Sorption of Nickel Ions on Iron(III) Hydroxide Freshly Precipitated from a Solution of Iron(II) Sulfate. Part 2. Structure and Composition of Iron(III) Hydroxide Precipitates
摘要
A comparative analysis of the composition and structure of freshly precipitated iron(III) hydroxide precipitates obtained from a solution of iron(II) sulfate in the presence of sodium sulfate (400 mg/L) at pH 7 and 8 before and after sorption of nickel ions on them was carried out. Using IR and Raman spectroscopy and X-ray phase and thermogravimetric analysis, it was shown that the precipitates have the gross formula Fe2O3⋅2H2O and contain small amounts of goethite (α-FeOOH) and lepidocrocite (γ-FeOOH). It has been established that the sorption of nickel ions on these precipitates is not accompanied by chemisorption, i.e., the formation of mixed compounds between iron and nickel. The ζ potential of precipitate particles at pH < 6 has a positive value, and at pH > 6 it becomes negative. The point of zero charge of precipitate particles corresponds to pH 6.