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Abstract: Selectively extracting tungsten to purify sodium molybdate solution was studied using primary amine N1923, including various conditions, such as equilibrium pH values, concentrations of extractant in organic phase and metals in feed solution, contact time of extraction and stripping, types of acidic solutions added, temperature of extraction and the dosage of stripping agent. Graphical method using McCabe-Thiele diagram and counter-current extraction simulation (CCES) were used to determine the required stages of deep removal of tungsten. The results show that appropriate concentrations of tungsten and molybdenum in feed solution have great influence on the difficult degree of the separation between the two metals. Organic phase including 0.051M of N1923 modified by LK-N21X diluted in kerosene can extract 92.7% of tungsten in sulfuric acid solution at equilibrium pH value of 7.07 for 10min in one-stage extraction at 15.5°C, and the separation factor reaches 329 under those optimum conditions. A two-stage CCES removes 99.83% of tungsten and obtains the purified sodium molybdate solution where W/Mo (mass ratio) reaches 2.9×10−5. Stripping can be accomplished by NaOH solution completely and quickly. Furthermore, the extraction and stripping reactions of tungsten and molybdenum in equilibrium were proposed. [Copyright &y& Elsevier]

A novel omniphobic nanofiber membrane for membrane distillation (MD) was successfully fabricated by one-step electrospinning of PVDF-HFP and fluorinated-decyl polyhedraloligomeric silsesquioxane (F-POSS) colloidal suspension solution. The fabricated F-POSS/PVDF-HFP membrane possessed uniform fiber structures and had extreme high F-POSS concentration on the surface. This F-POSS based membrane exhibited excellent omniphobicity, as indicated by its wetting resistance to different low surface tension liquids, including ethanol with a contact angle of 128.2°. Membrane distillation (MD) experiments showed that the water flux and water quality were stably maintained in highly saline feed solutions containing low surface tension substances, which successfully demonstrated its potential application for desalination of challenging industrial wastewater. [ABSTRACT FROM AUTHOR]

The effective V(V) and Cr(VI) separation is very difficult due to their similarity in physiochemical properties. In this research, almost completely separation of V(V) and Cr(VI) with primary amine N1923 was firstly demonstrated by employing multistage countercurrent extraction (MCE) with annular centrifugal contactors (ACCs). The optimum operation conditions of single-stage extraction with ACC were determined by systematic experiments, and best conditions of the rotor speed, the flow rate and the flow ratio of organic phase to aqueous phase were obtained. The loaded-organic phase can be reused for extraction process after stripping with ammonia/sodium hydroxide. Vanadium, in the leaching/aqueous solution with the initial pH of 6.1, was reached to extraction equilibrium by three-stage countercurrent extraction with ACCs. V(V) and Cr(VI) were separated through 21 stages of countercurrent extraction with ACCs. 95.1% of vanadium and almost none of chromium were extracted, with the separation factor approaching infinity. Through the mechanism of hydrogen bond association and different species of two metals in the leaching/aqueous solution, an in-depth analysis to correlate the results obtained and the chemical reactions with ACCs has been made in order to establish a firm conclusion with aim of the guidance in industrial application. [ABSTRACT FROM AUTHOR]

In this report the extraction of V(V) and Cr(VI) from a synthetic feed solution and real leaching solution of the chromium-bearing vanadium slag (V–Cr slag) using primary amine LK-N21 was studied. Detailed fundamental research work was conducted to investigate the primary amine extracting V(V) and Cr(VI). The mechanism and the difference between the two metals of extraction were studied and the experimental results were compared with previously published data. The optimum technological parameters for the separation of two metals were determined including: pH value in feed solution, phase ratio, mixing time, as well as others. The results showed that primary amine LK-N21 can extract V(V) selectively by hydrogen bonding association. Cr(VI) competed V(V) to combine with the primary amine, and the concentration of Cr(VI) decided the percentage extraction of V(V) and Cr(VI). Primary amine LK-N21 extracted more than 90% of V(V) which resulted in over 90% of Cr(VI) left in the leaching solution of the V–Cr slag in the optimal conditions. Based on the results of experiments, V(V) and Cr(VI) can be separated with a high degree of selectivity. [ABSTRACT FROM AUTHOR]

Highlights: [•] Higher numbers of basic sites on AC benefited the oxalate ozonation. [•] Pyridine groups on AC possibly decreased the surface oxidation of oxalate. [•] Pyrrole groups on AC may enhance HO generation in bulk solution. [•] Basic oxygen-containing groups and basal planes on AC enhanced surface oxidation. [•] Basicity of AC indirectly contribute to the weakened HO oxidation in bulk solution. [ABSTRACT FROM AUTHOR]

