Abstract The use of calcium thiosulfate (CaS2O3) as an alternative lixiviant to cyanide to treat double refractory gold ores has become an industrial reality. In this study, a novel adsorbent, polyethylenimine coated iron oxide magnetic nanoparticles (PEI-MNPs), was evaluated for the adsorption of gold from thiosulfate leaching systems that contain gold, copper and calcium thiosulfate. Particles were characterised in terms of their size and morphology, zeta potential, crystalline structure, surface properties, functional groups, magnetic properties and thermal degradation properties. The effect of nanoparticle dosage, thiosulfate concentration, copper concentration, solution pH and solution temperature on gold loading in synthetic leaching solutions was examined. In addition, adsorption kinetics and adsorption isotherms were investigated. PEI-MNPs demonstrated a positive surface charge up to a pH of 11, which facilitated electrostatic attraction of anionic gold thiosulfate complex. A higher nanoparticle dosage, lower free thiosulfate concentrations and lower temperatures favoured gold adsorption, while copper concentration and solution pH did not show a considerable effect. Gold adsorption kinetics were fast, irrespective of the solution content and reached equilibrium in less than 30 min. The adsorption isotherm data could be fitted with both the Langmuir and the Freundlich isotherm models. The adsorbent was able to be reused after a selective metal elution process.

中文翻译：

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聚乙烯亚胺功能化磁性纳米粒子在硫代硫酸金回收中的应用

摘要 利用硫代硫酸钙(CaS2O3) 作为氰化物的替代浸出剂处理双难熔金矿已成为工业现实。在这项研究中，评估了一种新型吸附剂、聚乙烯亚胺涂覆的氧化铁磁性纳米粒子 (PEI-MNP) 从含有金、铜和硫代硫酸钙的硫代硫酸盐浸出系统中吸附金的能力。颗粒的特征在于它们的尺寸和形态、zeta 电位、晶体结构、表面特性、官能团、磁性和热降解特性。研究了纳米颗粒用量、硫代硫酸盐浓度、铜浓度、溶液 pH 值和溶液温度对合成浸出溶液中金负载量的影响。此外，研究了吸附动力学和吸附等温线。PEI-MNPs 在 pH 值为 11 时表现出正表面电荷，这有助于阴离子硫代硫酸金复合物的静电吸引。较高的纳米颗粒剂量、较低的游离硫代硫酸盐浓度和较低的温度有利于金吸附，而铜浓度和溶液 pH 值没有显示出明显的影响。无论溶液含量如何，金吸附动力学都很快，并且在不到 30 分钟的时间内达到平衡。吸附等温线数据可以与 Langmuir 和 Freundlich 等温线模型拟合。在选择性金属洗脱过程之后，吸附剂能够重新使用。较低的游离硫代硫酸盐浓度和较低的温度有利于金吸附，而铜浓度和溶液 pH 值没有显示出明显的影响。无论溶液含量如何，金吸附动力学都很快，并且在不到 30 分钟的时间内达到平衡。吸附等温线数据可以与 Langmuir 和 Freundlich 等温线模型拟合。在选择性金属洗脱过程之后，吸附剂能够重新使用。较低的游离硫代硫酸盐浓度和较低的温度有利于金吸附，而铜浓度和溶液 pH 值没有显示出明显的影响。无论溶液含量如何，金吸附动力学都很快，并且在不到 30 分钟的时间内达到平衡。吸附等温线数据可以与 Langmuir 和 Freundlich 等温线模型拟合。在选择性金属洗脱过程之后，吸附剂能够重新使用。