Equilibrium Studies on Enantioselective Liquid−Liquid Amino Acid Extraction Using a Cinchona Alkaloid Extractant

The enantioselective extraction of aqueous 3,5-dinitrobenzoyl-R,S-leucine (AR,S) by a cinchona alkaloid extractant (C) in 1,2-dichloroethane was studied at room temperature (294 K) in a batch system for a range of intake concentrations (10−4−10−3 mol/L) and pH values (3.8−6.6). The experimental data were described by a reactive extraction model with a homogeneous organic phase reaction of AR,S with C. Important parameters of this model were determined experimentally. The acid dissociation constant, Ka, of AR,S was (1.92 ± 0.07) × 10−4 mol/L. The physical distribution coefficient of AR,S between the organic and aqueous phase was 8.04 ± 0.39. The equilibrium constants of the organic phase complexation reaction were (9.31 ± 0.76) × 104 L/mol and (2.71 ± 0.76) × 104 L/mol for the S- and R-enantiomers, respectively. With these parameters an optimum performance factor, PF, of 0.19 was predicted. The PF was independent of the pH provided that pH pKa. The model was verified experimentally with excellent results (±7.9%).

Experimental and modelling studies on the simultaneous absorption of NO and O2 in aqueous iron chelate solutions

The simultaneous absorption of NO and O2 in aqueous FeII(EDTA)2− solutions was studied experimentally in a stirred cell contactor at temperatures of 298–323 K; aqueous FeII(EDTA)2− concentrations of 10–50 mol/m3; and gaseous NO and O2 concentrations of 100–500 vppm and 5–10 vol%, respectively. The process is an interesting example of the simultaneous absorption of two gases followed by dependent parallel reactions with a third reactant. Explicit expressions for the enhancement factors for this system have not been reported to date. A volume-element model based on the film theory for reactive gas absorption was developed and novel, explicit analytical relations for the enhancement factors for both gases will be provided. The experimental results were modelled successfully using these relations. To promote NO and to suppress oxygen absorption, it is advantageous to perform the absorption process at low temperatures and low oxygen concentrations.

A rate based reactor model for BiodeNOx absorber units

The reactive absorption of NO in aqueous solutions of FeII(EDTA), resulting in the formation of a nitrosyl complex, FeII(EDTA)(NO), is a key step of the BiodeNOx process for the removal of NOx from industrial flue gas. Oxygen present in the flue gas will also absorb and oxidize FeII(EDTA). This is an undesired reaction, because the resulting FeIII(EDTA) does not react with NO. To explore the industrial applicability of the process, a rate based model for the simultaneous reactive absorption of NO and O2 in aqueous FeII(EDTA) solutions in a counter current packed column has been developed. The effect of process conditions on absorber performance (NO removal efficiency, selectivity, FeII(EDTA) conversion) have been assessed. Using standard conditions, the column height needed to remove 90% of an initial 250 ppm of NO was less than 1 m. The amount of oxidized iron was approximately equal to the amount of the nitrosyl complex, even though oxygen was present in a 200-fold excess over NO. The absorber performance was particularly dependent on the operating temperature, where lower temperatures favoured both the NO removal efficiency and selectivity. Remarkably, the model indicated that overdesign of the absorber can result in decreasing absorber performance.

Determination of the interfacial area of a continuous integrated mixer/separator (CINC) using a chemical reaction method

The effect of the liquid flow rates (18–100 mL/min) and rotor frequency (30–60 Hz) on the interfacial area of a liquid–liquid system in a CINC-V02 continuous integrated mixer/separator have been studied using a chemical reaction method. Typical specific interfacial areas were in the range of 3.2×10^2 to 1.3×10^4 m2 m−3 liquid volume, which is comparable with those for a continuously stirred tank reactor (CSTR). A pronounced maximum in the interfacial area with respect to the rotor frequency was found at about 45 Hz. The interfacial area increased considerably at higher aqueous phase flow rates whereas the organic phase flow rate had no significant effect. The experimental data were modelled using an empirical model. Good agreement between experiments and model was observed.