Extraction Efficiency Of Phenolics Research Articles

Fast and efficient extraction of phenol from aqueous phase using deep eutectic solvents: Experimental and density functional theory investigation for interactions studies

Phenol is carcinogenic and toxic to human beings and therefore it is necessary to remove this toxic pollutant from water. Hydrophobic deep eutectic solvents (DESs) were prepared using trioctylamine (TOA) as hydrogen bond acceptor (HBA) and 2-hydroxybenzoic acid and 4-dodecylbenzenesulfonic acid as hydrogen bond donors (HBDs) for extraction of phenol from aqueous media. Fourier transformer infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA) were performed for functional group and thermal stability determination, respectively. Phenol extraction efficiency of DESs was studied under different experimental parameters, such as initial pH of phenol solution (2–10), contact time (1–15 min), mixing ratio of volume of DESs to aqueous media (VDES:Vaq.) (1:10–1:50 mL), initial concentration of phenol (1000–5000 ppm) and temperature (25 °C–55 °C). More than 97 % extraction efficiency of DES for phenol was achieved using contact time of 5 min, initial phenol concentration of 2500 ppm, VDES:Vaq in a ratio of 1:10 mL, and temperature of 25 °C. The values of ΔG° calculated for phenol extraction at various temperatures have negative values, confirming that the phenol movement from water phase to DESs phase is spontaneous in nature. Density functional theory (DFT) simulations were conducted to study the interaction of DESs with water and phenol. In addition, DFT was used to determine the interaction energy of DESs with water and phenol. The considerably higher interaction energies (−20.4 and 18.2 kcal/mol) obtained with both DESs for phenol over water emphasize the selective separation efficiency of DESs for phenol. The experimental results confirmed that these synthesised DESs can effectively extract phenol from the aqueous phase to the organic phase.

Phosphonium-based ionic liquid immobilised in sodium alginate as a novel adsorbent: Kinetics, thermodynamics, and toxicity study on 2,4-dichlorophenol removal

This study aimed to immobilise a phosphonium-based ionic liquid (IL) (trihexyl(tetradecyl)phosphonium decanoate) in sodium alginate capsules, and its adsorption capacity was evaluated using 2,4-dichlorophenol (2,4-DCP) as pollutant target. This novel adsorbent was characterized in terms of equivalent diameter, moisture content, impregnated IL percentage, and by Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), and Brunauer, Emmett and Teller (BET) Surface Area Analysis. The effect of pH, temperature, contact time, and salt concentration on the adsorption efficiency was examined. In addition, the phytotoxicity and cytotoxicity of the capsules were also determined. Adsorption was hindered in alkaline and strongly acidic environments and favoured at pHs between 6 and 7, as well as at temperatures close to 15 °C. The pseudo-second-order kinetic model best suited the data, and equilibrium was reached with a contact time close to 50 minutes. After several batch cycles, the cumulative capacity resulted in 172.01–217.55 mg g−1. Also, the phenol extraction efficiency of immobilised IL on sodium alginate was similar to the free IL used on liquid-liquid extraction. The IL-impregnated capsules proved to be non-toxic for lettuce seeds and onion bulbs. Trihexyl(tetradecyl)phosphonium decanoate could be efficiently impregnated into sodium alginate capsules and potentially used as an adsorbent.

Incorporation of molecular hydrogen into solvents increases the extraction efficiency of phenolics, flavonoids, anthocyanins, and antioxidants: the case of lemon peels

The impact of hydrogen infusion into solvents on the extraction of phytochemicals was evaluated. Pure (water, ethanol, methanol) and hydrogen-rich solvents at temperatures (25°C and 35°C) were used for extracting phenolics, flavonoids, anthocyanins, and antioxidants from lemon peel. Incorporating hydrogen into all solvents increased the extraction of all phytochemicals. The hydrogen incorporation into solvents led to the highest increase in phenolics and flavonoid contents shown for hydrogen-rich methanol (HRM) followed by hydrogen-rich ethanol (HRE) at both 25°C and 35°C. The highest antioxidant extraction was shown for HRM. The hydrogen incorporation showed the highest phytochemical extraction in methanol and at 35°C. The increase in temperature increased the extraction efficiency, but less efficiently than the hydrogen incorporation. The HPLC phenolic profile confirmed the positive effect of both temperature and hydrogen incorporation on the extraction of flavonoids and non-flavonoids. The improvement of the phytochemical extraction by the proposed method can bring many economic and ecological advantages.

