scholarly journals How Photocatalyst Dosage and Ultrasound Application Influence the Photocatalytic Degradation Rate of Phenol in Water: Elucidating the Mechanisms Behind

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1672 ◽  
Author(s):  
Wim Van de Moortel ◽  
Mohammadreza Kamali ◽  
Kristel Sniegowski ◽  
Leen Braeken ◽  
Jan Degrève ◽  
...  
Keyword(s):  
Photocatalytic Degradation ◽  
Degradation Rate ◽  
Uv Light ◽  
Degradation Kinetics ◽  
Phenol Degradation ◽  
Process Conditions ◽  
Oh Radicals ◽  
Tio2 Particles ◽  
Ultrasound Application

Photocatalysis is of high interest for the treatment of wastewater containing non-biodegradable organic components. In this work, the photocatalytic degradation of phenol by TiO2 photocatalysis was assessed, the influence of ultrasound (US) treatment was evaluated, and the mechanisms behind it were elucidated. It was shown that the TiO2 concentration (in suspension) has a large influence on the degradation kinetics. At high TiO2 concentrations, a reduced efficiency was observed due to the shielding of the UV light by TiO2 particles. US treatment effectively increased phenol degradation by improving the mass transfer while it was shown by the experimental data that particle deagglomeration did not play a significant role. The degradation mainly occurred through indirect phenol oxidation by hydroxyl (OH*) radicals, which were formed in situ at the surface of the photocatalyst. Finally, based on the partial least squares (PLS) methodology, a mathematical model was developed, representing phenol degradation as a function of the selected process conditions.

scholarly journals Recovery of mangrove sediment contaminated with fuel oil by endogenous microbial consortium

2020 ◽  
Vol 42 ◽  
pp. e6
Author(s):  
Amanda Ferreira Santos Silva ◽  
Thomas Wendell Fernandes dos Santos ◽  
Norma Buarque de Gusmão ◽  
Persio Alexandre da Silva ◽  
Thais De Melo Castelo Branco ◽  
...  
Keyword(s):  
Degradation Rate ◽  
Microbial Consortium ◽  
Degradation Kinetics ◽  
Phenol Degradation ◽  
Fractional Factorial ◽  
Fuel Oil ◽  
Lubricating Oil ◽  
Mangrove Sediment ◽  
Process Conditions ◽  
Kinetics Of

This work aimed to select a microbial consortium enriched with isolated microorganisms of mangrove sediment as to its capacity to recover sediment contaminated by lubricating oil. The promising microorganisms were selected using the colorimetric dichlorophenol indophenol technique (DCPIP) using lubricating oil as the carbon source, to evaluate the emulsifying and enzymatic activity of the microorganisms. The antagonism test was also used for further evaluation of the consortia. The fractional factorial experimental design methodology (2n) was used to establish the process conditions for the subsequent accomplishment of the degradation kinetics of the lubricating oil by the selected microorganisms and consortium. Eight bacteria and three fungi were evaluated, of which five were selected with a 36 h turn of the DCPIP indicator. Eleven microorganisms produce emulsifying substances and five produce enzymes. The results showed that the best consortium was B5F2F4, with a degradation rate of 95% of the phenol at 70 rpm in 250 μL of the oil. The kinetics of oil degradation showed a phenol degradation rate of 65% after 24 days of treatment. The microorganisms are suitable for the degradation of phenol, the main constituent of the oil, and can be used as a recovery model for environments contaminated with hydrocarbons.

scholarly journals In situ degradability of dry matter and fibrous fraction of sorghum silage

2016 ◽  
Vol 38 (2) ◽  
pp. 171 ◽  
Author(s):  
Renê Ferreira Costa ◽  
Daniel Ananias de Assis Pires ◽  
Marielly Maria Almeida Moura ◽  
José Avelino Santos Rodrigues ◽  
Vicente Ribeiro Rocha Júnior ◽  
...  
Keyword(s):  
Experimental Design ◽  
Dry Matter ◽  
Degradation Rate ◽  
Degradation Kinetics ◽  
Grain Sorghum ◽  
Dual Purpose ◽  
Ruminal Degradability ◽  
Sorghum Silage ◽  
Kinetics Of

