Gold recovery from wastewater should be cost-effective, efficient, and environmentally friendly. In this study, adsorbents containing Fe(II,III) systems were prepared via thermal modification of pyrite. The effects of thermal modification temperature, the source of pyrite, pH, ionic strength, adsorbent solid–liquid ratio, and coexisting metal ions on adsorption were investigated. Further, the removability of iron ions was explored, and multiple adsorption–desorption experiments were conducted to verify the stability and recyclability of the adsorbent. The adsorption law and mechanisms were analyzed using adsorption isotherms, thermodynamics, kinetics, and spectroscopy. The results revealed that the natural pyrite modified at 300°C ( N-Py-300) was a more suitable gold adsorbent with a maximum adsorption of 1055.2 mg/g at 25 °C. When coexisting with other metal ions, N-Py-300 exhibited highly selective adsorption of Au(III). Using a mixture of 10 % thiourea and 2 % HCl as a desorbent facilitated the desorption of almost all Au from N-Py-300, resulting in the recovery of Au and the reuse of N-Py-300. The Fe ions released from the adsorbent were effectively reduced by the addition of Ca(OH)2. The adsorption kinetics and isotherm data were in strong agreement with the pseudo-secondary and Langmuir models, indicating that Au(III) was chemisorbed on N-Py-300 as a monolayer and that Au(III) was reduced to Au(0) and Au(Ⅰ). The pH and IS also affected the adsorption behavior, implying that an electrostatic effect exists. Our findings provide that the thermally modified pyrite can be used to recover precious metals from wastewater efficiently, and provides an experimental basis for the resourceful use of pyrite.

中文翻译：

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热改性黄铁矿高效回收金及其机理


从废水中回收黄金应具有成本效益、高效且环保。在本研究中，通过对黄铁矿进行热改性制备了含有 Fe（II，III） 体系的吸附剂。研究了热改性温度、黄铁矿来源、pH 值、离子强度、吸附剂固液比和共存金属离子对吸附的影响。进一步探究铁离子的可去除性，并进行了多次吸附-脱附实验，以验证吸附剂的稳定性和可回收性。使用吸附等温线、热力学、动力学和光谱分析吸附规律和机理。结果表明，在 300°C 下改性的天然黄铁矿 （N-Py-300） 是一种更合适的金吸附剂，在 25 °C 下的最大吸附率为 1055.2 mg/g。 当与其他金属离子共存时，N-Py-300 表现出对 Au（III） 的高选择性吸附。使用 10% 硫脲和 2% HCl 的混合物作为脱附剂，有助于从 N-Py-300 中解吸几乎所有的 Au，从而回收 Au 和 N-Py-300 的再利用。通过添加 Ca（OH）2 可有效还原吸附剂释放的 Fe 离子。吸附动力学和等温线数据与准二级模型和 Langmuir 模型非常吻合，表明 Au（III） 作为单层化学吸附在 N-Py-300 上，而 Au（III） 被还原为 Au（0） 和 Au（I.）。pH 值和 IS 也影响吸附行为，表明存在静电效应。我们的研究结果表明，热改性黄铁矿可用于有效地从废水中回收贵金属，并为黄铁矿的资源利用提供了实验基础。