Investigation of the extraction ability and mechanism of environmentally friendly ionic liquids for phenol in the model oil

The large number of phenolic compounds contained in coal tar and coal-converted oil seriously increased their cost of processing and transportation difficulties, so methods for efficient separation of phenolic compounds is of great industrial significance. Based on the flexible designability of ionic liquids, hydroxyl functional group that can interact with phenol were introduced into ionic liquid’s cations, eight ionic liquids were synthesized and their separation properties of phenol in model oil (methylbenzene) were studied. Cations of these ionic liquids have a significant influence the phenol extraction efficiency, which follows the order: [Ch]+ > [HEMIM]+. But the anions show a relatively small influence, and the order is: [Pro]- > [Lac]- > [Gly]- > [Ac]-. Other effects such as extraction temperature, molar ratio of phenol to ILs, extraction time and other factors on the extraction efficiency and distribution coefficient were investigated, also the optimum parameters were obtained. Hydroxyl modified ionic liquids showed good extraction performance for phenol, and the choline propionate ionic liquids showed the best separating capacity and were selected as the best extractant. The extraction performance was analyzed by 1H NMR and FT-IR spectra analysis. Hydrogen bond was confirmed to be one of the extraction mechanisms and we found that there was an optimal distance between the cation and anion of ionic liquids to form hydrogen bonds with phenol, also the π-π interaction between imidazole ring and benzene ring in phenol contributed to the extraction. In addition, the ionic liquid showed good recyclability and the regenerated ionic liquids could be reused five times with highly extraction efficiency.

Phenolics from Defatted Black Cumin Seeds (Nigella sativa L.): Ultrasound-Assisted Extraction Optimization, Comparison, and Antioxidant Activity.

An ultrasound-assisted method was used for the extraction of phenolics from defatted black cumin seeds (Nigella sativa L.), and the effects of several extraction factors on the total phenolic content and DPPH radical scavenging activity were investigated. To improve the extraction efficiency of phenolics from black cumin seed by ultrasonic-assisted extraction, the optimal extraction conditions were determined as follows: ethanol concentration of 59.1%, extraction temperature of 44.6 °C and extraction time of 32.5 min. Under these conditions, the total phenolic content and DPPH radical scavenging activity increased by about 70% and 38%, respectively, compared with conventional extraction. Furthermore, a complementary quantitative analysis of individual phenolic compounds was carried out using the HPLC-UV technique. The phenolic composition revealed high amounts of epicatechin (1.88–2.37 mg/g) and rutin (0.96–1.21 mg/g) in the black cumin seed extracts. Ultrasonic-assisted extraction can be a useful extraction method for the recovery of polyphenols from defatted black cumin seeds.

Highly efficient separation of phenolic compounds from low-temperature coal tar by composite extractants with low viscosity