This study aimed to evaluate in situ degradability and degradation kinetics of DM, NDF and ADF of silage, with or without tannin in the grains. Two isogenic lines of grain sorghum (CMS-XS 114 with tannin and CMS-XS 165 without tannin) and two sorghum hybrids (BR-700 dual purpose with tannin and BR-601 forage without tannin) were ensiled; dried and ground silage samples were placed in nylon bags and introduced through the fistulas. After incubation for 6, 12, 24, 48, 72 and 96 hours, bags were taken for subsequent analysis of fibrous fractions. The experimental design was completely randomized with 4 replicates and 4 treatments and means compared by Tukey’s test at 5% probability. As for the DM degradation rate, silage of CMSXS165without tannin was superior. Silages of genotypes BR700 and CMSXS 114 with tannin showed the highest values of indigestible ADF (59.54 and 43.09%). Regarding the NDF, the potential degradation of silage of CMSXS165 line without tannin was superior. Tannin can reduce ruminal degradability of the dry matter and fibrous fractions. 

scholarly journals Photocatalytic Degradation of Monolinuron and Linuron in an Aqueous Suspension of Titanium Dioxide Under Simulated Solar Irradiation

2007 ◽  
Vol 20 (2) ◽  
pp. 163-172 ◽  
Author(s):  
Razika Zouaghi ◽  
Abdennour Zertal ◽  
Bernard David ◽  
Sylvie Guittonneau
Keyword(s):  
Photocatalytic Degradation ◽  
Degradation Rate ◽  
Ph Value ◽  
Degradation Kinetics ◽  
Aqueous Suspension ◽  
Operating Conditions ◽  
Solar Irradiation ◽  
Point Of Zero Charge ◽  
Degradation Rates ◽  
Simulated Solar Irradiation

Abstract The photocatalytic degradation of two phenylurea herbicides, monolinuron (MLN) and linuron (LN), was investigated in an aqueous suspension of TiO2 using simulated solar irradiation. The objective of the study was to compare their photocatalytic reactivity and to assess the influence of various parameters such as initial pesticide concentration, catalyst concentration and photonic flux on the photocatalytic degradation rate of MLN and LN. A comparative study of the photocatalytic degradation kinetics of both herbicides showed that these two compounds have a comparable reactivity with TiO2/simulated sun light. Under the operating conditions of this study, the photocatalytic degradation of MLN and LN followed pseudo first-order decay kinetics. The kobs values indicated an inverse dependence on the initial herbicide concentration and were fitted to the Langmuir-Hinshelwood equation. Photocatalytic degradation rates increased with TiO2 dosage, but overdoses did not necessarily increase the photocatalytic efficiency. The degradation rate of MLN increased with radiant flux until an optimum at 580 W m‑2 was reached and then decreased. Under these conditions, an electron-hole recombination was favored. Finally, the photocatalytic degradation rate depended on pH, where an optimum was found at a pH value close to the pH of the point of zero charge (pH = 6).

scholarly journals Preparation and Properties of CaCO3-Supported Nano-TiO2 Composite with Improved Photocatalytic Performance

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3369
Author(s):  
Jie Wang ◽  
Sijia Sun ◽  
Lei Pan ◽  
Zhuoqun Xu ◽  
Hao Ding ◽  
...  
Keyword(s):  
Photocatalytic Degradation ◽  
Photocatalytic Performance ◽  
Uv Light ◽  
Interaction Mechanism ◽  
Pure Tio2 ◽  
Degradation Efficiency ◽  
Nano Tio2 ◽  
Composite Photocatalyst ◽  
Tio2 Particles ◽  
Grinding Machine

