Removal of humic substances (HS) from water by electro-microfiltration (EMF).
ABSTRACT 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 (Ecritical), i.e., the electrical field gradient that balances the advective and electrophoretic velocities of solute. At an applied voltage of 100 V (approximately 110 V/cm), it was able to reduce UV absorbance at 254 nm (UV254), total organic carbon (TOC) and trihalomethane formation potential (THMFP) by over 50% in the permeate. Results from 1H nuclear magnetic resonance (1H 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.
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ABSTRACT: An experimental evaluation of intertubular and peritubular dentin was performed using nanoindentation and Dynamic Mechanical Analysis (DMA). The objective of the investigation was to evaluate the differences in dynamic mechanical behavior of these two constituents and to assess whether their response is frequency dependent. Specimens of hydrated coronal dentin were evaluated by DMA using single indents over a range of parametric conditions and using scanning probe microscopy. The complex (E∗), storage (E') and loss moduli (E″) of the intertubular and peritubular dentin were evaluated as a function of the dynamic loading frequency and static load in the fully hydrated condition. The mean complex E∗ (19.6 GPa) and storage E' (19.2 GPa) moduli of the intertubular dentin were significantly lower than those for peritubular dentin (E∗ = 31.1 GPa, p < 0.05; E' = 30.3 GPa, p < 0.05). There was no significant influence of dynamic loading frequency on these measures. Although there was no significant difference in the loss modulus (E″) between the two materials (p > 0.05), both constituents exhibited a significant increase in E″ with dynamic load frequency and reduction in the quasi-static component of indentation load. The largest difference in dynamic behavior of the two tissues was noted at small quasi-static indentation loads and the highest frequency.Journal of the mechanical behavior of biomedical materials. 03/2012; 7:3-16.
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ABSTRACT: The aim of the present study was to identify the influence of process parameters and their interactions on the electro-ultrafiltration performance during the filtration of alumina suspensions at low cross-flow rates. Overall, a weak flux-pressure dependence was observed in the absence of an electric field, indicating mass transfer limitation. A clear enhancement of flux was achieved by superimposing an electric field on the transmembrane pressure. As the feed pH increased from the acidic range to the vicinity of the isoelectric point of the particles, the beneficial effect of the electric field on permeate flux decreased significantly. Statistical analyses showed that in addition to the experimental parameters, some of their interactions were quite influential for determining the performance of the electro-ultrafiltration (EUF) process. Thus, the electric field induced flux enhancement became less pronounced as the initial ionic strength of the feed solution increased. In addition, the three studied response factors were noticed to be interrelated, whereby inevitable pH and conductivity changes associated with the electrode reactions during the electrofiltration process were also important in determining the permeate flux and quality. Overall, the results indicated that a clear understanding of the EUF performance is only possible when considering different effects (such as flux improvement and pH shift) simultaneously.Journal of Membrane Science 03/2012; 403– 404 (2012):227– 235. · 4.09 Impact Factor