• Imidazolium IL-solvent composite extractants were applied for separation of phenolic compounds from oil. • The suitable composite extractants were identified by COSMO-RS calculation and viscosity determination. • [Emim][HSO 4 ]:EG (1:2) was selected due to its high phenol extraction efficiency, low oil entrainment, and low viscosity. • The separation mechanism was investigated by σ -profile, σ -potential, and FT-IR. Highly efficient separation of phenolic compounds from low-temperature coal tar (LTCT) is significant in the industry. In this work, composite extractants composed of imidazolium-based ionic liquids (ILs) and solvents were used to separate phenolic compounds from model oil and LTCT. First, the COSMO-RS model was used to screen composite extractants that combined the infinite dilution thermodynamic indexes and liquid–liquid equilibria (LLE) calculations. Meanwhile, the separation mechanism was analyzed by σ -profile and σ -potential. Then, the reliability of the COSMO-RS model was validated by LLE experiments and FT-IR. The viscosity of composite extractants with high separation performance was further determined. Among the composite extractants, 1-ethyl-3-methyl-imidazolium hydrogen sulfate ([emim][HSO 4 ])/ethylene glycol (EG) was selected as the most suitable extractant in the separation process. The m -cresol extraction efficiency and cumene entrainment were 98.1% and 8.3%, respectively, at a [emim][HSO 4 ]:EG molar ratio of 1:2, a temperature of 25 ℃, and a composite extractant: model oil mass ratio of 1:1. Moreover, the viscosity of [emim][HSO 4 ]:EG (1:2) was only 51.8 cP at 25 ℃ and decreased by 95.6% compared with pure [emim][HSO 4 ], which enhanced the mass transfer in the separation process. The [emim][HSO 4 ]:EG (1:2) could be regenerated and reused without significant reduction in separation performance. Finally, [emim][HSO 4 ]:EG (1:2) was applied to separate phenolic compounds from LTCT with a phenol extraction efficiency of more than 99.9% and a neutral oil entrainment of 8.3%, providing a promising prospect for the separation of phenolic compounds.

Efficient recovery of phenol from phenolic wastewater by emulsion liquid membrane

AbstractThe recovery of phenol from phenolic wastewater by emulsion liquid membrane (ELM) was investigated. The W/O emulsion was prepared with kerosene, Span−80, carrier, liquid paraffin, and NaOH solution. The effects of NaOH concentration, oil–internal solution ratio, shearing speed, Span−80 concentration, and carrier type and concentration on emulsion breakage were studied. In the single factor experiments of stability of W/O emulsion, the lowest percentages of emulsion breakage were achieved at a NaOH concentration of 0.03 g/ml, an oil–internal solution ratio of 2:1, a shearing speed of 1500 r/min, a Span−80 concentration of 8%, a tributyl phosphate (TBP) concentration of 0.8%, and an ethyl acetate concentration of 0.8%, respectively. Then, the effects of nine factors on extraction efficiencies of phenol were investigated. This indicated that the effects of shearing speed, oil‐internal solution ratio, emulsion‐external solution ratio, liquid paraffin concentration, and mixing speed on extraction efficiencies of phenol were limited. However, the carrier concentration, NaOH concentration, Span−80 concentration, and phenol concentration had important impacts on the extraction efficiency of phenol. The extraction efficiency of phenol could reach 99.7%. Besides, the results of orthogonal experiments indicated that during the extraction of phenol by ELM, the order of importance of factors was NaOH concentration > emulsion‐external solution ratio > volume fraction of Span−80 > volume fraction of TBP. After extraction, the recycled emulsion with Span−80 could not easily be effectively demulsified through heating, which only provided the highest demulsification efficiency of 18.2%. However, the recycled emulsion could be effectively demulsified through centrifugation, which could get the highest demulsification efficiency of 86% at a centrifugal rotational speed of 2000 r/min and a centrifugal time of 25 min.

Phenolic Content, Antioxidant Properties, Key Enzyme Inhibitory Potential and Photoprotective Activity of Lawsonia inermis L.

