Phenol Flux Research Articles

A novel electro-Fenton hybrid system for enhancing the interception of volatile organic compounds in membrane distillation desalination

Membrane distillation (MD) is a promising alternative desalination technology, but the hydrophobic membrane cannot intercept volatile organic compounds (VOCs), resulting in aggravation in the quality of permeate. In term of this, electro-Fenton (EF) was coupled with sweeping gas membrane distillation (SGMD) in a more efficient way to construct an advanced oxidation barrier at the gas-liquid interface, so that the VOCs could be trapped in this layer to guarantee the water quality of the distillate. During the so-called EF-MD process, an interfacial interception barrier containing hydroxyl radical formed on the hydrophobic membrane surface. It contributed to the high phenol rejection of 90.2% with the permeate phenol concentration lower than 1.50 mg/L. Effective interceptions can be achieved in a wide temperature range, even though the permeate flux of phenol was also intensified. The EF-MD system was robust to high salinity and could electrochemically regenerate ferrous ions, which endowed the long-term stability of the system. This novel EF-MD configuration proposed a valuable strategy to intercept VOCs in MD and will broaden the application of MD in hypersaline wastewater treatment.

Separation and phenol recovery from resin effluents by ultrafiltration. A proposal to use this method on an industrial scale

Phenol separation-concentration from phenolic resin effluents using ultrafiltration membranes for phenol recovery was studied for the purposes of this work. Ultrafiltration membranes, used at both laboratory and pilot scale, provided the requisite experimental data for the creation of an industrial-level proposal. The feasibility of the large-scale use of membranes was assessed, and phenol rejection and permeation at the industrial level were predicted by calculating mass transfer coefficients, using diffusion models and the Lévêque relationship. DWSIM - Open Source Chemical Process Simulator software was used to predict the rejection and permeation of phenol at the industrial scale. Scale experiments revealed that 82-84% of phenol was recovered; the mass transfer coefficient indicated a high level of water permeation through UF membranes, with a prediction of phenol rejection with an 8% margin for error, relative to pilot scale data. The membrane area for industrial requirements resulted in 9 m2 with 3000 Da. According to the simulation software, the phenol flux in the reject and permeate streams was consistent with experimental data, demonstrating the similarity between the membrane scales.

Enhancing the pervaporation performance of PEBA/PVDF membrane by incorporating MAF-6 for the separation of phenol from its aqueous solution

Phenol is highly toxic and carcinogenic even at low concentrations. This study focused on preparing high-performance mixed matrix membranes (MMMs) for the pervaporation separation of phenol from its aqueous solution. A highly-efficient zeolitic metal azolate framework, RHO-[Zn(Heim)2] (MAF-6, Heim = 2-ethylimidazole) was incorporated into the polyether block amide (PEBA-2533) supported on the polyvinylidene fluoride (PVDF) ultrafiltration membrane. The MAF-6 was chosen as the filler due to its inherent hydrophobic surfaces and aperture size (7.6 Å), which is larger than the molecular kinetic diameter of phenol (6.6 Å). Effects of the casting solution concentration, active layer thickness, MAF-6 loading, operating temperature, and phenol concentration were systematically investigated. With the increase of the MAF-6 loading ratio X from 0 to 7, the phenol flux of the membrane was gradually enhanced, but the water flux was reduced. For 1000 ppm phenol aqueous solution at 80 °C, MAF-6–7@MMM displayed the optimal separation factor of 25.9 with a phenol flux of 89.2 g∙m−2∙h−1. The pervaporation separation index (PSI) of the MAF-6–7@MMM was 1317.7 kg∙µm∙m−2∙h−1 at 80 °C, which was much higher than the PEBA/PVDF membrane (787 kg∙µm∙m−2∙h−1). Impressively, an increasing feed temperature enhanced the phenol flux more prominently than water, owing to the hydrophobicity and porosity of MAF-6. Consequently, the resultant MAF-6-X@MMMs broke the trade-off limitation between phenol permeability and selectivity. The as-prepared membrane also exhibited exceptional long-term stability, suggesting its prospect of industrial application.

