Antifouling and Chemical-Resistant Nanofiltration Membrane Modulated by a Functionalized MWCNT Interlayer for Efficient Dye/Salt Separation at High Salinity.

Dye/salt separation in textile wastewater is of great importance. Membrane filtration technology is an environmentally friendly and effective approach to solve this issue. In this study, a thin-film composite membrane with a tannic acid (TA)-modified carboxylic multiwalled carbon nanotube (MWCNT) interlayer (M-TA) was prepared by interfacial polymerization with amino-functionalized graphene quantum dots (NGQDs) acting as aqueous monomers. The addition of the M-TA interlayer favored the formation of a thinner, more hydrophilic, and smoother selective skin layer for the composite membrane. The pure water permeability of the M-TA-NGQDs membrane was ∼9.32 L m-2 h-1 bar-1, which was higher than that of the NGQDs membrane without the interlayer. Meanwhile, the M-TA-NGQDs membrane presented better methyl orange (MO) rejection (97.79%) than the NGQDs membrane (87.51%). The optimal M-TA-NGQDs membrane exhibited excellent dye rejection (Congo red (CR): 99.61%; brilliant green (BG): 96.04%) and low salt rejection (NaCl < 15%). Noticeably, the M-TA-NGQDs membrane displayed effective selective separation performance (CR and BG > 99%) for dye/NaCl mixed solutions even at a high NaCl concentration of 50,000 mg/L. Furthermore, the M-TA-NGQDs membrane presented high water permeability recovery ratio values (91.02-98.20%). Importantly, the M-TA-NGQDs membrane showed excellent chemical stability (acid/alkali resistance). Generally, the fabricated M-TA-NGQDs membrane exhibited a great prospect for applications in dye wastewater treatment and water recycling, especially for the effective selective separation of dye/salt mixtures for high-salinity textile dyeing wastewater.

Thin-Film Nanocomposite Membranes with Nature-Inspired MOFs Incorporated for Removing Fluoroquinolone Antibiotics.

A nanofiltration membrane functionalized with metal-organic frameworks (MOFs) is promising to enhance micropollutant removal and realize wastewater reclamation. However, the current MOF-based nanofiltration membranes still suffer from severe fouling problems with an indefinable mechanism when used for antibiotic wastewater treatment. Hence, we report a nature-inspired MOF-based thin-film nanocomposite (TFN-CU) membrane to explore its rejection and antifouling behavior. Compared with unmodified membranes, the optimal TFN-CU5 membrane (with 5 mg·mL-1 C-UiO-66-NH2) had high water permeance (17.66 ± 1.19 L·m-2·h-1·bar-1), exceptional rejection for norfloxacin (97.92 ± 2.28%) and ofloxacin (95.36 ± 1.03%), and excellent long-term stability for treating synthetic secondary effluent with antibiotic rejection over 90%. Furthermore, it also showed superior antifouling capability (flux recovery up to 95.86 ± 1.28%) in bovine serum albumin (BSA) filtration after fouling cycles. Deriving from the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) approach, the antifouling mechanism between BSA and the TFN-CU5 membrane was mainly attributed to the inhibited adhesion forces because the growing short-ranged acid-base interaction caused repulsive interfacial interactions. It is further revealed that BSA fouling behavior is slightly retarded under an alkaline environment, while strengthened in the presence of calcium ions and humic acid, as well as high ionic strength. In short, the nature-inspired MOF-based TFN membranes possess exceptional rejection and organic fouling resistance, giving insights into the design of antifouling membranes during antibiotic wastewater reclamation.

Low-pressure thin-film composite nanofiltration membranes with enhanced selectivity and antifouling property for effective dye/salt separation.

