Structural variations of a mineral dictate its adsorption capacity which affects the mobility and toxicity of contaminants in natural and engineered systems. Present batch study evaluates the adsorption of lead (Pb) and cadmium (Cd) onto three magnetites having nanometric (M1-30 nm and M2-60 nm) and micrometric particle sizes (M3-1.5 μm). Obtained data revealed that particle size of tested magnetites strongly affected the extent and kinetics of metal adsorption and desorption. Observed order of adsorption efficiency was M1 > M2 > M3 with optimum monolayer adsorption of 408.14, 331.40, 178.47 mg/g (for Pb) and 228.05, 170.86, 83.49 mg/g (for Cd), respectively. Adsorption data were well fitted to the Freundlich (R2 = 0.99), Langmuir (R2 = 0.99) and pseudo-first order models (R2 = 0.98). Electrostatic attraction and surface precipitation interaction via external mass transfer between bulk liquid-solid interfaces were the potential adsorption pathways. Pb showed higher affinity than Cd in multi-metal system. Desorption efficiency was higher in acidic environment (92%) than in distilled water (44%). Moreover, regenerated magnetite samples retained good adsorption capacity for six cycles. As soils are characterized by large variability of iron minerals, these findings have important implications regarding the transport and immobilization of contaminants particularly in the management of contaminated soils.

中文翻译：

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纳米/微磁铁矿用于减轻镉和铅污染的用途。

矿物的结构变化决定了其吸附能力，这影响了天然和工程系统中污染物的迁移率和毒性。当前的批量研究评估了铅（Pb）和镉（Cd）在三种具有纳米级（M1-30 nm和M2-60 nm）和微米级粒度（M3-1.5μm）的磁铁矿上的吸附。获得的数据表明，测试磁铁矿的粒径强烈影响金属吸附和解吸的程度和动力学。观察到的吸附效率顺序为M1> M2> M3，最佳单层吸附分别为408.14、331.40、178.47 mg / g（对于Pb）和228.05、170.86、83.49 mg / g（对于Cd）。吸附数据非常适合Freundlich（R2 = 0.99），Langmuir（R2 = 0.99）和伪一阶模型（R2 = 0.98）。潜在的吸附途径是通过本体液-固界面之间的外部质量转移进行的静电吸引和表面沉淀相互作用。在多金属体系中，铅的亲和力比镉高。在酸性环境中（92％）比在蒸馏水中（44％）的解吸效率更高。而且，再生磁铁矿样品在六个循环中保持了良好的吸附能力。由于土壤中铁矿物质的变异性很大，因此这些发现对污染物的运输和固定化具有重要意义，尤其是在污染土壤的管理中。在酸性环境中（92％）比在蒸馏水中（44％）的解吸效率更高。而且，再生磁铁矿样品在六个循环中保持了良好的吸附能力。由于土壤中铁矿物质的变异性很大，因此这些发现对污染物的运输和固定化具有重要意义，尤其是在污染土壤的管理中。在酸性环境中（92％）比在蒸馏水中（44％）的解吸效率更高。而且，再生磁铁矿样品在六个循环中保持了良好的吸附能力。由于土壤中铁矿物质的变异性很大，因此这些发现对污染物的运输和固定化具有重要意义，尤其是在污染土壤的管理中。