Background: Lawsonia inermis Linn (Lythraceae), commonly known as "Henna" is a medicinal plant widely used as a folk remedy and for its cosmetic properties. Objective: The objective of this present work was to evaluate biological activities and to quantify phenolics in extracts. Methods: The extracts were obtained from seeds of L. inermis by increasing the polarity of the solvent. The content of total phenolics, flavonoids, flavonols and tannins was determined using colorimetric methods. Also, to evaluate the antioxidant activity, six different assays, DPPH, ABTS, superoxide radical scavenging, inhibition of β-carotene bleaching, ferric reducing antioxidant power and phenanthroline assays were used. Enzyme inhibition activity was evaluated by acetylcholinesterase, butyrylcholinesterase and tyrosinase inhibition assays. Furthermore, photoprotective activity was determined by measuring sun protection factor. Results: The extraction efficiency of phenolics, as well as the biological activities of plant extracts, were affected by solvent polarity. The highest content of phenolics was determined in methanol extract (786.54 ± 0.00 mg GAEg-1 DW), followed by the aqueous and ethyl acetate extracts (526.48 ± 0.40 and 331.25 ± 0.00 GAEg-1 DW, respectively).The above extracts also exhibited the highest antioxidant activity, while low polar extracts were characterized with the lowest content of phenolics, as well as the lowest antioxidant capacity. The highest enzyme inhibition activities were found in ethyl acetate extract. Moreover, the methanol extract showed the best photoprotective activity with sun protection factor of 43.05 ± 0.37. Conclusion: These findings suggest a possible use of Henna seeds as a potential source of bioactive molecules with antioxidant, enzyme inhibition and skin protection properties.

Roles of Drying, Size Reduction, and Blanching in Sustainable Extraction of Phenolics from Olive Leaves

It is now known that olive leaves contain a sizable portion of polyphenols and there is much research highlighting that these natural ingredients favorably exhibit bio-functional activities. In this regard, many studies have focused on the exploration of optimum conditions involved directly in the extraction process. These investigations, while being highly valuable, may somewhat cast a shadow over other contributing factors such as those involved in the preprocessing of leaves, including size reduction, drying, and blanching. The use of these unit operations under appropriate conditions, together with other benefits, potentially exert improved surface area, homogeneity, and diffusion/mass transfer which may help develop the liberation of target bio-compounds. The research work in this area, particularly size reduction, is relatively limited. Although in various experiments they are incorporated, not many studies have focused on them as the main predictor variables. The performance of further research may help ascertain the magnitude of their effects. Consideration of the operational parameters in preprocessing step is equally important as those in the processing/extraction step that may comparably influence on the extraction efficiency. This review provides an overview of the potential roles of drying, size reduction, and blanching in the extraction efficiency of phenolics from olive leaves.

Effect of contacting pattern and various surfactants on phenol extraction efficiency using emulsion liquid membrane

Abstract Emulsions prepared using different surfactants, including Span-80, BKC and CTAB, are studied for their stability and phenol remsoval efficiency. The effect of contacting pattern on ELM extraction efficiency is compared in Beaker – Stirrer apparatus and Bubble Flow Recirculation column. The emulsion prepared using Span-80 is relatively more stable than emulsions prepared using other surfactants. The emulsion stability during the extraction process is relatively higher in the Bubble Flow Recirculation column (15 min) than in the Beaker – Stirrer apparatus (10 min). At optimized conditions, the phenol removal efficiency of the emulsion prepared using Span-80 in Beaker – Stirrer apparatus is 96% and in Bubble Flow Recirculation column is 78%. Kinetic studies reveal that the extraction follows zeroth-order kinetics with an average phenol effective diffusivity of 0.0004 s at an initial phenol concentration ranging from 100–500 PPM.

Microwave-assisted Extraction for Maximizing the Yield of Phenolic Compounds and Antioxidant Capacity from Cacao Pod Husk (Theobroma cacao L.)

