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ABSTRACT: In this study, a method was developed to immobilize silver onto polypropylene (PP) membrane surfaces for improved anti-biofouling performance. A commercial PP membrane was first grafted with the thiol functional groups, and then silver ions were immobilized onto the PP membrane surface through coordinating with the thiol groups. The immobilized silver was found to be very stable, with only ~1.1% of the immobilized silver being leached out during a leaching test. The surface of the modified membrane (PPS-Ag) was examined with ATR-FTIR and XPS analysis, which verified the successful grafting of the thiol groups and the coordination of silver ions on the membrane surface. The surface properties of the membrane were also characterized by SEM, AFM and water contact angle measurements. The PPS-Ag membrane was found to have a smoother and more hydrophilic surface than the PP membrane. Both Gram-negative bacteria, Escherichia coli, and Gram-positive bacteria, Staphylococcus aureus, were used to evaluate the antibacterial and anti-biofouling performance of the PPS-Ag membrane. From disk diffusion experiments, the PPS-Ag membrane exhibited the capability of inhibiting the growth of both the Gram-negative and Gram-positive bacteria tested. The anti-biofouling performance of the membrane was assessed by immersion in a mixed suspension of E. coli and S. aureus and filtration tests. The PPS-Ag membrane showed a stable and significantly enhanced anti-biofouling performance as compared with the PP membrane. The results in this study demonstrate that biofouling of a PP membrane can be sufficiently overcome through immobilizing silver onto the membrane surface.
Biofouling 08/2011; 27(7):773-86. · 4.43 Impact Factor
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ABSTRACT: In this paper, the adsorption selectivity and mechanism of diethylenetriamine (DETA)-functionalized PGMA adsorbent (denoted as P-DETA) toward a number of heavy metal ions, including Cu, Co, Ni, Zn, and Cd ions, were experimentally and analytically examined. Experimental results showed a selective adsorption sequence, based on the adsorption affinity, of Cu>Co>Ni>Zn>Cd ions on P-DETA. X-ray absorption fine structure (XAFS) analysis was used to reveal the adsorption coordination geometry, bond length, and coordination number of each type of metal ion with the DETA group. The analysis indicated that Cu, Ni, and Zn ions formed tetrahedral geometry (fourfold coordination) when adsorbed, while Co ion showed an octahedral geometry (sixfold coordination). However, the coordination geometry for Cd could not be obtained in the analysis due to the lack of reference information. The analysis from EXAFS further confirmed that the ratio of DETA ligand to the adsorbed metal ion was probably 1 for Cu, Ni, or Zn ions, while that ratio was 2 for Co ion. From the stability constant (in the log K form) for a metal ion-DETA ligand coordination (denoted as ML(n), where M indicates a heavy metal ion, and L(n) indicates n numbers of ligands involved), a relationship of log K (CuL)>log K (CoL(2))>log K (NiL)>log K (ZnL)>log K (CdL) is suggested. This sequence is in good correlation with the experimentally derived adsorption selective sequence of Cu>Co>Ni>Zn>Cd ions, indicating that the coordination geometry played an important role in the determination of the adsorption selectivity for heavy metal ions by the polyamine-functionalized adsorbent of P-DETA.
