Ján Marták

Phosphonium ionic liquids as new, reactive extractants of lactic acid

Solvent properties of ionic liquids with trihexyltetradecylphosphonium cation and bis(2,4,4-trimethylpentyl)phosphinate anion (Cyphos IL-104) or chloride anion (Cyphos IL-101) were studied. IL-104 effectively extracted lactic acid (LA) with distribution coefficients above 40 at low acid concentrations. IL-104 extracted only undissociated acid (LAH) what supported the coordination mechanism of lactic acid extraction via H-bonding. In the extraction of lactic acid by phosphonium chloride (IL-101) an ion-exchange mechanism contributed remarkably to the extraction especially at basic pH where anionic form of this acid predominated. A high solubility of water in hydrophobic IL-104 up to 14.4 mass % was connected with the formation of reverse micelles. A dual mechanism of water extraction to phosphonium ionic liquids was identified, which consisted of water incorporation into reverse micelles and the inclusion of water into the hydrated complex of lactic acid with ionic liquid (IL). The extraction of lactic acid caused splitting of reverse micelles with liberation of water from the solvent. In the saturated solvent only hydration water remained in the complex of lactic acid with phosphonium ionic liquid, with the suggested structure (LAH)p(IL)(H2O)2, where the value of p ranged from 1 to 3.

Liquid-liquid equilibria of butyric acid for solvents containing a phosphonium ionic liquid

L/L equilibrium data of butyric acid (BA) in aqueous solutions contacted with the solvents containing ionic liquid (IL), trihexyl-(tetradecyl)phosphonium bis 2,4,4-trimethylpentylphosphinate (Cyphos IL-104), and a related model are presented. IL-104 and its solutions in dodecane were found to be effective solvents of BA. The values of the distribution coefficients of BA were higher than those for solvents with the widely used extractant trioctylamine, especially at low acid concentrations and were also several-fold higher than those of lactic acid (LA). IL extracted BA only in its undissociated form (BAH) at pH well below pKa of the acid. The loading of IL was independent of IL concentration and it achieved a value higher than four at saturation. Complexes with 1–5 molecules of BA per one IL molecule were supposed in the mass action model in which the reactive formation of complexes (BAH)p(IL)(H2O)2 was supposed. Up to 10 % of the total extracted BA was extracted physically by dodecane as a monomer and dimer, in the solvent. The water content in the organic phase steeply decreased with the BA concentration, which was caused by splitting water-IL reverse micelles due to the formation of the BAH/IL complexes.

Fermentation of lactic acid with Rhizopus arrhizus in a stirred tank reactor with a periodical bleed and feed operation

Semicontinuous fungal fermentation of lactic acid (LA) by Rhizopus arrhizus was performed using a periodical bleed and feed (PBF) operation in a stirred tank bioreactor with a volume of 4.5 dm3. LA productivity up to 2.91 kg m−3 h−1 and yield up to 75.3% were achieved. Using PBF cycles, fermentation was prolonged to 240 h with an average LA productivity of 2.31 kg m−3 h−1 and a total yield of 67.3% at a mean pH of 5.30. The most effective production of LA required filamentous morphology of the biomass. When such morphology changed to pellets biomass growth stopped, the LA productivity decreased to 1.63 kg m−3 h−1 and the yield decreased to 62.6%. The filamentous morphology was successfully maintained for 152 h when the inoculation was with spores. CaCO3 initially used for pH neutralisation did not dissolve well since it was entrapped by biomass. It was successfully replaced by 25% ammonia. Long-time operation below pH 5 decreased LA productivity. Accumulating biomass in the fermenter did not increase the LA productivity. With an increase in the biomass growth rate, the LA productivity increased. The on-line extraction or pertraction of LA by trialkylamines demands a pH value of feed below 4. This can be achieved for a short time by interruption neutralisation at the end of each PBF cycle without a decrease in LA productivity after the restoration of the optimal pH value.

Toxicity of organic solvents used in situ in fermentation of lactic acid by Rhizopus arrhizus

Of 17 organic phases, some containing one of the five extractants for solvent extraction of lactic acid from Rhizopus arrhizus broth, solvents containing tertiary amines (Hostarex A327, trioctylamine) and secondary amine with isotridecanol modifier and trihexylphosphate, are from point of view of toxicity suitable for the in situ or on-line extraction. Pentaphosphinedipentylester is highly toxic. Toxicity of alcohols used as modifiers, decreases with an increase in the number of carbons in a molecule. Isotridecanol is medium toxic. Octanol and isodecanol and solvents containing them are toxic.

Mass-transfer in pertraction of butyric acid by phosphonium ionic liquids and dodecane

Transport of butyric acid (BA) through a supported liquid membrane (SLM) containing phosphonium ionic liquid (IL) Cyphos IL-104 and dodecane occurs by two mechanisms. The first is related to the physical solubility of undissociated acid in dodecane in the form of a monomer or dimer and the second to the reactive extraction of acid by IL. Although the model of pertraction indicates that increasing the mean concentration of acid in the feed, cF,lmv, increases the participation of pertraction based on the physical solubility; in the tested range of cF,lmv from 0 kmol m−3 to 0.45 kmol m−3 it does not play an important role and at the highest cF,lmv value, less than 10 % of the overall BA transport were achieved. The presence of IL in SLM considerably increases the value of the overall mass transfer coefficient in pertraction at low BA concentrations. However, at cF,lmv > 0.4 kmol m−3 its values are similar for SLMs with and without IL. Compared to lactic acid, the pertraction of BA through the same SLM is about five times faster. Reactive transport of BA is connected with the back transport of water via reverse micelles decomposition and formation on the extraction and stripping interfaces.

