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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.

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.

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.

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.

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.