Effects of pH on photocatalysis of 2,4,6-trichlorophenol in aqueous TiO2 suspensions

1994 ◽  
Vol 30 (9) ◽  
pp. 47-57 ◽  
Author(s):  
Shuzo Tanaka ◽  
Uttam Kumar Saha
Keyword(s):  
Sodium Chloride ◽  
Degradation Rate ◽  
Parent Compound ◽  
Photocatalytic Decomposition ◽  
Illumination Time ◽  
Effects Of Ph ◽  
Alkaline Conditions ◽  
Na Ions ◽  
Acidic Conditions

The effects of pH on the photocatalytic decomposition of 2,4,6-trichlorophenol (TCP) were investigated in the presence of titanium dioxide suspensions illuminated by a high pressure mercury lamp over the wavelength range of 302-405 nm. Higher degradation rate was observed under alkaline conditions than acidic conditions. Although a rapid adsorption of TCP onto the TiO2 surface was observed at low pH and no adsorption at high pH, the role of adsorption of TCP was found insignificant in photocatalysis. With sodium chloride addition, a decrease in reaction rate was observed at pH 5 due to Cl− ions inhibition, but at pH 10 the same anions had no adverse effect on the measured photocatalytic efficiency and Na+ ions enhanced the degradation rate of TCP. With no oxygen, however, the photocatalytic decomposition of TCP in sodium chloride solution gives lower degradation rate than with dissolved oxygen and no sodium chloride at various pH. Complete mineralization requires a longer illumination time than the decomposition of the parent compound. A mechanism for the reaction based on photogeneration of hydroxyl radicals was proposed.

scholarly journals Preparation of TiO2/Black Talc Composite Photocatalyst and the Research on Its Adsorption-Degradation Coupling Effects

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6038
Author(s):  
Huan Shuai ◽  
Yuxin Wang ◽  
Jiao Wang ◽  
Gaoxiang Du ◽  
Daimei Chen ◽  
...  
Keyword(s):  
Synergistic Effect ◽  
Tio2 Nanoparticles ◽  
Rhodamine B ◽  
Degradation Rate ◽  
Sol Gel ◽  
Coupling Effects ◽  
Illumination Time ◽  
Composite Photocatalyst ◽  
Gel Method

In this paper, a TiO2/black talc composite photocatalyst was prepared by the sol-gel method using TBOT as titanium source and black talc as carrier. Rhodamine B was used as the targeted pollutant to study the adsorption role of carbon in black talc. The results showed that with the adsorption-degradation cycles, the illumination time can be reduced by 40%. The adsorption rate and degradation rate of the composite photocatalyst was also increased. The degradation rate of Rhodamine B reached more than 95%, which fully shows the synergistic effect between TiO2 nanoparticles and black talc. In this way, the adsorption-degradation coupling of the photocatalyst could be realized.

scholarly journals Antimicrobial activity of DU-6681a, a parent compound of novel oral carbapenem DZ-2640.

1997 ◽  
Vol 41 (6) ◽  
pp. 1260-1268 ◽  
Author(s):  
M Tanaka ◽  
M Hohmura ◽  
T Nishi ◽  
K Sato ◽  
I Hayakawa
Keyword(s):  
Parent Compound ◽  
Inoculum Size ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Alkaline Conditions ◽  
In Vitro Antibacterial Activity ◽  
Acidic Conditions ◽  
Kill Curve ◽  
Time Kill

