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A pilot scale vapor permeation unit was assembled to study the dehydration of bioethanols with NaA membrane. The operational parameters, such as feed concentration, temperature, and downstream pressure in permeate, were varied. Long-term operation of an ethanol dehydration unit was demonstrated. Additionally, the lingocellulosic ethanol distillate was dehydrated to fuel grade ethanol with less than 1% water content. The changes in impurities, such as methanol, ethylacetate, 2-propanol, 1-propanol, 1-butanol, and Isoamyl alcohol, were dependent on the volatility of the compounds. The ethanol concentrations in the permeate stream were lower than 1%, indicating high separation performance of the membrane system.

Ternary alloys of ZnMgO samples with different magnesium contents have been grown by molecular beam epitaxy on the sapphire substrates. Room temperature photoluminescence energy of ZnMgO shifted as high as 3.677 eV by increasing Mg contents corresponding to the higher Urbach average localization energy which indicates more randomness in the alloys with higher Mg contents. XRD results are also verified that the c-axis length decreases as the increasing Mg contents linking to the increased tensile stress produced by the Mg atoms. Raman spectra analyzed by the spatial correlation model to describe that the linewidth Γ is decreased but the correlation length L is increased as the increasing of Mg contents.

One of the critical issues in the application of membrane filtration to drinking water treatment is fouling by natural organic matter (NOM). In order to better understand fouling, Aldrich humic substances (AHSs), a surrogate NOM, were fractionated into hydrophilic fraction (HPIF) and hydrophobic fraction (HPOF) using DAX-8 resin and then fed into an electro-ultrafiltration (EUF) system. The fractionation performance was validated by contact angle measurement. Results showed that the HPIF deposited membrane had a lower contact angle than the HPOF deposited one. The EUF cell was operated in a constant pressure mode for 5 h with and without electric voltage. It was observed that in the absence of an electric field, HPIF caused more severe fouling than HPOF. After applying the electrical voltage, the flux decline decreased due to electrokinetic interactions. In addition, HPOF had a lower flux decline and higher total permeate volume than HPIF, indicating a higher electrophoretic mobility of HPOF. Due to the relatively low apparent electrophoretic mobility (AEM) of HPIF, the flux decline was the highest after applying electricity. Furthermore, the removal efficiency of total organic carbon (TOC) increased by more than 10%, 30% and 13% for the un-fractionated, HPOF, and HIPF, respectively, at 2985 V/m.

A molecular dynamics (MD) technique was adopted to investigate the free volume, operational temperature effects, feed solution–membrane surface affinity, and water/alcohol diffusion mechanism of aromatic polyamide (PA) membranes for pervaporation (PV) applications. An isothermal–isobaric ensemble (i.e. NPT ensemble) was adopted to analyze the fractional free volume, the fractional accessible volume, and the cavity size distribution of PA membranes at different operational temperatures. The free volume and cavity size analyses indicated that bulkier side groups enhanced the formation of larger free volumes, which increased permeation rates. Increased temperature induced chain mobility and enlarged the cavity size of the membrane. During feed solution–membrane affinity analysis, the alcohols showed a higher interaction with the membrane surface as compared to the water molecules. The diffusion mechanism of water/methanol in the membrane matrix suggested that methanol had a shorter displacement distance relative to the water due to its larger size and stronger interaction with the membrane. Results from the MD simulation agreed well with those from experimental studies reported in the literatures, which demonstrated that this theoretical method is a promising tool for characterizing membrane structures and analyzing feed solution transport at a molecular scale during PV processes.

Natural organic matter (NOM) and inorganic particles are ubiquitous in many natural surface waters that serve as sources of drinking water. In addition to reacting with chlorine to form chlorinated disinfection by-products (DBPs), NOM and NOM sorbed on inorganic particles cause serious membrane fouling problems. We evaluated the feasibility of using a novel laboratory-scale electro-microfiltration (EMF) system to remove NOM and inorganic particles from water. Synthetic water samples containing 5 mg/L humic acid (HA) only (Kao0), 5 mg/L HA and 5 mg/L kaolin (Kao1), and 5 mg/L HA and 50 mg/L kaolin (Kao2) were used in the EMF study. Kao2 demonstrated the largest flux decline in the absence of an electrical field. When an electrical field was applied, the filtration flux, NOM removal, and decrease in specific ultraviolet absorbance (SUVA) were enhanced because of electrophoretic and electroosmotic effects. When the applied electrical field strength was greater than a critical electrical field strength ( E critical ), system operations and efficiency did not increase further. These results suggest that the applied electrical field should be close to E critical for maximum efficiency and cost-effectiveness. This study demonstrates that an EMF system is a highly effective way to treat water containing NOM and inorganic particles.

