Ultrasonic Irradiation Of The Removal Of Linear Alkylbenzene Sulphonates (LAS) From Wastewater

2012 ◽  
Author(s):  
Mohd Ariffin Abu Hassan ◽  
Dionissios Mantzavinos ◽  
Ian S. Metcalfe
Keyword(s):  
Ultrasonic Irradiation ◽  
Surfactant Concentration ◽  
Degradation Rate ◽  
Degradation Mechanism ◽  
Low Frequency ◽  
Degradation Pathway ◽  
H2o2 Production ◽  
Oh Radicals ◽  
Linear Alkylbenzene ◽  
Batch Time

Kesan frekuensi rendah (20 kHz) penyinaran ultrasonik untuk penyingkiran Linear Alkylbenzene Sulphonates (LAS) daripada larutan berair telah dikaji. Penyinaran ultrasonik terhadap tiga kepekatan berbeza LAS iaitu 500 μgmol/l, 750 μgmol/l and 1000 μgmol/l telah dijalankan. Kesemua eksperimen telah dijalankan pada suhu 30°C, pada frekuensi 20 kHz, kuasa pada 125 W dan masa eksperimen selama 120 minit tanpa pengawalan terhadap pH. Hasil kajian mendapati OH· radikal mendominasi proses pengdegradasian LAS. Kadar degradasi awal bertambah dengan bertambahnya kepekatan LAS di dalam skop kajian. Penghasilan H2O2 didapati rendah dengan proses penyinaran ultrasonik terhadap LAS pada kepekatan LAS yang tinggi. Keputusan penyinaran ultrasonik terhadap LAS dengan kehadiran Br¯ sebagai pemakan radikal membuktikan bahawa OH· radikal mendominasi pengdegradasian LAS. Kata kunci: Surfaktan, ultrasonik, sisa air, jumlah karbon organik (TOC) The effect of low frequency (20 kHz) ultrasonic irradiation on the removal of sodium Linear Alkylbenzene Sulphonates (LAS) from aqueous solutions has been investigated. Sonication of three different initial concentrations of LAS, 500 μgmol/l, 750 μgmol/l and 1000 μgmol/l, were performed. All experiments used a temperature of 30°C, frequency of 20 kHz, power of 125 W, a batch time of 120 min and the pH was left uncontrolled. It was found that the main degradation of LAS at micromolar concentrations proceeded via a reaction with OH· radicals. The initial degradation rate increased with an increase in the surfactant concentration over the whole concentration range studied. The sonolysis of LAS showed a strong inhibition of H2O2 production at a higher concentration. Sonication of LAS in the presence of Br¯ suggested that OH· radicals induced degradation pathway was the dominating sonochemical degradation mechanism. Key words: Surfactants, ultrasonic, wastewater, total organic carbon (TOC)

Anaerobic Degradation Pathway of Linear Alkylbenzene Sulfonates (LAS) in Sulfate-Reducing Marine Sediments

2010 ◽  
Vol 44 (5) ◽  
pp. 1670-1676 ◽  
Author(s):  
Pablo A. Lara-Martín ◽  
Abelardo Gómez-Parra ◽  
José Luis Sanz ◽  
Eduardo González-Mazo
Keyword(s):  
Marine Sediments ◽  
Anaerobic Degradation ◽  
Degradation Pathway ◽  
Linear Alkylbenzene ◽  
Sulfate Reducing ◽  
Linear Alkylbenzene Sulfonates

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.

scholarly journals The MCM v3.3 degradation scheme for isoprene

2015 ◽  
Vol 15 (6) ◽  
pp. 9709-9766 ◽  
Author(s):  
M. E. Jenkin ◽  
J. C. Young ◽  
A. R. Rickard
Keyword(s):  
Boundary Layer ◽  
Free Radical ◽  
Degradation Mechanism ◽  
Closed Shell ◽  
Chemical Mechanism ◽  
Formation Mechanisms ◽  
Oh Radicals ◽  
Atmospheric Conditions ◽  
Radical Species ◽  
Master Chemical Mechanism

