College of Resources and Environmental Science, South-Central Minzu University, Wuhan 430074, P. R. China.
Department of Chemistry, Umeå University, SE-90187 Umeå, Sweden.
Environ Sci Technol. 2023 Oct 17;57(41):15680-15692. doi: 10.1021/acs.est.3c05727. Epub 2023 Oct 5.
Interactions between aqueous Fe(II) and solid Fe(III) oxy(hydr)oxide surfaces play determining roles in the fate of organic contaminants in nature. In this study, the adsorption of nalidixic acid (NA), a representative redox-inactive quinolone antibiotic, on synthetic goethite (α-FeOOH) and akaganéite (β-FeOOH) was examined under varying conditions of pH and cation type and concentration, by means of adsorption experiments, attenuated total reflectance-Fourier transform infrared spectroscopy, surface complexation modeling (SCM), and powder X-ray diffraction. Batch adsorption experiments showed that Fe(II) had marginal effects on NA adsorption onto akaganéite but enhanced NA adsorption on goethite. This enhancement is attributed to the formation of goethite-Fe(II)-NA ternary complexes, without the need for heterogeneous Fe(II)-Fe(III) electron transfer at low Fe(II) loadings (2 Fe/nm), as confirmed by SCM. However, higher Fe(II) loadings required a goethite-magnetite composite in the SCM to explain Fe(II)-driven recrystallization and its impact on NA binding. The use of a surface ternary complex by SCM was supported further in experiments involving Cu(II), a prevalent environmental metal incapable of transforming Fe(III) oxy(hydr)oxides, which was observed to enhance NA loadings on goethite. However, Cu(II)-NA aqueous complexation and potential Cu(OH) precipitates counteracted the formation of ternary surface complexes, leading to decreased NA loadings on akaganéite. These results have direct implications for the fate of organic contaminants, especially those at oxic-anoxic boundaries.
水相 Fe(II) 和固相 Fe(III) 氧（氢）氧化物表面之间的相互作用在自然界中有机污染物的归宿中起着决定性的作用。在这项研究中，通过吸附实验、衰减全反射傅里叶变换红外光谱、表面络合模型（SCM）和粉末 X 射线衍射，在不同 pH 值和阳离子类型及浓度条件下，研究了代表氧化还原非活性喹诺酮类抗生素的萘啶酸（NA）在合成针铁矿（α-FeOOH）和纤铁矿（β-FeOOH）上的吸附。批式吸附实验表明，Fe(II) 对 akaganéite 上 NA 的吸附影响不大，但增强了 goethite 上 NA 的吸附。这种增强归因于 goethite-Fe(II)-NA 三元配合物的形成，而无需在低 Fe(II) 负载（2 Fe/nm）下进行异相 Fe(II)-Fe(III)电子转移，这通过 SCM 得到了证实。然而，更高的 Fe(II) 负载需要在 SCM 中使用针铁矿-磁铁矿复合材料来解释 Fe(II)驱动的重结晶及其对 NA 结合的影响。SCM 中表面三元配合物的使用在涉及环境中普遍存在的不能转化 Fe(III) 氧（氢）氧化物的 Cu(II)的实验中得到了进一步支持，观察到 Cu(II)增强了 goethite 上 NA 的负载。然而，Cu(II)-NA 水相络合和潜在的 Cu(OH)沉淀抵消了三元表面配合物的形成，导致 akaganéite 上 NA 的负载减少。这些结果对有机污染物的归宿有直接影响，特别是在好氧-缺氧边界处的有机污染物。