Journal of Colloid and Interface Science 10/2010; 350(1):282-9. · 3.07 Impact Factor
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ABSTRACT: A major problem in membrane technology for applications such as wastewater treatment or desalination is often the loss of membrane permeability due to biofouling initiated from protein adsorption and biofilm formation on the membrane surface. In this study, we developed a relatively simple and yet versatile approach to prepare polypropylene (PP) membrane with highly effective non-biofouling performance. Copolymer brushes were grafted to the surface of PP membrane through UV-induced polymerization of two oppositely charged monomers, i.e., [2-(methacryloyloxy)ethyl]trimethylammonium chloride (TM) and 3-sulfopropyl methacrylate potassium salt (SA), with varying TM:SA molar ratios. Surface analysis with scanning electron microscope (SEM) clearly showed the grafted copolymer brushes on the membrane surfaces and that with X-ray photoelectron spectroscope (XPS) revealed a similar TM:SA ratio of the grafted copolymer brushes to that of the monomer solution used for the polymerization. Water contact angle measurements indicated that the hydrophilicity of the membrane surfaces was remarkably improved by the grafting of the TM/SA copolymer brushes, with the lowest water contact angle of 27 degrees being achieved at the TM:SA ratio of around 1:1. Experiments for antiprotein adsorption with bovine serum album (BSA) and lysozyme (LYZ) and antibiofilm formation with Escherichia coli (E. coli) demonstrated a great dependence of the membrane performance on the TM:SA ratios of the grafted copolymer brushes. It was found that the characteristics of the surface charges of the membrane surfaces played a very important role in the non-biofouling performance, and the membrane surface with balanced positive and negative charges showed the best non-biofouling performance for the proteins and bacteria tested in this study.
The Journal of Physical Chemistry B 02/2010; 114(7):2422-9. · 3.70 Impact Factor
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ABSTRACT: A novel electrolyte-responsive membrane, RC-g-PSBMA, was successfully prepared from regenerated cellulose (RC) membrane through surface-initiated atom transfer radical polymerization (ATRP) of a zwitterionic monomer, sulfobetaine methacrylate (SBMA). Different degrees of polymerization for the grafted SBMA polymers (i.e., PSBMA) on the RC membrane were easily obtained by adjusting the ATRP reaction conditions. The electrolyte-responsive behavior of RC-g-PSBMA was first evaluated through the permeation experiments with sodium chloride (NaCl) solutions of different concentrations. It was found that the permeability of RC-g-PSBMA showed a clear dependence on NaCl concentration in the solutions. To further examine the potential of RC-g-PSBMA for protein purification, bovine serum album (BSA) was chosen as a model protein and polystyrene nanoparticles (NPs) of different sizes were used as representative impurities in the solutions. The rejection rates of BSA and NPs by RC-g-PSBMA were examined with the solutions containing BSA and NPs at different NaCl concentrations. The results showed that the rejection rates of BSA were at a very low level regardless of the concentration of NaCl in the solutions, indicating that the membrane allowed BSA to permeate. However, the rejection rates of NPs of different sizes by RC-g-PSBMA changed remarkably with the concentration of NaCl in the solutions. The study has demonstrated the possibility to separate BSA from NPs of different sizes by using the same membrane but simply altering the concentration of NaCl in the solutions. Membranes with such properties will have a great potential for protein purification as well as for many other separation applications.
ACS Applied Materials & Interfaces 01/2010; 2(1):203-11. · 4.53 Impact Factor
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ABSTRACT: This paper examines the characteristics of poly(glycidyl methacrylate) (PGMA) beads functionalized with different aliphatic polyamines as adsorbents and their performance in copper ion adsorption. The four aliphatic polyamines evaluated include ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA). Various analytical tools, including elemental analysis, BET, and XAFS (XANES+EXAFS), were used to characterize the adsorbents in terms of their immobilized amine contents, polyamine densities, and their coordination structures for the adsorption of a typical heavy metal ion, Cu(2+). It was found that the immobilized polyamine densities followed the order of EDA>DETA>TETA>TEPA, but the immobilized amine contents followed the opposite order of TEPA>TETA>DETA>EDA. XAFS analysis for the adsorbents after copper ion adsorption revealed that the average coordination number of copper ion with the nitrogen atoms (in the range between 3 and 4) followed the order of DETA<TETA<EDA<TEPA. Hence, the molecular length and structure of the polyamines appeared to have a great effect on the adsorption performance of the prepared adsorbents. The study leads to the conclusion that among the four aliphatic polyamines, DETA-functionalized PGMA adsorbent was the most efficient one for copper ion removal because of the relatively higher amine content and lower coordination number, easier regeneration, and shorter preparation time of the adsorbent. The results provide some useful information for future studies in the selection of polyamines for adsorbent functionalization.
