In this study, polyethylenimine (PEI) modified Lagerstroemia speciosa leaves powder (PEI-LS) as low-cost and eco-friendly biosorbent was efficiently applied for gold recovery from acidic solution. Our experimental data show that PEI-LS is effective in complete recovery of gold at pH 1, compared to the raw L. speciosa leaves powder (raw LS) biomass. The adsorption kinetic results show gold adsorption reaches equilibrium in 6 h and follows a pseudo-second order kinetic. The adsorption isotherm data were best explained by Freundlich model and the monolayer adsorption capacity of PEI-LS for gold are in the range 286–313 mg/g. Thermodynamic parameters suggest that gold adsorption on PEI-LS was spontaneous and endothermic in nature. The developed PEI-LS was reusable up to 4 cycles with ∼98% gold recovery. Further, the calculated separation factor values suggest the PEI-LS shows high selectivity for low concentration of gold over the other co-existing metal ions in binary mixtures. Various instrumental characterization of raw LS and PEI-LS confirms the successful grafting of PEI on biomass surface. Surface analytical techniques like X-ray photoelectron spectroscopic (XPS) analysis confirms the adsorption-reduction mechanism of gold ions on PEI-LS leading to the formation of zero-valent gold on the biosorbent surface. The XPS was also used to characterize the PEI-LS surface functional groups (N1s) responsible for gold adsorption-reduction mechanism. The PEI-LS was successfully applied for quantitative gold recovery (≥95%) from an acidic solution of electronic scrap, gold refining sludge and wastewater.

在这项研究中，聚乙烯亚胺（PEI）改性的紫薇叶粉（PEI-LS）作为低成本和生态友好型生物吸附剂，可有效地用于从酸性溶液中回收金。我们的实验数据表明，与原始L. speciosa相比，PEI-LS在pH为1时可以有效地完全回收金。留下粉末（原始LS）生物质。吸附动力学结果表明，金吸附在6 h内达到平衡，并遵循伪二级动力学。吸附等温线数据最好用Freundlich模型解释，PEI-LS对金的单层吸附容量在286-313 mg / g范围内。热力学参数表明，PEI-LS上的金吸附是自然的，并且是自然吸热的。研发的PEI-LS可重复使用多达4个循环，金回收率约为98％。此外，计算出的分离因子值表明，PEI-LS对于二元混合物中的其他共存金属离子而言，对于低浓度的金表现出较高的选择性。原始LS和PEI-LS的各种仪器表征证实了PEI在生物质表面的成功接枝。X射线光电子能谱（XPS）分析等表面分析技术证实了金离子在PEI-LS上的吸附还原机理，从而导致在生物吸附剂表面形成零价金。XPS还用于表征负责金吸附还原机理的PEI-LS表面官能团（N1s）。PEI-LS成功应用于从电子废料，金精炼污泥和废水的酸性溶液中定量回收金（≥95％）。