Perfluorinated compounds (PFCs) are negatively charged and have low pK(a) values in water; therefore, a laboratory-scale electro-microfiltration (EMF) unit that applies a direct-current electrical field across its membrane can greatly enhance their removal from aqueous systems. We examined the effects of an aqueous inorganic matrix (pH: 4, 7, or 10; ionic strength: 0.4-4.8 mM; ionic composition: Na(2)SO(4), NaCl, NH(4)Cl or CaCl(2)) and an organic matrix such as dissolved organic matter (DOM) on the ability of EMF to remove perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). Decreased removal of PFOX (X = A or S) was observed when the proton concentration and the ionic strength increased. When the applied electrical field strength was less than the critical electrical field strength (E(critical, HA)), PFOX removal was lower in the presence of DOM. We hypothesize that these matrices affect PFOX rejection by altering membrane zeta potential during filtration in the presence of an electrical field. In addition, EMF was found to remove three other PFCs effectively (perfluorodecanoic acid, perfluorohexane sulfonate, and perfluorohexanoic acid), and was also able to remove 70% PFOX and 80% DOC from real industrial wastewaters.

Lignocellulose has drawn great attention in the bioethanol industry as an alternative feedstock for ethanol production due to its renewability, abundance and non-food crop characteristics. Acid hydrolyzation of lignocellulose releases sugars (mainly d-xylose) and several derivatives. The sugars in the hydrolyzate are then converted into ethanol by fermentation. Since acetic acid is believed to be one of the inhibitors which limit the yield of ethanol, it is beneficial to remove acetic acid from the hydrolyzates before fermentation. In this study, a Desal-5 DK nanofiltration (NF) membrane was used to separate acetic acid from xylose, using a synthetic acetic acid–xylose solution as the model. The Desal-5 DK membrane had an isoelectric point of 3.7 and a pore size of 0.83 nm based on streaming potential measurement and model calculation. It was found that both the solution pH and the applied pressure affected the separation performance. The observed retention of xylose and acetic acid varied from 28% to 81% and −6.8% to 90%, respectively, depending on the solution pH and the applied pressure. The maximum separation factor was 5.4 when the system was operated at pH 2.9 and 24.5 bar. In addition, negative retention of acetic acid was observed only in the presence of xylose. The results suggested that intermolecular interactions play an important role in the separation of xylose and acetic acid.

The objective of this study was to examine the removal of arsenic from groundwater by a laboratory scale electro-ultrafiltration (EUF) system. Two groundwater samples taken from I-Ian County located in the northeastern part of Taiwan were studied. These well waters were selected based on their As(III) and As(V) contents; the As(III) to As(V) ratios of the well water were 1.8 and 0.4 for Well-#1 and Well-#2, respectively. In the absence of electrical voltage, the total arsenic removal efficiencies were 1% and 14% for Well-#1 and Well-#2 samples, respectively, using 100-kDa membranes. The higher As removal efficiency of Well-#2 than that of Well-#1 sample might be attributed to different charge characteristics of As(V) and As(III). Upon the application of an electrical voltage of 25 V to the ultrafiltration (UF) system, it was able to reduce the total arsenic concentrations in both groundwater samples by over 79%. The result suggested the possible association between As(III) species and dissolved organic matter which enhanced the As removal.

This study examined the effect of molecular weight (MW) fractions on electro-ultrafiltration (EUF). MW fractions fractionated from Aldrich humic substances (AHSs) were defined as G1 (3000 to >20,000 Da), G2 (500 to 3000 Da) and G3 (

A cross-flow filtration module with a large pore-size membrane and low operation pressure was built, as a first attempt, to test its performance on the separation of synthetic nano-sized alumina and silica particles in the presence of an electric field. For practicality sake, turbidity measurements were used primarily to evaluate the particle removal efficiency and to determine critical currents. The observed critical currents agreed well with theoretically calculated. The critical currents observed were found to be strongly dependent on the conductivity; there was a linear relationship between the critical current and conductivity. Further theoretical analysis of the electrical filtration module reveals that particles of different size or surface charge (e.g., zeta potential) can be separated within a particular size range by controlling the ionic strength or the conductivity of the solution.

