1
|
Tuncay Ö, Er Ö, Demirbuga S, Zorba YO, Topçuoğlu HS. Effect of gaseous ozone and light-activated disinfection on the surface hardness of resin-based root canal sealers. Scanning 2016; 38:141-147. [PMID: 25931289 DOI: 10.1002/sca.21222] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Revised: 04/09/2015] [Accepted: 04/17/2015] [Indexed: 06/04/2023]
Abstract
Although root canal instruments remove most of the content from the main root canal space, disinfection or irrigation plays an indispensable role in all areas of the root canal system, especially in parts that are inaccessible by instruments. The originality of this study was to investigate the effect of two novel disinfection techniques on the surface hardness of resin-based endodontic sealers using atomic force microscopy (AFM). Forty extracted single-rooted maxillary central human teeth were prepared and divided into four groups according to treatment methods. The first group was irrigated with saline and served as a control, other groups irrigated with sodium hypochlorite (NaClO); gaseous ozone; and light-activated disinfection (LAD). The groups were divided into two subgroups, according to the obturation method used: subgroup A: gutta-percha and AH plus; and subgroup B: EndoREZ/resin-coated cones. After obturation, atomic force microscopy (AFM) measurement was performed to analyze the surface hardness of the sealers. There was a significant difference between group 1A and group 3A (p < 0.05). Group 3B had the highest surface hardness values that were statistically different (p < 0.05). When disregarding the sealers, the ozone possessed statistically higher surface hardness values than the other groups in all root thirds (p < 0.05). The use of ozone and LAD may alter the surface hardness of resin-based sealers. The use of AFM can be considered an alternative hardness test techonology for sealing material.
Collapse
Affiliation(s)
- Öznur Tuncay
- Department of Endodontics, Faculty of Dentistry, Akdeniz University, Antalya, Turkey
| | - Özgür Er
- Department of Endodontics, Faculty of Dentistry, Trakya University, Edirne, Turkey
| | - Sezer Demirbuga
- Department of Restorative Dentistry, Faculty of Dentistry, Erciyes University, Kayseri, Turkey
| | - Yahya Orçun Zorba
- Department of Restorative Dentistry, Faculty of Dentistry, Erciyes University, Kayseri, Turkey
| | | |
Collapse
|
2
|
Ding W, Wang Y, Yu Y, Zhang X, Li J, Wu F. Photooxidation of arsenic(III) to arsenic(V) on the surface of kaolinite clay. J Environ Sci (China) 2015; 36:29-37. [PMID: 26456603 DOI: 10.1016/j.jes.2015.03.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 02/14/2015] [Accepted: 03/12/2015] [Indexed: 05/24/2023]
Abstract
As one of the most toxic heavy metals, the oxidation of inorganic arsenic has drawn great attention among environmental scientists. However, little has been reported on the solar photochemical behavior of arsenic species on top-soil. In the present work, the influencing factors (pH, relative humidity (RH), humic acid (HA), trisodium citrate, and additional iron ions) and the contributions of reactive oxygen species (ROS, mainly HO and HO2/O2(-)) to photooxidation of As(III) to As(V) on kaolinite surfaces under UV irradiation (λ=365nm) were investigated. Results showed that lower pH facilitated photooxidation, and the photooxidation efficiency increased with the increase of RH and trisodium citrate. Promotion or inhibition of As(III) photooxidation by HA was observed at low or high dosages, respectively. Additional iron ions greatly promoted the photooxidation, but excessive amounts of Fe(2+) competed with As(III) for oxidation by ROS. Experiments on scavengers indicated that the HO radical was the predominant oxidant in this system. Experiments on actual soil surfaces proved the occurrence of As(III) photooxidation in real topsoil. This work demonstrates that the photooxidation process of As(III) on the soil surface should be taken into account when studying the fate of arsenic in natural soil newly polluted with acidic wastewater containing As(III).
