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Author: search.filters.author.Nkosi, Nkululeko

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    Infinite dilution activity coefficients and thermodynamic properties of selected organic solutes and water dissolved in 1, 6-hexanediol
    (Elsevier BV, 2020-12) Nkosi, Nkululeko; Tumba, Kaniki; Ngema, Peterson; Ramsuroop, Suresh
    The experimental activity coefficients (γ13∞) and gas-to-liquid partition coefficients (KL) at infinite dilution for 34 organic solutes and water were determined in 1.6-hexanediol (HDO) by the gas–liquid chromatography technique (GLC) in the temperature range from (323.15 to 353.15) K. Fundamental thermodynamic functions such as excess partial molar enthalpy (ΔHiE,(∞)), excess partial molar Gibbs energy, (ΔGiE,∞) and entropy, (TrefΔSiE,∞) at infinite dilution were calculated from experimental values of γ13∞. Reported data were discussed in terms of solvent-solute interactions, heat effects and mixing spontaneity. Selectivity (Sij∞) and capacity (kj∞) related to different separation problems were calculated from γ13∞ data and compared to the literature values for selected ionic liquids (ILs), deep eutectic solvents (DESs) and industrial solvents. New data reported in this study suggest that HDO may be proposed as an alternative solvent for the separation of alkanes-pyridine and alkanes-thiophene systems. Furthermore, it was found that adding a hydrogen bond acceptor to HDO enhances its performance as a separation solvent.
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    Infinite dilution activity coefficient measurements for 1-Methyl-4-(1-methylethenyl)-cyclohexene as a green solvent for separation
    (American Chemical Society (ACS), 2022-04-14) Mbatha, Banzi Patrick; Ngema, Peterson Thokozani; Nkosi, Nkululeko; Ramsuroop, Suresh
    Infinite dilution activity coefficients for various solutes, which include alkanes, alkenes, alkynes, cycloalkanes, heterocycles, alcohols, aromatics, ketones, ethers, nitrile, and water, in a 1-methyl-4-(1-methylethenyl)-cyclohexene solvent were measured using gas-liquid chromatography at 303.15, 313.15, and 323.15 K. The focus of this study was to assess 1-methyl-4-(1-methylethenyl)-cyclohexene as a green solvent for separation processes. 1-Methyl-4-(1-methylethenyl)-cyclohexene, a nonpolar monoterpene solvent extracted from essential oils of citrus peels, was investigated as an alternative solvent to currently employed conventional organic solvents in separation processes. Through experimental infinite dilution activity coefficients, γ13∞, the values of partial molar excess enthalpy at infinite (δHiE,∞) were obtained using the Gibbs-Helmholtz equation. The infinite dilution selectivity (Sij∞) and capacity (δkj∞) values were calculated from the experimental limiting activity coefficients and were compared with deep eutectic solvents, ionic liquids, and industrial solvents. From this study, it was observed that 1-methyl-4-(1-methylethenyl)-cyclohexene is not suitable to be used as an alternative for separation processes. In addition, activity coefficients at infinite dilution of different organic solutes in hexadecane were measured at various temperatures to validate the reliability and accuracy of gas-liquid chromatography. Finally, the experimental data were modeled using Aspen Plus, compared with experimental data, and found to be in good agreement.