Abstract：
Recognizing the pervasive presence of alumina minerals and low-molecular-weight organic acids (LMWOAs) in the environment, this study addressed the gap in the interaction mechanisms within the ternary system involving these two components and Fe(II). Specifically, the impacts of LMWOAs on hydroxyl radicals (•OH) production and iron species transformation during Fe(II) oxidation on γ-Al2O3 mineral surface were examined. Results demonstrated that adding 0.5 mM oxalate (OA) or citrate (CA) to the γ-Al2O3/Fe(II) system (28.1 μM) significantly enhanced •OH production by 1.9-fold (51.9 μM) and 1.3-fold (36.2 μM), respectively, whereas succinate (SA) exhibited limited effect (30.7 μM). Raising OA concentration to 5 mM further promoted •OH yield to 125.0 μM after 24 h. Deeper analysis revealed that CA facilitated the dissolution of adsorbed Fe(II) and its subsequent oxygenation by O2 through both one- and two-electron transfer mechanisms, whereas OA enhanced the adsorption of dissolved Fe(II) and more efficient two-electron transfer for H2O2 production. Additionally, LMWOAs presence favored the formation of iron minerals with poor crystallinity like ferrihydrite and lepidocrocite rather than well-crystallized forms such as goethite. The distinct impacts of various LMWOAs on Fe(II) oxidation and •OH generation underscore their unique roles in the redox processes at mineral surface, consequently modulating the environmental fate of prototypical pollutants like phenol.
摘要：
认识到环境中普遍存在氧化铝矿物和低分子量有机酸（LMWOA），这项研究解决了涉及这两种成分和Fe（II）的三元系统中相互作用机制的差距。具体来说,研究了LMWOAs对γ-Al2O3矿物表面Fe（II）氧化过程中羟基自由基（•OH）产生和铁物种转化的影响。结果表明，向γ-Al2O3/Fe（II）系统（28.1μM）中添加0.5mM草酸盐（OA）或柠檬酸盐（CA）可显着提高•OH的产量1.9倍（51.9μM）和1.3倍（36.2μM），分别,而琥珀酸（SA）表现出有限的作用（30.7μM）。将OA浓度提高到5mM进一步促进•OH产量在24小时后达到125.0μM。更深入的分析显示，CA通过单电子和双电子转移机制促进了吸附的Fe（II）的溶解及其随后被O2的氧化，而OA增强了溶解的Fe（II）的吸附，并提高了H2O2生产的双电子转移效率。此外,LMWOAs的存在有利于形成结晶度差的铁矿物，例如水铁矿和锂铁矿，而不是结晶良好的形式，例如针铁矿。各种LMWOAs对Fe（II）氧化和•OH生成的不同影响强调了它们在矿物表面氧化还原过程中的独特作用，因此调节典型污染物如苯酚的环境命运。