Background: Extraction is an important step to obtain phytochemical compounds from natural materials. Among different extraction techniques, microwave-assisted extraction (MAE) is an advanced method with high extraction efficiency and low energy consumption. Objective: This study aimed to optimize the MAE parameters for obtaining the highest levels of phenolic compounds and antioxidant activity from cacao pod husk (CPH). Methods: The dried CPH was prepared using a microwave drying method. The CPH extract was prepared using a microwave-assisted extraction method. The powdered CPH extract was prepared using vacuum evaporation and freeze-drying methods. Phytochemical compounds and antioxidant capacity of CPH extracts were analyzed using spectrophotometric methods. Results: The optimal MAE parameters were 600 W microwave power, 5 s/min irradiation time, 30 min extraction time, and 50 mL/g solvent to sample ratio. Under these MAE parameters, total phenolic content (TPC), phenolic extraction efficiency (PEE), saponin content (SC), and DPPH radical scavenging capacity (DRSC) were achieved from the CPH to be 10.97 mg GAE/g dried sample, 76.82%, 70.10 mg EE/g dried sample, and 141.18 mg DPPH/g dried sample, respectively, which were not significantly different from the predicted values (10.38 mg GAE/g dried sample, 72.68%, 70.09 mg EE/g dried sample, and 121.49 mg DPPH/g dried sample, respectively). The residual moisture, water activity, density, water-soluble index and pH of powdered CPH extract were 9.72%, 0.38, 0.17 g/ml, 84.93% and 7.68, respectively. TPC, total flavonoid content (TFC) and SC of powdered CPH extract were 15.75 mg GAE/g dried sample, 27.03 mg CE/g dried sample and 133.67 mg EE/g dried sample, respectively. DRSC and ferric reducing antioxidant power (FRAP) of powdered CPH extract were 227.79 mg DPPH/g dried sample and 14.12 mg Fe(II)/g dried sample, respectively. Conclusion: The findings from this study reveal that the powdered extract obtained from the CPH at the optimal MAE parameters is a rich source of phytochemicals possessing great antioxidant activity. Therefore, it is a potential candidate to apply in functional foods.

Effects of Temperature and Extraction Time on Avocado Flesh (Persea americana) Total Phenolic Yields Using Subcritical Water Extraction

This paper investigates the optimum extraction temperature for enhanced total phenolic yields extracted from avocado fruit flesh (Persea americana) using subcritical water extraction, as well as the impact of fruit ripeness on phenol extraction efficiency. Additionally, extraction yield against extraction time was investigated for time intervals of 10 min over an overall extraction time of 30 min. The subcritical water conditions studied were 18 bar, 87 mL/min, and temperatures of 105 °C, 120 °C, and 140 °C. The total phenolic compounds content was compared for week one avocado flesh and ripe (week four) avocado flesh, with a four-week ripening period between the two samples. The results show that extracting with subcritical water at 105 °C provides the highest phenolic compounds yields of 0.11% and 0.26% by dried mass for week one and ripe fruit (week four), respectively. The experimental results also indicate that the implementation of lower extraction temperatures on week four avocado (i.e., following the selection of week one avocados and allowing them to ripen over a period of one month) enhances the phenolic compounds extraction yields by more than four times relative to the first week’s sample extract, specifically during the first 20 min of extraction.

Extraction of phenolic pollutants from industrial wastewater using a bulk ionic liquid membrane technique

ABSTRACT The academia and chemical industry are actively searching for alternative solvents to meet technology requirements since the most widely used solvents are harmful and volatile. For ionic liquids, there are several advantages over conventionally using organic membrane solvents, including high thermal stability, negligible vapour pressure, low volatility, etc. Here in this study, we have analyzed the abilities of ionic liquids as pure solvents as well as their binary mixtures, to recover phenolic compounds from the industrial wastewater. The field of phenol extraction from wastewater using ionic liquids remains less exposed, and we presume that the work of this kind would open up more and more opportunities for the scientific community as well as industrial people. Based on all these assumptions, the present work includes experimental data of a work which explains the possibilities of room temperature ionic liquids (RTILs) as potential bulk liquid membranes (BLM) for extracting phenol and other phenolic compounds from the industrial affluents. Four high hydrophobicity ionic liquids namely: 1-hexyl-3-methylimidazolium hexafluorophosphate [Hmim][PF6], 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide [Bmim][NTf2], 1-butyl-3-methylimidazolium hexafluorophosphate [Bmim] [PF6] and 1-ethyl-3-methyimidazolium bis(trifluoromethanesulfonyl) imide [Emim][NTf2] were used for investigating the Phenol extraction efficiency and stripping efficiency. To provide a best comprehension of the influence of the phenolic structure as well as the nature of cation on the extraction ability of the ILs, we tried to understand the molecular interactions between the phenolic compounds and the solvents. The influence of hydrophobicity of ionic liquids and different kinds of anions on the extraction of phenol and efficiencies of stripping were investigated. All the experimental investigations performed here indicated that the only cation part of the ionic liquid is not an important aspect directly in this extraction, but the hydrogen bonding and the solute-solvent interactions play a significant role in the phenol removal process from aqueous phase to IL phase. First, the optimal conditions of operating (settling time and stirring) were analyzed for the clarity of the experiments performed. Concentration of NaOH in enhancing the performance of ionic liquids was also inspected here in this study. A binary mixture of ionic liquids (BMILs) membrane was examined for the optimized parameters, and the efficiency of phenol extraction was analyzed with the efficiency obtained for the single ionic liquid (SIL) membranes. The phenol concentration was determined by UV/visible spectrophotometer absorbance measurements. The highest phenol extraction efficiencies of 91% and 98.5%, were achieved by using [Bmim][NTf2] and [Bmim][NTf2+PF6] respectively, and the higher stripping efficiencies came up with 79% and 84% respectively, for [Emim][NTf2] and [Bmim + Emim][NTf2]. The results show that the binary mixture ionic liquid (BMIL) membrane is a better choice than single ionic liquid (SIL) membrane solvents. Hence, [Bmim] [(NTf2+PF6)] is an excellent selection as it provides high phenol stripping and extraction efficiencies with a minimal solvent loss and better stability in transport process.

