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In this study, the Ag and Cu evolution in the sintering dust was extracted by chlorination roasting process, and the mechanism of the process was analyzed by atomic absorption spectroscopy, X-ray fluorescence, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectrometry. In addition, in order to better understand the chlorination roasting process, the mechanism and thermodynamics of roasting reaction were analyzed. The recovery of Ag and Cu reached 99.05% and 59.32%, respectively, under the conditions of roasting temperature of 1423 K, holding time of 60 min, and the air flow rate of 400 L/h. Thermodynamic analysis showed that MgO and SiO2 could promote the production of Cl2 and HCl and that CuO could be chlorinated by Cl2 at 1421 K, but it was not amenable for HCl. Compared with CuO, Ag was more easily chlorinated at high temperatures. Experimental results indicate that silver and copper can be efficiently extracted, indicating that the chlorination roasting is a promising pyrometallurgical treatment for the recycling of sintering dust. [ABSTRACT FROM AUTHOR]

Recovery of valuable metals is hindered by sulfur in cyanide tailings. In this work, a process for the clean recovery of multiple valuable metals through chlorination roasting was proposed. HSC software was used to find that the process of dissociation of chlorides is further accelerated by sulfur in the tailings. Experiments were carried out to study temperature variables and chlorinated agent variables. The optimum conditions were identified to be a CaCl2 dosage of 4%, roasting temperature of 1323 K, achieved maximum recovery of 84% of Au, 71% of Ag, 72% of Cu, 92% of Pb, and 69% of Zn. [ABSTRACT FROM AUTHOR]

In this work, a method for the extraction of gold from the cyanide tailings (CT) was investigated. Sulfuric acid was used as a pretreatment leaching solution and calcium hypochlorite was used as a chloride agent during the chlorination leaching. Under different conditions, the potential difference of the chlorination reaction is detected by electrochemical workstation. With calcium hypochlorite for chlorination leaching, under suitable conditions of calcium hypochlorite: adding amount 8%, chlorination temperature 333 K and chlorination time 2 h, gold was effectively recovered, the leaching rate is 81%. The chlorination leaching method showed a unique advantage for treating the secondary sources. [ABSTRACT FROM AUTHOR]

In this work, a chlorination roasting method for the extraction of precious metals (gold and silver) from the cyanide tailings (CT) was investigated. The decomposition mechanism of the CaCl 2 used as chloride agent was presented during the chlorination roasting. The Au and Ag recovery as high as 91.6% and 54.7% under the optimum experiment conditions would be achieved. The optimal process conditions were identified to be a CaCl 2 content 4%, chlorination temperature 1323 K and chlorination duration of 2 h. The microstructures of CT before and after roasting were examined by using scanning electron microscopy (SEM), and the volatilization process of the chloride of Au and Ag was assessed. The chlorination behaviors of all the phases in the CT in air atmosphere was analyzed using the thermogravimetric analysis (TGA), and the phase transformation of the main phase during roasting were analyzed by using X-ray diffraction (XRD). The chlorination roasting process shows unique advantage for treating the secondary sources of CT, additionally being environmentally benign. [ABSTRACT FROM AUTHOR]

The selective chlorination of cyanidation tailing (CT) for the extraction of gold and silver has been investigated. The reaction operated at different conditions and their effect on the extraction of Au and Ag was studied. The mineral samples were characterized by fire assay, X-ray diffraction (XRD), X-ray fluorescence (XRF) and scanning electronic microscopy (SEM). The best recovery values were 95.32% of Au and 85.32% of Ag at 1373 K and 1.5 h with 5% KCl. The results show that gold chlorination reaction was controlled by the interfacial chemical reaction, and the apparent activation energy was 40.05 kJ/mol. Silver has an activation energy of about 8.97 kJ/mol, and silver removal is performed by diffusion control. [ABSTRACT FROM AUTHOR]

