Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 19 de 19
Filter
Add more filters










Publication year range
1.
Arch Dermatol Res ; 316(7): 428, 2024 Jun 21.
Article in English | MEDLINE | ID: mdl-38904694

ABSTRACT

Cannabidiol (CBD), which is derived from hemp, is gaining recognition because of its anti-inflammatory and lipid-modulating properties that could be utilized to treat acne. We conducted experiments to quantitatively assess the effects of CBD on acne-related cellular pathways. SEB-1 sebocytes and HaCaT keratinocytes were exposed to various CBD concentrations. CBD exhibited a concentration-dependent impact on cell viability and notably reduced SEB-1 viability; furthermore, it induced apoptosis and a significant increase in the apoptotic area at higher concentrations. Additionally, CBD remarkably reduced pro-inflammatory cytokines, including CXCL8, IL-1α, and IL-1ß. Additionally, it inhibited lipid synthesis by modulating the AMPK-SREBP-1 pathway and effectively reduced hyperkeratinization-related protein keratin 16. Simultaneously, CBD stimulated the synthesis of elastin, collagen 1, and collagen 3. These findings emphasize the potential of CBD for the management of acne because of its anti-inflammatory, apoptotic, and lipid-inhibitory effects. Notably, the modulation of the Akt/AMPK-SREBP-1 pathway revealed a novel and promising mechanism that could address the pathogenesis of acne.


Subject(s)
Acne Vulgaris , Apoptosis , Cannabidiol , Cell Survival , Keratinocytes , Signal Transduction , Humans , Acne Vulgaris/drug therapy , Cannabidiol/pharmacology , Cannabidiol/therapeutic use , Apoptosis/drug effects , Keratinocytes/drug effects , Keratinocytes/metabolism , Cell Survival/drug effects , Signal Transduction/drug effects , Cicatrix/drug therapy , Cicatrix/pathology , Anti-Inflammatory Agents/pharmacology , Anti-Inflammatory Agents/therapeutic use , Sterol Regulatory Element Binding Protein 1/metabolism , HaCaT Cells , AMP-Activated Protein Kinases/metabolism , Proto-Oncogene Proteins c-akt/metabolism , Collagen Type I/metabolism , Collagen Type I/genetics , Collagen Type III/metabolism , Elastin/metabolism , Sebaceous Glands/pathology , Sebaceous Glands/drug effects , Sebaceous Glands/metabolism , Interleukin-1alpha/metabolism , Interleukin-1beta/metabolism , Interleukin-8/metabolism , Cell Line
2.
Australas J Dermatol ; 65(4): 311-318, 2024 Jun.
Article in English | MEDLINE | ID: mdl-38419202

ABSTRACT

BACKGROUND: Atrophic acne scarring is a common sequela of inflammatory acne, causing significant problems for affected patients. Although prolonged inflammation and subsequent aberrant tissue regeneration are considered the underlying pathogenesis, the role of epidermal stem cells, which are crucial to the regeneration of pilosebaceous units, remains unknown. OBJECTIVES: To examine the changes occurring in epidermal stem cells in atrophic acne scars. METHODS: Changes in collagen, elastic fibre and human leukocyte antigen (HLA)-DR expression were analysed in normal skin and inflammatory acne lesions at days 1, 3 and 7 after development. The expression of epidermal stem cell markers and proliferation markers was compared between normal skin and mature atrophic acne scar tissue. RESULTS: In acne lesions, inflammation had invaded into pilosebaceous units over time. Their normal structure had been destructed and replaced with a reduced amount of collagen and elastic fibre. Expression of stem cell markers including CD34, p63, leucine-rich repeat-containing G protein-coupled receptor (LGR)6 and LGR5, which are expressed in the interfollicular epidermis, isthmus and bulge of hair follicles, significantly decreased in atrophic acne scar tissue compared to normal skin. Epidermal proliferation was significantly reduced in scar tissue. CONCLUSIONS: These findings suggest that as inflammatory acne lesions progress, inflammation gradually infiltrates the pilosebaceous unit and affects the resident stem cells. This disruption impedes the normal regeneration of the interfollicular epidermis and adnexal structures, resulting in atrophic acne scars.