Application of a Sustainable Bioderived Solvent (Biodiesel) for Phenol Extraction.

Replacement of volatile organic compound solvents by greener or more environmentally sustainable solvents is becoming increasingly important due to the increasing health and environmental concerns. In the present work, a bioderived solvent, soybean oil methyl ester, which is better known as biodiesel and is a nonvolatile organic compound, was used as a solvent to replace the fossil solvent (kerosene) for phenol extraction. First, biodiesel was selected as an optional solvent to replace kerosene based on Hansen solubility parameter calculation results. Second, the effects of solvent concentration, equilibrium pH of the aqueous phase, temperature, extraction time, etc. on phenol extraction were examined. The results show that biodiesel has strong extraction ability on phenol extraction than that of kerosene. An acidic environment decreases the phase disengagement time. Phenol extraction reached equilibrium in 30 s of contact time at room temperature. McCabe–Thiele diagram calculation results show that the phenol extraction efficiency can reach 98% in three theoretical stages at an A/O ratio of 10:1 (Cyanex923 + biodiesel). Finally, the extraction mechanism indicated that biodiesel could reduce the intermolecular hydrogen bond forces in the extractant so as to improve the extraction efficiency.

Enhanced mechanical properties of PDMS/PMMA composite membrane using MWCNTs and its application in phenol separation from saline wastewater

ABSTRACTThis work describes the enhanced mechanical properties of composite polydimethylsiloxane/poly(methyl methacrylate) (PDMS/PMMA)/multi‐walled carbon nanotubes (MWCNTs) nanofiber membrane and its application in the phenol separation from saline wastewater. MWNCTs with varied content were immobilized in the membrane matrix using electric field of electrospinning. The neat PDMS/PMMA and composite PDMS/PMMA/MWCNTs membranes were characterized by scanning electron microscopy, universal testing machine, contact angle measurement, 3D automatic optical profiler, and pore size analyzer. Results indicated that tensile strength of composite PDMS/PMMA/MWNCTs membrane was drastically increased six times with a water contact angle (WCA) of 163.3° due to increased roughness parameters compared to neat membrane. However, porosity and fiber diameter of PDMS/PMMA/MWCTs membrane decreased with the increase of MWCNTs content. Moreover, phenol extraction efficiency of PDMS/PMMA/MWNCTs membrane was found to be 34.5% higher than neat one with similar salt rejection efficiency of 99.97%. The stability of MWCNTs in the membrane matrix was confirmed by the cross‐sectional morphology, which indicated the robust and novel design of membrane. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47123.