Preparation of a thin-film nanocomposite forward osmosis membrane for the removal of organic micro-pollutants from aqueous solutions

ABSTRACT In this study, a thin-film nanocomposite forward osmosis (TFN FO) membrane was synthesized. The properties and structures of membranes were evaluated for the removal of three organic micro-pollutants from synthetic and real industrial wastewater samples. Laboratory scale fabrication thin-film nanocomposite forward osmosis (FO) membranes composed of a support layer and an active layer. The former was constructed by adding different weight ratios of polyethylene glycol 400 (PEG-400) (0–8 wt.%), polysulfone (PSf), and 1-methyl, 2-pyrrolidone via the phase inversion process, while the latter was synthesized by the incorporation of different weight ratios of graphene oxide (GO) (0–0.012 wt.%), M-phenylenediamine, and 1, 3, 5-benzene trichloride into polyamide layer through the interfacial polymerization reaction. In comparison with thin-film composite (TFC) membranes, the TFN membranes revealed higher hydrophilicity, porosity, water permeability, water flux and salt rejection and lower internal concentration polarization (ICP), reverse salt flux and specific reverse salt flux. The TFN membrane containing 0.008% GO in the active layer and 4% PEG 400 in the support layer exhibited maximum water flux (34.3 LMH) and rejection rate of benzene, phenol and toluene (97%, 84%, and 91%, respectively). The results revealed that the TFN-FO membranes possess a promising potential to improve the water flux and wastewater treatment.

Pervaporation properties of oleyl alcohol-filled polydimethylsiloxane membranes for the recovery of phenol from wastewater

In the present work, the modified polydimethylsiloxane (PDMS) membranes incorporated by oleyl alcohol (OA) were prepared for the first time. The polymeric membranes were characterized by Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), and scanning electron microscopy (SEM) before and after modification. These membranes were used for the pervaporative separation of phenol from wastewater. The effects of OA loading and feed temperature on the pervaporation performances have been investigated. The influence of ignoring the partial pressure at the permeate side was compared and discussed. The results showed that the OA presence increased phenol flux and separation factor, and decreased water flux greatly with less than 9 wt% OA loading. The highest pervaporation separation index was obtained with 5 wt% OA loading. The driving force of phenol across the membranes was much lower than that of water, and permeation of phenol was much higher than water in nature. It is necessary to discuss and compare the intrinsic properties of different membranes using permeation and selectivity, even though the membranes are tested under the same feed temperature and concentration. The partial pressure of phenol at the permeation side cannot be simply omitted for its great effect on the permeation. Increasing feed temperature will result in the increase of flux and separation factor, but decrease of permeation.

Pervaporative performance of polydimethylsiloxane–graphene/polyethersolfune hybrid membrane: Effects of graphene structure and surface properties

Graphene was produced either by chemical reduction of graphene oxide (GO) using hydrazine hydrate (HG)/sodium borohydride (BG) or by straight electrochemically exfoliation of graphite (EG). The X-ray diffraction and Raman spectroscopy confirmed smaller in-plane crystalline sizes for the chemically produced graphenes, and more number of layers and therefore lower structural defects for the EG sample.The graphene samples were used to prepare polydimethylsiloxane (PDMS)–graphene (G)/polyethersulfone (PES) hybrid membranes to investigate their pervaporative performances. All three produced hybrid membranes had better separation performances for removal of phenol from water in terms of phenol flux and selectivity compared to the unfilled membrane (1.3g/m2h and 11.09, respectively). An appropriate interfacial structure for the BG- and HG-filled membranes (having lower number of layers) was achieved at 0.2wt% graphene content while for the EG-filled membrane, it was attained at 0.4wt% graphene content. PDMS–BG/PES had the highest phenol flux of 3.6g/m2h due to the lowest carboxylic functional groups and highest C/O ratio of the filler, and PDMS–HG/PES had the best selectivity of 40.02 due to the lowest C/O ratio of the filler and hence the lowest water flux.

