For the sustainable development of the ecological environment in gold recycling, it is urgently desired to develop a more efficient and highly selective process for gold ions from ewaste or mineral lixivium. As a kind of emerging two-dimensional nanomaterials, Ti 3 C 2 T x has emerged as a rapidly developing novel water treatment material. Herein, the preparation of few-layer Ti 3 C 2 T x nanosheets and their performance for recycling of gold ions were studied. Notably, it exhibits an impressive capacity of 2973.57 mg/g at room temperature, almost 124 times that of commercially available activated carbon (24 mg/g), and an exciting selectivity for Au(III) in the presence of competing ions due to perfectly weak reduction caused by the removal of the Al layer. The Langmuir isotherm and pseudo-second-order kinetic model can accurately depict the rapid adsorption process. Additionally, it can be regenerated effectively by thiourea and exhibits excellent reutilization. A critical mechanism involves an adsorptive−reduction pathway between Au(III) and active Ti sites. Excellent performance in real lixiviums from e-waste and gold-bearing sludge is also exhibited, demonstrating great potential for Au(III) recycling. It may be a sustainable direction for the capture and separation of Au(III) and also lays the foundation for the interface control of Ti 3 C 2 T x and Au NPs as a catalyst and other functional materials.

Arsenious and sulphur-bearing micro-disseminated gold ore is a kind of typical refractory Carlin-Type. The gold in Carlin-Type gold ore grains is distributed finely, existing as invisible or submicroscopic gold, encapsulated in arsenopyrite and pyrite. The technical difficulty of treatment Carlin-Type gold ore lies in how to release the fine gold wrapped in pyrite and arsenopyrite. In this study, the oxidation roasting pre-treatment technique was used to treat the Carlin-Type gold ore. This included a two-stage roasting process: the arsenic was removed in the first roasting process, and the sulphur was removed in the second roasting process. The thermodynamic of the roasting process was analyzed, and the mineral phase evolution of the roasting process was investigated by using XRD, SEM and EDS. Finally, the influence of sodium cyanide dosage and leaching time on leaching efficiency was investigated. The results suggest that for the first roasting temperature at 550 °C, and the second roasting at temperature 700 °C with air flow 2.5 L/min, the sodium cyanide dosage is 1.75 kg/t and leaching time is 27 h; a good leaching efficiency is obtained with 83.85%.

The role of silica in the chlorination–volatilization of cobalt oxide, using calcium chloride, is investigated in this paper. It is found that the Co volatilization percentage of the CoO–Fe2O3–CaCl2 system is not larger than 12.1%. Silica plays an important role in the chlorination–volatilization of cobalt oxide by using calcium chloride. In the CoO–SiO2–Fe2O3–CaCl2 system, the Co volatilization percentage is initially positively related to the molar ratio of SiO2 to CaCl2, and remains almost constant when the molar ratio of SiO2 to CaCl2 rises from zero to eight. The critical molar ratios of SiO2 to CaCl2 are 1 and 2 when the molar ratios of CaCl2 to CoO are 8.3 and 16.6, respectively. The Co volatilization percentage remains almost constant with the increase in CaO concentration, and decreases when Al2O3 and MgO are added. Ca2SiO3Cl2 is determined after roasting at 1073 K and 1173 K, and disappears at temperatures in excess of 1273 K in the calcines from the CoO–SiO2–CaCl2 system. CaSiO3 always exists in the calcines at temperatures in excess of 973 K.