Sulfonate based zwitterions: A new class of extractants for separating phenols from oils with high efficiency via forming deep eutectic solvents

To develop a greener method to separate phenols from oils, four kinds of halogen-free zwitterions, including 1-(propyl-3-sulfonate)-triethylaminium (TEA-PS), 1-(propyl-3-sulfonate)-tripropylaminium (TPA-PS), 1-(butyl-4-sulfonate)-triethylaminium (TEA-BS) and 1-(butyl-4-sulfonate)-tripropylaminium (TPA-BS), were designed and synthesized to separate phenols from model oils via forming deep eutectic solvents (DESs) based on the formation of hydrogen bonding between OH group on phenol and the oxygen atom on SO3− group of the zwitterions. The effects of time, temperature, dosage of zwitterions, initial phenol content, and structure of zwitterions were investigated. The results show that the extraction process can reach equilibrium within 2 min and the extraction efficiency is not sensitive to temperature. The zwitterions separate well phenol from model oils at room temperature, and the minimum phenol contents follow the order: TEA-PS > TPA-PS > TEA-BS > TPA-BS. The minimum phenol content and the maximum extraction efficiency at 25 °C can reach 4.8 g dm−3 and 98.6%, respectively, by using TPA-BS. All the maximum extraction efficiency can be obtained with nzwitterions:nphenol of less than 0.4, which greatly reduces the dosages of extractants. Importantly, these zwitterions can avoid the introduction of halide ion, which can seriously corrode the process equipment. All these zwitterions can be easily regenerated by an anti-solvent method without an obvious mass loss and a decrease in phenol extraction efficiency. Lastly, the extraction mechanism was studied with FT-IR and the freezing points of DESs indicate that the DESs are formed through hydrogen bonding.

Efficient separation of phenolic compounds from model oils by dual-functionalized ionic liquids

Four kinds of dual-functionalized ionic liquids (DFILs, [Et2NEmim][Cl]2, [Et2NEmmor][Cl]2, [Et2NEmpyr][Cl]2 and [Et2NEmpic][Cl]2) were synthesized and used to efficiently separate phenolic compounds from model oils. The effects of stirring time, temperature, mole ratio of DFIL to phenol and initial phenol content on the separation were investigated. The results indicate that at a DFIL:phenol mole ratio of 0.3, the content of phenol in the oil phase can reach the minimum value and the extraction efficiency of phenol is more than 96%. The minimum phenol content in the oil phase and the best phenol extraction efficiency were 5.9 g/m3 and 98.5%, respectively, when [Et2NEmpyr][Cl]2 was used. Compared with traditional ionic liquids, these DFILs not only reduce the dosage of extraction agents but also greatly decrease the content of Cl− in the oil phase due to the double anion in the DFILs. The DFILs can be reused for 4 cycles without losses in phenol extraction efficiency and masses of the DFILs. The separation mechanism of extraction was studied using FT-IR. The result indicates that the two anions Cl− on DFILs can form a hydrogen bond with phenol.

Design, development and evaluation of nanofibrous composite membranes with opposing membrane wetting properties for extractive membrane bioreactors

Extractive membrane bioreactors (EMBRs) are promising wastewater treatment processes combining an aqueous-aqueous extractive membrane process and biodegradation. The target contaminants diffuse through an extractive membrane and are metabolized by the active biofilm attached on the downstream membrane surface and microorganisms in the bioreactor. The benefit of EMBRs is that the biomass is not exposed to the potentially hostile feed conditions (high salinity, pH extremes etc.). The physicochemical properties of membrane surfaces on the receiving side facing the bioreactor are critical in controlling the extent and nature of the membrane-attached biofilm. In this work, novel nanofibrous composite membranes with a superhydrophobic surface (coded as NC) or a superhydrophilic surface (coded as M-NC) on the receiving side have been designed, developed and evaluated in EMBRs. Compared to commercial polydimethysiloxane (PDMS) tubular membranes, both NC and M-NC possessed 10 times higher phenol extraction efficiency in an aqueous-aqueous extractive membrane process. The uncontrolled biofilm growth on the membrane surface after 12 days of cross flow EMBR (CF-EMBR) operation resulted in 62% reductions of overall mass transfer coefficients (k0) of both NC and M-NC. However, both membranes exhibited better performance in a submerged EMBR (S-EMBR) configuration due to the presence of air bubbles scouring on the membrane surface. Moreover, the fouling-releasing fluoro-polymeric surface of the hydrophobic NC was able to attenuate the tendency of microbial attachment and encourage biofilm scouring from the membrane surface in the S-EMBR. In contrast, more polysaccharides were present in the biofilm on the poly (ethylene glycol) (PEG)-modified M-NC surface, which acted as adhesives to tightly immobilize the biofilm on the membrane surface. Lastly, the NC which exhibited a higher stable k0 of 5.7 × 10−7m/s in 12 days of S-EMBR operation, has been tested in a pilot S-EMBR to treat actual industrial wastewater. It showed a stable and competitive k0 of 6.5 × 10−7m/s in 31 days operation, demonstrating its feasibility for hostile industrial wastewater treatment.

