scholarly journals Revealing the membrane fouling mechanism caused by the denitrification filter effluent during ozonation by model assessment

2021 ◽  
Author(s):  
Yuan Bai ◽  
Yin-Hu Wu ◽  
Xin Tong ◽  
Yun-Hong Wang ◽  
Nozomu Ikuno ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Membrane Fouling ◽  
Redundancy Analysis ◽  
Model Parameters ◽  
Stable Operation ◽  
Model Assessment ◽  
Predominant Role ◽  
Fouling Mechanism ◽  
Organic Fractions ◽  
Molecular Weight Fractions

Abstract Membrane fouling has been a major obstacle for stable operation of ultrafiltration. In this study, prevailing fouling models were applied to assess the fouling behavior of the denitrification filter (DNF) effluent during ozonation. In order to clarify the fouling mechanism, correlation analysis and redundancy analysis (RDA) were conducted to investigate the correlations among model parameters, fouling potential and water features of the DNF effluent. The combined intermediate-standard model exhibited superior determination coefficients (R2 > 0.99). Based on analytical results, the model parameter of intermediate blocking (Ki) and standard blocking (Ks) was fairly applicable to describe the fouling of higher molecular weight (MW > 4,000 Da) fractions (F1) and lower molecular weight fractions (F2, MW = 2,000–4,000 Da and F3, MW < 2,000 Da), respectively. In comparison, F1 played a predominant role in the fouling behavior of the DNF effluent. Increased ozone dosage resulted in decreased membrane fouling contribution of F1 and increased fouling contribution of F2 and F3 during ozonation. The change of fouling contributions was attributed to the transformation of high MW fractions into lower MW fractions by ozonation. This study clarified the relationships between model parameters and the membrane fouling process caused by organic fractions with specific molecular weight, thus demonstrating the membrane fouling mechanism of the DNF effluent during ozonation.

Ceramic microfiltration – influence of pretreatment on operational performance

2015 ◽  
Vol 10 (4) ◽  
pp. 747-760 ◽  
Author(s):  
J. Zheng ◽  
G. Galjaard ◽  
H. Shorney-Darby
Keyword(s):  
Molecular Weight ◽  
Ion Exchange ◽  
Membrane Fouling ◽  
Complete Removal ◽  
Economic Feasibility ◽  
Stable Operation ◽  
Pilot Studies ◽  
Virus Removal ◽  
Pre Treatment ◽  
The Impact

A sustainable membrane operation often requires pretreatment of the feed liquor to improve its technical and economic feasibility. This paper reports the impact of pretreatment on the performance of ceramic microfiltration for several pilot studies at different locations. Four different pretreatment processes were investigated: (1) in-line coagulation (to remove high molecular weight, HMW, dissolved organic carbon, DOC); (2) ion exchange (to remove low molecular weight, LMW, DOC); (3) ozone (for disinfection, taste and odor control, and modifying the character of DOC) (4) ion exchange followed by in-line coagulation (for almost complete removal of DOC). Pretreatment in all cases was needed to control membrane fouling, to establish a technically and economically feasible process. These studies seem to show that the DOC's HMW (which includes biopolymers) and LMW fractions (the latter includes humics/acids), are primarily responsible for the TMP increase after filtration followed by backwashing (irreversible fouling). Removing one of these organic fractions often results in more stable operation. Ozonation in all cases led to better operation, but is not always economically feasible. The feasibility of ozone as pre-treatment depends largely on the initial ozone demand, and whether or not there are secondary treatment targets (e.g., higher virus removal, taste, and/or odor).

Applications of Algal Polysaccharides and Derivatives in Therapeutic and Agricultural Fields

2019 ◽  
Vol 25 (11) ◽  
pp. 1187-1199 ◽  
Author(s):  
Soukaina Bouissil ◽  
Guillaume Pierre ◽  
Zainab El Alaoui-Talibi ◽  
Philippe Michaud ◽  
C. El Modafar ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Wound Dressing ◽  
Chemical Processes ◽  
Bioactive Molecules ◽  
Present Review ◽  
Agricultural Fields ◽  
Low Molecular Weight ◽  
Molecular Weight Fractions ◽  
Algal Polysaccharides ◽  
Agricultural Fertilizer

Background: Recently, researchers have given more and more consideration to natural polysaccharides thanks to their huge properties such as stability, biodegradability and biocompatibility for food and therapeutics applications. Methods: a number of enzymatic and chemical processes were performed to generate bioactive molecules, such as low molecular weight fractions and oligosaccharides derivatives from algal polysaccharides. Results: These considerable characteristics allow algal polysaccharides and their derivatives such as low molecular weight polymers and oligosaccharides structures to have great potential to be used in lots of domains, such as pharmaceutics and agriculture etc. Conclusion: The present review describes the mains polysaccharides structures from Algae and focuses on the currents agricultural (fertilizer, bio-elicitor, stimulators, signaling molecules and activators) and pharmaceutical (wound dressing, tissues engineering and drugs delivery) applications by using polysaccharides and/or their oligosaccharides derivatives obtained by chemical, physical and enzymatic processes.