Humic substances (HS) represent the common agents contributing to flux decline during membrane filtration of natural water. In order to minimize the fouling during microfiltration (MF) of HS, modifying the operation of MF presents a promising alternative. A laboratory-scale electro-microfiltration (EMF) module was used to separate Aldrich HS from water by applying a voltage across the membrane. The presence of an electric field significantly reduced the flux decline. A flux comparable to that of ion-free water was attained when the voltage was near the critical electric field strength ( E critical ), i.e., the electrical field gradient that balances the advective and electrophoretic velocities of solute. At an applied voltage of 100 V (∼110 V/cm), it was able to reduce UV absorbance at 254 nm (UV 254 ), total organic carbon (TOC) and trihalomethane formation potential (THMFP) by over 50% in the permeate. Results from 1 H nuclear magnetic resonance ( 1 H NMR) analysis suggest that the aromatic and functionalized aliphatic fractions decreased significantly in the permeate. The charged HS have large molecule weight compared with those passing through membrane. Results clearly indicate that a combination of electric force with MF can increase HS rejection and decrease flux decline. Electrophoretic attraction was the major mechanism for the improvement of flux and rejection over time.

Disposal and penetration of carbon nanotubes (CNTs) into the environment have raised increasing concerns over the years. In this study, a laboratory scale electro-microfiltration (EMF) was used to treat water containing single wall carbon nanotubes (SWCNTs) and multi-wall carbon nanotubes (MWCNTs). The goal was to examine and compare the performance during EMF of SWCNT and MWCNT. The results showed that the initial flux was increased as the applied electrical voltage increased. At an applied pressure of 49 kPa, the final flux was comparable to pure water flux when the applied electrical field strength was greater than the critical electrical field strength (Ecritical). In addition, dissolved organic carbon (DOC) removal efficiency increased as the electrical voltage increased. Due to high convective transport of organic matter toward the membrane at 98 kPa, a decrease in DOC removal efficiency with increasing electrical field strength was observed. Overall, the fluxes and DOC removal efficiencies for EMF of SWCNT and MWCNT were not significantly different with a 95% confidence.

This work studied the concentration of hydrolyzates obtained from dilute acid hydrolysis of rice straw using nanofiltration (NF). In order to minimize the Donnan exclusion effect of the membrane, the hydrolyzate solution was controlled at low pH value. Negative retentions of both furans and carboxylic acids were observed. The maximum separation factor of acetic acid over xylose was 49, while the maximum separation factor of acetic acid over arabinose was 52, when the system was operated at pH 2.9 and an applied pressure of 24.5–34.3 bar. The separation factors of inhibitors over glucose became infinity due to the complete retention of glucose. The separation performance decreased when the operating temperature was increased from 25 to 40 °C. The flux deterioration was recovered by flushing with 0.01 N of NaOH and water.

A laboratory scale electro-ultrafiltration (EUF) system was developed and used to explore the removal of arsenic and humic substances (HSs) from water. As a negatively charged species, arsenate(V) was readily removed after applying voltage to the EUF cell. Arsenite(III) was removed via EUF after the pH of the water had been adjusted. Meanwhile, the rejection of HSs increased due to the presence of an electric field. This study also showed that the removal of arsenite(III) from water relies primarily on electrostatic and non-electrostatic mechanisms. In the presence of HSs, arsenate(V) complexed with the HSs and was then able to be removed by EUF. This study demonstrates that EUF is a highly promising means of removing arsenic from water.

The effect of carrier localization in InGaN/GaN multiple quantum wells (MQWs) light-emitting diodes is investigated by photoluminescence (PL) and time-resolved PL (TRPL) measurements. PL results show that two peaks obtained by Gaussian fitting both relate to the emission from localized states. By fitting the TRPL lifetimes at various emission energies, two localization depths corresponding to the In-rich regions and quasi-MQWs regions are obtained. Using a model we proposed, we suggest that compositional fluctuations of In content and variation of well width are responsible for carrier localization in In-rich regions and quasi-MQWs regions, respectively.