In order to improve the photocatalytic degradation efficiency of nano-TiO2, reduce its usage and realize recycling and reuse, CaCO3–TiO2 composite photocatalyst was prepared with calcium carbonate (CaCO3) and TiO2 in a grinding machine through the integration of grinding depolymerization, dispersion and particle composition. The photocatalytic degradation performance, recycling performance, structure and morphology of CaCO3–TiO2 were studied. The interaction mechanism between CaCO3 and TiO2 and the improvement mechanism for the photocatalytic performance of TiO2 were also discussed. The results show that under the UV light irradiation for 20 and 40 min, the degradation efficiency of methyl orange by the composite photocatalyst with 40% TiO2 (mass fraction) was 90% and 100%, respectively. This was similar to that of pure TiO2, and the performance of the composite photocatalyst was almost unchanged after five cycles. CaCO3–TiO2 is formed by the uniform loading of nano-TiO2 particles on the CaCO3 surface, and the nano-TiO2 particles are well dispersed. Due to the facts that the dispersion of nano-TiO2 is improved in the presence of CaCO3 and the charge transport capability is improved through the interfacial chemical bonds between CaCO3 and TiO2, the formation of this complex is an intrinsic mechanism to improve the photocatalytic efficiency of nano-TiO2 and reduce its usage in application processes.

scholarly journals Enhanced Photocatalytic Degradation of Perfluorooctanoic Acid by Mesoporous Sb2O3/TiO2 Heterojunctions

2021 ◽  
Vol 9 ◽  
Author(s):  
Xinyun Yao ◽  
Jiaqi Zuo ◽  
Yu-Jue Wang ◽  
Ning-Ning Song ◽  
Huang-Hao Li ◽  
...  
Keyword(s):  
Photocatalytic Degradation ◽  
Active Sites ◽  
Uv Light ◽  
Degradation Kinetics ◽  
Direct Electron Transfer ◽  
Perfluorooctanoic Acid ◽  
Term Operation ◽  
Spin Resonance ◽  
Light Utilization

Perfluorooctanoic acid (PFOA), a typical perfluorinated carboxylic acid, is an emerging type of permanent organic pollutants that are regulated by the Stockholm Convention. The degradation of PFOA, however, is quite challenging largely due to the ultra-high stability of C-F bonds. Compared with other techniques, photocatalytic degradation offers the potential advantages of simple operation under mild conditions as well as exceptional decomposition and defluorination efficiency. Titanium dioxide (TiO2) is one of the most frequently used photocatalysts, but so far, the pristine nanosized TiO2 (e.g., the commercial P25) has been considered inefficient for PFOA degradation, since the photo-generated hydroxyl radicals from TiO2 are not able to directly attack C-F bonds. Mesoporous Sb2O3/TiO2 heterojunctions were therefore rationally designed in this work, of which the confined Sb2O3 nanoparticles in mesoporous TiO2 framework could not only tune the band structure and also increase the number of active sites for PFOA degradation. It was found that, after loading Sb2O3, the absorption of UV light was enhanced, indicating a higher efficiency of light utilization; while the band gap was reduced, which accelerated the separation of photo-generated charge carriers; and most importantly, the valence band edge of the Sb2O3/TiO2 heterojunction was significantly lifted so as to prevent the occurrence of hydroxyl radical pathway. Under the optimal ratio of Sb2O3–TiO2, the resulting catalysts managed to remove 81.7% PFOA in 2 h, with a degradation kinetics 4.2 times faster than the commercial P25. Scavenger tests and electron spin resonance spectra further revealed that such improvement was mainly attributed to the formation of superoxide radicals and photo-generated holes, in which the former drove the decarboxylation from C7F15COOH–C7F15•, and the latter promoted the direct electron transfer for the conversion of C7F15COO−–C7F15COO•. The Sb2O3/TiO2 photocatalysts were highly recyclable, with nearly 90% of the initial activity being retained after five consecutive cycles, guaranteeing the feasibility of long-term operation.

scholarly journals Au/ZnO Hybrid Nanostructures on Electrospun Polymeric Mats for Improved Photocatalytic Degradation of Organic Pollutants

Water ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1787 ◽  
Author(s):  
Laura Campagnolo ◽  
Simone Lauciello ◽  
Athanassia Athanassiou ◽  
Despina Fragouli
Keyword(s):  
Photocatalytic Degradation ◽  
Organic Pollutants ◽  
Uv Light ◽  
High Surface ◽  
High Surface Area ◽  
Thermal Conversion ◽  
Hybrid Nanostructures ◽  
Dipping Process ◽  
Porous Nanocomposites

