The present study investigated the capability of magnetite nanoparticles (MNP) synthesized from the direct reduction iron sludge and green tea extract for the single and competitive adsorption of copper (Cu²⁺) and cadmium (Cd²⁺). Moreover, we assessed the desorption of Cu²⁺ and Cd²⁺ in a ten-day cycle (both single and competitive systems) to evaluate their release amount from the adsorbent’s surface. The adsorption process was described using three well-known adsorption isotherms: Langmuir, Freundlich, and Dubinin-Radushkevich. The Freundlich isotherm was employed to describe the desorption process. The maximum adsorption capacity of Cu²⁺ and Cd²⁺ by MNP according to the Langmuir curve was 21.24 and 19.36 mg/g, respectively. A significant difference was observed in the adsorbed value of heavy metals in the competitive mode and MNP selectively preferred Cu²⁺ against Cd²⁺. Results of energy-dispersive X-ray (EDX) and elemental mapping analyses corroborated the Cu²⁺ and Cd²⁺ adsorption in both single and competitive systems. The findings of Fourier-transform infrared spectroscopy (FTIR) analysis revealed the role of functional groups in Cu²⁺ and Cd²⁺ adsorption. The results of the desorption evaluation demonstrated the higher tendency of MNP to retain Cu²⁺ than Cd²⁺. We developed economical and environmentally friendly magnetite nanoparticles, promising in individual and competitive adsorption of Cu²⁺ from aqueous solutions while resisting to release it. Moreover, the adsorbent’s performance in singular removal of Cd²⁺ was noticeable.

本研究调查了由直接还原铁污泥和绿茶提取物合成的磁铁矿纳米颗粒（MNP）对铜（Cu ²⁺）和镉（Cd ²⁺）的单一和竞争吸附的能力。此外，我们评估了 Cu ²⁺和 Cd ²⁺在 10 天周期（单系统和竞争系统）中的解吸，以评估它们从吸附剂表面的释放量。使用三个众所周知的吸附等温线描述吸附过程：Langmuir、Freundlich 和 Dubinin-Radushkevich。Freundlich 等温线用于描述解吸过程。^{Cu 2+}和Cd ²⁺的最大吸附容量根据 Langmuir 曲线，MNP 分别为 21.24 和 19.36 mg/g。竞争模式下重金属的吸附值存在显着差异，MNP对Cu ²⁺的选择性优于Cd ²⁺。能量色散 X 射线 (EDX) 和元素映射分析的结果证实了单系统和竞争系统中的 Cu ²⁺和 Cd ^2+吸附。傅里叶变换红外光谱 (FTIR) 分析结果揭示了官能团在 Cu ²⁺和 Cd ²⁺吸附中的作用。解吸评价结果表明，MNP保留Cu ²⁺的趋势高于Cd ²⁺. 我们开发了经济环保的磁铁矿纳米颗粒，有望在水溶液中单独和竞争吸附 Cu ^{2+ ，同时抵抗释放。此外，吸附剂对Cd 2+}的单次去除效果显着。