Gatifloxacin (GAT) is a new generation fluoroquinolone antibiotic and its adsorption onto iron minerals influenced by coexisting trace elements [e.g., Cu(II)] has not been well investigated. To evaluate the adsorption behavior of GAT and Cu(II) onto goethite and hematite, the complexation constants of GAT with Cu(II) were determined using potentiometric titration, and the effects of Cu(II) concentration and solution pH on GAT adsorption were investigated using batch experiments. It was observed that GAT adsorption was negatively correlated with molar concentration ratio of Cu(II) to GAT. In our experimental pH range (i.e., 3.0-10.8), the calculated main species involved in GAT adsorption were Cu(GAT± )2+ and Cu(GAT± )2 2+ under acidic to neutral conditions, and formation of Cu(GAT- )2 (s) facilitated the removal of GAT from solution under alkaline condition. The adsorption data were well fitted by the Freundlich model and showed high nonlinearity. In adsorption onto goethite, the primary interactions shifted from electrostatic repulsion to formation of goethite-Cu(II)-GAT ternary surface complexes with increase of GAT concentration. For hematite, electrostatic repulsion was the main inhibiting mechanism and became stronger with increase of Cu(II) concentration. Our findings suggest that it is necessary to consider the complexation between GAT and coexisting metal cations in evaluating its transport in soils rich in different iron minerals.

中文翻译：

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Cu(II)络合对针铁矿和赤铁矿吸附加替沙星的影响

加替沙星 (GAT) 是新一代氟喹诺酮类抗生素，其在受共存微量元素 [例如，Cu(II)] 影响的铁矿物质上的吸附尚未得到充分研究。为了评估 GAT 和 Cu(II) 在针铁矿和赤铁矿上的吸附行为，使用电位滴定法测定 GAT 与 Cu(II) 的络合常数，并研究了 Cu(II) 浓度和溶液 pH 值对 GAT 吸附的影响使用批量实验。观察到 GAT 吸附与 Cu(II) 与 GAT 的摩尔浓度比呈负相关。在我们的实验pH范围内（即3.0-10.8），在酸性到中性条件下，计算出的参与GAT吸附的主要物质是Cu(GAT±)2+和Cu(GAT±)2 2+，Cu(GAT-)2(s)的形成促进了碱性条件下GAT从溶液中的去除。吸附数据与 Freundlich 模型拟合良好，表现出高度非线性。在针铁矿的吸附过程中，随着 GAT 浓度的增加，主要的相互作用从静电排斥转变为针铁矿-Cu(II)-GAT 三元表面复合物的形成。对于赤铁矿，静电排斥是主要的抑制机制，并且随着 Cu(II) 浓度的增加而增强。我们的研究结果表明，在评估 GAT 在富含不同铁矿物质的土壤中的运输时，有必要考虑 GAT 与共存金属阳离子之间的络合。随着 GAT 浓度的增加，主要相互作用从静电排斥转变为针铁矿-Cu(II)-GAT 三元表面复合物的形成。对于赤铁矿，静电排斥是主要的抑制机制，并且随着 Cu(II) 浓度的增加而增强。我们的研究结果表明，在评估其在富含不同铁矿物质的土壤中的运输时，有必要考虑 GAT 与共存金属阳离子之间的络合。随着 GAT 浓度的增加，主要相互作用从静电排斥转变为针铁矿-Cu(II)-GAT 三元表面复合物的形成。对于赤铁矿，静电排斥是主要的抑制机制，并且随着 Cu(II) 浓度的增加而增强。我们的研究结果表明，在评估 GAT 在富含不同铁矿物质的土壤中的运输时，有必要考虑 GAT 与共存金属阳离子之间的络合。