scholarly journals On the Nature of Hydrodynamic Cavitation Process and Its Application for the Removal of Water Pollutants

2019 ◽  
Vol 12 ◽  
pp. 117862211988048 ◽  
Author(s):  
Erick R Bandala ◽  
Oscar M Rodriguez-Narvaez
Keyword(s):  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
High Energy ◽  
Optimal Operation ◽  
Hydrodynamic Cavitation ◽  
Radical Scavenger ◽  
Process Conditions ◽  
Cavitation Process ◽  
Operation Conditions ◽  
Hydroxyl Radical Scavenger

Cavitation is considered a high energy demanding process for water treatment. For this study, we used a simple experimental setup to generate cavitation at a low pressure (low energy) and test it for hydroxyl radical production using a well-known chemical probe as a hydroxyl radical scavenger. The conditions for generating the cavitation process (eg, pressure, flow velocity, temperature, and other significant variables) were used to degrade model contaminants, an azo dye and an antibiotic. The amount of hydroxyl radicals generated by the system was estimated using N,N-dimethyl-p-nitrosoaniline (pNDA) as hydroxyl radical scavenger. The capability of hydrodynamic cavitation (HC) to degrade contaminants was assessed using Congo red (CR) and sulfamethoxazole (SMX) as model contaminants. Different chemical models were analyzed using UV-visible spectrophotometry (for pNDA and CR) and high-performance liquid chromatography (HPLC) (for SMX) after HC treatment under different process conditions (ie, pressure of 13.7 and 10.3 kPa, and flow rates of 0.14 to 3.6 × 10−4 m3/s). No pNDA bleaching was observed for any of the reaction conditions tested after 60 minutes of treatment, which suggests that there was no hydroxyl radical generation during the process. However, 50% degradation of CR and 25% degradation of SMX were observed under the same process conditions, comparable with previously reported results. These results suggest that the process is most likely thermally based rather than radically based, and therefore, it can degrade organic pollutants even if no hydroxyl radicals are produced. Hydrodynamic cavitation, either alone or coupled with other advanced water technologies, has been identified as a promising technology for removing organic contaminants entering the water cycle; however, more research is still needed to determine the specific mechanisms involved in the process and the optimal operation conditions for the system.

scholarly journals Contribution of Oxidative Damage to Antimicrobial Lethality

2009 ◽  
Vol 53 (4) ◽  
pp. 1395-1402 ◽  
Author(s):  
Xiuhong Wang ◽  
Xilin Zhao
Keyword(s):  
Oxidative Stress ◽  
Escherichia Coli ◽  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Fenton Reaction ◽  
Iron Chelator ◽  
Radical Scavenger ◽  
Alkyl Hydroperoxide ◽  
Hydroxyl Radical Scavenger ◽  
Rapid Conversion

ABSTRACT A potential pathway linking hydroxyl radicals to antimicrobial lethality was examined by using mutational and chemical perturbations of Escherichia coli. Deficiencies of sodA or sodB had no effect on norfloxacin lethality; however, the absence of both genes together reduced lethal activity, consistent with rapid conversion of excessive superoxide to hydrogen peroxide contributing to quinolone lethality. Norfloxacin was more lethal with a mutant deficient in katG than with its isogenic parent, suggesting that detoxification of peroxide to water normally reduces quinolone lethality. An iron chelator (bipyridyl) and a hydroxyl radical scavenger (thiourea) reduced the lethal activity of norfloxacin, indicating that norfloxacin-stimulated accumulation of peroxide affects lethal activity via hydroxyl radicals generated through the Fenton reaction. Ampicillin and kanamycin, antibacterials unrelated to fluoroquinolones, displayed behavior similar to that of norfloxacin except that these two agents showed hyperlethality with an ahpC (alkyl hydroperoxide reductase) mutant rather than with a katG mutant. Collectively, these data are consistent with antimicrobial stress increasing the production of superoxide, which then undergoes dismutation to peroxide, from which a highly toxic hydroxyl radical is generated. Hydroxyl radicals then enhance antimicrobial lethality, as suggested by earlier work. Such findings indicate that oxidative stress networks may provide targets for antimicrobial potentiation.

scholarly journals Effect of Process Parameters on Catalytic Incineration of Solvent Emissions

2008 ◽  
Vol 2008 ◽  
pp. 1-7 ◽  
Author(s):  
Satu Ojala ◽  
Ulla Lassi ◽  
Paavo Perämäki ◽  
Riitta L. Keiski
Keyword(s):  
Laboratory Experiments ◽  
Butyl Acetate ◽  
Space Velocity ◽  
Optimal Operation ◽  
Process Conditions ◽  
Statistical Experimental Design ◽  
Operation Conditions ◽  
A Minor ◽  
Increasing Temperature ◽  
By Products