Existence of lipid vesicles containing platelet-activating factor in endothelial cell lysate

1992 ◽  
Vol 12 (1) ◽  
pp. 15-21
Author(s):  
S. Kojima ◽  
K. Nara ◽  
Y. Inada ◽  
S. Hirose ◽  
Y. Saito
Keyword(s):  
Molecular Weight ◽  
Endothelial Cell ◽  
Specific Activity ◽  
Gel Filtration ◽  
Platelet Activating Factor ◽  
Lipid Vesicles ◽  
Specific Factor ◽  
Cell Lysate ◽  
Aggregation Activity ◽  
Molecular Weight Fractions

Platelet aggregation activity due to platelet-activating factor (PAF) was detected at high molecular weight (HMW) and low molecular weight fractions after gel-filtration chromatography of cell lysate of endothelial cells. [3H]PAF added to the cell lysate was similarly distributed after chromatography. The radioactivity associated with HMW fraction was not reduced by digesting the lysate with trypsin, suggesting that PAF was not making complexes with proteins but was included in lipid vesicles in cell lysate. Further evidence showed that an unknown specific factor(s) was needed to form these PAF-containing lipid vesicles. Radioactivity was not found in HMW fraction when [3H]PAF was mixed with cell lysate of vascular smooth muscle cells. When monomeric PAF was added to endothelial cell lysate, the specific activity of aggregation decreased to the level exerted by endogenous PAF-containing lipid vesicles due to incorporation into lipid vesicles. PAF in the form of lipid vesicles was more stable in plasma than monomeric form.

scholarly journals α-Crystallin. The isolation and characterization of distinct macromolecular fractions

1971 ◽  
Vol 124 (2) ◽  
pp. 337-343 ◽  
Author(s):  
Abraham Spector ◽  
Lu-Ku Li ◽  
Robert C. Augusteyn ◽  
Arthur Schneider ◽  
Thomas Freund
Keyword(s):  
Molecular Weight ◽  
Amino Acid ◽  
Gel Filtration ◽  
Deae Cellulose ◽  
Chemical Difference ◽  
Molecular Weights ◽  
Isolation And Characterization ◽  
Different Populations ◽  
Molecular Weight Fractions

α-Crystallin was isolated from calf lens periphery by chromatography on DEAE-cellulose and gel filtration. Three distinct populations of macromolecules have been isolated with molecular weights in the ranges approx. 6×105−9×105, 0.9×106−4×106and greater than 10×106. The concentration of macromolecules at the molecular-weight limits of a population are very low. The members of the different populations do not appear to be in equilibrium with each other. Further, in those molecular-weight fractions investigated, no equilibrium between members of the same population was observed. The population of lowest molecular weight comprises 65–75% of the total material. The amino acid and subunit composition of the different-sized fractions appear very similar, if not identical. The only chemical difference observed between the fractions is the presence of significant amounts of sugar in the higher-molecular-weight fractions. Subunit molecular weights of approx. 19.5×103and 22.5×103were observed for all α-crystallin fractions.

Degradation of natural and Kraft lignins by the microflora of soil and water

1977 ◽  
Vol 23 (4) ◽  
pp. 434-440 ◽  
Author(s):  
Don L. Crawford ◽  
Suellen Floyd ◽  
Anthony L. Pometto III ◽  
Ronald L. Crawford
Keyword(s):  
Molecular Weight ◽  
Microbial Degradation ◽  
Lignin Degradation ◽  
Kraft Lignin ◽  
Lignin Biodegradation ◽  
Incubation Periods ◽  
Molecular Weight Fractions ◽  
Soil And Water ◽  
Different Molecular Weight ◽  
Microbial Attack

The comparative rates of microbial degradation 14C-lignin-labeled lignocelluloses and 14C-Kraft lignins were investigated using selected soil and water samples as sources of microorganisms. Natural lignocelluloses containing 14C primarily in their lignin components were prepared by feeding plants uniformly labeled L-[14C]phenylalanine through their cut stems. 14C-Kraft lignins were prepared by pulping lignin-labeled lignocelluloses. Rates of lignin biodegradation were determined by monitoring 14CO2 evolution from incubation mixtures over incubation periods of up to 1000 h. Observed rates of lignin degradation were slow in all cases. Kraft lignins appeared more resistant to microbial attack than natural lignins, even though they were decomposed more rapidly during the first 100–200 h of incubation. Similar degradation patterns were observed in both soil and water. Individual samples, however, varied greatly in their overall rates of degradation of either lignin type. A Kraft-lignin preparation was separated into a variety of molecular weight fractions by column chromatography on LH-20 Sephadex and the biodegradability of the different molecular weight fractions determined. The lower molecular weight fractions of the Kraft lignin were decomposed at a significantly faster rate by the microflora of soil than were the fractions of higher molecular weight.

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