Abstract Photochemical transformation of iron plays crucial roles in the geochemical evolution of marine, terrestrial and atmospheric systems. In the present work, the photo-conversion of ferric iron and ferrous iron were studied in the presence of four naturally abundant organic compounds (OCs): two carboxylic acids [oxalic acid, salicylic acid] and two diketones [acetylacetone (Hacac), diacetyl]. The key finding is that the two diketones significantly accelerated both the photo-reduction of Fe(III) and the photo-oxidation of Fe(II) in acidic solutions. The quantum yields (Φ) of [Fe(acac)]2+ and Fe(III)-salicylate at 254 nm were estimated to be 0.23 and 0.02, respectively. The formation of photoactive Fe(III)-OC complexes accounted for the changed photo-steady state of iron but was not the exclusive factor. The enhanced consumption of dissolved oxygen (6 and 16 times in Fe(III) and Fe(II)-initiated systems) was attributed to the effects of the nonchelating diacetyl on the photo redox cycling of iron. Although the photoactivity of Fe(III)-oxalate (Φ254 nm = 1.25) was much higher than those of Fe(III)-acac and Fe(III)-salicylate, the effect of oxalate did not last, because oxalate was rapidly depleted in several minutes. The addition of the two diketones kept either the Fe(III)-initiated system or the Fe(II)-initiated system at the Fe(II) state for hours, which is of great environmental significance, because Fe(II) is more active in both engineered and natural environments.

中文翻译：

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配体对水性铁物质光氧化还原循环影响的关键因素

摘要 铁的光化学转化在海洋、陆地和大气系统的地球化学演化中起着至关重要的作用。在目前的工作中，在四种天然丰富的有机化合物 (OC) 存在下研究了三价铁和二价铁的光转化：两种羧酸 [草酸、水杨酸] 和两种二酮 [乙酰丙酮 (Hacac)、双乙酰]。关键发现是这两种二酮显着加速了 Fe(III) 的光还原和 Fe(II) 在酸性溶液中的光氧化。[Fe(acac)]2+ 和 Fe(III)-水杨酸盐在 254 nm 处的量子产率 (Φ) 估计分别为 0.23 和 0.02。光活性 Fe(III)-OC 配合物的形成解释了铁的光稳态变化，但不是唯一的因素。溶解氧消耗的增加（在 Fe(III) 和 Fe(II) 引发的系统中是 6 倍和 16 倍）归因于非螯合双乙酰对铁的光氧化还原循环的影响。尽管 Fe(III)-草酸盐 (Φ254 nm = 1.25) 的光活性远高于 Fe(III)-acac 和 Fe(III)-水杨酸盐，但草酸盐的作用并未持续，因为草酸盐在几分钟。两种二酮的加入使 Fe(III) 引发的体系或 Fe(II) 引发的体系保持在 Fe(II) 状态数小时，这对环境具有重要意义，因为 Fe(II) 更活跃在工程和自然环境中。尽管 Fe(III)-草酸盐 (Φ254 nm = 1.25) 的光活性远高于 Fe(III)-acac 和 Fe(III)-水杨酸盐，但草酸盐的作用并未持续，因为草酸盐在几分钟。两种二酮的加入使 Fe(III) 引发的体系或 Fe(II) 引发的体系保持在 Fe(II) 状态数小时，这对环境具有重要意义，因为 Fe(II) 更活跃在工程和自然环境中。尽管 Fe(III)-草酸盐 (Φ254 nm = 1.25) 的光活性远高于 Fe(III)-acac 和 Fe(III)-水杨酸盐，但草酸盐的作用并未持续，因为草酸盐在几分钟。两种二酮的加入使 Fe(III) 引发的体系或 Fe(II) 引发的体系保持在 Fe(II) 状态数小时，这对环境具有重要意义，因为 Fe(II) 更活跃在工程和自然环境中。