The effect of particle breakage mechanisms during regrinding on the subsequent cleaner flotation

Stirred mills have been widely used for regrinding, and are acknowledged to be more energy efficient than tumbling mills. These two types of mills present different particle breakage mechanisms during grinding. In this study, the effect of regrinding by both mills on surface properties and subsequent mineral flotation was studied, using chalcocite as the mineral example. A rod mill and a stirred mill with the same stainless steel media were used to regrind rougher flotation concentrates. Different chalcocite flotation recovery was achieved in the cleaner stage after regrinding in tumbling and stirred mills. The factors contributing to the different recovery included particle size, the amount of created fresh surfaces, surface oxidation and the redistribution of collector carried from rougher flotation. All the factors were examined. It was determined that the predominating factor was the different distribution of collector resulting from different particle breakage mechanisms in the stirred and tumbling mills, in line with ToF-SIMS analysis. In the tumbling mill, the impact particle breakage mechanism predominates, causing the collector to remain on the surface of newly produced particles. In the stirred mill, the attrition breakage removes collector from the surface, and decreases particle floatability. Furthermore, the type of grinding media in the stirred mill also influences the subsequent flotation, again due to the change of particle breakage mechanisms. The results of this study demonstrate that the selection of regrinding mills and grinding media should not only depend on the required energy efficiency, but also on the properties of the surfaces produced for subsequent flotation.     

Control of redox potential by oxygen limitation in selective bioleaching of chalcocite and pyrite

Based on the bioleaching mechanism and electrochemical studies of metal sulfides, the dissolution rates of chalcocite and pyrite are controlled by redox potentials. Experiment on the bioleaching of chalcocite and pyrite under constant redox potential by sparging with nitrogen gas was demonstrated. By leaching at low and constant redox potential（〈760 mV, vs SHE）, copper recoveries of 90 %–98 % are achieved, which are 10 times more than iron recoveries. The iron-oxidizing bacterial populations are observed to continue to reduce under oxygen limitation conditions, but the Acidithiobacillus that have only sulfur-oxidizing capabilities are an attractive alternative for redox-controlled bioleaching of chalcocite.Thus, the described redox control technique might be one of the effective approaches to balance acid and iron in Zijinshan copper bio-heap leaching practice.     

云南大姚铜矿银的赋存状态与成矿地质特征

矿床产于白垩系上统长石石英砂岩中,为典型的砂岩型铜矿。对矿床的矿石物质成分,银、铜、金的赋存状态及分布规律和矿床成矿特征研究结果:该矿床的银矿物有辉银矿、自然银、硫铜银矿、硫砷铜银矿、硫铁铜银矿、角银矿、银辉铜矿和银砷黝铜矿8种,其中后5种为本次工作发现;与铜矿带相对应,矿体有银矿物相带,并发现两个不同成因的“高银带”——原生高银带与次生高银带;原生矿体中银的峰值位于铜峰值的东侧,两者相距80～120m,规律性显著;矿床成因类型为多次叠加的沉积热卤水改造矿床;指出了大雪山背斜东翼南部倾伏部位为矿区外围找矿远景区,并在已知铜矿床内提出了两个高银预测区。     

Chalcocite (bio)hydrometallurgy-current state,mechanism,and future directions:A review

There has been a strong interest in technologies suited for mining and processing of low-grade ores because of the rapid depletion of mineral resources in the world.In most cases,the extraction of copper from such raw materials is achieved by applying the leaching procedures.However,its low extraction efficiency and the long extraction period limit its large-scale commercial applications in copper recovery,even though bioleaching has been widely employed commercially for heap and dump bioleaching of sec-ondary copper sulfide ores.Overcoming the technical challenges requires a better understanding of leaching kinetics and on-site microbial activities.Herein,this paper reviews the current status of main commercial biomining operations around the world,identifies factors that affect chalcocite dissolution both in chemical leaching and bioleaching,summarizes the related kinetic research,and concludes with a discussion of two on-site chalcocite heap leaching practices.Further,the challenges and innovations for the future development of chalcocite hydrometallurgy are presented in the end.     

