[Adsorption of Sb(Ⅴ) in Water by Natural Pyrite: Performance and Mechanism]

The adsorption performance of three iron ores (pyrite, hematite, and magnetite) on Sb(Ⅴ) was compared and pyrite was shown to exhibit the highest adsorption performance. The effects of particle size, concentration, and pH on the adsorption performance were investigated with pyrite as the absorbent. The rejection of Sb(Ⅴ) was the highest (>80%) when pyrite (particle size <0.074 mm) was used as the absorbent with a concentration of 1 g ·L^-1 and pH=7. The ion competition experiment indicated that PO₄^3- can inhibit the adsorption of Sb(Ⅴ), while SO₄^2- and CO₃^2- have no significant effects on the adsorption of Sb(Ⅴ) because PO₄^3- can compete with Sb(Ⅴ) for active adsorption sites on the surface of pyrite. The results also showed that the quasi-second-order kinetic model and Langmuir model can better simulate the adsorption process, which shows a single-layer adsorption behavior and chemisorption plays a main role in the rejection of Sb(Ⅴ). FTIR analysis suggested that the removal of Sb(Ⅴ) by pyrite was a coordinated ion exchange reaction. EDS and XPS results further confirmed that Sb(Ⅴ) was adsorbed on the surface of pyrite and was not reduced to Sb(Ⅲ), which is more toxic.