Journal of Colloid and Interface Science 01/2010; 345(2):454-60. · 3.07 Impact Factor
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ABSTRACT: A membrane-aerated biofilm reactor (MABR) was developed to degrade acetonitrile (ACN) in aqueous solutions. The reactor was seeded with an adapted activated sludge consortium as the inoculum and operated under step increases in ACN loading rate through increasing ACN concentrations in the influent. Initially, the MABR started at a moderate selection pressure, with a hydraulic retention time of 16 h, a recirculation rate of 8 cm/s and a starting ACN concentration of 250 mg/l to boost the growth of the biofilm mass on the membrane and to avoid its loss by hydraulic washout. The step increase in the influent ACN concentration was implemented once ACN concentration in the effluent showed almost complete removal in each stage. The specific ACN degradation rate achieved the highest at the loading rate of 101.1 mg ACN/g-VSS h (VSS, volatile suspended solids) and then declined with the further increases in the influent ACN concentration, attributed to the substrate inhibition effect. The adapted membrane-aerated biofilm was capable of completely removing ACN at the removal capacity of up to 21.1 g ACN/m(2) day, and generated negligible amount of suspended sludge in the effluent. Batch incubation experiments also demonstrated that the ACN-degrading biofilm can degrade other organonitriles, such as acrylonitrile and benzonitrile as well. Denaturing gradient gel electrophoresis studies showed that the ACN-degrading biofilms contained a stable microbial population with a low diversity of sequence of community 16S rRNA gene fragments. Specific oxygen utilization rates were found to increase with the increases in the biofilm thickness, suggesting that the biofilm formation process can enhance the metabolic degradation efficiency towards ACN in the MABR. The study contributes to a better understanding in microbial adaptation in a MABR for biodegradation of ACN. It also highlights the potential benefits in using MABRs for biodegradation of organonitrile contaminants in industrial wastewater.
Biodegradation 02/2009; 20(4):569-80. · 2.02 Impact Factor
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ABSTRACT: Extracellular polymeric substances (EPS) are one of the main components of the biofilm and perform important functions in the biofilm system. In this study, two membrane-aerated biofilms (MABs) were developed for the thin and thick biofilms under different surface loading rates (SLRs). Supplies of oxygen and substrates in the MAB were from two opposite directions. This counter diffusion of nutrients resulted in a different growth environment, in contrast to conventional biofilms receiving both oxygen and substrates from the same side. The compositions, distributions and physicochemical properties (solubility and bindability) of EPS in the MABs of different thicknesses under different SLRs were studied. The effect of dissolved oxygen (DO) concentration within the MAB on EPS properties and distribution was investigated. Experimental results showed the different biofilm thicknesses produced substantially different profiles of EPS composition and distribution. Soluble proteins were more dominant than soluble polysaccharides in the inner aerobic layer of the biofilms; in contrast, bound proteins were greater than bound polysaccharides in the outer anoxic or anaerobic layer of the biofilms. The biofilm-EPS matrix consisted mainly of bound EPS. Bound EPS exhibited a hump-shaped profile with the highest content occurring in an intermediate region in the thin MAB and relatively more uniformly in the one half of the biofilm close to the membrane side and then declined towards the biofilm-liquid interface in the thick MAB. The profiles of soluble EPS presented a similar declining trend from the membrane towards the outer region in both thin and thick MABs. The study suggested that not only EPS composition but also EPS distribution and properties (solubility and bindability) played a crucial role in controlling the cohesiveness and maintaining the structural stability and stratification of the MABs.