Subject(s)
Acne Vulgaris , Cicatrix , Hair Follicle , Stem Cells , Humans , Acne Vulgaris/complications , Acne Vulgaris/pathology , Cicatrix/pathology , Cicatrix/etiology , Stem Cells/metabolism , Stem Cells/pathology , Hair Follicle/pathology , Atrophy , Collagen/metabolism , Elastic Tissue/pathology , Male , Female , HLA-DR Antigens/metabolism , Cell Proliferation , Young Adult , Adult , Epidermal Cells/metabolism , Epidermis/pathology , Epidermis/metabolism
3.
Photodermatol Photoimmunol Photomed ; 40(1): e12922, 2024 Jan.
Article in English | MEDLINE | ID: mdl-37898983

ABSTRACT

BACKGROUND: Differences in clinical efficacy based on the fluence of fractional picosecond laser treatment for acne scars are unknown. OBJECTIVE: To compare the efficacy and safety of low-fluence versus high-fluence fractional picosecond Nd:YAG 1064-nm laser treatment in acne scar patients. METHODS: In this 12-week, investigator-blinded, randomized, split-face study, 25 patients with moderate-to-severe acne scars received three sessions of high-fluence laser treatment (1.0 J/cm2 ) on one side of their face and low-fluence (0.3 J/cm2 ) on the other side every 4 weeks. Patients were assessed using acne scar counts, the scar global assessment (SGA), and the ECCA scar grading scale every 4 weeks. The histological analysis compared the acne scars obtained before and 4 weeks after treatment. RESULTS: At their last visit, 88.00% and 92.00% of the subjects achieved >30% reduction in scar counts on the low- and high-fluence sides, respectively, without a significant difference between the two sides. On both sides, the scar counts, SGA, and ECCA score significantly improved 4 weeks after the last treatment. Although the high-fluence side showed a greater reduction in scar counts (-66.73%) than the low-fluence side (-62.13%), the two sides had no significant difference in the grading scores. The high-fluence side showed significantly more severe pain and higher side-effect scores immediately and 4 weeks after treatment. Histological analysis revealed a significantly increased collagen, elastin, and vimentin expression after treatment on the low-fluence side. CONCLUSIONS: The low-fluence setting demonstrated comparable efficacy and superior safety in treating acne scars compared with the high-fluence setting.


Subject(s)
Acne Vulgaris , Lasers, Solid-State , Humans , Cicatrix/etiology , Cicatrix/radiotherapy , Acne Vulgaris/complications , Acne Vulgaris/radiotherapy , Treatment Outcome , Lasers, Solid-State/adverse effects , Elastin
4.
JAMA Dermatol ; 160(2): 220-221, 2024 Feb 01.
Article in English | MEDLINE | ID: mdl-38117504

ABSTRACT

This case report describes a central cobblestone-like mass and bone lesion on the spinous process of the L3 vertebra underlying the skin mass.


Subject(s)
Lymphadenopathy , Plasmacytoma , Humans , Plasmacytoma/complications , Plasmacytoma/diagnosis , Syndrome
5.
Dermatol Pract Concept ; 13(2)2023 Apr 01.
Article in English | MEDLINE | ID: mdl-37196254
6.
Am J Clin Dermatol ; 24(4): 649-659, 2023 Jul.
Article in English | MEDLINE | ID: mdl-37160644

ABSTRACT

BACKGROUND: Although lesion counting is an evaluation method that effectively analyzes facial acne severity, its usage is limited because of difficult implementation. OBJECTIVES: We aimed to develop and validate an automated algorithm that detects and counts acne lesions by type, and to evaluate its clinical applicability as an assistance tool through a reader test. METHODS: A total of 20,699 lesions (closed and open comedones, papules, nodules/cysts, and pustules) were manually labeled on 1213 facial images of 398 facial acne photography sets (frontal and both lateral views) acquired from 258 patients and used for training and validating algorithms based on a convolutional neural network for classifying five classes of acne lesions or for binary classification into noninflammatory and inflammatory lesions. RESULTS: In the validation dataset, the highest mean average precision was 28.48 for the binary classification algorithm. Pearson's correlation of lesion counts between algorithm and ground-truth was 0.72 (noninflammatory) and 0.90 (inflammatory), respectively. In the reader test, eight readers (100.0%) detected and counted lesions more accurately using the algorithm compared with the reader-alone evaluation. CONCLUSIONS: Overall, our algorithm demonstrated clinically applicable performance in detecting and counting facial acne lesions by type and its utility as an assistance tool for evaluating acne severity.


