硫化零价铁去除水中钼酸盐的效能与机理

Nowadays, molybdenum (Mo) pollution in natural waters has become an increasing threat to human beings and microorganisms. Although zero-valent iron (ZVI) is considered to be an environmentally friendly approach for effective Mo(VI) sequestration, the low reactivity of traditional ZVI particles largely limits the ZVI application in real practice. To address this issue, sulfidated ZVI (S-ZVI^bm) was prepared by a ball-milling method and its performance toward Mo(VI) removal was systematically evaluated in this work. Results showed that the sulfidation treatment could greatly accelerate the ZVI corrosion in the presence of oxygen, and thereby markedly improve both the rate and capacity of Mo(VI) removal by ZVI. In specific, the observed rate constants (k_obs) of Mo(VI) removal by S-ZVI^bm were determined to be 0.059~0.866h^–1 at initial pH 6.0, which were 3.6~42.3 folds higher than that of unmodified ZVI. Likewise, the Mo(VI) removal capacity was increased from 9.86 to 31.9mg/g upon sulfidation. Collectively, it was found that the sulfidation treatment could eliminate the passivating impact of Mo(VI) on ZVI corrosion and thus enable the S-ZVI^bm particles to sequestrate Mo(VI) effectively. Mechanically, X-ray absorption fine structure spectroscopy revealed that Mo(VI) was mainly sequestrated via chemical adsorption rather than via reduction. Moreover, it was found that sulfidation amendment did not alter the Mo(VI) removal pathway by ZVI, despite it can improve the Mo(VI) removal efficiency greatly. These findings could provide some insights into the application of S-ZVI^bm in metal(loid)s-contaminated water treatment.