Study on the Passivation Effect of Natural and Modified Attapulgite on Heavy Metal Lead in Soils of the Rare Earth Tailings

Abstract

BACKGROUND The large-scale mining of ion-type rare earth mines in southern Jiangxi and the unreasonable disposal of tailings and slag caused heavy metal lead content to be deposited in the surrounding environment of the mining area, exceeding the standard level, and destroying the ecological environment of the mining area. OBJECTIVES To passivate the lead in the soil of the mining area to reduce its bioavailability and ecological risks. METHODS Natural and modified attapulgite with different dosages (mass fractions of 5%, 10%, and 15%) were used as passivating agents. Scanning electron microscopy and Fourier infrared were used to analyze the surface characteristics and functional groups of the two passivating agents. Passivation ability and effect were evaluated by BCR continuous extraction method of heavy metals, and form changes of lead in the soil were also studied by this method. Environmental quality of heavy metal contaminated soil was also evaluated using foreign heavy metal TCLP extraction methods. RESULTS After 50 days of cultivation, the modified attapulgite reduced the acid-extracted content of lead from 25.69 to 7.42mg/kg, the residual content increased by 1.38 times and the TCLP extracted content decreased by 65.70% compared to the control group, significantly reducing the bioavailability and ecological risk from lead. CONCLUSIONS Compared with the natural attapulgite, the modified attapulgite has a better effect on the soil remediation of rare earth tailings.

Keywords

• rare earth tailings
• in situ immobilization
• passivating agent
• form transformation
• soil remediation