Catalytic oxidation is a feasible and affordable technology for solvent emission abatement. However, finding optimal operation conditions is important, since they are strongly dependent on the application area of VOC incineration. This paper presents the results of the laboratory experiments concerning four most central parameters, that is, effects of concentration, gas hourly space velocity (GHSV), temperature, and moisture on the oxidation of n-butyl acetate. Both fresh and industrially aged commercial Pt/Al2O3catalysts were tested to determine optimal process conditions and the significance order and level of selected parameters. The effects of these parameters were evaluated by computer-aided statistical experimental design. According to the results, GHSV was the most dominant parameter in the oxidation of n-butyl acetate. Decreasing GHSV and increasing temperature increased the conversion of n-butyl acetate. The interaction effect of GHSV and temperature was more significant than the effect of concentration. Both of these affected the reaction by increasing the conversion of n-butyl acetate. Moisture had only a minor decreasing effect on the conversion, but it also decreased slightly the formation of by products. Ageing did not change the significance order of the above-mentioned parameters, however, the effects of individual parameters increased slightly as a function of ageing.

Evidence suggesting a role for hydroxyl radical in glycerol-induced acute renal failure

1988 ◽  
Vol 255 (3) ◽  
pp. F438-F443 ◽  
Author(s):  
S. V. Shah ◽  
P. D. Walker
Keyword(s):  
Renal Failure ◽  
Acute Renal Failure ◽  
Hydroxyl Radical ◽  
Tissue Injury ◽  
Iron Chelator ◽  
Radical Scavenger ◽  
Reactive Oxygen Metabolites ◽  
Protective Effects ◽  
Hydroxyl Radical Scavenger ◽  
Hydroxyl Radical Scavengers

Reactive oxygen metabolites, in particular hydroxyl radical, have been shown to be important mediators of tissue injury in several models of acute renal failure. The aim of the present study was to examine the role of hydroxyl radical in glycerol-induced acute renal failure, a model for myoglobinuric renal injury. Rats injected with glycerol alone (8 mg/kg im following dehydration for 24 h) developed significant renal failure compared with dehydrated controls. Rats treated with glycerol and a hydroxyl radical scavenger, dimethylthiourea (DMTU), had significantly lower blood urea nitrogen (BUN) and creatinine. In contrast, urea, which is chemically similar to DMTU but is not a hydroxyl radical scavenger, provided no protection. In addition, DMTU prevented the glycerol-induced rise in renal cortical malondialdehyde content (a measure of lipid peroxidation that serves as a marker of free radical-mediated tissue injury). A second hydroxyl radical scavenger, sodium benzoate, had a similar protective effect on renal function (as measured by both BUN and creatinine). Because the generation of hydroxyl radical in biological systems requires the presence of a trace metal such as iron, we also examined the effect of the iron chelator, deferoxamine on glycerol-induced renal failure. Deferoxamine was also protective. The interventional agents were also associated with a marked reduction in histological evidence of renal damage. The protective effects of two hydroxyl radical scavengers as well as an iron chelator implicate a role for hydroxyl radical in glycerol-induced acute renal failure.

scholarly journals Involvement of a local Fenton reaction in the reciprocal modulation by O2 of the glucagon-dependent activation of the phosphoenolpyruvate carboxykinase gene and the insulin-dependent activation of the glucokinase gene in rat hepatocytes

1998 ◽  
Vol 335 (2) ◽  
pp. 425-432 ◽  
Author(s):  
Thomas KIETZMANN ◽  
Torsten PORWOL ◽  
Karl ZIEROLD ◽  
Kurt JUNGERMANN ◽  
Helmut ACKER
Keyword(s):  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Fenton Reaction ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Gene Activation ◽  
Three Dimensional ◽  
Rat Hepatocytes ◽  
Confocal Laser ◽  
Radical Scavenger ◽  
Insulin Dependent