Collapse
Affiliation(s)
- Wei Ding
- Hubei Key Lab of Biomass Resource Chemistry and Environmental Biotechnology, School of Resources and Environmental Science, Wuhan University, Wuhan 430079, China.
| | - Yajie Wang
- Hubei Key Lab of Biomass Resource Chemistry and Environmental Biotechnology, School of Resources and Environmental Science, Wuhan University, Wuhan 430079, China
| | - Yingtan Yu
- Hubei Key Lab of Biomass Resource Chemistry and Environmental Biotechnology, School of Resources and Environmental Science, Wuhan University, Wuhan 430079, China
| | - Xiangzhi Zhang
- Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204, China.
| | - Jinjun Li
- Hubei Key Lab of Biomass Resource Chemistry and Environmental Biotechnology, School of Resources and Environmental Science, Wuhan University, Wuhan 430079, China
| | - Feng Wu
- Hubei Key Lab of Biomass Resource Chemistry and Environmental Biotechnology, School of Resources and Environmental Science, Wuhan University, Wuhan 430079, China.
| |
Collapse
|
3
|
Sharma J, Mishra IM, Kumar V. Degradation and mineralization of Bisphenol A (BPA) in aqueous solution using advanced oxidation processes: UV/H2O2 and UV/S2O8(2-) oxidation systems. J Environ Manage 2015; 156:266-75. [PMID: 25889275 DOI: 10.1016/j.jenvman.2015.03.048] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2015] [Revised: 03/25/2015] [Accepted: 03/28/2015] [Indexed: 05/03/2023]
Abstract
This work reports on the removal and mineralization of an endocrine disrupting chemical, Bisphenol A (BPA) at a concentration of 0.22 mM in aqueous solution using inorganic oxidants (hydrogen peroxide, H2O2 and sodium persulfate, Na2S2O8;S2O8(2-)) under UV irradiation at a wavelength of 254 nm and 40 W power (Io = 1.26 × 10(-6) E s(-1)) at its natural pH and a temperature of 29 ± 3 °C. With an optimum persulfate concentration of 1.26 mM, the UV/S2O8(2-) process resulted in ∼95% BPA removal after 240 min of irradiation. The optimum BPA removal was found to be ∼85% with a H2O2 concentration of 11.76 mM. At higher concentrations, either of the oxidants showed an adverse effect because of the quenching of the hydroxyl or sulfate radicals in the BPA solution. The sulfate-based oxidation process could be used over a wider initial pH range of 3-12, but the hydroxyl radical-based oxidation of BPA should be carried out in the acidic pH range only. The water matrix components (bicarbonate, chloride and humic acid) showed higher scavenging effect in hydroxyl radical-based oxidation than that in the sulfate radical-based oxidation of BPA. UV/S2O8(2-) oxidation system utilized less energy (307 kWh/m(3)) EE/O in comparison to UV/H2O2 system (509 kWh/m(3)) under optimum operating conditions. The cost of UV irradiation far outweighed the cost of the oxidants in the process. However, the total cost of treatment of persulfate-based system was much lower than that of H2O2-based oxidation system.
Collapse
Affiliation(s)
- Jyoti Sharma
- Department of Chemical Engineering, Indian Institute of Technology, Roorkee, Roorkee 247667, Uttarakhand, India
| | - I M Mishra
- Department of Chemical Engineering, Indian Institute of Technology, Roorkee, Roorkee 247667, Uttarakhand, India.
| | - Vineet Kumar
- Department of Chemical Engineering, Indian Institute of Technology, Roorkee, Roorkee 247667, Uttarakhand, India
| |
Collapse
|
4
|
Guo Y, Lou X, Xiao D, Xu L, Wang Z, Liu J. Sequential reduction-oxidation for photocatalytic degradation of tetrabromobisphenol A: kinetics and intermediates. J Hazard Mater 2012; 241-242:301-306. [PMID: 23046696 DOI: 10.1016/j.jhazmat.2012.09.044] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Revised: 09/08/2012] [Accepted: 09/17/2012] [Indexed: 06/01/2023]
Abstract
C-Br bond cleavage is considered as a key step to reduce their toxicities and increase degradation rates for most brominated organic pollutants. Here a sequential reduction/oxidation strategy (i.e. debromination followed by photocatalytic oxidation) for photocatalytic degradation of tetrabromobisphenol A (TBBPA), one of the most frequently used brominated flame retardants, was proposed on the basis of kinetic analysis and intermediates identification. The results demonstrated that the rates of debromination and even photodegradation of TBBPA strongly depended on the atmospheres, initial TBBPA concentrations, pH of the reaction solution, hydrogen donors, and electron acceptors. These kinetic data and byproducts identification obtained by GC-MS measurement indicated that reductive debromination reaction by photo-induced electrons dominated under N(2)-saturated condition, while oxidation reaction by photoexcited holes or hydroxyl radicals played a leading role when air was saturated. It also suggested that the reaction might be further optimized for pretreatment of TBBPA-contaminated wastewater by a two-stage reductive debromination/subsequent oxidative decomposition process in the UV-TiO(2) system by changing the reaction atmospheres.
