In this paper, green and facile synthesis of sulfur- and nitrogen-codoped carbon nanospheres (CNs) was prepared from the extract of Hibiscus sabdariffa L by a direct hydrothermal method. Finally, sulfur-carbon nanospheres (CNs) were used as the adsorbent to remove Pb⁺² ions from aqueous solutions because of the high surface area of S-CNs from CNs and N-CNs. The synthesized nanospheres were examined by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy, transmission electron microscopy (TEM), and nitrogen adsorption-desorption isotherms. The results show spherical shapes have a particle size of up to 65 nm with a high surface area capable of absorbing lead ions efficiently. Additionally, the factors affecting the process of adsorption that include equilibrium time, temperature, pH solution, ionic intensity, and adsorbent dose were studied. The equilibrium removal efficiency was studied employing Langmuir, Freundlich, and Temkin isotherm forms. The kinetic data were analyzed with two different kinetic models, and both apply to the adsorption process depending on the values of correlation coefficients. The thermodynamic parameters including Gibbs free energy (ΔG°), standard enthalpy change (ΔH°), and standard entropy change (ΔS°) were calculated for the adsorption process.

中文翻译：

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S和N掺杂碳纳米球的绿色合成及其在水溶液中吸附Pb（II）的应用

在本文中，通过直接水热法从芙蓉叶的提取物中制备了绿色且易于合成的硫和氮共掺杂碳纳米球（CN）。最后，将硫碳纳米球（CNs）用作吸附剂以去除Pb ⁺²由于来自CN和N-CN的S-CN的表面积较大，因此水溶液中的离子含量较高。通过傅立叶变换红外（FTIR）光谱，X射线衍射（XRD），场发射扫描电子显微镜，透射电子显微镜（TEM）和氮吸附-解吸等温线对合成的纳米球进行了检查。结果表明球形具有高达65 nm的粒径，具有高表面积，能够有效吸收铅离子。此外，还研究了影响吸附过程的因素，包括平衡时间，温度，pH溶液，离子强度和吸附剂量。使用Langmuir，Freundlich和Temkin等温线形式研究了平衡去除效率。用两种不同的动力学模型分析了动力学数据，两者都取决于相关系数的值应用于吸附过程。热力学参数包括吉布斯自由能（Δ对于吸附过程，计算出了G °），标准焓变（ΔH °）和标准熵变（ΔS °）。