Journal of Biotechnology 06/2008; 135(1):52-7. · 3.05 Impact Factor
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ABSTRACT: The selective removal of copper and lead ions from aqueous solutions by diethylenetriamine (DETA)-functionalized polymeric adsorbent was investigated. The adsorbent was prepared by amination of the micro-beads synthesized from glycidyl methacrylate and trimethylolpropane trimethacrylate co-polymerization (denoted as P-DETA). In the single metal species system (only copper or lead ions present), P-DETA was found to adsorb copper ions or lead ions significantly (with a slightly higher adsorption uptake capacity for lead ions than copper ions). However, P-DETA displayed an excellent selectivity in the adsorption of copper ions over lead ions in the binary metal species system (with both copper and lead ions present). It was also found that initially (or previously) adsorbed lead ions on P-DETA were displaced, even completely, by subsequently adsorbed copper ions from the solution but the case was not vice versa. The greater electronegativity of copper ions than lead ions was identified as the major factor that caused P-DETA to selectively adsorb copper ions over lead ions during competitive adsorption in the binary metal species system. It was speculated that the displacement of already adsorbed lead ions on P-DETA by subsequently adsorbed copper ions was through an adjacent attachment and repulsion mechanism. P-DETA has been shown to have the potential to be used as an effective adsorbent for the removal as well as selective recovery of heavy metal ions in water or wastewater treatment.
Water Research 04/2008; 42(6-7):1511-22. · 4.86 Impact Factor
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ABSTRACT: A membrane-aerated biofilm reactor (MABR) was studied for the treatment of wastewater containing acetonitrile, a typical organonitrile compound. The MABR used hydrophobic hollow fiber membranes as the diffusers for bubbleless aeration as well as the carriers for biofilm growth. The objectives were to prevent the stripping-loss of acetonitrile during aeration and to achieve acetonitrile biodegradation plus nitrogen removal simultaneously in a single biolfilm on the membranes. In the MABR, oxygen and substrates were supplied to the biofilm from opposite sides, in contrast to those from the same side in conventional biofilm bioreactors. Operational factors, including surface loading rate and upflow fluid velocity in the bioreactor, on the effect of acetonitrile biodegradation performance were examined. The profiles of dissolved oxygen concentration and microbial activities and populations in the biofilm were investigated. Experimental results showed that, with the adapted microorganisms, removal of acetonitrile at approximately 98.6 and 83.3%, in terms of total organic carbon and total nitrogen, were achieved at a surface loading rate (in terms of membrane surface) of up to 11.29 g acetonitrile/ m2 x d with an upflow fluid velocity of 12 cm/s and a hydraulic retention time of 30 h. The biofilm on the membranes developed an average thickness of about 1.6 mm in the steady state and consisted of oxic/anoxic/anaerobic zones that provided different functions for acetonitrile degradation, nitrification, and denitrification. The acetonitrile-degrading bacteria in the MABR appeared to secrete more extracellular polymeric substances that enhanced the attachment and development of the biofilm on the membranes. The study demonstrated the potential of using the MABR for the treatment of organonitrile wastewater.
Environmental Science and Technology 04/2008; 42(6):2099-104. · 5.23 Impact Factor
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ABSTRACT: Membrane aerated biofilm reactors (MABRs) represent a relatively new biotreatment technology. In a MABR, biofilm is grown on a gas-permeable membrane (often a hollow fiber membrane). Soluble organic compounds in the liquid are supplied to the biofilm from the biofilm-liquid interface whereas oxygen supply to the biofilm is from the biofilm-membrane interface (by oxygen diffusing through the membrane). MABRs can achieve bubble-less aeration and high oxygen utilization efficiency (up to 100%) and the biofilm can be stratified into aerobic/anoxic/anaerobic zones to simultaneously achieve removal of carbonaceous organic pollutants as well as nitrification and denitrification (if needed) in a single biofilm. This article briefly reviews the MABR process, including the characteristics, membrane materials, modular design, operation parameters and the potential applications, from relevant recent patents and literature.
Recent patents on biotechnology. 02/2008; 2(2):88-93.
