Abstract：
Ferrihydrite is a poorly crystalline iron (hydr)oxide and highly efficient adsorbent for heavy metals. Al-substitution in ferrihydrite is ubiquitous in nature. However, the effect of Al-substitution on the surface reactivity of ferrihydrite remains unclear due to its low crystallinity. The present study aims to clarify the microstructure and interfacial reaction of Al-substituted ferrihydrite. Al-substitution had little effect on the morphology and surface site density of ferrihydrite, while the presence of ≡AlOH-0.5 sites resulted in higher proton affinity and surface positive charge of ferrihydrite. Besides, the affinity constant of Pb2+ adsorption on the surface of ferrihydrite decreased at higher Al content, which further decreased the adsorption performance of ferrihydrite for Pb2+. The modeling results revealed that bidentate complex was the dominant Pb complexation species on the surface of ferrihydrite, which was less affected by Al-substitution. The present study provides important insights into the effect of Al-substitution on the interfacial reaction at the ferrihydrite-water interface. The obtained parameters may facilitate the future advance of surface complexation model.
摘要：
水铁矿是一种结晶不良的氧化铁（氢），是重金属的高效吸附剂。水铁矿中的Al取代在自然界中普遍存在。然而,由于其结晶度低，Al取代对水铁矿表面反应性的影响尚不清楚。本研究旨在阐明Al取代的水铁矿的微观结构和界面反应。Al取代对水铁矿的形貌和表面密度影响不大，而εAlOH-0.5位点的存在导致水铁矿的质子亲和力和表面正电荷更高。此外,在较高的Al含量下，水铁矿表面Pb2+吸附的亲和常数降低，这进一步降低了水铁矿对Pb2+的吸附性能。模拟结果表明，二齿络合物是水铁矿表面的主要Pb络合物种，其受Al取代的影响较小。本研究为Al取代对水铁矿-水界面界面反应的影响提供了重要见解。获得的参数可以促进表面络合模型的未来发展。