Thesolubility of ammonium metavanadate (NH4VO3)in ammonium salt solution is significant for the precipitationof NH4VO3from the vanadium-containing solution.The solubilities of NH4VO3in the (NH4)2SO4–H2O, NH4Cl–H2O, and (NH4)2SO4–NH3–H2O systems weremeasured using dynamic method in the temperature range from (298 to343) K. The investigated concentration is up to 3.0 mol·kg–1, 2.5 mol·kg–1, and 5.2 mol·kg–1for (NH4)2SO4, NH4Cl, and NH3, respectively. The solubility of NH4VO3decreases sharply with the addition of (NH4)2SO4or NH4Cl while thesolubility of NH4VO3in the mixed NH3and (NH4)2SO4(0.10 mol·kg–1) solution increases first and then levels off withincreasing NH3concentration. The solubility product constant(KSP) of NH4VO3wasalso determined using the standard-state thermodynamic data. The Bromley–Zemaitismodel was applied to model the solubility of NH4VO3in the systems mentioned above, and five pairs of new modelparameters were obtained via the regression of the experimental solubilities.A chemical model was established to successfully calculate the solubilityof NH4VO3in all systems. All of the work donein this research will provide a thermodynamic basis for industrialdevelopment in the precipitation of NH4VO3. [ABSTRACT FROM AUTHOR]

The solubility of gypsum (CaSO4·2H2O) in ammonium solutions plays a significant role to preventgypsum scaling on the heater and tower in the treatment of ammonium-Nwastewater bearing sulfate ions by the steam stripping process. Inthis work solubilities of calcium sulfate dihydrate in NH4Cl, NH4NO3, and mixed NH4Cl and(NH4)2SO4solutions up to 343.15K were measured using the classic isothermal dissolution method. Theinvestigated concentration (at ambient temperature) is up to 1.50mol·dm–3for both NH4Cl and NH4NO3. The solubility of CaSO4·2H2O was found to increase sharply with either NH4Cl or NH4NO3concentration, whereas the temperaturehas a limited effect. The XRD analysis of equilibrated solids forthese systems shows that CaSO4·2H2O isstable in all cases over the temperature range (298.15 to 343.15)K. The electrolyte nonrandom two-liquid (the electrolyte NRTL) modelembedded in AspenPlus was applied to model the solubility of CaSO4·2H2O in the above systems. The newly obtainedmodel parameters were used to well estimate the solubility of CaSO4·2H2O in all cases with a relative deviationof 1.52 %. [ABSTRACT FROM AUTHOR]

Abstract: After leaching of the waste printed circuit boards with HNO3, the leach liquor bearing 5.13kg/m3 Cu, 0.63kg/m3 Fe (III), 0.36kg/m3 Zn, 1.31kg/m3 Ni and 34.59kg/m3 nitrate was obtained. Development of a solvent extraction flow chart for the separation and recovery of Cu, Ni and Fe (III) using LK-C2 as the extractant from nitrate solution was investigated. Extraction of the metals depends on the equilibrium pH in the aqueous phase and the increases with rise in equilibrium pH. Based on the difference in their extraction behavior as a function of equilibrium pH in the aqueous phase, it was possible to separate and recover copper, nickel and iron. Copper is extracted using 15% LK-C2 in kerosene at two stages at initial pH of 2.60 and the extraction percentage is 99.98%. Copper is stripped by 2.00mol/L H2SO4 at three stages and the stripping percentage is 97.51%. Fe and Ni are extracted using 20% LK-C2 in kerosene at two stages at initial pH of 3.00 and 10.00, and the extraction percentages are 96.14 and 99.35%, respectively. Fe is stripped by 2.00mol/L HCl at two stages and the stripping rate is 99.18%. Ni is stripped by 3.00mol/L H2SO4 at three stages and the stripping percentage is 98.32%. [Copyright &y& Elsevier]

Abstract: Three-liquid-phase systems containing polyethylene glycol with different molecular weight were explored to investigate the partitioning behavior of simulated wastewater-containing isomers of p-Nitrophenol (p-NP) and o-Nitrophenol (o-NP). The distribution behaviors of p-NP and o-NP with different parameters in three-liquid-phase system were investigated. The results showed a great effect of the solution pH, extractant type on the partition coefficient of the two isomers. In the three-liquid-phase systems, the satisfying separation results were obtained with hexane as extractant. At pH=4.00, about 85% o-NP and 90% p-NP partitioned into the top organic phase and middle polymer-rich phase, respectively. The separation factor decreased sharply with the increase of the solution pH from 6.5 to 8.5. After once back extraction with 10wt.% sodium hydroxide, high recovery percentage of o-NP was obtained from the top phase. The removal efficiency of phenolic compounds in the polymer-rich phase could reach 95% when the middle phase was extracted with butyl acetate (BA) twice. p-NP could be recovered when the BA phase was back extracted with 10wt.% sodium hydroxide aqueous solution. [Copyright &y& Elsevier]