Characterisation and quantification of changes in odorants from litter headspace of meat chickens fed diets varying in protein levels and additives

The effect of dietary crude protein (CP) and additives on odor flux from meat chicken litter was investigated using 180 day-old Ross 308 male chicks randomly allocated to five dietary treatments with three replicates of 12 birds each. A 5 × 3 factorial arrangement of treatments was employed. Factors were: diet (low CP, high CP, high CP+antibiotic, high CP+probiotic, high CP+saponin) and age (15, 29, 35 days). The antibiotic used was Zn bacitracin, the probiotic was a blend of three Bacillus subtilis strains and the saponin came from a blend of Yucca and Quillaja. Odorants were collected from litter headspace with a flux hood and measured using selective ion flow tube mass spectrometry (SIFT-MS). Litter moisture, water activity (Aw), and litter headspace odorant concentrations were correlated. The results showed that low CP group produced lower flux of dimethyl amine, trimethyl amine, H2 S, NH3, and phenol in litter compared to high CP group (P < 0.05). Similarly, high CP+probiotic group produced lower flux of H2 S (P < 0.05) and high CP+saponin group produced lower flux of trimethylamine and phenol in litter compared to high CP group (P < 0.05). The dietary treatments tended (P = 0.065) to have higher flux of methanethiol in high CP group compared to others. There was a diet × age interaction for litter flux of diacetyl, 3-hydroxy-2-butanone (acetoin), 3-methyl-1-butanol, 3-methylbutanal, ethanethiol, propionic acid, and hexane (P < 0.05). Concentrations of diacetyl, acetoin, propionic acid, and hexane in litter were higher from low CP group compared to all other treatments on d 35 (P < 0.05) but not on d 15 and 29. A high litter moisture increased water activity (P < 0.01) and favored the emissions of methyl mercaptan, hydrogen sulfide, dimethyl sulfide, ammonia, trimethyl amine, phenol, indole, and 3-methylindole over others. Thus, the low CP diet, Bacillus subtilis based probiotic and the blend of Yucca/Quillaja saponin were effective in reducing the emissions of some key odorants from meat chicken litter.

Threshold flux and limiting flux for micellar enhanced ultrafiltration as affected by feed water: experimental and modeling studies

Micellar enhanced ultrafiltration is a promising technology for removing trace amounts of organic pollutants in wastewater, but membrane fouling caused by Gemini micelles is a significant problem restricting its industrial application. In this study, a flat sheet ultrafiltration membrane with four types of Gemini surfactant systems and various feed concentrations was used to treat phenol wastewater, while the flux behavior and fouling mechanism were investigated. The optimal permeate flux of phenol decreased in the sequence as follows: CG12 > CG16 > CG12 − Brij35 > CG16 − Brij35. In order to study the rate of membrane fouling, a developed liner regression method was utilized to help determine the threshold flux, as well the degree of concentration polarization and membrane fouling. Furthermore, limiting flux was investigated to avoid extensive cake layer formation. Threshold flux and limiting flux strongly depended on the feed concentration and the type of micelles. The threshold flux reduced gradually with feed concentration, due to the increased fouling rate and presence of irreversible fouling. Owing to the effect of charge density and hydrophobicity of micelles, CG12 exhibited the highest threshold flux and limiting flux. Flux-TMP relation was divided into three regions for analyzing the corresponding changes of permeate flux, filtration resistance and conceptual particle deposition model. Besides, fouling mechanism of MEUF was discussed. This study provides a guideline for analyzing membrane fouling and seeking an optimum operation strategy for controlling fouling in membrane water treatment.

