Porous maghemite (PM) was prepared by two-step calcinations. The crystallographic and magnetic changes of PM upon SO42− and CO32− adsorption were investigated. The crystallite size (~ 27 nm) and PM texture remain unchanged after adsorption. Fourier transform infrared spectra showed that SO42− and CO32− are adsorbed on the PM mainly through outer- and inner-sphere surface complexations, respectively. X-ray photoelectron spectra showed the increase and decrease of binding energy for Fe 2p3/2 electrons after SO42− and CO32− adsorption, respectively. Sulfate adsorption increases the magnetic susceptibility (χ) of PM by ~ 4.5%, and decreases the saturation magnetization (Ms) of PM by 24.6%. By comparison, carbonate adsorption decreases χ by ~ 3.7% and increases Ms by 17.8%. The magnetic changes upon SO42− and CO32− adsorption are attributed both to the electronegativity of anions and the size distribution of PM.

中文翻译：

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吸附无机阴离子对煅烧制备多孔磁赤铁矿磁性的影响

通过两步煅烧制备多孔磁赤铁矿 (PM)。研究了 SO42- 和 CO32- 吸附后 PM 的晶体学和磁学变化。吸附后微晶尺寸 (~ 27 nm) 和 PM 纹理保持不变。傅里叶变换红外光谱表明 SO42- 和 CO32- 分别主要通过外球和内球表面络合吸附在 PM 上。X 射线光电子能谱显示，在 SO42− 和 CO32− 吸附后，Fe 2p3/2 电子的结合能分别增加和减少。硫酸盐吸附使 PM 的磁化率 (χ) 增加约 4.5%，并将 PM 的饱和磁化强度 (Ms) 降低 24.6%。相比之下，碳酸盐吸附使 χ 降低约 3.7%，并使 Ms 增加 17.8%。