Subject(s)
Acne Vulgaris , Dermatologists , Humans , Acne Vulgaris/pathology , Algorithms , Photography , Blister
7.
Front Med (Lausanne) ; 10: 1249796, 2023.
Article in English | MEDLINE | ID: mdl-38249976

ABSTRACT

Introduction: Lentigo maligna (LM) and lentigo maligna melanoma (LMM) are rare in Asian countries. The histopathological diagnosis of LM is often challenging, and misdiagnosis is common. Although histopathologic features of LM/LMM are known, statistical analysis of them were scarcely reported. In this study, we aimed to investigate the histopathological characteristics of LM/LMM in Korean patients and identify key histopathological clues distinguishing LM from benign lentigo. Methods: We performed a retrospective study of the clinical and histopathological features of patients diagnosed with LM/LMM at our center between 2011 and 2022. We assessed the histopathological features in each case based on 16 pathological criteria according to previous literature. Pathologically confirmed cases of benign lentigo were analyzed for comparison. Results: Twenty-one patients (10 with LM and 11 with LMM) were analyzed. Several statistically significant difference existed between the features of LM and benign lentigo (N = 10), including asymmetry of overall structure (p < 0.001), cytologic atypia (p < 0.001), predominant single-cell proliferation (p < 0.001), melanocytic nests (p = 0.033), melanocytes forming rows (p = 0.003), pagetoid spread of melanocytes (p < 0.001), and hair follicle invasion by atypical melanocytes (p < 0.001). Degree of solar elastosis was more severe in group "Age ≥ 60" (p = 0.015), and group "Diameter ≥ 20 mm" (p = 0.043). Presence of elongated rete ridges were less common in the older than 60 age group (p = 0.015) and group "Diameter ≥ 20 mm." Invasion was associated with mitosis (p = 0.001, OR 49.285), multinucleated cells (p = 0.035, OR 17.769), and degree of lymphocyte infiltration (p = 0.004). Conclusion: This study investigated the clinical and histopathologic characteristics of LM and LMM in Koreans. Although histopathological diagnosis is challenging, especially in the early stages of LM, our data showed essential histopathological changes in architectural, cytological, and dermal patterns. Considering the potential aggressiveness of LM/LMM, it is essential to recognize its histopathological features and provide timely management.

