In this study, iron nanoparticles (FeNPs) were synthesized via a green method using loquat (Eriobotrya japonica) leaves aqueous extract as a renewable reducing agent. The synthesized FeNPs were characterized by DLS, XRD, FT-IR, SEM/EDX, and TEM analysis, and then, they were used as an adsorbent for Cr(VI) removal from aqueous solutions. Batch adsorption experiments were carried out to investigate the optimum adsorption parameters such as the initial pH of the solution, temperature, initial Cr(VI) concentration, and adsorbent concentration. The optimum adsorption conditions were determined as initial pH 3.0, temperature 45°C, and adsorbent concentration 1 g/L. Also, a linear increase was observed in adsorbed Cr(VI) amounts with the increasing initial Cr(VI) concentrations. The biosynthesized FeNPs showed the high removal levels higher than 90% for Cr(VI) adsorption at a wide range of initial Cr(VI) concentrations (50–500 mg/L). The experimental equilibrium data were modelled with Langmuir and Freundlich isotherm models, and it was found that experimental equilibrium data could be well described by the Langmuir isotherm model. The maximum monolayer coverage capacity of FeNPs for Cr(VI) adsorption was found to be 312.5 mg/g. The pseudo-first-order and the pseudo-second-order kinetic models were applied to the experimental adsorption data, and it was concluded that the data were defined as the best agreement with the pseudo-second-order kinetic model. Weber–Morris model was used to investigate the effect of mass transfer on the adsorption of Cr(VI) onto FeNPs; it was observed that both the film (boundary layer) and intraparticle diffusion affected the studied adsorption process. The thermodynamic studies suggested that Cr(VI) adsorption onto FeNPs was endothermic and nonspontaneous, and the positive ΔS value indicated increased disorder at the solid-solution interface during the adsorption.

中文翻译：

---

铁纳米颗粒的生物合成和表征，可有效吸附Cr（VI）

在这项研究中，使用lo （Eriobotrya japonica）通过绿色方法合成了铁纳米颗粒（FeNPs ）。留下水提取物作为可再生还原剂。通过DLS，XRD，FT-IR，SEM / EDX和TEM分析对合成的FeNPs进行表征，然后将其用作从水溶液中去除Cr（VI）的吸附剂。进行了批量吸附实验以研究最佳吸附参数，例如溶液的初始pH，温度，初始Cr（VI）浓度和吸附剂浓度。确定最佳吸附条件为初始pH 3.0，温度45°C和吸附剂浓度1 g / L。同样，观察到随着初始Cr（VI）浓度的增加，吸附的Cr（VI）量呈线性增加。生物合成的FeNPs在很宽的初始Cr（VI）浓度（50-500 mg / L）范围内，对Cr（VI）的吸附去除率高于90％。用Langmuir和Freundlich等温线模型对实验平衡数据进行建模，发现Langmuir等温线模型可以很好地描述实验平衡数据。发现FeNPs对Cr（VI）吸附的最大单层覆盖能力为312.5 mg / g。将准一级动力学模型和准二级动力学模型应用于吸附实验数据，得出结论认为该数据与准二级动力学模型具有最佳的一致性。Weber–Morris模型用于研究传质对FeNPs上Cr（VI）吸附的影响。观察到膜（边界层）和颗粒内扩散都影响所研究的吸附过程。S值表明在吸附过程中固溶体界面处无序增加。