Preparation and Photocatalytic Properties of ZnO Thin Films

Highly photoactive ZnO thin films on glass substrates and quartz substrates have been prepared by sol-gel process. Structural features, surface morphology and UV absorption spectrum have been studied by XRD, SEM and UV-Vis scanning spectrophotometer. The influence of degradation temperatures, original concentration of phenol and air flux on degradation rates have also been studied. And the results show the best conditions, degradation temperature is between 25oC and 45 oC, air flux is 40ml/min, the lower original concentration, the higher degradation rates. Excellent adhesion as well as recyclable and efficient in phenol degradation of ZnO thin films were found in this experiment.

Pervaporation Process with PDMS/PVDF Hollow Fiber Composite Membrane to Recycle Phenol from Coal Chemical Wastewater

To treat coal gasification wastewater containing phenol, polydimethylsiloxane (PDMS)/polyvinylidene fluoride (PVDF) hollow fiber composite membrane was made by dynamic negative pressure coating method, using PVDF hollow fiber membrane as base membrane, PDMS as modifying membrane material, to improve pervaporation performance of PDMS by the cross-linking modification. The influence of cross-linking agent, PDMS concentration, coating time on pervaporation performance of the composite membrane was investigated. Actual coal chemical wastewater with phenol concentration 1600-1800 mg/L, COD 13000-15000 mg/L was treated by the obtained PDMS/PVDF composite membrane, and at temperature 70℃, the flow rate of 10 L/h, pressure under membrane 3KPa, phenol flux 16.81 g/(m2·h), separation factor reaches 8.103.

Benzene Hydroxylation and Simultaneous Extraction of Phenol in Two Membrane Contactors Made with Three-Compartment Cells

Two different three-compartment membrane contactors [called solid membrane contactor (SMC) and liquid membrane contactor (LMC)] were tested in the synthesis and separation of phenol produced by direct hydroxylation of benzene using a Fenton reaction. Phenol produced in the aqueous reacting phase was extracted in the organic phase and simultaneously stripped in the basic aqueous phase. Preliminary tests on phenol recovery evidenced better performances (86.5% of phenol recovered in the strip phase) using the SMC with 0.1 M Na2SO4 in the aqueous feed phase at 35 °C. In the tests of partial oxidation, higher phenol productivity (0.62 gph gcat–1 h–1) was obtained in this last system because the high phenol flux away from the reacting phase permitted one to extract a high amount of phenol in the organic and aqueous (strip) phases. This extraction protected phenol by its subsequent oxidation. It was evidenced that the use of a third compartment containing an alkaline aqueous stripping phase permitted one to reco...

Separation of Phenol from Aqueous Streams by a Composite Hollow Fiber Based Pervaporation Process Using Polydimethyl siloxane (PDMS)/Polyether-Block-Amide (PEBA) as Two-Layer Membranes

In order to simultaneously achieve both high permselectivity and permeability (flux) for the recovery of aromatic compounds such as phenol from aqueous streams, a composite organophilic hollow fiber based pervaporation process using PDMS/PEBA as two-layer membranes has been developed. The process employed a hydrophobic microporous polypropylene hollow fiber, having thin layers of silicones (PDMS) and PEBA polymers coating on the inside diameter. The composite membrane module is used to investigate the pervaporation behavior of phenol in water in a separate study; and that of a mixture of phenol, methanol, and formaldehyde in an aqueous stream (a typical constituent of wastewater stream of phenol-formaldehyde resin manufacturing process) in another study. The fluxes of phenol and water increase relatively linearly with increasing concentration especially at low feed concentration, and exhibit a near plateau with further increase in concentration. As a result, the phenol/water separation factor decreases as the feed concentration increases. Significant improvement in phenol/water separation factor and phenol flux is achieved for this two-layer (PDMS/PEBA) membranes as compared to that achieved using only PDMS membrane. The phenol and water fluxes and the separation factor are highly sensitive to permeate pressure as all decrease sharply with increase in permeate pressure. For this membrane, an increase in temperature increases the separation factor, and also permeation fluxes of phenol and water. An increase in feed-solution velocity does not have a significant effect on phenol and water fluxes, and also on the separation factor at least within the range of the feed-solution velocity considered. In the study of pervaporation behavior of a typical constituent of wastewater stream of phenol-formaldehyde resin manufacturing process, phenol permeation shows a much higher flux and a higher increase in flux with increase in concentration is also exhibited as compared to that exhibited by methanol permeation. This thus indicates that the membrane is more permeable to phenol than to methanol and formaldehyde.