The in vitro antibacterial activity of DU-6681a, a parent compound of DZ-2640, against gram-positive and -negative bacteria was compared with those of penems and cephalosporins currently available. MICs at which 90% of the isolates are inhibited (MIC90s) of the compound for clinical isolates of methicillin-susceptible and -resistant Staphylococcus aureus and Staphylococcus epidermidis, including methicillin-susceptible and -resistant strains, were 0.10, 25, and 12.5 microg/ml, respectively. DU-6681a inhibited the growth of all strains of Streptococcus pyogenes and of penicillin-susceptible and -insusceptible Streptococcus pneumoniae at 0.006, 0.025, and 0.20 microg/ml, respectively, and MIC90s of the compound were 6.25 and >100 microg/ml for Enterococcus faecalis and Enterococcus faecium, respectively. MIC90s of DU-6681a were 0.20, 0.10, and 0.025 microg/ml for Haemophilus influenzae, Moraxella catarrhalis, and Neisseria gonorrhoeae, respectively. For Pseudomonas aeruginosa, the MIC50 and MIC90 of DU-6681a were 25 and 50 microg/ml, respectively. DU-6681a activity was not affected by different media, varied inoculum size (10(4) to 10(7) CFU), or the addition of human serum but was decreased under acidic conditions against gram-negative bacteria, under alkaline conditions against gram-positive bacteria, and in human urine, as was the activity of the other antibiotics tested. The frequency of spontaneous resistance to DU-6681a was less than or equal to those of the reference compounds. Time-kill curve studies demonstrated the bactericidal action of DU-6681a against S. aureus, S. pneumoniae, Escherichia coli, and H. influenzae.

scholarly journals Photooxidation Contribution Study on the Decomposition of Azo Dyes in Aqueous Solutions by VUV-Based AOPs

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
Chih-Ming Ma ◽  
Gui-Bing Hong ◽  
Hua-Wei Chen ◽  
Nguyen-Thi Hang ◽  
Yung-Shuen Shen
Keyword(s):  
Azo Dyes ◽  
Ph Value ◽  
Reaction Rates ◽  
Degradation Of Dyes ◽  
Degradation Rates ◽  
Effects Of Ph ◽  
Alkaline Conditions ◽  
Acidic Conditions ◽  
High Concentrations ◽  
Acid Blue

The effects of pH value, VUV intensity, initial dye concentration, initial H2O2concentration, and TiO2loading dose on the degradation of three azo dyes: acid Orange 8, acid Blue 29, and acid Blue 113 were studied to explore and compare the treatment efficiencies among the adopted AOPs. It was found that pH played an important role in the degradation of dyes using VUV irradiation. For VUV/H2O2, VUV/TiO2, and VUV/TiO2/H2O2processes, the decoloration rates of the three azo dyes were more efficient under acidic conditions relative to alkaline conditions. The degradation rates of dyes increased with increasing concentrations of H2O2, but reaction rates were retarded at high concentrations of H2O2because the H2O2compound acted as a scavenger of the hydroxyl radical. In this paper, three azo dyes were decomposed efficiently by VUV irradiation only demonstrating the effectiveness of VUV direct photolysis.

scholarly journals Single and combined removal of Cr(VI) and Cd(II) by nanoscale zero-valent iron in the absence and presence of EDDS

2017 ◽  
Vol 76 (5) ◽  
pp. 1261-1271 ◽  
Author(s):  
Haoran Dong ◽  
Yalan Zeng ◽  
Yankai Xie ◽  
Qi He ◽  
Feng Zhao ◽  
...  
Keyword(s):  
Dissolved Oxygen ◽  
Zero Valent Iron ◽  
Inhibition Effect ◽  
Insignificant Effect ◽  
Removal Process ◽  
Nanoscale Zero Valent Iron ◽  
Effects Of Ph ◽  
Alkaline Conditions ◽  
Acidic Conditions ◽  
Ph Dependent

