Organic ligands are commonly believed to decrease the toxicity of metal ions, but there is few experimental evidence, especially for chromium (Cr(III)), which often coexists with organic compounds in industrial effluents. Here, the complexation of Cr(III) with acetate, lactate, l-tartrate, biphthalate and oxalate was tested under the conditions of a toxicity test, with high ion strength, by spectroscopic techniques. The stability constants of the complexes were found to follow the order Cr(III) oxalate > Cr(III) lactate > Cr(III) biphthalate > Cr(III) L-tartrate > Cr(III) acetate. Then, aquatic toxicity of Cr(III) to Photobacterium phosphoreum for a 15-min exposure period was tested in the absence and presence of organic ligands. Results unexpectedly show that the complexation of Cr(III) with acetic, lactate, l-tartrate and biphthalate resulted in enhanced toxicity to luminescent bacteria, whereas the coordination of Cr(III) with oxalate sharply alleviated the toxicity of individual oxalate and inorganic Cr(III), which was further confirmed by the scanning electron microscopy (SEM). Our findings show thus that organics do not always mitigate the toxicity of Cr(III) in acidic water.

中文翻译：

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有机配体出乎意料地增加了铬（III）对发光细菌的毒性

通常认为有机配体会降低金属离子的毒性，但是很少有实验证据，尤其是对于铬（Cr（III）），铬通常与工业废水中的有机化合物共存。在此，在高离子强度的毒性试验条件下，通过光谱技术对Cr（III）与乙酸盐，乳酸盐，1-酒石酸盐，双邻苯二甲酸盐和草酸盐的络合物进行了测试。发现配合物的稳定常数遵循草酸Cr（III）>乳酸Cr（III）> Cr（III）双邻苯二甲酸酯> Cr（III）L-酒石酸盐>乙酸Cr（III）的顺序。然后，Cr（III）对磷光细菌的水生毒性在不存在有机配体的情况下测试了15分钟的暴露时间。结果出乎意料地表明，Cr（III）与乙酸，乳酸，l-酒石酸和双邻苯二甲酸酯的络合导致对发光细菌的毒性增强，而Cr（III）与草酸盐的配位作用显着降低了草酸和无机Cr（III）的毒性。 III），这由扫描电子显微镜（SEM）进一步证实。因此，我们的发现表明，有机物并不总是能够减轻Cr（III）在酸性水中的毒性。