A green hydrophobic deep eutectic solvent for extraction of phenol from aqueous phase.

Deep eutectic solvents (DESs), have been recognized as effective materials for the extraction of different compounds. In this study, the performance of a novel hydrophobic DES was evaluated for the extraction of phenol from aqueous solutions. Octanoic and dodecanoic fatty acid precursors with a definite molar ratio of 3:1, respectively, were used for the DES having a low melting point of 8.3 °C. The purity and stability of the product were confirmed via characterizing by FTIR, 1H and 13C NMR methods. The liquid-liquid equilibrium of the water + phenol + DES ternary system at different temperatures of 293.2, 298.2 and 308.2 K was accordingly studied through cloud point titration method and refractive index measurement. Interestingly, the important parameters of the solute distribution coefficient and the separation factor were, respectively, within the high levels of (6.8321-9.7787) and (895.76-2770.17), indicating the amazing capability of the DES. Reasonably, both of these parameters decreased with temperature. The NRTL and UNIQUAC thermodynamic models were employed to reproduce the obtained tie-lines and to determine the interaction parameters at each temperature. The low level root mean square deviations for the mentioned models were, respectively, within (0.0014-0.0027) and (0.0045-0.0063); confirming satisfactorily agreement with the experimental data.

A comparative study on the design and application of new nano benzimidazolium gemini ionic liquids for curing interfacial properties of the crude oil-water system.

Gemini surface active ionic liquids (GSAILs) are considered a new prosperous class of ionic liquids and recognized as high performance materials. The present study explores the capabilities of the newly synthesized GSAILs, constructed from two benzimidazole rings attached via a four or a six carbon spacer, namely [C4benzim-Cn-benzimC4][Br2], n = 4 and 6. The products were characterized with FT-IR, NMR, XRD, TGA, DTG and SEM methods and were used in curing interfacial properties of the crude oil-water system. The interfacial tension (IFT) was reduced to about 64 and 71% under critical micelle concentrations (CMCs) of 0.028 and 0.025 mol dm-3 at 298.2 K for n = 4 and 6 GSAILs, respectively. Temperature significantly assisted this effect. Both the GSAILs could transfer the wettability of the solid surface from oil-wet to water-wet. Further, stable oil/water emulsions were produced, having emulsion indices of 74.2 and 77.3% for n = 4 and 6 GSAILs, respectively. Compared to homologous imidazolium GSAILs, the benzimidazolium products revealed better performance in the sense of exhibiting desired effects on the investigated interfacial properties. These can be attributed to the stronger hydrophobicity of the benzimidazolium rings as well as better spreading of the molecular charges. The Frumkin isotherm could exactly reproduce the IFT data, leading to precise determination of the important adsorption and thermodynamic parameters.

Upgrading the Properties of the Crude Oil-Water System for EOR with Simultaneous Effects of a Homologous Series of NanoGemini Surface-Active Ionic Liquids, Electrolytes, and pH.

This study investigated the simultaneous effects of electrolytes, NaCl and MgCl2 electrolytes, individually and as a mixture, and pH on a homologous series of imidazolium nano-Gemini surface-active ionic liquids (GSAILs), [C4im-C m -imC4][Br2], where m = 2, 4, and 6. These can improve the properties of the crude oil-water system and consequently enhance the oil recovery. The results precisely revealed that interfacial tension (IFT) and critical micelle concentration were initially decreased with electrolyte concentration up to 55.7 and 58.6%, respectively, in comparison to the salt-free condition, followed by a slight increase. Moreover, adjusting the pH can provide a further improvement so that 79.2% IFT reduction is attained at pH 9.5 compared to that at the natural pH and that GSAILs show high stability in the pH range of 2.5-9.5. Meanwhile, aqueous solutions of crude oil and electrolyte presented 1 day emulsification indices within 43-53%, followed by minor changes after 1 week. Interestingly, the emulsification index of 77.1% was attained at pH 9.5. Surface wettability was also favorably altered from oil-wet to water-wet with the nanoGSAILs. The findings of this study help gain a better understanding of the effects of nanosurface active materials to improve oil extraction under reservoir conditions.

Mass transfer intensification for carbon quantum dot nanofluid drops under pulsed electric fields.

