MXene (Ti₃C₂T_x) was used to remove heavy metals from aqueous solutions; we focused principally on Pb(II) adsorption by MXene using several performance tests and various forms of characterization. Powder activated carbon (PAC) served as the control material of MXene. We used scanning electron microscopy, porosimetry, and a zeta potential analyzer to evaluate the intrinsic properties of MXene and PAC. Although the surface area of MXene was ∼50-fold less than that of PAC, MXene exhibited better adsorption because of its higher negative surface charge. We systematically evaluated MXene-mediated Pb(II) adsorption both kinetically and isothermally, and found that adsorption was well-explained by a pseudo-second-order kinetic and the Freundlich isotherm models, respectively. Notably, attainment of equilibrium within 30 min is valuable when MXene serves as an adsorbent. The principal Pb(II) adsorption mechanism in play was electrostatic attraction, as revealed by experimental results using solutions of different pH levels, ionic strengths, and humic acid concentrations. MXene exhibited good adsorption of four different heavy metals [Pb(II), Cu(II), Zn(II), and Cd(II)] from single-electrolyte solutions. The Pb(II) adsorption mechanisms in play were ion exchange and inner-sphere complex formation, as revealed by Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. Additionally, MXene exhibited good re-usability over four cycles of adsorption/desorption. Therefore, MXene may be very valuable when heavy metals must be removed from wastewater, judging from good adsorption properties and re-usability.

中文翻译：

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使用Ti3C2Tx MXene有效去除合成废水中的Pb（II）

MXene（Ti ₃ C ₂ T _x）用于去除水溶液中的重金属；我们主要使用几种性能测试和多种形式的表征，重点研究了MXene对Pb（II）的吸附。粉末活性炭（PAC）用作MXene的对照材料。我们使用扫描电子显微镜，孔隙率法和zeta电位分析仪来评估MXene和PAC的固有性质。尽管MXene的表面积比PAC小约50倍，但由于其较高的负表面电荷，MXene表现出更好的吸附性。我们系统地评估了MXene介导的Pb（II）动力学和等温吸附，发现分别用拟二阶动力学模型和Freundlich等温模型可以很好地解释吸附。值得注意的是，当MXene用作吸附剂时，在30分钟内达到平衡是很有价值的。发挥作用的主要Pb（II）吸附机理是静电吸引，这是通过使用不同pH值，离子强度和腐殖酸浓度的溶液进行的实验结果揭示的。MXene从单一电解质溶液中表现出对四种不同重金属[Pb（II），Cu（II），Zn（II）和Cd（II）]的良好吸附。铅（II）傅里叶变换红外光谱和X射线光电子能谱表明，吸附的机理是离子交换和内球络合物的形成。此外，MXene在四个吸附/解吸循环中均显示出良好的可重复使用性。因此，从良好的吸附性能和可重复使用性来看，当必须从废水中去除重金属时，MXene可能非常有价值。