An innovative approach for the fabrication of hybrid photocatalysts on a solid porous polymeric system for the heterogeneous photocatalytic degradation of organic pollutants is herein presented. Specifically, gold/zinc oxide (Au/ZnO)-based porous nanocomposites are formed in situ by a two-step process. In the first step, branched ZnO nanostructures fixed on poly(methyl methacrylate) (PMMA) fibers are obtained upon the thermal conversion of zinc acetate-loaded PMMA electrospun mats. Subsequently, Au nanoparticles (NPs) are directly formed on the surface of the ZnO through an adsorption dipping process and thermal treatment. The effect of different concentrations of the Au ion solutions to the formation of Au/ZnO hybrids is investigated, proving that for 1 wt % of Au NPs with respect to the composite there is an effective metal–semiconductor interfacial interaction. As a result, a significant improvement of the photocatalytic performance of the ZnO/PMMA electrospun nanocomposite for the degradation of methylene blue (MB) and bisphenol A (BPA) under UV light is observed. Therefore, the proposed method can be used to prepare flexible fibrous composites characterized by a high surface area, flexibility, and light weight. These can be used for heterogeneous photocatalytic applications in water treatment, without the need of post treatment steps for their removal from the treated water which may restrict their wide applicability and cause secondary pollution.

Photocatalytic degradation kinetics of humic acid in aqueous TiO2 dispersions: the influence of hydrogen peroxide and bicarbonate ion

1996 ◽  
Vol 34 (9) ◽  
pp. 73-80 ◽  
Author(s):  
Miray Bekbölet ◽  
Isil Balcioglu
Keyword(s):  
Hydrogen Peroxide ◽  
Humic Acid ◽  
Photocatalytic Degradation ◽  
Rate Constants ◽  
Degradation Rate ◽  
Ph Value ◽  
Degradation Kinetics ◽  
Color Removal ◽  
Degradation Data ◽  
Kinetics Of

The degradation of humic acid in water by means of photocatalytic method has been studied. The influence of hydrogen peroxide and bicarbonate has also been investigated. The kinetics of the photocatalytic degradation of humic acid in various concentrations (50-500 mg/L) has been followed by the determination of TOC, COD and UV-vis spectra of the reaction solution. While the pseudo first order rate constants of 50 mg/L humic acid were found 0.016, 0.03 and 0.036 for TOC, Color400 and UV254, the degradation rate constants for these parameters were found 0.029, 0.069 and 0.057 in the presence of 1×10−2M H2O2. The Langmuir-Hinshelwood kinetic has also been sucessfully applied to the photocatalytic degradation data. It was found that bicarbonate ions slowed down the degradation rate by scavenging the hydroxyl radicals. Low pH value has been found to be favorable for color removal in the absence of hydrogen peroxide whereas natural pH gave the best results for color removal in the presence of hydrogen peroxide.

Development and characterization of a new dolomite-based catalyst: application to the photocatalytic degradation of pentachlorophenol

2019 ◽  
Vol 79 (4) ◽  
pp. 741-752
Author(s):  
Ilhem Belarbi ◽  
Ali Çoruh ◽  
Rachida Hamacha ◽  
Kheira Marouf-Khelifa ◽  
Amine Khelifa
Keyword(s):  
Degradation Rate ◽  
Uv Light ◽  
Raw Materials ◽  
Uv Spectroscopy ◽  
Simple Procedure ◽  
Degradation Process ◽  
Oh Radicals ◽  
X Ray ◽  
Rate Constant Ratio ◽  
The Fourier Transform