Collapse
Affiliation(s)
- Yaoguang Guo
- State Environmental Protection Engineering Center for Pollution Treatment and Control in Textile Industry, College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China
| | | | | | | | | | | |
Collapse
|
5
|
Stathis I, Hela DG, Scrano L, Lelario F, Emanuele L, Bufo SA. Novel imazethapyr detoxification applying advanced oxidation processes. J Environ Sci Health B 2011; 46:449-453. [PMID: 21726140 DOI: 10.1080/03601234.2011.583834] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Different degradation methods have been applied to assess the suitability of advanced oxidation process (AOPs) to promote mineralization of imazethapyr [(RS)-5-ethyl-2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)nicotinic acid], a widely used imidazolinone class herbicide, the persistence of which has been demonstrated in surface and ground waters destined to human uses. Independent of the oxidation process assessed, the decomposition of imazethapyr always followed a pseudo-first order kinetic. The direct UV-irradiation (UV) of the herbicide as well as its oxidation with ozone (O₃), and hydrogen peroxide tied to UV-irradiation (H₂O₂/UV) were sufficiently slow to permit the identification of intermediate products, the formation pathway of which has been proposed. Ozonation joined to UV-irradiation (O₃/UV), ozonation joined to titanium dioxide photo-catalysis (TiO₂/UV+O₃), sole photo-catalysis (TiO₂/UV), and photo-catalysis reinforced with hydrogen peroxide-oxidation (TiO₂/UV+H₂O₂) were characterized by a faster degradation and rapid formation of a lot of small molecules, which were quickly degraded to complete mineralization. The most effective oxidation methods were those using titanium dioxide photo-catalysis enhanced either by ozonation or hydrogen peroxide. Most of all, these last processes were useful to avoid the development of dangerous by-products.
Collapse
Affiliation(s)
- Ioannis Stathis
- Department of Farm Organization & Management, University of Ioannina, Agrinio, Greece
| | | | | | | | | | | |
Collapse
|
6
|
Dong Y, Han Z, Liu C, Du F. Preparation and photocatalytic performance of Fe (III)-amidoximated PAN fiber complex for oxidative degradation of azo dye under visible light irradiation. Sci Total Environ 2010; 408:2245-2253. [PMID: 20170939 DOI: 10.1016/j.scitotenv.2010.01.020] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2009] [Revised: 12/01/2009] [Accepted: 01/11/2010] [Indexed: 05/28/2023]
Abstract
Polyacrylonitrile (PAN) fiber was modified with hydroxylamine hydrochloride to introduce amidoxime groups onto the fiber surface. These amidoxime groups were used to react with Fe (III) ions to prepare Fe (III)-amidoximated PAN fiber complex, which was characterized using SEM, XRD, FTIR, XPS, DMA, and DRS respectively. Then the photocatalytic activity of Fe-AO-PAN was evaluated in the degradation of a typical azo dye, C. I. Reactive Red 195 in the presence of H(2)O(2) under visible light irradiation. Moreover, the effect of the Fe content of Fe-AO-PAN on dye degradation was also investigated. The results indicated that Fe (III) ions can crosslink between the modified PAN fiber chains by the coordination of Fe (III) ions with the amino nitrogen atoms and hydroxyl oxygen atoms of the amidoximation groups to form Fe (III)-amidoximated PAN fiber complex, and the Fe content of which is mainly determined by Fe (III) ions and amidoximation groups. Fe (III)-amidoximated PAN fiber complex is found to be activated in the visible light region. Moreover, Fe (III)-amidoximated PAN fiber complex shows the catalytic activity for dye degradation by H(2)O(2) at pH=6.0 in the dark, and can be significantly enhanced by increasing light irradiation and Fe content, therefore, it can be used as a new heterogeneous Fenton photocatalyst for the effective decomposition of the dye in water. In addition, ESR spectra confirm that Fe (III)-amidoximated PAN fiber complex can generate more OH radicals from H(2)O(2) under visible light irradiation, leading to dye degradation. A possible mechanism of photocatalysis is proposed.
