The adsorption of Pb²⁺ onto zinc–iron layered double hydroxide (ZnFe–LDH) and its composites coupled with single-walled carbon nanotubes (ZnFe–CNTs) and biochar, which had been obtained from orange peel waste biomass (ZnFe–OPb), was studied in detail. The successful formations of Zn²⁺- and Fe³⁺-LDH were investigated by scanning electron microscopy. Moreover, energy-dispersive X-ray spectroscopy revealed that Pb²⁺ was adsorbed successfully on ZnFe-LDH. Further, both ZnFe-LDH and ZnFe–CNTs exhibited ~ 60% removal efficiencies for Pb²⁺ at 20 mgL^–1 with rapid adsorption at an initial contact time of 30 min, while the equilibrium was achieved at ~ 60 min with a 95% removal efficiency with ZnFe–OPb. Furthermore, the pseudo-second-order kinetics demonstrated the best fit, thus supporting the chemisorption essence of the adsorption mechanism. ZnFe–OPb demonstrated a twofold increase in the adsorption efficiency compared with simple LDH or ZnFe–CNTs, as the initial Pb²⁺ concentration was enhanced from 10 to 100 mgL^–1. The percentage removal and adsorption capacity increased almost linearly as the pH of the solution changed from 2 to 5, suggesting that the optimum pH value was approximately 5 or 6 for all adsorbents. The percentage removal of Pb²⁺ also increased on increasing the dose. Additionally, the optimum removal efficiency of 99% was obtained with 0.7 g of ZnFe–OPb. The Langmuir model corresponds best with the adsorption data, while the Sips isotherm indicated that ZnFe-LDH exhibited the highest degree of heterogeneity compared with the other adsorbents in this study.

Pb ²⁺在锌-铁层状双氢氧化物（ZnFe-LDH）及其复合材料与单壁碳纳米管（ZnFe-CNTs）和生物炭上的吸附，这是从橘皮废料生物质（ZnFe-OPb）获得的，进行了详细的研究。通过扫描电子显微镜研究了Zn 2 ⁺ -和Fe ³⁺ -LDH的成功形成。此外，能量色散X射线光谱表明，Pb ²⁺被成功吸附在ZnFe-LDH上。此外，ZnFe-LDH和ZnFe-CNT在20 mgL ^–1时对Pb ^2+的去除率均约为60％。初始接触时间为30分钟时具有快速吸附能力，而在〜60分钟时达到平衡，而ZnFe–OPb的去除效率为95％。此外，拟二级动力学显示出最佳拟合，从而支持了吸附机理的化学吸附本质。与简单的LDH或ZnFe-CNT相比，ZnFe-OPb的吸附效率提高了两倍，因为初始Pb ²⁺浓度从10 mgL- ¹增加到100 mgL- ¹。随着溶液的pH从2变为5，去除百分率和吸附容量几乎呈线性增加，这表明所有吸附剂的最佳pH值约为5或6。Pb ^2+的去除百分比在增加剂量时也增加了。此外，使用0.7 g ZnFe–OPb可获得99％的最佳去除效率。Langmuir模型与吸附数据最吻合，而Sips等温线表明，与本研究中的其他吸附剂相比，ZnFe-LDH具有最高的异质性。