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ABSTRACT: A microbial process for the degradation of three types of structurally distinct organonitriles (i.e., saturated and unsaturated aliphatic nitrile and aromatic nitrile) was studied. Microorganisms were enriched from the activated sludge of a pharmaceutical wastewater treatment plant and adapted through providing acetonitrile as the sole carbon and nitrogen source for their growth. The adapted mixed culture was then examined for their capability of degrading acetonitrile, acrylonitrile and benzonitrile under various operational conditions. The performance of biodegradation and the metabolic intermediate- and end-products in the process were monitored. The results show that an average removal rate of 0.083 g acetonitrile g(-1)-VSS h(-1), 0.0074 g acrylonitrile g(-1)-VSS h(-1) or 0.0029 g benzonitrile g(-1)-VSS h(-1) was achieved in the batch bioreactor under the common operational condition of 25 degrees C and pH 7. The biodegradation of acetonitrile and acrylonitrile showed a two-step pathway, with the generation of acetamide followed by acetic acid and ammonia for acetonitrile or acrylamide followed by acrylic acid and ammonia for acrylonitrile. However, the biodegradation of benzonitrile appeared to have only one step, with the direct production of benzoic acid and ammonia, but without benzamide being detected in the process. The results suggest that, depending on the substrates, the adapted mixed culture can develop very different degradation pathways, such as nitrile hydratase plus amidase for acetonitrile or acrylonitrile and nitrilase for benzonitrile. Therefore, the adapted mixed culture has a great potential and flexibility for actual applications in biodegradation of various organonitrile compounds.
Water Research 09/2007; 41(15):3465-73. · 4.86 Impact Factor
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ABSTRACT: Amine-functionalized adsorbents have attracted increasing interest in recent years for heavy metal removal. In this study, diethylenetriamine (DETA) was successfully grafted (through a relatively simple solution reaction) onto poly(glycidyl methacrylate) (PGMA) microgranules to obtain an adsorbent (PGMA-DETA) with a very high content of amine groups and the PGMA-DETA adsorbent was examined for copper ion removal in a series of batch adsorption experiments. It was found that the PGMA-DETA adsorbent achieved excellent adsorption performance in copper ion removal and the adsorption was most effective at pH>3 in the pH range of 1-5 examined. X-ray photoelectron spectroscopy (XPS) revealed that there were different types of amine sites on the surfaces of the PGMA-DETA adsorbent but copper ion adsorption was mainly through forming surface complexes with the neutral amine groups on the adsorbent, resulting in better adsorption performance at a higher solution pH value. The adsorption isotherm data best obeyed the Langmuir-Freundlich model and the adsorption capacity reached 1.5 mmol/g in the case of pH 5 studied. The adsorption process was fast (with adsorption equilibrium time less than 1-4 h) and closely followed the pseudo-second-order kinetic model. Desorption of copper ions from the PGMA-DETA adsorbent was most effectively achieved in a 0.1 M dilute nitric acid solution, with 80% of the desorption being completed within the first 1 min. Consecutive adsorption-desorption experiments showed that the PGMA-DETA adsorbent can be reused almost without any loss in the adsorption capacity.
Journal of Colloid and Interface Science 11/2006; 303(1):99-108. · 3.07 Impact Factor
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ABSTRACT: Cross-linked chitosan granules (denoted as CTS) were surface-functionalized with poly(acrylic acid) (PAAc) and examined for the adsorption of lead ions from aqueous solutions. PAAc was successfully grafted on CTS through a simple two-step reaction in a solution. The PAAc-functionalized chitosan granules (denoted as CTS-PAAc) showed significantly greater adsorption capacities for lead ions than CTS, and the performance improved with the increase of pH in the pH range of 1−6 examined. An adsorption isotherm and kinetic study conducted at pH 4 and room temperature showed a maximum adsorption capacity of 294.12 mg/g and an adsorption equilibrium time of less than 5 h for lead ions on CTS-PAAC, in contrast to only 95.15 mg/g and up to 8 h on CTS. Mechanism study revealed that the excellent adsorption performance of CTS-PAAc for lead ions was attributed to the many carboxyl groups grafted on CTS-PAAc. It was found that adsorbed lead ions on CTS-PAAc can be effectively desorbed and the regenerated CTS-PAAc can be reused almost without any loss of adsorption capacity.