Collapse
Affiliation(s)
- Yongchun Dong
- Division of Textile Chemistry & Ecology, School of Textile Science and Engineering, Tianjin Polytechnic University, Tianjin 300160, China.
| | | | | | | |
Collapse
|
7
|
Abstract
DNA-protein cross-links (DPCs) in nucleosome core particles (NCPs), the fundamental building block of chromatin, arise during times of cellular oxidative stress. These lesions are expected to be detrimental to the cell due to interference with processes like chromatin remodeling, transcription, DNA replication, and epigenetic marking. However, much is still unknown about the mechanisms leading to the formation of DPCs in NCPs, and the exact sites of these lesions in chromatin have not been delineated. During DNA charge transport (CT), an oxidant leads to the formation of a guanine radical cation (G*+) which then becomes mobile and migrates away from the initial site of damage. Since previous studies have established that reactions between a G*+ and some amino acids lead to DPC formation in both DNA-peptide and DNA-protein complexes, we hypothesized that DNA CT could lead to DPC formation within NCPs. To test this hypothesis, we studied DNA CT reactions in NCPs reconstituted with DNA containing (i) the 601 NCP positioning sequence and (ii) 14 bp of a linker DNA with a covalently attached anthraquinone (AQ) photooxidant. Collectively, the results from Western blotting, EMSAs, and DNA footprinting reactions lead to the conclusion that AQ-initiated DNA CT is responsible for DNA-H3 cross-linking in one specific region of these NCPs. Furthermore, these DPCs are stable for days at 37 degrees C, indicating that DNA CT in chromatin can lead to long-lived DNA lesions which the cell must somehow find and excise.
Collapse
Affiliation(s)
- Chad C Bjorklund
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164-4660, USA
| | | |
Collapse
|
8
|
Abstract
Visual perception occurs when radiation with a wavelength between 400 and 760 nm reaches the retina. The retina has evolved to capture photons efficiently and initiate visual transduction. The retina, however, is vulnerable to damage by light, a vulnerability that has long been recognized. Photochemical damage has been widely studied, because it can cause retinal damage within the intensity range of natural light. Photochemical lesions are primarily located in the outer layers at the central region of the retina. Two classes of photochemical damage have been recognized: Class I damage, which is characterized by the rhodopsin action spectrum, is believed to be mediated by visual pigments, with the primary lesions located in the photoreceptors; whereas Class II damage is generally confined to the retinal pigment epithelium. The action spectrum peaks in the short wavelength region, providing the basis for the concept of blue light hazard. Several factors can modify the susceptibility of the retina to photochemical damage. Photochemical mechanisms, in particular mechanisms that arise from illumination with blue light, are responsible for solar retinitis and for iatrogenic retinal insult from ophthalmological instruments. Further, blue light may play a role in the pathogenesis of age-related macular degeneration. Laboratory studies have suggested that photochemical damage includes oxidative events. Retinal cells die by apoptosis in response to photic injury, and the process of cell death is operated by diverse damaging mechanisms. Modern molecular biology techniques help to study in-depth the basic mechanism of photochemical damage of the retina and to develop strategies of neuroprotection.
Collapse
Affiliation(s)
- Jiangmei Wu
- Department of Vitreoretinal Diseases, Saint Erik's Eye Hospital and Karolinska Institutet, Stockholm, Sweden
| | | | | |
Collapse
|
9
|
Runia WT, Boonstra S. Disinfection of Pythium-infested recirculation water by UV-oxidation technology. Meded Rijksuniv Gent Fak Landbouwkd Toegep Biol Wet 2001; 66:73-82. [PMID: 12425022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/19/2023]
Abstract
Selective disinfection against Pythium aphanidermatum in recirculation water was tested with UV-irradiation and with UV-oxidation technology with the objective to reduce the electrical energy consumption per cubic meter treated water. UV-oxidation technology is based on injection of hydrogen peroxide in recirculation water, just before passage along a UV-lamp, thus creating hydroxyl radicals. Pythium aphanidermatum was applied artificially to recirculation water from tomatoes, grown, in rockwool and coconut fibre. Other parameters in this study were pH and transmission value (T10) of the infested recirculation water. Results indicated that the recommended UV-C dose of 100 mJ/cm2 for elimination of fungal pathogens in general can be lowered in case recirculation water is infected with Pythium aphanidermatum only. When UV-oxidation technology was applied with 1 mmol hydrogen peroxide per litre recirculation water, the UV-C dose could be reduced even more in comparison with merely UV irradiation.
Collapse
Affiliation(s)
- W T Runia
- Applied Plant Research, P.O. Box 8, 2670 AA Naaldwijk, The Netherlands.
| | | |
Collapse
|