Sodium hydrogen sulfide (NaHS) is commonly used as a copper depressant in the selective flotation of copper and molybdenum ores. However, the process is facing health and safety issues because NaHS readily yields toxic hydrogen sulfide gas (H 2 S) under acidic conditions. In this study, Na 2 SO 3 was proposed as an alternative copper depressant. The effect of Na 2 SO 3 on the surface wettability and floatability of chalcopyrite and molybdenite-typical copper and molybdenum minerals, respectively-was intensively studied using contact angle measurements and flotation tests. Contact angle readings show that the chalcopyrite surface became hydrophilic after the Na 2 SO 3 treatment. Meanwhile, the molybdenite surface was relatively more hydrophobic compared with that of chalcopyrite after the treatment. Flotation tests using pure minerals of chalcopyrite and molybdenite demonstrate that the floatability of chalcopyrite decreased with increasing concentration of Na 2 SO 3. On the other hand, the floatability of molybdenite gradually increased under similar conditions, suggesting that Na 2 SO 3 might have the potential to be used for selective flotation of chalcopyrite and molybdenite. A possible mechanism is proposed in this study to explain the phenomenon using X-ray photoelectron spectroscopy analysis.

An excellent corrosion protection for copper nanoparticles by nitrogen-doped few-layer graphene via solution plasma process.

Carbon materials are widely utilized to support platinum (Pt) catalysts for proton exchange membrane fuel cells (PEMFCs). However, carbon surfaces generally promote hydrophobicity, which limits the transport of active species and lowers the efficiency of PEMFCs. Consequently, functional groups should be introduced on the carbon surface to create transport channels. One promising strategy is to modify the amphiphilic functional group on a carbon surface. In this study, the liquid-phase plasma process was applied to realizing a facile one-step synthesis of amphiphilic functional group-modified carbon-supported platinum (Am@C/Pt) to serve as a catalyst. This novel synthesis strategy provides several advantages over conventional processes, such as reducing the number of steps and minimizing the chemical and energy consumptions. Experimental results revealed that the PEMFCs' efficiency with Am@ C/Pt is mainly controlled by the number of hydrophilic and hydrophobic characters on the carbon surface. A single PEMFC demonstrated a maximum current and power density of 2.41 A cm −2 and 1.68 W cm −2 , respectively, at 0.7 V, which was significantly higher than those of commercially available carbon-supported Pt catalysts. Furthermore, Am@C/Pt demonstrated superior durability after 5000 test cycles.