Harrington Laura F, Cooper Ellen M, Vasudevan Dharni
Nicholas School of the Environment and Earth Sciences, Duke University, Box 90328, Durham, NC 27708-0328, USA.
J Colloid Interface Sci. 2003 Nov 15;267(2):302-13. doi: 10.1016/s0021-9797(03)00609-x.
Fluoride sorption and related aluminum (Al) release are evaluated in two iron-oxide-rich soils as a function of soil depth, composition, and physical-chemical properties and potential mechanisms of fluoride-surface interaction are suggested. Measured Al concentrations at equilibrium fluoride sorption, reflective of the net balance between Al dissolution and sequestration of the released Al by the solid phase, suggest net fluoride-assisted dissolution of Al-bearing amorphous and crystalline soil minerals. Strikingly, soils of similar depth and horizonation from the same soil order but of distinct soil series exhibited markedly different susceptibility to Al loss in the presence of fluoride, possibly a combined result of differences in the mechanism of fluoride sorption, soil mineralogy, reactivity of the surficial Al and Fe, and soil solution chemistry. Fluoride sorption is strongly correlated with soil Al and Fe present as high-surface-area amorphous and crystalline oxide phases. Fluoride complexation to surficial Al and Fe ions via ligand exchange with surficial OH groups and water molecules appears to be the dominant sorption mechanism. At high dissolved fluoride concentrations (>7 mM), other mechanisms of fluoride retention including adsorption of AlF solution complexes, entrapment in the interparticle pore fluid, and precipitation into solution and/or onto the soil surface are also likely.
在两种富含铁氧化物的土壤中评估了氟吸附及相关铝（Al）释放情况，这是作为土壤深度、组成、物理化学性质的函数进行的，并提出了氟与表面相互作用的潜在机制。平衡氟吸附时测得的铝浓度反映了铝溶解与固相固定释放铝之间的净平衡，表明含铝无定形和结晶土壤矿物存在净氟辅助溶解现象。令人惊讶的是，来自同一土纲但不同土系、深度和层位相似的土壤在氟存在下对铝损失的敏感性明显不同，这可能是氟吸附机制、土壤矿物学、表面铝和铁的反应性以及土壤溶液化学差异共同作用的结果。氟吸附与以高比表面积无定形和结晶氧化物相形式存在的土壤铝和铁密切相关。通过与表面羟基和水分子进行配体交换，氟与表面铝和铁离子形成络合物似乎是主要的吸附机制。在高溶解氟浓度（>7 mM）下，其他氟保留机制，包括AlF溶液络合物的吸附、截留于颗粒间孔隙流体中以及沉淀到溶液中和/或土壤表面也有可能发生。