Highly efficient extraction of phenolic compounds from oil mixtures by trimethylamine-based dicationic ionic liquids via forming deep eutectic solvents

In this article, dicationic ionic liquids (DILs), including N,N,N,N′,N′,N′-hexaethyl-ethane-1,2-diammonium dibromide (HEDBr), N,N,N,N′,N′,N′-hexaethyl-propane-1,3-diammonium dibromide (HPDBr) and N,N,N,N′,N′,N′-hexaethyl-butane-1,4-diammonium dibromide (HBDBr), were designed and used to extract phenolic compounds from model oil and coal tar oil. The effects of stirring time, temperature, DIL:phenol mole ratio, and initial phenol concentration on the extraction of phenol were studied. It is found that the DIL:phenol mole ratio is only around 0.3 when the highest extraction efficiency of phenol is obtained. The extraction process completes within 5min at room temperature, and the extraction efficiency is not dependent on temperature. Also, the ultimate phenol concentration remains constant despite the difference in initial phenol concentrations. Of these DILs, HPDBr shows the lowest ultimate phenol concentration of 3.9g/dm3, and the extraction efficiency of phenol can reach as high as 97.0%. These DILs can be regenerated by anti-solvent method and reused several times without significant reduction in extraction efficiency. In addition, HPDBr was demonstrated to extract phenolic compounds from real coal tar oil, and its extraction efficiency of phenolic compounds is 92.7%. The mechanism, analyzed by FT-IR, shows that there is a hydrogen bond between phenol and DIL.

Determination of Phenols Isomers in Water by Novel Nanosilica/Polydimethylsiloxane-Coated Stirring Bar Combined with High Performance Liquid Chromatography-Fourier Transform Infrared Spectroscopy

A novel nanosilica/polydimethylsiloxane (SiO2/PDMS) coated stirring bar was adopted in the sorption extraction (SBSE) of phenols in water, and the high performance liquid chromatography-fourier transform infrared spectroscopy (HPLC-FTIR) was subsequently used to determination of phenol concentration. The SiO2/PDMS coating was prepared by sol-gel method and characterized with respect to morphology and specific surface area. The results of field-emission scanning electron microscope (FE-SEM) and N2 adsorption-desorption as well as phenol adsorption experiments denoted that SiO2/PDMS has larger surface area and better adsorption capacity than commercial PDMS. The extraction efficiency of phenol with SiO2/PDMS coated stirring bar was optimized in terms of ion strength, flow rate of phenol-involved influent, type of desorption solvent and desorption time. More than 75% of phenol desorption efficiency could be kept even after 50 cycles of extraction, indicating the high stability of the SiO2/PDMS coated stirring bar. Approximately 0.16 mg/L 2, 5-dimethylphenol (2, 5-DMP), which was 34-fold more toxic than phenol, was detected in water through HPLC-FTIR. However, 2, 5-DMP could be oxidized to 5-methy-2-hydroxy benzaldehyde after disinfection in drinking water treatment process. Therefore, the proposed method of SiO2/PDMS-SBSE-HPLC-FTIR is successfully applied in the analysis of phenols isomers in aqueous environment.