This study examined the feasibility of nanoscale zero-valent iron (nZVI) for the single and combined removal of Cr(VI) and Cd(II) with or without ethylene diamine disuccinic acid (EDDS). The effects of pH and dissolved oxygen (DO) on the removal process were investigated. Results show that the single removal of either Cr(VI) or Cd(II) by nZVI was pH dependent, where the higher Cr(VI) removal was achieved under acidic conditions, whereas the higher Cd(II) removal was achieved under alkaline conditions. The presence of DO enhanced Cd(II) removal but inhibited Cr(VI) removal under alkaline conditions. In the co-existence of Cr(VI) and Cd(II), it was found that Cd(II) exerted insignificant effect on Cr(VI) removal, while the presence of Cr(VI) remarkably enhanced the Cd(II) removal. The addition of EDDS exhibited different influences on Cr(VI) and Cd(II) removal, which were associated with pH and DO. The EDDS enhanced Cr(VI) removal at pH 5.6–9.0 in the absence of DO, but decreased Cr(VI) removal at pH 9.0 in the presence of DO. For the removal of Cd(II) at pH 5.6–7.0, either facilitation or inhibition effect of EDDS was observed, depending on EDDS concentration and the co-existence of Cr(VI). However, Cd(II) removal was always significantly inhibited by EDDS at pH 9.0.

scholarly journals The Role of H2C2O4 and Na2CO3 as Precipitating Agents on The Physichochemical Properties and Photocatalytic Activity of Bismuth Oxide

2020 ◽  
Vol 18 (1) ◽  
pp. 129-137
Author(s):  
Yayuk Astuti ◽  
Rizka Andianingrum ◽  
Abdul Haris ◽  
Adi Darmawan ◽  
Keyword(s):  
Photocatalytic Activity ◽  
Methyl Orange ◽  
Physicochemical Properties ◽  
Bismuth Oxide ◽  
Rate Constants ◽  
Degradation Rate ◽  
Precipitation Method ◽  
Methyl Orange Degradation ◽  
Methyl Orange Dye

AbstractSynthesis of bismuth oxide synthesis through the precipitation method using H2C2O4 and Na2CO3 precipitating agents, identification of physicochemical properties and its photocatalysis activity for methyl orange degradation were conducted. The bismuth oxide synthesis was undertaken by dissolving Bi(NO3)3.5H2O in HNO3, then added precipitating agents to form precipitate. The results showed that bismuth oxide produced by H2C2O4 precipitating agent was a yellow powder containing a mixture of α-Bi2O3 (monoclinic) and β-Bi2O3 (tetragonal), porous with size of 28-85 μm. Meanwhile, the use of Na2CO3 as precipitating agent resulted in bismuth oxide consisting of α-Bi2O3 and β-Bi2O3 and Bi2O4, irregular shape without pore being 40-115 μm in size. Bismuth oxide synthesized with H2C2O4 precipitating agent showed higher photocatalytic activity compared to bismuth oxide synthesized using Na2CO3 on degrading methyl orange dye with degradation rate constants of 2.35x10-5 s-1 for H2C2O4 and 1.81x10-5 s-1 for Na2CO3.

scholarly journals Role of Branched-Chain Fatty Acids in pH Stress Tolerance in Listeria monocytogenes

2006 ◽  
Vol 73 (3) ◽  
pp. 997-1001 ◽  
Author(s):  
Efstathios S. Giotis ◽  
David A. McDowell ◽  
Ian S. Blair ◽  
Brian J. Wilkinson
Keyword(s):  
Fatty Acids ◽  
Listeria Monocytogenes ◽  
Stress Tolerance ◽  
Ph Sensitive ◽  
Branched Chain Fatty Acids ◽  
Alkaline Conditions ◽  
Branched Chain ◽  
Ph Adaptation ◽  
Chain Fatty Acids

ABSTRACT In alkaline conditions, Listeria monocytogenes cells develop higher proportions of branched-chain fatty acids (FAs), including more anteiso forms. In acid conditions, the opposite occurs. Reduced growth of pH-sensitive mutants at adverse pH (5.0/9.0) was alleviated by the addition of 2-methylbutyrate (an anteiso-FA precursor), suggesting that anteiso-FAs are important in adaptation to adverse pH. The balance between anteiso- and iso-FAs may be more important than changes in the amounts and/or degrees of saturation of FAs in pH adaptation.

