化学
等温滴定量热法
氧烷
焓
铁酸盐
X射线吸收精细结构
吸附
齿合度
金属
光谱学
吸附
物理化学
有机化学
量子力学
物理
作者
Hansong Chen,Wenfeng Tan,Wei Lv,Juan Xiong,Xiaoming Wang,Hui Yin,Linchuan Fang
标识
DOI:10.1021/acs.est.9b06288
摘要
Binding of Pb(II) to ferrihydrite–Bacillus subtilis composites formed in the presence of bacterial cells were investigated through macroscopic and microscopic techniques. Diffuse layer model (DLM) fitting and isothermal titration calorimetry (ITC) analysis indicated that the hydroxyl group played a key role in Pb(II) sorption onto composites by masking reactive sites, such as carboxyl and phosphoryl groups of bacterial cells. Negative enthalpy (from −39.29 to −57.87 kJ mol–1) and positive entropy (from 135.61 to 193.47 kJ mol–1) of Pb(II) sorption onto composites revealed that inner-sphere complexes formed through exothermic reactions and was driven by both entropy and enthalpy. Spatial distribution of these inner-sphere species at varied Pb(II) loading demonstrated that interactions between Pb(II) and bacterial cells preceded that of mineral components in composites, using microfocus X-ray fluorescence spectroscopy (μ-XRF) maps and microfocus X-ray absorption near edge structure (μ-XANES) spectra. Combined with bulk Pb LIII-edge X-ray absorption fine structure (XAFS) spectrum, we inferred that mononuclear bidentate edge-sharing hydroxyl-Pb complexes, monodentate mononuclear carboxyl-Pb and phosphoryl-Pb complexes predominantly contributed to Pb(II) inner-sphere binding with mineral and bacterial fractions in composites, respectively. The molecular binding mechanisms obtained in this study provide further insight into the sequestration and migration of toxic metals in natural environments.
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