An Experimental Study on High Temperature Corrosion of TP347H Stainless Steel in Molten Chloride and Sulfate

The corrosion resistance of TP347H stainless steel was evaluated by measuring mass loss in molten salt at 500-650°C. The corrosion mechanism was characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). The results show that the corrosion resistance of TP347H stainless steel increases with the increase of corrosion temperature. When the temperature is below 600°C, TP347H mainly generate low-stable FexOy, and the oxides such as Fe2O3, Fe3O4, Ni1.43Fe1.7O4 and NiFe2O4 are dissolved with the increase of temperature. NbO with higher stability is formed on the surface at 650 °C, which help Cr2O3 and NiO retain for a longer time. Mn-containing compounds on the surface further improve corrosion resistance of TP347H. The corrosion of TP347H stainless steel is mainly intergranular corrosion, and the temperature range of corrosion is consistent with the melting range of alkali metal chloride. Therefore, the molten alkali metal chloride plays a decisive role in the corrosion of TP347H stainless steel.

Rice husk hydrochars from metal chloride-assisted hydrothermal carbonization as biosorbents of organics from aqueous solution

Hydrochar a carbon-rich material resulting from hydrothermal carbonization of biomass, has received substantial attention because of its potential application in various areas such as carbon sequestration, bioenergy production and environmental amelioration. A series of hydrochars were prepared by metal chloride-assisted hydrothermal carbonization of rice husk and characterized by elemental analysis, zeta potential, X-ray diffraction, Brunauer–Emmett–Teller measurements, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy and scanning electron microscopy. The results reveal that the prepared hydrochars have carbon contents ranging from 45.01 to 58.71%, BET specific areas between 13.23 and 45.97 m2/g, and rich O-containing functional groups on the surfaces. The metal chlorides added in the feedwater could improve the degree of carbonization and show significant effects on the physical, chemical and adsorption properties of the hydrochars. The adsorption of the selected organics on the hydrochars is a spontaneous and physisorption-dominated process. The hydrochars possess larger adsorption capacities for 2-naphthol than for berberine hydrochloride and Congo red, and the modeling maximum adsorption capacities of 2-naphthol are in the range of 170.1–2680 mg/g. The adsorption equilibrium could be accomplished in 10, 40 and 30 min for 2-naphthol, berberine hydrochloride and Congo red, respectively. These results suggest metal chloride-assisted hydrothermal carbonization a promising method for converting biomass waste into effective adsorbents for wastewater treatment.

Effect of Cathode Microstructure on Electrochemical Properties of Sodium Nickel-Iron Chloride Batteries

Sodium metal chloride batteries have become a substantial focus area in the research on prospective alternatives for battery energy storage systems (BESSs) since they are more stable than lithium ion batteries. This study demonstrates the effects of the cathode microstructure on the electrochemical properties of sodium metal chloride cells. The cathode powder is manufactured in the form of granules composed of a metal active material and NaCl, and the ionic conductivity is attained by filling the interiors of the granules with a second electrolyte (NaAlCl4). Thus, the microstructure of the cathode powder had to be optimized to ensure that the second electrolyte effectively penetrated the cathode granules. The microstructure was modified by selecting the NaCl size and density of the cathode granules, and the resulting Na/(Ni,Fe)Cl2 cell showed a high capacity of 224 mAh g−1 at the 100th cycle owing to microstructural improvements. These findings demonstrate that control of the cathode microstructure is essential when cathode powders are used to manufacture sodium metal chloride batteries.

Selective Leaching Trace Elements from Bauxite Residue (Red Mud) without and with Adding Solid NH4Cl Using Microwave Heating

Bauxite residue (red mud), which is an industrial byproduct, contains valuable trace elements. Solid NH4Cl was used as a chlorinating agent during the microwave heating of red mud to convert trace elements into soluble metal chloride. Red mud was heated using microwave ovens under various conditions (i.e., with the addition of solid NH4Cl and with a range of microwave output powers and microwave heating times). Leaching tests were then conducted using deionized (DI) water on the microwave-heated red mud to leach trace elements from red mud. V, Cr, and As were selectively leached from the microwave heated red mud slurry (30% water content), whereas Mn, Cu, Co, Ni, Zn, and Pb were selectively leached from the microwave-heated red mud with the addition of solid NH4Cl. The oxides of V, Cr, and As in red mud could be transformed into metal chlorides by chlorination, which are insoluble in water, or could be easily volatilized when red mud was microwave-heated in the presence of solid NH4Cl. On the other hand, the oxides of Mn, Cu, Co, Zn, Ni, and Pb in red mud could be heated rapidly by microwave irradiating, resulting in metal chlorides in the presence of solid NH4Cl. Those metal chlorides are relatively soluble in water, leading to higher leaching efficiency for microwave-heated red mud with the addition of solid NH4Cl. Experimental results suggest that trace elements from red mud can be selectively leached by microwave heating of red mud without or with the addition of solid NH4Cl.