A new solvent sublation (SS) system for chiral separation is introduced by using phenylsuccinic acid (H2A) as the model enantiomers. The experiments were carried out in a traditional SS apparatus but with collaborative chiral selectors: dibenzoyl-L-tartaric acid (L-DBTA) in the organic phase and hydroxypropyl-β-cyclodextrin (HP-β-CD) in the aqueous phase. The chiral recognition abilities of the two selectors are opposite for the H2A enantiomers. Several important parameters were investigated. The results demonstrate that enantioselective sublation and partitioning behavior are mainly dependent on the pH of the solution, the concentrations of chiral selectors and H2A. Furthermore, the flow rate of air and flotation time also have some effects on the enantioseparation. Under the optimized conditions, the enantioselectivity expressed by the separation factor (β) and enantiomer excess (e.e.%) are 2.47 and 29.50%, and the yields of R-H2A and S-H2A are 0.23 and 0.13 g·L−1, respectively. Compared with the SS system with the single selector HP-β-CD in the aqueous phase (or L-DBTA in the organic phase), the increased values of β and e.e.% in the new SS system with collaborative selectors are 1.31 (or 1.38) and 5.90% (or 13.82%), respectively.

•Phase compositions of iron were varied with microwave roasting conditions.•5% alkali lignin was favorable for improving the magnetic properties of roasted ore.•Better magnetic properties of roasted ore were achieved at 200 °C, 600 W for 30 min.•Magnetic properties of roasted ores were associated with phase compositions of iron.•The iron concentrate with Fe recovery of 82.92% was obtained by magnetic separation.Phase transformation and magnetic properties of limonite ore with 40.10% Fe via microwave roasting with addition of alkali lignin were investigated by chemical phase analysis and vibrating sample magnetometer (VSM) analysis, respectively. The results of chemical phase analysis indicated that phase compositions and contents of iron in microwave roasted limonite ore were varied with the dosage of alkali lignin, the roasting temperature, the roasting time and the microwave power, and among them the dosage of alkali lignin exerted more significant influence. Iron oxides in limonite ore could be reduced to magnetic iron oxides including γ-Fe2O3 and Fe3O4 in the following sequence during microwave roasting process by evenly distribution of alkali lignin below 5%: FeOOH/α-Fe2O3→γ-Fe2O3→Fe3O4, accompanied with small amount of FeO, and as the dosage was over 5%, γ-Fe2O3 and Fe3O4 could be in turn successively transformed into α-Fe2O3. Magnetic property studies demonstrated that an iron concentrate containing 88.72% magnetic iron oxides with a maximum saturation magnetization of 41.393 emu/g could be produced from roasted ore which was obtained by microwave roasting at 200 °C and 600 W with 5% alkali lignin for 30 min. In addition, the roasted ore was further used for magnetic separation, and the results showed that combining microwave roasting with addition of 5% alkali lignin could improve the iron recovery from the roasted ore distinctively. It was concluded that the microwave roasting process in the presence of alkali lignin could be a promising approach to effective utilization of limonite ore resources.Download high-res image (818KB)Download full-size image

The influences of tetraborate anions on manganese electrodeposition in an anion-exchange membrane electrolysis reactor were investigated. The experimental results of manganese electrodeposition indicate that a certain amount of tetraborate anions can increase cathode current efficiency and initial pH 7.0–8.0 is suitable for high cathode current efficiency. X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis show the nanocrystalline structure and impact morphology of electrodeposited manganese. The purity of electrodeposited manganese is above 99.88 %. The tests of tetraborate anions on buffer capacity (β) and pH value of the electrolyte near the cathode surface confirm that tetraborate anions facilitate manganese electrodeposition. Tetraborate anions can improve concentration polarization of Mn2+ ions and then increase the overpotential of hydrogen evolution reaction. Therefore, ammonium tetraborate can reduce the hydrogen embrittlement, pore, and pitting negative effect on electrodeposit surface, to improve the corrosion resistance of electrodeposited manganese. After tetraborate anions being added in electrolyte, weight loss measurement indicates that the corrosion resistance of electrodeposited manganese is improved. Electrochemical measurements testify that corrosion resistance of electrodeposited manganese containing tetraborate anions in electrolyte is reflected by less negative corrosion potential and higher impedance.

•Cu2O/ZnAl-CLDH composite has been prepared by a facile method.•The Cu2O/ZnAl-CLDH photocatalysts improve the utilization of visible light.•The Cu2O/ZnAl-CLDH catalysts exhibit better photocatalytic activity and stability for the photodegradation of Methyl Orange (MO).The Cu2O/ZnAl calcined layered double hydroxides (Cu2O/ZnAl-CLDH) composites had been successfully synthesized by a facile method. The prepared photocatalysts were characterized by X-ray diffraction, Scanning electron microscopy, X-ray photoelectron spectroscopy and UV–vis diffuse reflectance spectra to show the structure of the as-synthesized materials. The results revealed that the Cu2O nanoparticles were evenly distributed on the surface or the internal frame of ZnAl-CLDH to form the heterostructure of ZnO-Cu2O. The photocatalytic performance of Cu2O/ZnAl-CLDH was evaluated by the photodegradation of Methyl Orange (MO) under visible light irradiation. The effects of the Cu/CLDH molar ratio, calcination temperature and MO concentration were investigated. The photocatalyst shows a high photocatalytic activity (90.18%) at the optimum of Cu/CLDH molar ratio of 1:1, calcination temperature of 500 °C and initial MO concentration of 20 mg/L. In addition, after three cycles the removal efficiency of MO is still higher than 80% for reused Cu2O/ZnAl-CLDH, demonstrating its great potential application in the field of photocatalysis. From the experimental results, a possible photocatalytic mechanism of the Cu2O/ZnAl-CLDH composite was proposed.

