The well-known toxicity of conventional chemical oil spill dispersants demands the development of alternative and environmentally friendly dispersant formulations. Therefore, in the present study we have developed a pair of less toxic and green dispersants by combining lactonic sophorolipid (LS) biosurfactant individually with choline myristate and choline oleate ionic liquid surfactants. The aggregation behavior of resulted surfactant blends and their dispersion effectiveness was investigated using the baffled flask test. The introduction of long hydrophobic alkyl chain with unsaturation (attached to choline cation) provided synergistic interactions between the binary surfactant mixtures. The maximum dispersion effectiveness was found to be 78.23% for 80:20 (w/w) lactonic sophorolipid-choline myristate blends, and 81.15% for 70:30 (w/w) lactonic sophorolipid-choline oleate blends at the dispersant-to-oil ratio of 1:25 (v/v). The high dispersion effectiveness of lactonic sophorolipid-choline oleate between two developed blends is attributed to the stronger synergistic interactions between surfactants and slower desorption rate of blend from oil-water interface. The distribution of dispersed oil droplets at several DOR were evaluated and it was observed that oil droplets become smaller with increasing DOR. In addition, the acute toxicity analysis of developed formulations against zebra fish (Danio rerio) confirmed their non-toxic behavior with LC50 values higher than 400 ppm after 96 h. Overall, the proposed new blends/formulations could effectively substitute the toxic and unsafe chemical dispersants.
Ionic liquids (ILs) have been demonstrated as promising alternatives to conventional entrainers in separation of azeotropic mixtures mostly investigating phase equilibrium and process design scenarios. However, proper selection of ILs for a specific task always remains challenging. Hence a simulation tool, i.e. conductor like screening model for real solvents (COSMO-RS) was applied to address this challenge. Furthermore, screened ILs were simulated as entrainers for ethanol water separation by extractive distillation. The current study also aims to demonstrate a systematic approach to retrofit existing processes, by employing ILs as green entrainers. Screening of twenty-five (25) ILs was carried out using COSMO-RS to select suitable ILs as green entrainers based on activity coefficient, capacity and selectivity. Results illustrated that tetramethylammonium chloride ([TMAm][Cl]) due to its strong hydrogen bonding ability was found to be the best ILs entrainer. Moreover, in order to reduce the operating costs without compromising desired product purity (ethanol purity ≥99.5% in top product), the selected ILs (8 kg/h) in a mixture with ethylene glycol (72 kg/h) were simulated using Aspen plus v.11. The simulation results revealed that by combining tetramethylammonium chloride (2 kg/h) with ethylene glycol (78 kg/h) reduced 7.26 tons of CO2 emissions/year through heat integration by saving 1.49*108 kJ/year energy besides minimizing operating costs. In conclusion, the systematic selection of ILs as green entrainers in combination with ethylene glycol and then the appropriate simulation of the whole system will ultimately reduce the cost of the separation process and reduce the emission of greenhouse gases as well utilization of toxic conventional entrainers.
The main obstacles in adopting solvent-based CO2 capture technology from power plant flue gases at the industrial scale are the energy requirements for solvent regeneration and their toxicity. These challenges can be overcome using new green and more stable ionic liquids (ILs) as solvents for post-combustion CO2 capture. In the current study, tributyl-tetradecyl-phosphonium chloride [P44414][Cl] as an IL, was immobilized on hydrophobic porous supports of polypropylene (PP), polyvinylidene fluoride (PVDF), and polytetrafluoroethylene (PTFE) at 298 ± 3 K and pressures up to 2 bar. The surface morphology indicated homogenous immobilization of the IL on the membrane support. Supported ionic liquid membranes (SILMs) were tested for CO2 permeability and CO2/N2 selectivity. None of the SILMs exhibited IL leaching up to 2 bar. The PTFE-based SILM performed better than other supports with minimum loss in water contact angle (WCA) and achieved good antiwetting with a maximum CO2 permeability and selectivity over N2 of 2300 ± 139 Barrer and 31.60 ± 2.4, respectively. This work achieves CO2 permeability about two-fold more than other works having CO2/N2 selectivity range of 25-35 in similar SILMs. The diffusivity of CO2 and N2 in [P44414][Cl] was measured as 3.64 ± 0.18 and 2.01 ± 0.09 [10-8 cm2 s-1] and CO2 and N2 solubility values were 9.79 ± 0.47 and 0.19 ± 0.001 [10-2 cm3(STP) cm-3 cmHg-1], respectively. The high values of Young's modulus and tensile strength of the PTFE support-based SILM (234 ± 12 MPa and 6.07 ± 0.31 MPa, respectively) indicated the long-term application of SILM in flue gas separation. The results indicated phosphonium chloride-based ILs could be better solvent candidates for CO2 removal from large volumes of flue gases than amine-based ILs.