10/2006;
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ABSTRACT: Enhanced and selective removal of mercury ions was achieved with chitosan beads grafted with polyacrylamide (chitosan-g-polyacrylamide) via surface-initiated atom transfer radical polymerization (ATRP). The chitosan-g-polyacrylamide beads were found to have significantly greater adsorption capacities and faster adsorption kinetics for mercury ions than the chitosan beads. At pH 4 and with initial mercury concentrations of 10-200 mg/L, the chitosan-g-polyacrylamide beads can achieve a maximum adsorption capacity of up to 322.6 mg/g (in comparison with 181.8 mg/g for the chitosan beads) and displayed a short adsorption equilibrium time of less than 60 min (compared to more than 15 h for the chitosan beads). Coadsorption experiments with both mercury and lead ions showed that the chitosan-g-polyacrylamide beads had excellent selectivity in the adsorption of mercury ions over lead ions at pH < 6, in contrast to the chitosan beads, which did not show clear selectivity for either of the two metal species. Mechanism study suggested that the enhanced mercury adsorption was due to the many amide groups grafted onto the surfaces of the beads, and the selectivity in mercury adsorption can be attributed to the ability of mercury ions to form covalent bonds with the amide. It was found that adsorbed mercury ions on the chitosan-g-polyacrylamide beads can be effectively desorbed in a perchloric acid solution, and the regenerated beads can be reused almost without any loss of adsorption capacity.
Langmuir 12/2005; 21(25):11780-7. · 4.19 Impact Factor
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ABSTRACT: A new amine-shielded cross-linking method of the chitosan hydrogel beads (CHBs) was investigated to improve the metal adsorption performance of the cross-linked beads. The CHBs were reacted with formaldehyde before the beads were cross-linked with EGDE, and, finally, the amine groups of cross-linked CHBs were released by HCl treatment. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy clearly showed that most of the amine groups in chitosan were converted to the −NCH2 groups after the formaldehyde treatment and they were not involved in the cross-linking reaction with EGDE, and the HCl treatment after the cross-linking reaction effectively released these shielded nitrogen atoms into the form of the primary amine again. Copper ion adsorption experiments confirmed that the CHBs cross-linked with the new method had significantly greater adsorption capacities than the beads cross-linked directly with EGDE. Mechanism study revealed that the increased adsorption performance was attributed to the large number of primary amine groups available on the surfaces of the cross-linked beads from the new cross-linking method.
07/2005;
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ABSTRACT: Chitosan hydrogel beads were studied for the adsorption of lead ions and humic acid from aqueous solutions to examine the adsorption behaviors and mechanisms. The experiments were carried out at room temperature with solution pH ranging from 5 to 7.5 (in near neutral pH range). Three types of batch adsorption experiments, including single species adsorption, sequential adsorption of one species after another and co-adsorption of both species, were investigated. The results show that: (1) adsorption of either species mainly results from the complexations between adsorbate and functional groups at the surface of the hydrogel beads; (2) previously adsorbed species can either act as additional binding sites for, or occupy the same binding sites as the subsequent species to be adsorbed, resulting in enhanced or retarded adsorption of the subsequent species; and (3) for co-adsorption, metal-organic interactions play a very important role in determining the extent of adsorption. It is concluded that multi-species adsorption can be significantly affected by adsorbate interactions and the understanding of these interactions needs great attention in adsorption study in the future.