Abstract. The chemistry of isoprene degradation in the Master Chemical Mechanism (MCM) has been systematically refined and updated to reflect recent advances in understanding, with these updates appearing in the latest version, MCM v3.3. The complete isoprene degradation mechanism in MCM v3.3 consists of 1935 reactions of 605 closed shell and free radical species, which treat the chemistry initiated by reaction with OH radicals, NO3 radicals and ozone (O3). A detailed overview of the updates is provided, within the context of reported kinetic and mechanistic information. The revisions mainly relate to the OH-initiated chemistry, which tends to dominate under atmospheric conditions, although these include updates to the chemistry of some products that are also generated from the O3 - and NO3-initiated oxidation. The revisions have impacts in a number of key areas, including HOx recycling, NOx recycling and the formation of species reported to play a role in SOA-formation mechanisms. The performance of the MCM v3.3 isoprene mechanism has been compared with those of earlier versions (MCM v3.1 and MCM v3.2) over a range of relevant conditions, using a box model of the tropical forested boundary layer. The results of these calculations are presented and discussed, and are used to illustrate the impacts of the mechanistic updates in MCM v3.3.

scholarly journals Electrochemical Reaction in Hydrogen Peroxide and Structural Change of Platinum Nanoparticle-Supported Carbon Nanowalls Grown Using Plasma-Enhanced Chemical Vapor Deposition

2019 ◽  
Vol 5 (1) ◽  
pp. 7
Author(s):  
Masakazu Tomatsu ◽  
Mineo Hiramatsu ◽  
Hiroki Kondo ◽  
Kenji Ishikawa ◽  
Takayoshi Tsutsumi ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Degradation Mechanism ◽  
Chemical Vapor ◽  
Oh Radicals ◽  
Platinum Nanoparticle ◽  
H2o2 Reduction ◽  
Carbon Nanowalls ◽  
Cv Measurements

Hydrogen peroxide (H2O2) reactions on platinum nanoparticle-decorated carbon nanowalls (Pt-CNWs) under potential applications were investigated on a platform of CNWs grown on carbon fiber paper (CFP) using plasma-enhanced chemical vapor deposition. Through repeated cyclic voltammetry (CV), measurements of 1000 cycles using the Pt-CNW electrodes in phosphate-buffered saline (PBS) solution with 240 μM of H2O2, the observed response peak currents of H2O2 reduction decreased with the number of cycles, which is attributed to decomposition of H2O2. After CV measurements for a total of 3000 cycles, the density and height of CNWs were reduced and their surface morphology changed. Energy-dispersive X-ray (EDX) compositional mapping revealed agglomeration of Pt nanoparticles around the top edges of CNWs. The degradation mechanism of Pt-CNWs under potential application with H2O2 is discussed by focusing on the behavior of OH radicals generated by the H2O2 reduction.

scholarly journals A rapid and efficient removal approach for degradation of metformin in pharmaceutical wastewater using electro-Fenton process; optimization by response surface methodology

2019 ◽  
Vol 80 (4) ◽  
pp. 685-694 ◽  
Author(s):  
Maryam Dolatabadi ◽  
Saeid Ahmadzadeh
Keyword(s):  
Response Surface Methodology ◽  
Response Surface ◽  
Removal Efficiency ◽  
Degradation Mechanism ◽  
Pharmaceutical Products ◽  
Oh Radicals ◽  
Order Kinetic ◽  
Pharmaceutical Wastewater ◽  
Efficient Removal ◽  
Solution Ph

Abstract Presence of emerging contaminants such as pharmaceutical products in aquatic environments has received high concern due to their undesirable effect on wildlife and human health. Current work deals with developing a treatment model based on the electro- Fenton (EF) process for efficient removal of metformin (MET) from an aqueous medium. The obtained experimental results revealed that over the reaction time of 10 min and solution pH of 3, the maximum removal efficiency of 98.57% is achieved where the value of MET initial concentration, current density, and H2O2 dosage is set at 10 mg.L−1, 6 mA.cm−2, and 250 μL.L−1, respectively, which is in satisfactory agreement with the predicted removal efficiency of 98.6% with the desirability of 0.99. The presence of radical scavengers throughout the mineralization of MET under the EF process revealed that the generation of •OH radicals, as the main oxidative species, controlled the degradation mechanism. The obtained kinetics data best fitted to the first order kinetic model with the rate constant of 0.4224 min−1 (R2 = 0.9940). The developed treatment process under response surface methodology (RSM) was employed for modeling the obtained experimental data and successfully applied for efficient removal of the MET contaminant from pharmaceutical wastewater as an adequate and cost-effective approach.