Membrane based solvent extraction and stripping of a heterocyclic carboxylic acid in hollow fiber contactors

Abstract Simultaneous membrane based solvent extraction (MBSE) and membrane based solvent stripping (MBSS) in HF contactors of a heterocyclic carboxylic acid (HCA) of industrial importance from sulphate solutions with solvent containing trioctylamine (TOA) were studied. An effective transport of HCA was achieved. The proposed reaction-diffusion model gives a much better fit to experimental values than the diffusion model. The mean values of the lumped rate constants of extraction and stripping reactions for HCA are 2.19.10 −6 and 5.92.10 −6 m.s −1 , respectively. The mass-transfer resistances based on reaction kinetics play a decisive role in MBSE and MBSS of HCA and participate in their overall resistances by about 65 and 40%, respectively.

Simulation of a hybrid fermentation-separation process for production of butyric acid ‡

Simulation of a hybrid fermentation-separation process for the production of butyric acid (BA) based on published data was done. A unit consisting of a bioreactor with immobilized cells in the fibrous bed and of separation by pertraction through supported liquid membranes (SLM) was considered. Productivities of the unit volume of a fixed bed bioreactor in continuous and fed-batch fermentation at pH 5.5 and 6.0 were used. Concentration of BA in the bioreactor outlet stream was assumed to be in the interval from 0.11 kmol m−3 to 0.45 kmol m−3. Data on the pertraction through SLM with phosphonium ionic liquid (IL) and bulk liquid membrane with trioctylamine (TOA) as carriers were used. A strong increase in the required membrane area was found for both carriers at the pH of pertraction above 4. pH values of fermentation and pertraction should be optimized independently. It is advantageous to have pH of the feed into the pertraction unit of about 4. Dependences of the membrane area on the pertraction efficiency are nearly linear and not very sharp, especially for IL, what enables working at the pertractor efficiency exceeding 90 %. Application of phosphonium IL is promising compared to classical extractant TOA because of lower demand of the membrane area in a large interval of BA concentrations in the pertractor feed.

New approach to regeneration of an ionic liquid containing solvent by molecular distillation

A promising new process for the regeneration of solvents with ionic liquid by molecular distillation has been proposed. The main advantage of this process compared with the classic stripping of acids with alkali solution is that the volatile organic acid is recovered with a yield of about 88 % in the form of free acid, not as its salt. Furthermore, improvement on the yield of the stripping can be assumed. The consumption of chemicals in stripping by molecular distillation is reduced.

Toxicity of organic solvents used in situ in microbial fermentation

Toxicity of organic solvents for in situ solvent extraction of carboxylic acids from aqueous solutions was studied on bacteria Bacillus subtillis and Acetobacter spp., yeasts Kluyveromyces marxianus and Pichia fermentans and fungi Aspergillus terreus and Rhizopus arrhizus. It has been found that trialkylamine and tributylphosphate are much more toxic than other carriers as trialkylphosphineoxide, triisobutylphosphinesulfide and trihexylphosphate. For R. arrhizus trihexylphosphate was found to be the less toxic solvent.

Mass-transfer in membrane based solvent extraction and stripping of 5-methyl-2-pyrazinecarboxylic acid and co-transport of sulphuric acid in HF contactors

Simultaneous membrane based solvent extraction (MBSE) and membrane based solvent stripping (MBSS) of 5methyl-2-pyrazine carboxylic acid (MPCA) in hollow fibre contactors with solvent containing trioctylamine (TOA) have been studied. An effective transport of MPCA was achieved. The analysis of mass-transfer resistances showed, that the kinetics of the acid-carrier complexes formation and/or decomposition should be taken into account. The contribution of the mass-transfer resistances based on reaction kinetics to the overall resistances in MBSE and/or MBSS is from 40 to 80%. The proposed reaction-diffusion model gives a much better fit to the experimental values than a pure diffusion model. The mean value of the lumped rate constant of the extraction reaction for MPCA is 14.2ˆ×10 –6 m.s –1 . Depending on the stripping solution composition, i.e. aqueous solution of NaOH or aqueous solution of NaOH with an addition of NH 4 OH with lower basicity, the mean value of the lumped rate constant of the stripping reaction is 6.02×10 –6 m.s –1 and 2.65×10 –6 m.s –1 , respectively. It has been found that sulphuric acid is cotransported with MPCA. An excess of H 2 SO 4 in the feed decreases the selectivity of MPCA separation. The molar ratio of the transported H 2 SO 4 to MPCA decreases with increasing the MPCA concentration in the solvent. When the feed solution pH was kept at 2.2 the value of this ratio ranged from 1 to 2.5, while when it was kept at 2.5 and NH 4 OH was added to the stripping solution, the molar ratio of the transported H 2 SO 4 to MPCA was in the interval from 0.2 to 1.5.