Direct benzene conversion to phenol in a hybrid photocatalytic membrane reactor

The one-step conversion of benzene to phenol in a photocatalytic membrane reactor (PMR) coupling simultaneous reaction and product separation by means a membrane contactor is reported. The effects of parameters such as pH of aqueous TiO 2 suspensions, initial amount of benzene and catalyst concentration were investigated in the batch tests. L–L extraction experiments and transport tests, using benzene as organic extractant, showed a phenol distribution coefficient of 2.1 and an extraction percentage of 24 ± 2%, assuring, also, a constant feed of substrate in the reactive environment. Phenol production and separation was carried out in the PMR investigating the influence of pH and catalyst concentration on the performance of the system. Despite a negligible difference on the phenol flux in the benzene phase (1.16 ± 0.11 mmol h −1 m −2), a better control of formation and extraction of oxidation intermediates at pH of 3.1 was obtained. To enhance the performance of the system, photocatalytic experiments with dissolved ions (Fe 3+, Cu 2+ and V 3+) were carried out. The results showed a positive effect in presence of iron(III) ion with a phenol flux in the organic phase almost two times greater than those measured without salts.

Use of pervaporation for the separation of phenol from dilute aqueous solutions

Separation of phenol from dilute aqueous solutions by pervaporation using poly(ether block amide) (PEBA 2533) membranes was investigated as a means of recovering phenol from wastewater streams. The effects of feed concentration (up to 1 wt%) and operating temperature (50–80 °C) on the separation performance were studied in terms of permeation flux and selectivity. Although the phenol flux increased as its feed concentration rose, the rate at which it increased diminished at higher concentration, resulting in a decrease in the enrichment factor. It was also shown that an increase in temperature increased both the phenol flux and selectivity. Experiments conducted to study the preferential sorption of the permeant in the membrane with respect to the membrane permselectivity found that the phenol concentration in the sorbed phase could reach as high as 80–90 wt% at a phenol concentration of ∼2 wt% in the aqueous solution. The high permselectivity of the membrane to phenol was primarily due to its high solubility selectivity. It should be noted that this high permselectivity can cause the concentration of phenol in the permeate to become high enough for it to precipitate. This is of particular interest from an industrial point of view because the enriched phenol permeate can be easily recovered upon phase separation.

Micellar enhanced ultrafiltration of phenol in synthetic wastewater using polysulfone spiral membrane

The micellar enhanced ultrafiltration (MEUF) of phenol in synthetic wastewater using two polysulfone spiral membranes of 6- and 10-kDa molecule weight cut-off (MWCO) and cetylpyridinium chloride (CPC) as cationic surfactant was studied. The effects on the permeate flux, permeate and retentate concentrations of phenol and CPC of various factors in the practical application of MEUF were studied, including surfactant and phenol concentrations, retentate flux, operating pressure, temperature and electrolyte. It was found that these two membranes could adsorb free phenol so the concentration of permeate phenol was lower than that of free phenol. The retentate phenol concentration kept increasing, then decreased slightly with the increase of the feed CPC concentration. Retentate flux and temperature had great effect on the performance of MEUF, and operating pressure did not. The addition of sodium carbonate (Na 2CO 3) could increase the retentate phenol concentration and decrease the permeate concentrations of phenol and CPC significantly.

