As(Ⅲ)adsorption performance and mechanisms of natural Fe-bearing manganese ores with different Mn/Fe ratios
Arsenic in water is mainly present in the form of arsenite(As(Ⅱ)).Metal oxides are commonly used for arsenic removal in water,but their affinity with As(Ⅲ)is weak,making it difficult to remove arsenic from water.Therefore,seeking efficient,inexpensive,and environmentally friendly As(Ⅱ)removal materials is of great environmental significance.Natural iron-manganese-containing minerals are efficient arsenic adsorbents,but different iron-manganese-containing minerals have significantly different As(Ⅱ)removal performances due to their complex natural formation conditions.In this study,two natural iron-manganese-containing minerals with different Mn/Fe ratios(NFM-L and NFM-H)were selected as research subjects to evaluate their adsorption performances for As(Ⅲ).XPS,XRD,and other spectroscopic characterization methods were used to explore the arsenic removal mechanism.The results showed that the Fe content of NFM-L was 5.61 times that of NFM-H,and its maximum adsorption capacity for As(Ⅲ)(24.82 mg·g-1)and adsorption rate were significantly higher than that of NFM-H(18.94 mg·g-1).And the isothermal adsorption curves for As(Ⅲ)by NFM-L and NFM-H were more consistent with the Freundlich model.The influence factor experiments showed that the solution pH had a greater impact on NFM-L,and the coexisting ion H2PO4-could significantly inhibit the adsorption of As(Ⅲ)by both materials,while material particle size had a smaller effect on As(Ⅲ)removal.Spectroscopic characterization showed that the structure of the two minerals did not change significantly after arsenic adsorption,but manganese oxide could oxidize As(Ⅲ)to As(Ⅴ),significantly enhancing the adsorption capacity of iron-manganese-containing minerals for arsenic.In conclusion,this study revealed the arsenic removal mechanism of natural iron-manganese-containing minerals,providing theoretical support for the exploration of efficient,inexpensive and environmentally friendly As(Ⅲ)removal materials and offering new ideas for the treatment of arsenic pollution in water environments.
natural iron manganese oreAs(Ⅲ)Mn/Feoxidationadsorption
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