Ahmet Alp Sayar

Liquid-liquid equilibria of some water + tetrahydrofurfuryl alcohol + solvent ternaries at 293.2 ± 0.1 K and 101.3 ± 0.8 kPa

Abstract Isothermal solubility curves and tie-line end compositions for five water tetrahydrofurfuryl alcohol + solvent ternaries were experimentally determined at 293.2 ± 0.1 K and 101.3 ± 0.8 kPa. Cyclohexanone, 2-methylbutyl ethanoate, 1,2-dichloroethane, 1-octanol and ethyl acetate were used as solvents. Tie-lines were predicted using the LLE-data UNIFAC model. Somewhat acceptable results were obtained for the 1,2-dichloroethane and 1-octanol ternaries, whereas the model failed to generate reliable results for the remaining ternaries. Comparison of the extracting capabilities of the investigated solvents were made with respect to distribution coefficients, separation factors and solvent-free selectivity bases. 1,2-Dichloroethane and 1-octanol exhibited the best solvent performance in the separation of tetrahydrofurfuryl alcohol, especially from its dilute aqueous solutions.

EXTRACTION OF TITANIUM(IV) FROM AQUEOUS HYDROCHLORIC ACID SOLUTIONS INTO ALAMINE 336-M-XYLENE MIXTURES

Extraction of Ti(IV) from its aqueous hydrochloric acid solutions into organic Alamine 336-m-xylene systems was investigated. Extraction experiments were conducted with three different initial metal concentrations of 1, 3, and 6 mg/mL, each at three acidic molarities of 1, 5, and 10 M. It was observed that the extractability of Ti(IV) increases with increasing acidic molarities. Alamine 336 diluted with m-xylene was found to be a suitable extractant for Ti(IV) across this acidic range. In parallel, a mathematical model was developed to correlate metal extractability and Alamine 336 volume content. Optimal Alamine 336 contents were estimated for single-stage extraction.

Liquid-liquid equilibrium of water + 2-propanol + 2,2,4-trimethylpentane ternary at 293.2 ± 0.1 K

Abstract Arda, N. and Sayar, A.A., 1992. Liquid-liquid equilibrium of water + 2-propanol+ 2,2,4-trimethylpentane ternary at 293.2 ± 0.1 K. Fluid Phase Equilibria, 73: 129-138. Tie-lines and the isothermal solubility curve of water + 2-propanol + 2,2,4-trimethylpentane were experimentally determined at 293.2 ± 0.1 K. The reliability of tie-line measurements was checked via Campbells method and the correlation using Hands equation. Tie-lines were predicted from the liquid-liquid equilibrium data UNIFAC model. The extracting capability of 2,2,4-trimethylpentane for separating 2-propanol from its aqueous solutions was investigated in terms of distribution coefficients, separation factors and selectivity.

A sigmoidal model for biosorption of heavy metal cations from aqueous media

A novel multi-input single output (MISO) black-box sigmoid model is developed to simulate the biosorption of heavy metal cations by the fission yeast from aqueous medium. Validation and verification of the model is done through statistical chi-squared hypothesis tests and the model is evaluated by uncertainty and sensitivity analyses. The simulated results are in agreement with the data of the studied system in which Schizosaccharomyces pombe biosorbs Ni(II) cations at various process conditions. Experimental data is obtained originally for this work using dead cells of an adapted variant of S. Pombe and represented by Freundlich isotherms. A process optimization scheme is proposed using the present model to build a novel application of a cost-merit objective function which would be useful to predict optimal operation conditions.

(Liquid + liquid) equilibria of (water + tetrahydrofuran + 1-methylcyclohexanol) and of (water + tetrahydrofuran + 2-methylbutyl ethanoate) at the temperature (293.16±0.30) K and pressure (101.325±0.070) kPa

Solubility curve and tie-line measurements for (water + tetrahydrofuran + 1-methylcyclohexanol) and (water + tetrahydrofuran + 2-methylbutyl ethanoate) at the temperature (293.16±0.30)K and the pressure (101.325±0.070)kPa are reported. Tie-lines were correlated using a Hand equation. Consistency of our results was ascertained through an Othmer-Tobias correlation. Distribution coefficients of tetrahydrofuran and water from aqueous solutions to selected high-boiling solvents were determined and separation factors were evaluated. It is concluded that the high-boiling solvent, 2-methylbutyl ethanoate, may be considered a separating agent for dilute aqueous tetrahydrofuran solutions.

Assessment of the effects of medium composition on growth, lipid accumulation and lipid profile of Chlorella vulgaris as a biodiesel feedstock

Microalgae serve as a potential feedstock for renewable energy- biodiesel production due to their lipid content. Nowadays, it is possible to maximize the lipid content of microalgal cells via biochemical engineering methods. The aim of the presented study is to observe the effects of six different medium compositions on the growth, lipid content and lipid profile of Chlorella vulgaris.

Schizosaccharomyces pombe and its Ni(II)-insensitive mutant GA1 in Ni(II) uptake from aqueous solutions: a biodynamic model

In the present study, Ni(II) uptake from aqueous solution by living cells of the Schizosaccharomyces pombe haploid 972 with h− mating type and a Ni(II)-insensitive mutant GA1 derived from 972 was investigated at various initial glucose and Ni(II) concentrations. A biodynamic model was developed to predict the unsteady and steady-state phases of the uptake process. Gompertz growth and uptake process parameters were optimized to predict the maximum growth rate μm and the process metric Cr, the remaining Ni(II) content in the aqueous solution. The simulated overall metal uptake values were found to be in acceptable agreement with experimental results. The model validation was done through regression statistics and uncertainty and sensitivity analyses. To gain insight into the phenomenon of Ni(II) uptake by wild-type and mutant S. pombe, probable active and passive metal transport mechanisms in yeast cells were discussed in view of the simulation results. The present work revealed the potential of mutant GA1 to remove Ni(II) cations from aqueous media. The results obtained provided new insights for understanding the combined effect of biosorption and bioaccumulation processes for metal removal and offered a possibility for the use of growing mutant S. pombe cell in bioremediation.

Biosorption of Co(II) by Schizosaccharomyces pombe : Kinetic and Thermodynamic Studies for Process Design

The characterisation of biosorption by Schizosaccharomyces pombe of Co(II) was done under varying experimental conditions including pH, temperature, initial metal concentration and biosorbent dose. Optimum pH was found to be 5.0 with optimal biosorbent dose for highest adsorption capacity at 1.0 g L-1. Higher initial metal concentrations helped enhance qe slightly with the highest value, 2.7 mg g-1, being achieved at 25°C and 50 mg L-1 initial Co(II). Temkin isotherm model showed the best statistical fit for equilibrium data while Freundlich isotherm model exhibited thermodynamic consistency. Pseudo-first order kinetics was found to represent Co(II) biosorption. Increasing ΔG0 values calculated with respect to higher operational temperatures were in agreement with kinetic profiling simulations whereby higher temperatures were found to be less favourable. Overall efficiency of S. pombe as a biosorbent for Co(II) was found to be significantly less than Ni(II), for this reason it can be regarded as a potential bioseparation agent for aqueous mixtures containing both Co(II) and Ni(II).