Leaching of heavy metals from tungsten mining tailings: A case study based on static and kinetic leaching tests

Heavy metal (HM) leaching from tungsten mine tailings is a serious environmental risk. In this study, we assess the HM pollution level of tungsten tailings, determine the HM leaching patterns and mechanisms, and estimate the HM fluxes from a tailings reservoir. The results showed that the comprehensive pollution index (CRSi) values that decreased in order of the HM pollution levels in the tailings were cadmium (Cd) > tungsten (W) > lead (Pb) > copper (Cu) = zinc (Zn) > arsenic (As) > manganese (Mn). This result indicated that Cd, W, and Pb were priority pollutants in tailings. The Res fraction of all HMs was greater than 50%. Pb and Cd had similar species fractions with high Exc fractions, and tungsten had a considerable proportion of the Wat fraction. The general acid neutralizing capacity (GANC) test divides the leaching process of HMs into two stages, and each of stage is affected by different mechanisms. A neutral environment promoted tungsten leaching in the column leching test, while an acidic environment promoted Cd and Pb leaching. In addition, the pH effect was more obvious in the early stage. The kinetic fitting results showed that the second-order dynamic model well simulated the leaching of W, Pb, and Cd in most cases. Based on column kinetic leaching test results and tailings parameters, the annual W, Pb, and Cd fluxes were estimated to be 6.35 x 10(8), 1.3288 x 10(9), and 1.012 x 10(8) mg/year, respectively. The above results can guide the environmental management of tungsten tailing reservoirs, such as selecting suitable repair materials and estimating repair service times.