For better sustainable resource recovery and elevating the separation efficiency of dye/salt mixture, it is essential to develop an appropriate nanofiltration membrane for the treatment of textile dyeing wastewater containing relatively smaller molecule dyes. In this work, a novel composite polyamide-polyester nanofiltration membrane was fabricated by tailoring amino functionalized quantum dots (NGQDs) and ß-cyclodextrin (CD). An in-situ interfacial polymerization occurred between the synthesized NGQDs-CD and trimesoyl chloride (TMC) on the modified multi-carbon nanotubes (MWCNTs) substrate. The incorporation of NGQDs significantly elevated the rejection (increased by âˆ¼ 45.08%) of the resultant membrane for small molecular dye (Methyl orange, MO) compared to the pristine CD membrane at low pressure (1.5 bar). The newly developed NGQDs-CD-MWCNTs membrane exhibited enhanced water permeability without compromising the dye rejection compared to the pure NGQDs membrane. The improved performance of the membrane was primarily attributed to the synergistic effect of functionalized NGQDs and the special hollow-bowl structure of CD. The optimal NGQDs-CD-MWCNTs-5 membrane expressed pure water permeability of 12.35 L m-2h-1 bar-1 at the pressure of 1.5 bar. Noteworthily, the NGQDs-CD-MWCNTs-5 membrane not only showed high rejection for the larger molecular dye of Congo Red (CR, 99.50%) but also for the smaller molecular dye of MO (96.01%) and Brilliant Green (BG, 95.60%) with the permeability of 8.81, 11.40, and 6.37 L m-2h-1 bar-1, respectively at low pressure (1.5 bar). The rejection of inorganic salts by the NGQDs-CD-MWCNTs-5 membrane was 17.20% for sodium chloride (NaCl), 14.30% for magnesium chloride (MgCl2), 24.63% for magnesium sulfate (MgSO4), and 54.58% for sodium sulfate (Na2SO4), respectively. The great rejection of dyes remained in the dye/salt binary mixed system (higher than 99% for BG and CR, <21% for NaCl). Importantly, the NGQDs-CD-MWCNTs-5 membrane exhibited favorable antifouling performance and potential good operation stability performance. Consequently, the fabricated NGQDs-CD-MWCNTs-5 membrane suggested a prospective application for the reuse of salts and water in textile wastewater treatment owing to the effective selective separation performance.

Aerobic denitrification in permeable Wadden Sea sediments.

Permeable or sandy sediments cover the majority of the seafloor on continental shelves worldwide, but little is known about their role in the coastal nitrogen cycle. We investigated the rates and controls of nitrogen loss at a sand flat (Janssand) in the central German Wadden Sea using multiple experimental approaches, including the nitrogen isotope pairing technique in intact core incubations, slurry incubations, a flow-through stirred retention reactor and microsensor measurements. Results indicate that permeable Janssand sediments are characterized by some of the highest potential denitrification rates (> or =0.19 mmol N m(-2) h(-1)) in the marine environment. Moreover, several lines of evidence showed that denitrification occurred under oxic conditions. In intact cores, microsensor measurements showed that the zones of nitrate/nitrite and O(2) consumption overlapped. In slurry incubations conducted with (15)NO(3)(-) enrichment in gas-impermeable bags, denitrification assays revealed that N(2) production occurred at initial O(2) concentrations of up to approximately 90 microM. Initial denitrification rates were not substantially affected by O(2) in surficial (0-4 cm) sediments, whereas rates increased by twofold with O(2) depletion in the at 4-6 cm depth interval. In a well mixed, flow-through stirred retention reactor (FTSRR), (29)N(2) and (30)N(2) were produced and O(2) was consumed simultaneously, as measured online using membrane inlet mass spectrometry. We hypothesize that the observed high denitrification rates in the presence of O(2) may result from the adaptation of denitrifying bacteria to recurrent tidally induced redox oscillations in permeable sediments at Janssand.

Isolation and characterization of a new strain of Methanothermobacter marburgensis DX01 from hot springs in China.

Strain DX01, a thermophilic methanogen, was isolated from a hot spring in China. Strain DX01 grew only on H2/CO2. The DNA G+C content is 52 mol% and optimal growth temperature is 65 degrees C. The cell pellet is brick red. By analyzing 16S rRNA sequence, methyl-coenzyme M reductase I, gamma subunit protein sequences, we determined the DX01 strain to be closely related to the species of Methanothermobacter marburgensis. In addition, Methanothermobacter thermautotrophicus delta H(T) and strain DX01 had clear differences in their biochemical composition and protein expression profiles. Based on the above analysis, we propose that strain DX01 is a novel strain within thermoautotrophicus the species of M. marburgensis, namely M. marburgensis DX01. The isolation and characterization of the new M. marburgensis DX01 strain expands the known range of the Methanothermobacter genus.