy metals. A laboratory study was conducted to investigate the influence of different kinds of amendments on cadmium (Cd) stabilization in a Cd-spiked soil. The amendments were municipal solid waste compost (MSWC), Coal fly ash (CFA), rice husk biochars prepared at 300°C (B300) and 600°C (B600), zero valent iron (Fe0) and zero valent manganese (Mn0). The Cd-spiked soils were separately incubated with selected amendments at the rates of 2 and 5% (W/W) for 90 days at 25 °C. Soil samples were extracted by EDTA for periods of 5 to 97 min. In addition, sequential extraction was used as a suitable method for identification of chemical forms of Cd and their plant availability. The addition of amendments to soil had significant effects on desorption and chemical forms of Cd. Changes in Cd fractions and their conversion into less soluble forms were clear in all treated soils. The addition of amendments resulted in a significant reduction in mobility factor of Cd compared to the control treatment. Among all amendments tested, Fe0 was the most effective treatment in decreasing dynamic of Cd. Biphasic pattern of Cd desorption kinetic was fitted well by the model of two first-order reactions. In general, from the practical point of view, Fe0, MSWC and Mn0 treatments are effective in Cd immobilization, while application of Fe0 at 5% (W/W) was the best treatment for stabilization of Cd.