Abstract The development of new catalysts from abundant raw materials, generating attractive photocatalytic activity, constitutes a real challenge in the context of sustainable development concerns. In this setting, a dolomite was treated at 800 °C (D800) and then chemically modified by Ca(NO3)2 (CaD800) using a simple procedure. The resulting materials were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy (EDS), solid state UV spectroscopy, and used as catalysts of pentachlorophenol (PCP) degradation in aqueous solutions under UV light irradiation. The treatment of dolomite at 800 °C enabled a full decarbonation of CaMg(CO3)2, with formation of CaO, Ca(OH)2, and MgO. Additional CaO was generated after chemical treatment as revealed by EDS analysis; the Ca/Mg ratio increased from 1.29 (D800) to 1.44 for CaD800. This CaO in aqueous medium hydrates by giving Ca(OH)2. CaD800 was found to be the best photocatalyst with a PCP degradation rate of 95% after only 1 h of treatment, for a CaD800/D800 degradation rate constant ratio of 1.58. In this regard, we investigated the Fourier transform infrared spectra of CaD800, PCP, and CaD800 loaded with PCP after degradation. We thus evidenced the involvement of Ca(OH)2 in the PCP degradation process. Catalytic activity was discussed through the contribution of OH radicals and electrodonation.

Oxidation of Phenol by Persulfate Activated with UV-Light and Ag+

2012 ◽  
Vol 610-613 ◽  
pp. 1806-1809
Author(s):  
De Dong Sun ◽  
Huan Zheng ◽  
Wen Ping Xue
Keyword(s):  
Uv Irradiation ◽  
Advanced Oxidation Process ◽  
Oxidation Process ◽  
Uv Light ◽  
Irradiation Time ◽  
Phenol Degradation ◽  
Oxygen Demand ◽  
Mercury Vapor ◽  
Cod Reduction

Phenol degradation with a UV/Ag+/K2S2O8 advanced oxidation process (AOP) was studied in a batch photolytic reactor. The UV irradiation source was a low-pressure mercury vapor lamp that was axially centered and was immersed in the phenol solution. In the UV/ K2S2O8 and Ag+/K2S2O8 system, the degradation of phenol was inefficient with an low concentration K2S2O8 at ambient temperature, and only around 26% and 23%of the phenol was degraded in 3 h , respectively. In the UV/Ag+/K2S2O8 oxidation process, persulfate (S2O82-) was activated by UV irradiation and Ag+ catalysis to produce powerful oxidants, SO4– •.The effects of K2S2O8 concentration, UV irradiation time and Ag+ concentration on the oxidation had been investigated. The experimental results indicated that optimum K2S2O8 concentration was 0.37mmol/L, and Ag+ concentration was 0.185 mmol/L. Phenol and chemical oxygen demand (COD) reduction was analyzed to determine the efficiency of the UV/Ag+/K2S2O8 process in mineralization, where we obtained 77% phenol reduction, and 65% COD reduction, respectively . The efficient mineralization of phenol is based on the in situ formation of the strong oxidant sulfate anion radical.

Degradation kinetics of reactive dye by UV/H2O2/US process under continuous mode operation

2001 ◽  
Vol 44 (6) ◽  
pp. 67-72 ◽  
Author(s):  
P. C. Fung ◽  
C. S. Poon ◽  
C. W. Chu ◽  
S. M. Tsui
Keyword(s):  
Degradation Rate ◽  
Feeding Rate ◽  
Uv Light ◽  
Degradation Kinetics ◽  
Irradiation Time ◽  
Reactive Dye ◽  
Color Removal ◽  
Order Kinetic ◽  
Continuous Mode ◽  
Dyeing Wastewater

Degradation of a dye, C.I. Reactive Red 120, in dyeing wastewater by the process of UV/H2O2/US was studied with a bench-scale reactor under the continuous mode of operation. The effects of dyeing wastewater flow rate and the feeding rate of an oxidant, H2O2, on the color removal efficiency of the process were investigated. The significance of ultrasonic (US) combined with UV irradiation was also investigated and the performances of the process on color removal were evaluated. The results showed that the decoloration process followed a pseudo first-order kinetic model and the UV light is the most significant factor on dye removal. Besides, at higher flow rates, incomplete color removal was observed due to relatively insufficient irradiation time (low degradation rate). In order to achieve a higher degradation rate, the feeding rate of H2O2 should be increased.

Sign in / Sign up

Export Citation Format

Share Document