Interaction with Endogenous Microorganisms, Comamonas testosteroni Enhanced the Degradation of Polycyclic Aromatic Hydrocarbon in Soil

2021 ◽  
Author(s):  
Xueting Sun ◽  
Xin Li ◽  
Yue Cui ◽  
Ziwei Jiang ◽  
Qiao Wang ◽  
...  
Keyword(s):  
Contaminated Soil ◽  
Structural Equation ◽  
Functional Role ◽  
Degradation Rate ◽  
Structural Equation Models ◽  
Low Molecular Weight ◽  
Comamonas Testosteroni ◽  
Functional Bacteria ◽  
Polycyclic Aromatic

Abstract This study was to explore the functional role of Comamonas testosteroni (Ct) on soil indigenous microorganisms, and analyze the effect of Ct on PAHs degradation in PAH-contaminated soil. Results showed that inoculation of Ct could degrade naphthalene (Nap), phenanthrene (Phe), and benzo [α] pyrene (BaP) significantly. The degradation rate of Nap, Phe and BaP was 81.18%, 63.38% and 37.98% on day 25, respectively, suggesting that the low molecular weight of Nap and Phe were easier to be degraded by microorganisms than BaP. Network analysis showed that inoculation of Ct significantly increased the bacteria closely related to PAHs. Structural equation models confirmed Steroidobacter as functional bacteria could affect the degradation of Nap and BaP. Inoculated Ct could effectively enhance the synergy among indigenous bacteria to degrade PAHs. This would be helpful to understand the function of inoculated strains in PAH-contaminated soil and identify functional microorganisms of PAHs remediation.

The Role of Biotransformation in the Activity of Endocrine Disruptors

2021 ◽  
Vol 22 ◽  
Author(s):  
Elif Ince Erguc ◽  
Alev Tascioglu-Aliyev ◽  
Bita Entezari ◽  
Hande Gurer-Orhan
Keyword(s):  
Parent Compound ◽  
Endocrine System ◽  
Decisive Role ◽  
Industrial Chemicals ◽  
Toxic Metabolites ◽  
Synthetic Chemicals ◽  
Polybrominated Biphenyls ◽  
Diverse Groups ◽  
Natural Hormones

: An “endocrine disruptor” has been broadly defined as an exogenous chemical that interferes with the production, release, transport, metabolism, binding, action, or elimination of endogenous hormones which are responsible for homeostasis, reproduction, development or behaviour. Diverse groups of chemicals such as pharmaceuticals, phytoestrogens, natural hormones, and synthetic chemicals such as pesticides, plasticizers, phthalates, parabens, polychlorinated/polybrominated biphenyls, bisphenols are shown to interfere with the endocrine system and defined as EDs in the last three decades. As for all chemicals, the biotransformation of EDs has a decisive role in their potential toxic effects. Humans are exposed to vast amounts of diverse chemicals throughout their life. Fortunately, most of the chemicals are converted, via biotransformation reactions catalysed by enzymes, into more hydrophilic metabolites, which are readily excreted in urine or bile. Biotransformation reactions resulting in less toxic metabolites are known as detoxification. However, some biotransformation reactions are called bioactivation in which more toxic metabolites are formed. In the case of EDs, metabolites formed via bioactivation usually have a higher affinity for a hormone receptor or induce/inhibit an enzyme involved in the synthesis or catabolism of an endogenous hormone more dramatically compared to their parent compound. In the present review, the role of bioactivation in endocrine modulating effects of chemicals from all groups of Eds is highlighted, namely endogenous estrogens, phytoestrogens, synthetic/industrial chemicals, and pharmaceuticals.

Role of sodium-calcium exchange in regulation of intracellular calcium in nerve terminals

1987 ◽  
Vol 252 (6) ◽  
pp. C595-C603 ◽  
Author(s):  
S. Sanchez-Armass ◽  
M. P. Blaustein
Keyword(s):  
Hill Coefficient ◽  
Nerve Terminals ◽  
Physiological Load ◽  
Carbonyl Cyanide ◽  
Ca Uptake ◽  
Na Ions ◽  
Presynaptic Nerve Terminals ◽  
45Ca Efflux ◽  
Mitochondrial Uncoupler