Simultaneous use of carbon quantum dot (CQD) nanofluids and pulsed electric fields exhibits amazing mass transfer intensification in liquid-liquid extraction of circulating drops. Here, the chemical system of kerosene-acetic acid-water with mass transfer resistance in the organic phase was used in which organic nanofluid drops contained CQD or modified CQD-Fe. These products with extremely small sizes of 7.2 and 13.4 nm were synthesized and characterized by DLS, Zeta potential, XRD, EDS and SEM techniques. To find optimum conditions, CQD concentrations within (0.0005-0.003) wt%, electric field frequencies within (50-550) Hz and electric field strengths to 16 V/cm were examined. From hydrodynamic point of view, the flow pattern of drops was in circulating mode, and that terminal velocity of drops correctly followed the Grace model. The substantial effect of pulsed electric field on the CQD and CQD-Fe nanofluids, brought about mass transfer enhancements to 263.5 and 291.6%. This can be attributed to the electro-induced motion of global CQDs with pulsed electric fields. For the aim of modelling, the adapted Kumar and Hartland equation with a developed correlation of the enhancement factor versus involved dimensionless variables were satisfactory to reproduce the mass transfer coefficient data.

Review on Amphiphilic Ionic Liquids as New Surfactants: From Fundamentals to Applications.

The demand for lowering interfacial tension (IFT) in different processes has persuaded researchers to use stable and resistant surfactants with low environmental impact. For this purpose, surface-active ionic liquids (SAILs) have attracted much attention owing to their good amphiphilic nature and prominent properties like recyclability and high performance under harsh conditions. This review initially explains how the IFT and critical micelle concentration of different systems vary in the presence of different SAILs with a variety of alkyl chain lengths, head groups, and counter anions. Towards this aim, some physicochemical properties of SAILs as well as the corresponding theoretical aspects of adsorption are considered. Then, recent advances in utilizing SAILs for reducing IFT of different chemical systems are surveyed. Relevantly, the role of important operating parameters of temperature, pH, presence of electrolytes, and the chemical nature of involved phases are adequately discussed. Further, an overview of different SAILs applications in stabilization, separation, and in petroleum industries is scrutinized. To allow better judgment, precise comparisons between different types of SAILs and conventional surfactants are provided. Finally, challenges and possible directions of future research on SAILs are highlighted.

Incorporating Pb2+ Templates into the Crystalline Structure of MnO2 Catalyst Supported on Monolith: Applications in H2O2 Decomposition.

Several MnO2 catalysts, promoted with Pb2+ ions and supported on a wash-coated monolith (WMon), briefly, xPbyMn-WMon (x = 0, 0.5, 1.0, 1.5, 2, and 2.5 and y = 8 wt %), were prepared. The presence of Pb2+ affects the manganese oxidation state, crystalline phase, thermal resistance, metal dispersion, and catalytic performance. According to XPS spectra, XRD patterns and HRTEM images, manganese was dispersed on the monolith surface as Mn3+ and Mn4+ species in both α and ß crystalline phases. The ratios of Mn4+/Mn3+ states and α/ß phases were highly enhanced, and the desired Pb x Mn8O16 phase (coronadite) was formed. Concentrations of the defect oxygen (Mn-O-H) and oxygen vacancies, which improve the catalyst reducibility and the MnO2 reduction temperature, were also increased. Further, based on the H2 chemisorption analysis, the Pb2+ template would increase the manganese dispersion and the reaction sites. Meanwhile, the average MnO2 crystallite size was decreased from 13.26 to 8.15 nm. The optimum catalyst 1.5Pb8Mn-WMon exhibited an activity 149% more than the manganese-only catalyst in decomposition of H2O2. Evaluation of catalyst stability in the presence of Pb2+ after 10 recycles showed only a 6.8% decrease. The catalytic reaction was evaluated based on different criteria.

Simultaneous photocatalytic reduction/degradation of divalent nickel/naphthalene pollutants in aqueous solutions.

Toxic heavy metals and organic pollutants simultaneously exist in the wastewater of some industries. This study explores reduction of toxic divalent nickel ions, from either nitrate or sulfate salts, coupled with naphthalene (NA) degradation using titania photocatalyst in an efficient photo-sono reactor. A synergism appears when reduction and degradation treatments occur simultaneously in the media. With initial concentrations of [Ni(II)]0 = 5 mg/L and [NA]0 = 10 mg/L, under dominant mild conditions, removal efficiencies of 54.5% and 56.6% were obtained for Ni(II) and NA, respectively, when nickel nitrate was used. These efficiencies were enhanced to 59.2% and 57.5%, respectively, with nickel sulfate, all after 90 min operation. For evaluating the mechanism of reactions, reactive oxygen species analysis on solutions as well as Fourier transform infrared, scanning electron microscopy and Brunauer-Emmett-Teller analyses on the titania nanoparticles, before and after usage, was performed. The reaction kinetics was also followed for individual species in the mixed solution and, accordingly, the energy consumption was evaluated for one order of magnitude decrease in pollutant concentration. The high performance of the used method was revealed in comparison to the similar reported reduction/degradation processes.

