Jeon Byong-Hun, Dempsey Brian A, Burgos William D
Department of Civil and Environmental Engineering, The Pennsylvania State University, 212 Sackett Building, University Park, Pennsylvania 16802-2450, USA.
Environ Sci Technol. 2003 Aug 1;37(15):3309-15. doi: 10.1021/es025900p.
Uptake of Fe(II) onto hematite (alpha-Fe2O3), corundum (alpha-Al2O3), amorphous ferric oxide (AFO), and a mixture of hematite and AFO was measured. Uptake was operationally divided into adsorption (extractable by 0.5 N HCl within 20 h) and fixation (extractable by 3.0 N HCl within 7 d). For 0.25 mM Fe(II) onto 25 mM iron(III) hematite at pH 6.8: (i) 10% of Fe(II) was adsorbed within 1 min; (ii) 20% of Fe(II) was adsorbed within 1 d; (iii) uptake slowly increased to 24% of Fe(II) during the next 24 d, almost all adsorbed; (iv) at 30 d, the uptake increased to 28% of Fe(II) with 6% of total Fe(II) fixed; and (v) uptake slowly increased to 30% of Fe(II) by 45 d with 10% of total Fe(II) fixed. Similar results were observed for 0.125 mM Fe(II) onto 25 mM iron(III) hematite, except that percent of adsorption and fixation were increased. There was adsorption but no fixation for 0.25 mM Fe(II) onto corundum [196.2 mM Al(III)] at pH 6.8, for 0.125 mM Fe(II) onto 25 mM iron(III) hematite at pH 4.5, and for 0.25 mM Zn(II) onto 25 mM iron(III) hematite at pH 6.8. A small addition of AFO to the hematite suspension increased Fe(II) fixation when 0.25 mM Fe(II) was reacted with 25 mM iron(III) hematite and 0.025 mM Fe(III) AFO at pH 6.8. Reaction of 0.125 mM Fe(II) with 2.5 mM Fe(III) AFO resulted in rapid adsorption of 30% of added Fe(II), followed by conversion of AFO to goethite and a decrease in adsorption without Fe(II) fixation. The fixation of Fe(II) by hematite at pH 6.8 is consistent with interfacial electron transfer and the formation of new mineral phases. We propose that electron transfer from adsorbed Fe(II) to structural Fe(III) in hematite results in oxidation of Fe(II) to AFO on the surface of hematite and that solid-phase contact among hematite, AFO, and structural Fe(II) produces magnetite (Fe3O4). The unique interactions of Fe(II) with iron(III) oxides would be environmentally important to understand the fate of redox-sensitive chemicals.
测定了Fe(II)在赤铁矿（α-Fe₂O₃）、刚玉（α-Al₂O₃）、无定形氧化铁（AFO）以及赤铁矿与AFO混合物上的吸附量。吸附量在操作上被分为吸附（20小时内可被0.5N HCl萃取）和固定（7天内可被3.0N HCl萃取）。对于在pH 6.8条件下，0.25 mM Fe(II)在25 mM铁(III)赤铁矿上的吸附情况：（i）1分钟内10%的Fe(II)被吸附；（ii）1天内20%的Fe(II)被吸附；（iii）在接下来的24天内，吸附量缓慢增加到24%的Fe(II)，几乎全部被吸附；（iv）在30天时，吸附量增加到28%的Fe(II)，6%的总Fe(II)被固定；（v）到45天时，吸附量缓慢增加到30%的Fe(II)，10%的总Fe(II)被固定。对于0.125 mM Fe(II)在25 mM铁(III)赤铁矿上的吸附，观察到了类似结果，只是吸附和固定的百分比有所增加。在pH 6.8条件下，0.25 mM Fe(II)在刚玉[196.2 mM Al(III)]上、pH 4.5条件下0.125 mM Fe(II)在25 mM铁(III)赤铁矿上以及pH 6.8条件下0.25 mM Zn(II)在25 mM铁(III)赤铁矿上，均有吸附但无固定现象。当在pH 6.8条件下，0.25 mM Fe(II)与25 mM铁(III)赤铁矿和0.025 mM Fe(III) AFO反应时，向赤铁矿悬浮液中少量添加AFO会增加Fe(II)的固定量。0.125 mM Fe(II)与2.5 mM Fe(III) AFO反应时，会迅速吸附30%添加的Fe(II)，随后AFO转化为针铁矿，吸附量减少且无Fe(II)固定。在pH 6.8条件下，赤铁矿对Fe(II)的固定与界面电子转移和新矿物相的形成一致。我们认为，从吸附的Fe(II)向赤铁矿结构中的Fe(III)的电子转移导致Fe(II)在赤铁矿表面氧化为AFO，并且赤铁矿、AFO和结构Fe(II)之间的固相接触产生磁铁矿（Fe₃O₄）。Fe(II)与铁(III)氧化物的独特相互作用对于理解氧化还原敏感化学品的归宿在环境方面具有重要意义。