Ca efflux from rat brain presynaptic nerve terminals (synaptosomes) was examined after loading the terminals with 45Ca during a brief depolarization, usually in media containing 20 microM Ca labeled with 45Ca, to assure a small (physiological) load. Efflux of 45Ca was very slow in the absence of external Na and Ca (approximately 0.5% of the load/s) and was greatly accelerated by Na and/or Ca (presumably Na+-Ca2+ and Ca2+-Ca2+ exchange, respectively). The dependence of 45Ca efflux on external Na was sigmoid, with a Hill coefficient of approximately 2.5; this implies that more than two external Na ions are required to activate the efflux of one Ca ion. The external Na (Nao)-dependent Ca efflux was inhibited by 1 mM external La, by low temperature (Q10 congruent to 2.3), and by raising external K (to depolarize the synaptosomes). With small Ca loads, the mitochondrial uncoupler, carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP), had negligible effect on either Ca uptake or efflux; with large loads (greater than or equal to 5 nmol/mg protein), however, FCCP reduced the depolarization-stimulated Ca uptake and increased the Nao-dependent Ca efflux. These effects may be attributed to reduction of mitochondrial Ca sequestration. Mitochondria do not appear to sequester much Ca when the loads are smaller (and more physiological). Estimations of Ca efflux indicate that approximately 20% of a small 45Ca load (approximately 0.75 nmol Ca/mg protein) may be extruded via Na+-Ca2+ exchange within 1 s; this corresponds to a net Ca efflux of approximately 110 pmol Ca X mg protein-1 X s-1.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Maintenance Role of a Glutathionyl-Hydroquinone Lyase (PcpF) in Pentachlorophenol Degradation by Sphingobium chlorophenolicum ATCC 39723

2008 ◽  
Vol 190 (23) ◽  
pp. 7595-7600 ◽  
Author(s):  
Yan Huang ◽  
Randy Xun ◽  
Guanjun Chen ◽  
Luying Xun
Keyword(s):  
Degradation Rate ◽  
Tricarboxylic Acid Cycle ◽  
Degradation Pathway ◽  
Tricarboxylic Acid ◽  
Metabolic Intermediate ◽  
Reductive Dehalogenase ◽  
Cell Extracts ◽  
Toxic Pollutant ◽  
Sphingobium Chlorophenolicum

ABSTRACT Pentachlorophenol (PCP) is a toxic pollutant. Its biodegradation has been extensively studied in Sphingobium chlorophenolicum ATCC 39723. All enzymes required to convert PCP to a common metabolic intermediate before entering the tricarboxylic acid cycle have been characterized. One of the enzymes is tetrachloro-p-hydroquinone (TeCH) reductive dehalogenase (PcpC), which is a glutathione (GSH) S-transferase (GST). PcpC catalyzes the GSH-dependent conversion of TeCH to trichloro-p-hydroquinone (TriCH) and then to dichloro-p-hydroquinone (DiCH) in the PCP degradation pathway. PcpC is susceptible to oxidative damage, and the damaged PcpC produces glutathionyl (GS) conjugates, GS-TriCH and GS-DiCH, which cannot be further metabolized by PcpC. The fate and effect of GS-hydroquinone conjugates were unknown. A putative GST gene (pcpF) is located next to pcpC on the bacterial chromosome. The pcpF gene was cloned, and the recombinant PcpF was purified. The purified PcpF was able to convert GS-TriCH and GS-DiCH conjugates to TriCH and DiCH, respectively. The GS-hydroquinone lyase reactions catalyzed by PcpF are rather unusual for a GST. The disruption of pcpF in S. chlorophenolicum made the mutant lose the GS-hydroquinone lyase activities in the cell extracts. The mutant became more sensitive to PCP toxicity and had a significantly decreased PCP degradation rate, likely due to the accumulation of the GS-hydroquinone conjugates inside the cell. Thus, PcpF played a maintenance role in PCP degradation and converted the GS-hydroquinone conjugates back to the intermediates of the PCP degradation pathway.

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