To develop a cleaner production technology for the construction of secondary resources, this study researched the best chlorine source for the sustainable recovery of gold from gold-bearing tailings via chlorination heat treatment. A thermal analysis of different chlorine sources, NaCl, MgCl 2 , KCl and CaCl 2 , was performed via Factsage 7.2 (thermodynamic software) and thermogravimetric analysis - differential scanning calorimetry. The results showed that CaCl 2 has a stronger chlorine supply capacity during the chlorination roasting process. Moreover, the positioning of CaCl 2 during the heat treatment was investigated by studying the gold recovery rate and chlorine removal rate at different temperatures. Meanwhile, using an electronic probe microanalysis and X-ray diffraction, the key mechanism in the process of chlorinated gold recovery was analyzed. It was found that as long as it was an alkaline chlorine source, it damaged the gangue structure. However, the trend of the slagging reaction with CaCl 2 was more intense. Under the best conditions, roasting tailings with 5 wt% CaCl 2 at 1273 K yielded an 85.99 wt% gold recovery and 82.84 wt% chlorine removal. Thus, the harmless management of roasting tailings under the premise of effective gold recovery can be achieved. This research promotes the industrialization of secondary resources via the chlorinated roasting clean treatment. Image 1 • This study proposes a cleaner chlorine for effective utilization of cyanide tailings. • Thermodynamic analyses reveal that the theoretical best chlorine source is CaCl 2. • The rate of gold recovery was 85.99% by using CaCl 2. • CaCl 2 is the most environmentally friendly in regard to pollution. • CaCl 2 is the best chlorine source for industrial production. [ABSTRACT FROM AUTHOR]

This paper describes cleaner chlorination thermal treatment for the recovery of gold from waste materials generated in gold manufacturing. Chlorination thermal treatment was conducted, and thermogravimetric-mass spectrometry (TG-MS) analyses were performed on the cyanide tailings (CTs). The results, along with thermodynamic calculations performed using FactSage, showed that Cl 2 was the main compound participating in the chlorination reaction, and almost no HCl was generated. The recovery mechanism of gold was explored by studying the influence of roasting temperature on changes in contents of Au, Cl, S and the phase composition. The results showed that the gold was not recovered simultaneously from different carriers in the slag, but was instead recovered successively according to the degree of wrapping. Under the best conditions, roasting CTs with 5 wt% CaCl 2 at 1273 K yielded close to 90 wt% gold recovery. A toxicity analysis showed that the pollution risk posed by the roasted CTs was eliminated as much as possible, as the cyanide content in the roasted slag was only 0.77 vol% of that of the raw material, which further meets the national emission standards. In a word, clean-roasted CTs can greatly reduce the pollution control costs for a factory. Chlorination heat treatment is a promising method for cleaning cyanide tailings. This figure further demonstrates that the chlorination roasting process is superior to the traditional process. Image 1 • This study proposes a cleaner method for effective utilization of cyanide tailings. • Roasting cyanide tailings with 5 wt% CaCl 2 at 1273 K yields close to 90 wt% gold recovery. • The decomposition of CaCl 2 at different temperatures was described in detail. • The pollution risk of product was reduced as compared to that of raw material. [ABSTRACT FROM AUTHOR]

• A novel microwave-assisted recycling gold process is provided in this work. • The microwave roasting behavior and trajectory of gold was deeply explored. • The combine of solid chlorinating agents and microwave roasting is a harmless and resource treatment. A new technology for treating cyanide tailings (CT) by microwave chlorination roasting was first proposed in this study. A green process with prospective environmental and economic significance was experimentally and theoretically established for the sustainable extraction of gold from CT. The microwave roasting behavior and trajectory of gold in different gold-bearing bodies under microwave-enhanced roasting and conventional roasting conditions were explored and compared by introducing the concept of thermal and non-thermal effects provided by the microwave field. At the same time, the superiority of microwave chlorination roasting was verified by a series of experiments. Under the same conditions of the roasting experiments, the energy consumption of conventional calcination was more than double greater than that of microwave roasting. Finally, the essence of microwave chlorination roasting in the treatment of CT was summarized as a non-polluting process. [ABSTRACT FROM AUTHOR]