Surface free energy of synthetic chalcocite from zeta potential and contact angle techniques

—The zeta potentials of synthetic chalcocite wetted with n-alkanes were determined in doubly-distilled water. Then the relationship between the coverage of the chalcocite surface with n-heptane or n-hexanol and the zeta potential in water was found. Using an empirical relation, the film pressure of n-heptane and n-hexane was determined. Next the dispersive and polar components of the surface free energy were calculated. The value of the dispersive component was also determined by contact angle measurements. The values obtained were 81.0 and 22.7 mJ/m², for the dispersive and the polar components of the surface free energy, respectively.     

辉铜矿氧化溶解行为的研究

辉铜矿是较易被氧化的硫化矿物之－，其氧化溶解行为受到多种因素的影响。本文重点研究了Ｆｅ￣（３＋）、Ｃｕ￣（２＋）、ｐｈ值、温度和其它硫化矿物的存在对辉铜矿氧化溶解行为的影响及其作用规律，采用多种现代分析测试手段分析了氧化前后辉铜矿的表面特性。     

氯化铁预浸铜金精矿选择性提铜

本工作试验了用氯化铁浸出法预提取回收铜全精矿中的铜，使之适于氰化提取其中的金研究了各种主要浸出参数并加以优化试验证明该浸出法可有效而选择性地提取精矿中的铜，在优化的条件下铜的提取几近完全、而不包裹金的黄铁矿未受触动     

低品位次生硫化铜矿的细菌浸出研究

在硫酸体系中 ,对含有辉铜矿、蓝辉铜矿和铜蓝的低品位次生硫化铜矿的Fe3+ 浸出和细菌浸出进行了研究 ,通过对浸出过程的动力学进行分析 ,揭示了次生硫化铜矿的浸出过程和细菌浸出的作用机理 ,得出了细菌浸铜主要以间接机理进行的结论 ,提出了加快铜浸出速率的 2条途径。     

Mechanism study on flotation separation of molybdenite from chalcocite using thioglycollic acid as depressant

Effects of collectors(butyl xanthate(BX), O-isopropyl-N-sulfur ethyl carbamate(Z-200) and emulsified kerosene), dereagent(sodium sulfide) and depressant thioglycollic acid(TGA) on the flotation of chalcocite and molybdenite were investigated through flotation. The first principle theory was adopted to understand the difference of their surfaces and reaction between minerals and reagents. Results of flotation tests revealed that selectivity of emulsified kerosene is the best of three collectors in separation of chalcocite and molybdenite, though the others also display excellent collecting properties. Sodium sulfide can effectively remove collectors adsorbed on chalcocite surface, and TGA is an effective depressant of chalcocite at pH 8-9. Through first principle study, molybdenite displays relatively stronger covalence property while bonding interaction between copper atoms in chalcocite enhanced its ionicity. Bonding interaction is weaker in reaction of TGA and molybdenite, so it shows higher hydrophobicity and better flotability. Therefore, TGA is an effective inhibitor in the separation.     

The effect of surface oxidation of copper sulfide minerals on clay slime coating in flotation

The industry is well aware of the difficulty in treating copper ores in the presence of clay minerals. In this study, the effect of bentonite on the flotation of chalcopyrite (a primary copper sulfide mineral) and chalcocite (a secondary copper sulfide mineral) was investigated in terms of surface coating. Based on the flotation of copper ores containing both chalcopyrite and chalcocite, the flotation of chalcopyrite and chalcocite single minerals in the presence and absence of bentonite, and the zeta potential measurement of chalcopyrite, chalcocite and bentonite, it was found that the oxidation of chalcopyrite and chalcocite had a different effect on their interaction with bentonite. Under the normal grinding and flotation condition, significant oxidation occurred on the surface of chalcocite which was electrostatically attractive to bentonite resulting in bentonite slime coating and the depressed flotation of chalcocite. The reduction of oxidation on chalcocite could mitigate bentonite slime coating due to electrostatic repulsion between unoxidized chalcocite and bentonite. Unlike chalcocite, chalcopyrite with and without surface oxidation exhibited an electrostatic repulsion to bentonite. Its flotation was less affected by bentonite slimes.