The influences of oxalate anions on manganese electrodeposition in sulfate solution were investigated on the basis of cathode current efficiency, characterization of SEM-EDX and XRD, solution chemistry calculation, thermodynamics and electrochemical test. The experimental results show that the range of (NH4)2C2O4 was adjusted from 0 mol/L to 4.8 × 10−3 mol/L. And 1.5 × 10−3 mol/L (NH4) 2C2O4 was suitably used with initial pH 7.0. The characterization of SEM indicates that oxalate anions can improve the morphology of electrodeposited films. The electrodeposited films containing manganese were characterized and determined by EDX and XRD. The solution chemistry calculation of catholyte and oxalate anions shows that the main active species are MnSO4, Mn(SO4)2− 2, Mn2+, Mn(SO4)C2O2− 4, MnC2O 4, Mn(NH3)2+, and C2O2− 4. The reaction trend between C2O2− 4 and Mn2+ ions is confirmed by computation of reaction energy. Electrochemical test analysis indicates oxalate anions increase the overpotentials of hydrogen evolution reaction and manganese electrodeposition.

The leaching kinetics of reductive leaching of manganese from manganese dioxide ores (MDO) in dilute sulfuric acid in the presence of Phytolacca americana powder (PAP) was investigated. The effects of stirring speed, leaching temperature and leaching time, particle size, weight ratio of PAP to MDO (CW) and sulfuric acid concentration (CH) on the leaching efficiency of manganese were studied. The leaching efficiency of manganese based on the shrinking core model was found to be controlled by diffusion through the ash/inert layer composed of the associated minerals. The apparent activation energy is 15.18 kJ mol−1. The experimental results indicate reaction order of 0.797 for CH and 1.25 for CW. The overall leaching efficiency equations for MDO dissolution reaction with PAP in dilute sulfuric acid were proposed by a semi-empirical model.

•Low-cost ZnSi composites were prepared from zinc ash waste.•The SZC-1 showed steady adsorption capacities in the recycle process.•The amorphous morphology suggested a positive impact on adsorption capacity.•The adsorption mechanism was ascribed to the nature sulphophile.•The adsorption parameters responded best to Langmuir and pseudo-second order models.Zinc ash, a waste in hot dip galvanizing, was firstly used for the successful synthesis of SiZn composites (SZC) and for the removal of methylene blue (MB) from effluent. Materials were characterized by XRD, FE-SEM, FT-IR and XPS. The adsorption properties and optimum parameters were determined by operating different conditions (contact time, concentration of the dye, pH and temperature). Interestingly, the morphology was found to have significant impact on adsorption results. The adsorption quantities of SZC-1, SZC-2 and SZC-3 were 60.06 mg g−1, 20.13 mg g−1 and 11.76 mg g−1, respectively. The equilibrium data were analyzed by different isothermal models (Langmuir and Freundlich) and the mechanistic studies demonstrated that the pseudo-second-order kinetic model was fitted well to the adsorption. The increased values of enthalpy indicated an endothermic process. The result of XPS was discussed and the binding energy of Zn and S showed negative shifts, which suggested a chemisorption process due to the generation of the coordinate bond. The regeneration assessment was carried out by conducting a calcination method at 773 K and the material indicated a steady mass ratio (89%) and adsorption capacity (55.76 mg g−1) after four-time reuse.Download high-res image (131KB)Download full-size image Zinc ash, a waste in hot dip galvanizing, was firstly used for the successful synthesis of SiZn composites (SZC) and for the removal of methylene blue (MB) from effluent. Materials were characterized by XRD, FE-SEM, FT-IR and XPS. The adsorption properties and optimum parameters were determined by operating different conditions (contact time, concentration of the dye, pH and temperature). Interestingly, the morphology was found to have significant impact on adsorption results. The adsorption quantities of SZC-1, SZC-2 and SZC-3 were 60.06 mg g−1, 20.13 mg g−1 and 11.76 mg g−1, respectively. The equilibrium data were analyzed by different isothermal models (Langmuir and Freundlich) and the mechanistic studies demonstrated that the pseudo-second-order kinetic model was fitted well to the adsorption. The increased values of enthalpy indicated an endothermic process. The result of XPS was discussed and the binding energy of Zn and S showed negative shifts, which suggested a chemisorption process due to the generation of the coordinate bond. The regeneration assessment was carried out by conducting a calcination method at 773 K and the material indicated a steady mass ratio (89%) and adsorption capacity (55.76 mg g−1) after four-time reuse.