Water Research 03/2005; 39(4):688-98. · 4.86 Impact Factor
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ABSTRACT: Biodegradation of poorly soluble polycyclic aromatic hydrocarbons (PAHs) has been a challenge in bioremediation. In recent years, surfactant-enhanced bioremediation of PAH contaminants has attracted great attention in research. In this study, biodegradation of phenanthrene as a model PAHs solubilized in saline micellar solutions of a biodegradable commercial alcohol ethoxylate nonionic surfactant was investigated. The critical micelle concentration (CMC) of the surfactant and its solubilization capacity for phenanthrene were examined in an artificial saline water medium, and a type of marine bacteria, Neptunomonas naphthovorans, was studied for the biodegradation of phenanthrene solubilized in the surfactant micellar solutions of the saline medium. It is found that the solubility of phenanthrene in the surfactant micellar solutions increased linearly with the surfactant concentrations, but, at a fixed phenanthrene concentration, the biodegradability of phenanthrene in the micellar solutions decreased with the increase of the surfactant concentrations. This was attributed to the reduced bioavailability of phenanthrene, due to its increased solubilization extent in the micellar phase and possibly lowered mass transfer rate from the micellar phase into the aqueous phase or into the bacterial cells. In addition, an inhibitory effect of the surfactant on the bacterial growth at high surfactant concentrations may also play a role. It is concluded that the surfactant largely enhanced the solubilization of phenanthrene in the saline water medium, but excess existence of the surfactant in the medium should be minimized or avoided for the biodegradation of phenanthrene by Neptunomonas naphthovorans.
Biodegradation 03/2005; 16(1):57-65. · 2.02 Impact Factor
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ABSTRACT: Aminated polyacrylonitrile fibers (APANFs) were prepared by surface modification and were used as an adsorbent to remove humic acid from aqueous solutions. The APANFs were found to be very effective in removing humic acid at the pH range from 2 to 10. The adsorption isotherm obeyed both the Langmuir and Freundlich models, and the adsorption kinetics followed an initial diffusion-controlled and then an attachment-controlled adsorption pattern. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy revealed that chemical bonds were formed between the nitrogen atoms in the amine groups on the fibers and humic acid molecules adsorbed, suggesting that, besides electrostatic interaction, surface complexation also played an important role in humic acid adsorption on the APANFs. The humic acid adsorbed on the APANFs can be effectively desorbed in a 0.1 M NaOH solution, and the regenerated APANFs can be reused in the subsequent adsorption cycles without significant loss of the adsorption capacities.
Journal of Colloid and Interface Science 01/2005; 280(1):36-43. · 3.07 Impact Factor
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Langmuir 08/2004; 20(14):6068-70. · 4.19 Impact Factor
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ABSTRACT: Aminated polyacrylonitrile fibers (APANFs) were prepared and used as an adsorbent in a series of batch adsorption experiments for the removal of Cr(III) and Cr(VI) species from aqueous solutions of different pH values. The results show that significant amounts of Cr(III) or Cr(VI) species can be adsorbed by the APANFs, although the adsorption performances was greatly dependent upon the solution pH values. In general, the amounts of adsorption for Cr(III) species increased whereas that for Cr(VI) decreased with the increase of the solution pH values, which suggests that different adsorption mechanisms dominated the removal of Cr(III) or Cr(VI) species on the APANFs. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy revealed that the adsorption of Cr(III) species on the APANFs was largely attributed to the formation of surface complexes between the nitrogen atoms on the APANFs and the Cr(III) species adsorbed, but the adsorption of Cr(VI) species on the APANFs was more likely effected through the formation of hydrogen bonds at high solution pH values or through both electrostatic attraction and surface complexation at low solution pH values. It was found that the Cr(VI)-adsorbed APANFs can be effectively regenerated in a basic solution and be reused almost without any loss of the adsorption capacity, while the Cr(III)-adsorbed APANFs needed to be regenerated in an acidic solution and the regeneration appeared to be less effective.
Water Research 06/2004; 38(9):2423-31. · 4.86 Impact Factor
