The thermodynamic model of the extraction of W with primary amine under near neutral conditions is reported in this paper. The activity coefficients of the nonelectrolytes in organic phase are calculated by the Margules and NRTL equations which are based on previously tested liquid-liquid extraction equilibrium data in combination with mass balances and charge balance formula. The activity coefficients of the electrolytes in aqueous phase are calculated by the Pitzer equation. The thermodynamic model of the extraction of W by a primary amine is constructed from the calculated activity coefficients of electrolytes and nonelectrolytes. The extraction of W using primary amine is also predicated, and the data is compared to the calculated results of the thermodynamic model. It is concluded that Margules equation proves to be suitable and reliable for calculating the activity coefficients of nonelectrolytes in complex organic phase systems.
The primary aliphatic amine Primene JM-T was investigated as a potential absorbent for H2S removal.The solubility of H2S in JM-T was measured at 298,313,333,353,and 368 K with H2S partial pressures from 20 to760 kPa and H2S loading from 0.02 to 0.8 mol H2S per mol JM-T.Relevant physical properties,such as density,viscosity and dielectric constant,of the material were measured.The thermodynamic model with two-suffix Margules equation was used to correlate the experimental vapor-liquid equilibrium data.Furthermore,the absorption mechanism in non-aqueous system is suggested and the difference between non-aqueous and aqueous absorption system is pointed out.
The development of low-cost and efficient new mineral adsorbents has been a hot topic in recent years. In this study, Friedel's salt (FS:3CaO·A12O3 ·CaCl2 ·10H2O), a hexagonal layered inorganic absorbent, was synthesized to remove Cd2+ from water. The adsorption process was simulated by Langmuir and Freundlich models. The adsorption mechanism was further analyzed with TEM, XRD, FT-IR analysis and monitoring of metal cations released and solution pH variation. The results indicated the adsorbent FS had an outstanding ability for Cd(Ⅱ) adsorption. The maximum adsorption capacity of the FS for Cd(Ⅱ) removal can reach up to 671.14 mg/g. The nearly equal numbers of Cd2+ adsorbed and Ca2+ released demonstrated that ion-exchange (both surface and inner) of the FS for Cd(Ⅱ) played an important role during the adsorption process. Furthermore, the surface of the FS after adsorption was microscopically disintegrated while the inner lamellar structure was almost unchanged. The behavior of Cd(Ⅱ) adsorption by FS was significantly affected by surface reactions. The mechanisms of Cd2+ adsorption by the FS mainly included surface complexation and surface precipitation. In the present study, the adsorption process was fitted better by the Langmuir isotherm model (R2 = 0.9999) than the Freundlich isotherm model (R2 = 0.8122). Finally, due to the high capacity for ion-exchange on the FS surface, FS is a promising layered inorganic adsorbent for the removal of Cd(Ⅱ) from water.
Juanjuan ZhangHe ZhaoHongbin CaoHeping LiZhibao Li
The optimization-based design of solvent mixtures used for phenolic wastewater treatment was investigated in this work.A nonlinear programming(NLP)model was formulated based on the concepts of computer-aid molecule design(Computer-Aided Molecular Design,CAMD)to select solvent mixtures with the best extraction performance considering the constraints of extraction process and the environmental impact.Due to the complexity of the NLP model,multi-start method was adopted to solve this problem in order to get near global optimal solution.The results of the calculations suggested that the optimal mixture consisted of 70.1%n-octanol and 29.9%2-octanone(molar fraction).The 119 sets of experimental results showed that the extraction ability of the optimal solvent mixture identified by CAMD technique was among the top 6 sets compared to the experiment results.The results suggested that the developed NLP model could be able to screen the optimal solvent mixture in phenolic wastewater treatment.
This work presented the results of tungstic precipitation from Na_2WO_4-Na_2SO_4-H_2O system at 293.15 K, with which the Pitzer parameters of β_(Na2WO4)^(0) and β(Na2WO4)^(1) were determined from Pitzer equation by regression. Thus the mean ionic activity coefficients of sodium tungstate were calculated. The obtained β_(Na2WO4)^(0) and β(Na2WO4)^(1) were substituted as fixed values in extraction modeling from Na_2WO_4-H_2SO_4-H_2O system by primary amine(N1923) in toluene as diluent. Meanwhile the activity coefficient expressions in organic phase were varied based on Pitzer theory that the interaction term for the solvent should not be included. The Pitzer parameters for organic phase were re-regressed in order to make the model more accurate. The average absolute relative deviation(AARD) for calculated and experimental molality of WO_4～(2-) in aqueous phase was 5.24%. The results showed that the model can not only correlate but also predict the liquid-liquid equilibrium(LLE) data.
