The promising performance of manganese gluconate as a liquid redox sulfur recovery agent against oxidative degradation.

This work studied the oxidative degradation performance of manganese gluconate as a liquid redox sulfur recovery (LRSR) agent. The degradation of gluconate in an aerated sulfide containing 0.1 M manganese/0.8 M gluconate/pH 13 solution was 11% in 47 h and 20% in 100 h of reaction time. With the total price of chelates being more or less comparable, these were superior to the degradation resistance of EDTA chelate in a solution of 0.1 M iron/0.2 M EDTA/pH 8 which degraded by about 30% in 47 h, and NTA in Fe-NTA (0.1 M metal/0.2 M chelate/pH 6.5), which was degraded by 40% in 100 h of reaction time. At pH of 13, 0.1 M Metal, and 0.8 M gluconate, manganese degraded gluconate more severely than iron and copper. At a lower chelate to metal molar ratio (RCM) of 2 and as well as at a lower pH of 10, the manganese gluconate degradation, expressed as relative concentration to its initial concentration, was faster than at RCM of 8 and pH of 13. All of these observations can be explained among others by the well-known Fenton reaction hydroxyl radicals mechanism as the main cause of the degradation process.

Manganese gluconate, A greener and more degradation resistant agent for H2S oxidation using liquid redox sulfur recovery process.

Iron chelate liquid redox sulfur recovery (LRSR) has been one of the most frequently recommended technologies for the oxidation of H2S in natural gas into elemental sulfur, particularly when the acid gas has a high CO2/H2S molar ratio. The process is however known to suffer from extensive oxidative ligand degradation that results in high operational costs. Moreover, poor biodegradability or toxicity of the existing ligand has become a concern. In this research, we demonstrated that gluconate, a naturally greener ligand, when coupled with manganese as the metal, has considerable potential to be a better redox agent. Manganese gluconate solution was more resistant against ligand degradation compared with iron NTA. As required, aerated solution was capable of converting dissolved NaHS into elemental sulfur. At sufficiently high pH, manganese gluconate solutions were stable enough from precipitation of manganese hydroxide, carbonate, or sulfides. An equilibrium calculation has been developed to understand the precipitation behavior.

Cationic Defect Engineering for Controlling the Infrared Absorption of Hexagonal Cesium Tungsten Bronze Nanoparticles.

Cesium tungsten bronzes (Cs0.32WO3) have attracted much attention as a near-infrared absorbing material. We report the successful synthesis of highly crystalline and high purity Cs0.32WO3 nanoparticles through a spray pyrolysis route. Careful analyses disclosed the presence of cationic defects, that is, a tungsten deficiency and insufficient Cs doping in the Cs0.32WO3 nanoparticles. These cationic defects can be controlled by facile heat treatment in a mildly reducing atmosphere. In particular, we clarify that the tungsten deficiency is a key factor among the cationic defects to obtain high near-infrared absorption properties. Furthermore, this study clearly demonstrates the precise tunability of the optical properties by means of the lattice constants of the Cs0.32WO3 crystal. The realized range of lattice constants is significantly wider than those previously reported. These findings should contribute to the engineering of Cs0.32WO3 structure and properties.

Electrochemical properties of TiO x /rGO composite as an electrode for supercapacitors.

Transition metal oxides are known as the active materials for capacitors. As a class of transition metal oxide, Magnéli phase TiO x is particularly attractive because of its excellent conductivity. This work investigated the electrochemical characteristics of TiO x and its composite with reduced graphene oxide (rGO). Two types of TiO x , i.e. low and high reduction extent, were employed in this research. Electrochemical impedance spectroscopy revealed that TiO x with lower reduction extent delivered higher electro-activity and charge transfer resistance at the same time. However, combining 10% of low-reduction state TiO x and rGO using a simple mixing process delivered a high specific capacitance (98.8 F g-1), which was higher than that of standalone rGO (49.5 F g-1). A further improvement in the specific capacitance (102.6 F g-1) was given by adding PEDOT:PSS conductive polymer. Results of this research gave a basic understanding in the electrochemical behavior of Magnéli phase TiO x for the utilization of this material as supercapacitor in the future.

Correlations between Reduction Degree and Catalytic Properties of WO x Nanoparticles.

Degrading organic dyes via catalytic processes for waste water purification is an important research topic from the environmental conservation point of view. Herein, the catalytic performance of tungsten blue oxide (WO x ) nanoparticles was investigated systematically by varying the reduction temperature. The optimum reduction temperature to obtain the most stable WO x phase was obtained when plasma-synthesized WO3 nanoparticles were thermally reduced at 425 °C. The as-synthesized nanoparticles had an average diameter of 10 nm and a calculated band gap of 2.37 eV, which is lower than that of the WO3 nanoparticles (2.61 eV). The WO x nanoparticles exhibited an excellent performance in degrading rhodamine B under dark conditions and visible light irradiation, with a reaction rate constant 93 times higher than that of the WO3 nanoparticles.