H2O2 mimicked the action of periportal pO2 in the modulation by O2 of the glucagon-dependent activation of the phosphoenolpyruvate carboxykinase (PCK) gene and the insulin-dependent activation of the glucokinase (GK) gene. H2O2 can be converted in the presence of Fe2+ in a Fenton reaction into hydroxyl anions and hydroxyl radicals (•OH). The hydroxyl radicals are highly reactive and might interfere locally with transcription factors. It was the aim of the present study to investigate the role of and to localize such a Fenton reaction. Hepatocytes cultured for 24 h were treated under conditions mimicking periportal or perivenous pO2 with glucagon or insulin plus the iron chelator desferrioxamine (DSF) or the hydroxyl radical scavenger dimethylthiourea (DMTU) to inhibit the Fenton reaction. PCK mRNA was induced by glucagon maximally under conditions of periportal pO2 and half-maximally under venous pO2. GK mRNA was induced by insulin with reciprocal modulation by O2. DSF and DMTU reduced the induction of PCK mRNA to about half-maximal and increased the induction of GK mRNA to maximal under both O2 tensions. Hydroxyl radical formation was maximal under arterial pO2. Perivenous pO2, DSF and DMTU each decreased the formation of •OH to about 70% of control. The Fenton reaction could be localized in a perinuclear space by confocal laser microscopy and three-dimensional reconstruction techniques. In the same compartment, iron could be detected by electron-probe X-ray microanalysis. Thus a local Fenton reaction is involved in the O2 signalling, which modulated the glucagon- and insulin-dependent PCK gene and GK gene activation.

scholarly journals A NOVEL HYDROXYL RADICAL SCAVENGER, NICARAVEN, ATTENUATES ISCHEMIA REPERFUSION INJURY OF THE LIVER

1998 ◽  
Vol 65 (Supplement) ◽  
pp. 148
Author(s):  
R. Yokota ◽  
T. Shimamura ◽  
T. Suzuki ◽  
M. Fukai ◽  
M. Taniguchi ◽  
...  
Keyword(s):  
Hydroxyl Radical ◽  
Reperfusion Injury ◽  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Radical Scavenger ◽  
Hydroxyl Radical Scavenger

Synthesis of New Carnosine Derivatives ofβ-Cyclodextrin and Their Hydroxyl Radical Scavenger Ability

2002 ◽  
Vol 85 (6) ◽  
pp. 1633-1643 ◽  
Author(s):  
Diego La Mendola ◽  
Salvatore Sortino ◽  
Graziella Vecchio ◽  
Enrico Rizzarelli
Keyword(s):  
Hydroxyl Radical ◽  
Radical Scavenger ◽  
Hydroxyl Radical Scavenger

scholarly journals Stimulation of vagal pulmonary C fibers by inhaled wood smoke in rats

1998 ◽  
Vol 84 (1) ◽  
pp. 30-36 ◽  
Author(s):  
C. J. Lai ◽  
Y. R. Kou
Keyword(s):  
Hydroxyl Radical ◽  
Combined Treatment ◽  
Wood Smoke ◽  
Radical Scavenger ◽  
C Fibers ◽  
Hydroxyl Radical Scavenger ◽  
C Fiber ◽  
Delayed Phase ◽  
Stimulation Of ◽  
Sustained Increase

Lai, C. J., and Y. R. Kou. Stimulation of vagal pulmonary C fibers by inhaled wood smoke in rats. J. Appl. Physiol. 84(1): 30–36, 1998.—This study investigated the stimulation of vagal pulmonary C fibers (PCs) by wood smoke. We recorded impulses from PCs in 58 anesthetized, open-chest, and artificially ventilated rats and delivered 6 ml of wood smoke into the lungs. Within 1 or 2 s after the smoke delivery, an intense and nonphasic burst of discharge [Δ = +7.4 ± 0.7 (SE) impulses/s, n = 68] was evoked in 60 of the 68 PCs studied and lasted for 4–8 s. This immediate stimulation was usually followed by a delayed and more sustained increase in C-fiber activity (Δ = +2.0 ± 0.4 impulses/s). The overall stimulation was not influenced by removal of smoke particulates ( n = 15) or by pretreatment with vehicle ( n = 8) for dimethylthiourea (DMTU; a hydroxyl radical scavenger) or indomethacin (Indo; a cyclooxygenase inhibitor). The immediate-phase stimulation was not affected by pretreatment with Indo ( n= 8) but was largely attenuated by pretreatment with DMTU ( n = 12) or by a combined treatment with DMTU and Indo (DMTU+Indo; n = 8). Conversely, the delayed-phase stimulation was partially suppressed either by DMTU or by Indo but was totally abolished by DMTU+Indo. These results suggest that 1) the stimulation of PCs is linked to the gas phase of wood smoke and 2) hydroxyl radical, but not cyclooxygenase products, is involved in the immediate-phase stimulation, whereas both metabolites are responsible for evoking the delayed-phase stimulation.

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