Compensating effect of ultrasonic waves on retarding action of nanoparticles in drops liquid-liquid extraction.

The influence of ultrasonic waves on liquid-liquid extraction of circulating drops and in the presence of magnetite nanoparticles was investigated. Experiments were conducted in a column equipped with an ultrasound transducer. The frequency and intensity of received waves, measured by the hydrophone standard method, were 35.40 kHz and 0.37 mW/cm2, respectively. The recommended chemical system of cumene-isobutyric acid-water was used in which mass transfer resistance lies in the aqueous phase. Nanoparticles, within concentration range of (0.0003-0.0030) wt%, were added to the aqueous continuous phase. The presence of nanoparticles and ultrasonic waves provided no sensible change in drop size (within 2.49-4.17 mm) and measured terminal velocities were close to Grace model. However, presence of nanoparticles, caused mass transfer to decrease. This undesired effect was significantly diminished by using ultrasonic waves so that mass transfer coefficient increased from (73.0-178.2) to (130.2-240.2) µm/s, providing a 55.6% average enhancement. It is presumably due to disturbing the accumulated nanoparticles around the drops. The current innovative study highlights the fact that using ultrasonic waves is an interesting way to improve liquid-liquid extraction in the presence and absence of nanoparticles.

Homogenous UV/periodate process in treatment of p-nitrophenol aqueous solutions under mild operating conditions.

Aqueous solutions of p-nitrophenol (PNP) were treated with UV-activated potassium periodate (UV/KPI) in an efficient photo-reactor. Either periodate or UV alone had little effect; however, their combination led to a significant degradation and mineralization. The response surface methodology was employed for design of experiments and optimization. The optimum conditions for treatment of 30 mg/L of the substrate were determined as [KPI] = 386.3 mg/L, pH = 6.2 and T = 34.6°C, under which 79.5% degradation was achieved after 60 min. Use of 25 and 40 kHz ultrasound waves caused the degradation to enhance to 88.3% and 92.3%, respectively. The intermediates were identified by gas chromatography-mass spectroscopy analysis, leading to propose the reaction pathway. The presence of water conventional bicarbonate, chloride, sulfate and nitrate anions caused unfavorable effects in efficiency. Meanwhile, the kinetic study showed that PNP degradation follows a pseudo-first-order reaction and the activation energy was determined. The irradiation energy consumption required for one order of magnitude degradation was estimated as 11.18 kWh/m3. Accordingly, comparison with the previously reported processes showed the superiority of PNP treatment with the employed process.

Experimental studies on the effect of ultrasonic waves on single drop liquid-liquid extraction.

The influence of ultrasonic waves on hydrodynamics and mass transfer of circulating drops in liquid-liquid extraction process was studied. The recommended chemical systems of toluene-acetic acid-water with mass transfer resistance mainly in the organic phase, and cumene-isobutyric acid-water in the aqueous phase were used. An extraction column, equipped with an ultrasonic emitter of 35.40kHz real frequency and 0.37mW/cm2 intensity, was employed. The ultrasound properties were measured using the hydrophone standard method. Drops terminal velocity was comparable with the Grace model. In mass transfer study, significant enhancement was revealed in overall mass transfer coefficient for different drop sizes and for the both mass transfer directions by using ultrasonic waves. The average and maximum enhancements were, respectively, 20.8 and 31.7% for toluene-acetic acid-water, and 40.3 and 55.1% for cumene-isobutyric acid-water. Small drops exhibited a higher enhancement percentage. Regarding the mass transfer direction, the system of cumene-isobutyric acid-water with continuous to dispersed phase direction, was benefited more as the consequence of creating effective agitation in continuous phase than in dispersed phase.

Synthesis and characterization of novel polymer-drug conjugates based on the poly(styrene-alt-maleic anhydride) as a potential method for drug release.

Six well known drugs, captopril, metformin-HCl, metroniazole, nortriptyline-HCl, fluoxetine-HCl and betahistin-HCl, were grafted to poly(styrene-alt-maleic anhydride) (PSMA). Grafting was attained by combining of anhydride groups in the PSMA with therapeutic agents containing NH, OH or SH groups. The covalently grafted drugs were identified by infrared, (1)H NMR and UV-Vis spectroscopy. The drug release data at different times fits well to the Korsmeyer-Peppas equation. The analysis of the exponent n of this model revealed a dominant Fickian diffusion mechanism under the in vitro conditions. Furthermore, mean dissolution time values (45.9 to 86.7 h) indicate a high resistance against drugs transport, the highest being obtained for betahistin-HCL.