OH Radical-Induced Main-Chain Scission of Poly(Ribonucleic Acids) under Anoxic Conditions

1983 ◽  
Vol 38 (1-2) ◽  
pp. 100-106 ◽  
Author(s):  
Komei Washino ◽  
Otmar Denk ◽  
Wolfram Schnabel
Keyword(s):  
Light Scattering ◽  
Main Chain ◽  
Degradation Mechanism ◽  
Chain Scission ◽  
Oh Radicals ◽  
Ribonucleic Acids ◽  
Chemical Mechanisms ◽  
Dilute Aqueous Solution ◽  
Ribose Moiety ◽  
Rayleigh Light

Poly(ribonucleic acids), poly A, poly C and poly U, were irradiated in O2-free dilute aqueous solution at pH 7 to 8 with single pulses (50 to 200 ns) of 16MeV electrons. With the aid of Rayleigh light scattering measurements main-chain scission, induced by OH radicals, was observed with the three polynucleotides. From the time dependence of the decrease of the light scattering intensity (LSI), the existence of two modes of decrease was inferred, indicating at least two different chemical mechanisms were operative in main-chain degradation. Evidence for the assignment of the slow mode of LSI decrease to the lifetime of a free radical was obtained from quenching experiments with cysteamine. It is noteworthy, that the extent and the lifetime of LSI decrease are not the same for the three polynucleotides. The differences indicate the influence of the chemical nature of the bases on main-chain scission. Consequently, it is concluded that OH attack at carbons in 1′ and/or 2′ position of the ribose moiety contributes essentially to the degradation mechanism.

scholarly journals Optimization Parameters, Kinetics and Mechanism of Naproxen Removal by Catalytic Wet Peroxide Oxidation with a Hybrid Iron-Based Magnetic Catalyst

Catalysts ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 287 ◽  
Author(s):  
Ysabel Huaccallo-Aguilar ◽  
Silvia Álvarez-Torrellas ◽  
Marcos Larriba ◽  
V. Ismael Águeda ◽  
José Antonio Delgado ◽  
...  
Keyword(s):  
Degradation Kinetics ◽  
Degradation Mechanism ◽  
Treatment Plant ◽  
Operating Conditions ◽  
Surface Model ◽  
Oh Radicals ◽  
Order Kinetic ◽  
Peroxide Oxidation ◽  
Wet Peroxide Oxidation ◽  
Catalytic Wet Peroxide Oxidation

This work presents a study of the assessment of the operating parameters of the catalytic wet peroxide oxidation (CWPO) of naproxen (NAP) using magnetite/multi-walled carbon nanotubes (Fe3O4/MWCNTs) as a catalyst. The effect of pH, temperature, and H2O2 dosage on CWPO process was evaluated by using the response surface model (RSM), allowing us to obtain an optimum NAP removal of 82% at the following operating conditions: pH = 5, T = 70 °C, [H2O2]0 = 1.5 mM, and [NAP]0 = 10.0 mg/L. Therefore, NAP degradation kinetics were revealed to follow a pseudo-second-order kinetic model, and an activation energy value of 4.75 kJ/mol was determined. Adsorption and using only H2O2 experiments, both considered as blank tests, showed no significant removal of the pollutant. Moreover, Fe3O4/MWCNTs material exhibited good recyclability along three consecutive cycles, finding an average NAP removal percentage close to 80% in each cycle of 3 h reaction time. In addition, the scavenging tests confirmed that the degradation of NAP was mainly governed by •OH radicals attack. Two reaction sequences were proposed for the degradation mechanism according to the detected byproducts. Finally, the versatility of the catalyst was evidenced in the treatment of different environmentally relevant aqueous matrices (wastewater treatment plant effluent (WWTP), surface water (SW), and a hospital wastewater (HW)) spiked with NAP, obtaining total organic carbon (TOC) removal efficiencies after 8 h in the following order: NAP-SW > NAP-HW > NAP-WWTP.

Degradation mechanism of amylopectin under ultrasonic irradiation

2021 ◽  
Vol 111 ◽  
pp. 106371
Author(s):  
Benxi Wei ◽  
Hongna Qi ◽  
Jin Zou ◽  
Hongyan Li ◽  
Jing Wang ◽  
...  
Keyword(s):  
Ultrasonic Irradiation ◽  
Degradation Mechanism
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