Permeation Flux of Organic Molecules through Silica-surfactant Nanochannels in a Porous Alumina Membrane

The permeation fluxes of phenol, benzene sulfonate (BS) and benzene disulfonate (BDS) through a porous anodic alumina membrane with the perpendicularly oriented silica-surfactant nanochannel assembly membrane (NAM) were measured in water-ethanol mixture media. The permeation flux depended on solute charges and on solvent composition. As the ethanol ratio increased, the fluxes of BS and BDS increased and the flux of phenol decreased. The results of extraction/elution experiments also depended on the solute charges and the solvent composition. Chromatographic experiments in n-hexane showed that dipole and hydrophobic interactions affect the retention of solutes. Permeation of the solute across the NAM in water-ethanol mixture is likely to be determined by various factors such as dipole interaction, hydrophobic interaction, solvation, and anion-exchange efficiencies.

Separation of phenol from aqueous solution by membrane pervaporation using modified polyurethaneurea membranes

AbstractHydroxy‐terminated polybutadiene‐based porous and nonporous polyurethaneurea membranes were prepared and used to study the phenol separation efficiency from dilute aqueous solution. The porosity was developed by incorporation of lithium chloride in polymer matrix with subsequent leaching of the same in hot water. The porous membrane showed higher phenol flux over that of nonporous membrane. Permeate containing about 97 wt % phenol was obtained from feed containing 7 wt % phenol, when pervaporation was carried out with porous polyurethaneurea membrane at 75°C. The activation energies for diffusion, permeation, and pervaporation were calculated from Arrhenius plots. From the activation energy values, it was observed that the pervaporation process became easier with increased phenol concentration in the feed and porosity of the membrane used. The membrane boundary resistance was observed to decrease with increase in temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1857–1865, 2006

Extraction and pertraction of phenol through bulk liquid membranes

AbstractThe extraction and pertraction of phenol through a bulk liquid membrane (BLM) with Cyanex® 923, Amberlite® LA‐2 and trioctylamine (TOA) as carriers were studied. Cyanex® 923 was selected as the best carrier for pertraction. The distribution coefficient of phenol for solvents with carrier and pure n‐alkanes, the individual mass‐transfer coefficient at the extraction interface and the initial flux of phenol through the extraction interface (JFo) decreased in the order: Cyanex® 923 &gt; Amberlite® LA‐2 &gt; TOA ≫ pure n‐alkanes. The opposite order was observed for the value of the mass‐transfer coefficient in BLM and the maximum flux of phenol through the stripping interface (JRmax). At constant driving forces the maximum fluxes through the extraction and stripping interfaces were similar when amine carriers were used. However, JRmax was lower than JFo for Cyanex® 923. Although the kinetics of stripping was the rate‐determining step, the flux of phenol was significantly higher than in pertraction with amine carriers. The adsorption of the carrier at aqueous phase/membrane interfaces was probably responsible for the rapid and slow transfer of phenol through the extraction and stripping interface, respectively. Copyright © 2004 Society of Chemical Industry

Method to determine molecular diffusivities of phenol in bitumen

AbstractPhenols, carboxylic acids and other water‐soluble compounds in bitumen constitute a potential source of groundwater pollution. To assess the extent of damages that could result from a spill, a water extraction method was used to determine the molecular diffusion of phenol in bitumen. This method involves the diffusion of phenol through bitumen into the flowing water in a well‐stirred cell. From the phenol concentration in water, the phenol flux and hence the phenol diffusion coefficient in bitumen can be deduced. An approximate dimensionless solution was obtained by de‐coupling the diffusional flux from the concentration buildup in water. The phenol diffusion coefficient was determined to be 4.0 ± 0.3 × 10−8 m2/s at 22°C. The derivation and the properties of the dimensionless solution were also discussed in the paper.

Phenol Removal by Supported Liquid Membranes

Abstract This paper examines the application of the supported liquid membrane (SLM) to phenol removal. n-Decanol was proven to be a suitable membrane liquid. The phenol transfer kinetics through the SLMs is quantitatively estimated according to models based on the resistance-in-series concept. The models can be modified to describe the performance of decayed SLMs and thereby provide insight into the effect of membrane liquid loss and penetration of aqueous solutions on the phenol flux. An experimental method is described for the measurement of mass transfer coefficients in the bulk phases using the well-characterized Anopore membrane.