9.
JAMA Dermatol ; 158(6): 650-660, 2022 06 01.
Article in English | MEDLINE | ID: mdl-35476054

ABSTRACT

Importance: Palmoplantar pustulosis (PPP) has been reported to be accompanied by systemic conditions. However, the risks of comorbidities in patients with PPP have rarely been evaluated. Objective: To assess the risks of comorbidities in patients with PPP compared with patients with psoriasis vulgaris or pompholyx. Design, Setting, and Participants: This nationwide population-based cross-sectional study used data from the Korean National Health Insurance database and the National Health Screening Program collected from January 1, 2010, to December 31, 2019. Data were analyzed from July 1, 2020, to October 31, 2021. Korean patients diagnosed with PPP, psoriasis vulgaris, or pompholyx who visited a dermatologist between January 1, 2010, and December 31, 2019, were enrolled. Exposures: Presence of PPP. Main Outcomes and Measures: The risks of comorbidities among patients with PPP vs patients with psoriasis vulgaris or pompholyx were evaluated using a multivariable logistic regression model. Results: A total of 37 399 patients with PPP (mean [SD] age, 48.98 [17.20] years; 51.7% female), 332 279 patients with psoriasis vulgaris (mean [SD] age, 47.29 [18.34] years; 58.7% male), and 365 415 patients with pompholyx (mean [SD] age, 40.92 [17.63] years; 57.4% female) were included in the analyses. Compared with patients with pompholyx, those with PPP had significantly higher risks of developing psoriasis vulgaris (adjusted odds ratio [aOR], 72.96; 95% CI, 68.19-78.05; P < .001), psoriatic arthritis (aOR, 8.06; 95% CI, 6.55-9.92; P < .001), ankylosing spondylitis (aOR, 1.91; 95% CI, 1.61-2.27; P < .001), type 1 diabetes (aOR, 1.33; 95% CI, 1.16-1.52; P < .001), type 2 diabetes (aOR, 1.33; 95% CI, 1.29-1.38; P < .001), Graves disease (aOR, 1.25; 95% CI, 1.11-1.42; P < .001), Crohn disease (aOR, 1.63; 95% CI, 1.11-2.40; P = .01), and vitiligo (aOR, 1.87; 95% CI, 1.65-2.12; P < .001) after adjusting for demographic covariates. The risks of ankylosing spondylitis (aOR, 1.37; 95% CI, 1.16-1.62; P < .001) and Graves disease (aOR, 1.40; 95% CI, 1.23-1.58; P < .001) were significantly higher among patients with PPP vs psoriasis vulgaris. However, the risks of psoriatic arthritis (aOR, 0.54; 95% CI, 0.47-0.63; P < .001), systemic lupus erythematosus (aOR, 0.67; 95% CI, 0.46-0.97; P = .04), Sjögren syndrome (aOR, 0.70; 95% CI, 0.50-0.96; P = .03), systemic sclerosis (aOR, 0.29; 95% CI, 0.11-0.77; P = .01), vitiligo (aOR, 0.53; 95% CI, 0.47-0.60; P < .001), and alopecia areata (aOR, 0.88; 95% CI, 0.81-0.95; P = .001) were significantly lower among those with PPP vs psoriasis vulgaris. Conclusions and Relevance: The results of this cross-sectional study suggest that patients with PPP have an overlapping comorbidity profile with patients with psoriasis vulgaris but not patients with pompholyx. However, the risks of comorbidities among patients with PPP may be substantially different from those among patients with psoriasis vulgaris.


Subject(s)
Arthritis, Psoriatic , Diabetes Mellitus, Type 2 , Eczema, Dyshidrotic , Graves Disease , Psoriasis , Soft Tissue Injuries , Spondylitis, Ankylosing , Vitiligo , Acute Disease , Adult , Arthritis, Psoriatic/complications , Arthritis, Psoriatic/epidemiology , Chronic Disease , Comorbidity , Cross-Sectional Studies , Diabetes Mellitus, Type 2/complications , Eczema, Dyshidrotic/complications , Female , Graves Disease/complications , Humans , Male , Middle Aged , Psoriasis/diagnosis
10.
J Am Acad Dermatol ; 87(2): 366-372, 2022 08.
Article in English | MEDLINE | ID: mdl-35395360

ABSTRACT

BACKGROUND: Large studies on the clinical features and natural course of pediatric longitudinal melanonychia (LM) are lacking. OBJECTIVE: To investigate the clinical features and natural course of pediatric LM. METHODS: Retrospective cohort analysis of pediatric patients (age ≤ 18 years) with LM. RESULTS: We examined 703 LM lesions in 381 children. Single, narrow, and homogeneously pigmented fingernail lesions were most frequently observed. Our results suggested that within 3, 4.5, and 9.5 years after onset, approximately 3%, 5%, and 10% of LM lesions, respectively, will completely regress and that single, left-sided, and homogeneously pigmented lesions are more likely to disappear completely. The age of onset, sex, finger/toe position, Hutchinson's sign, and nail dystrophy were not associated with complete regression. During follow-up, most cases demonstrated no change in color or width between the first and last visit, and early darkening/widening before stabilization or lightening/narrowing was common. The lightning of pigmentation was associated with complete regression, whereas change in width was not. LIMITATIONS: Retrospective study at a tertiary center. CONCLUSION: Our results suggest that clinicians ought to follow pediatric patients with LM without intervention for several years even if lesions grow darker or wider. Single, left-sided, and homogeneously colored lesions are more likely to regress.


Subject(s)
Melanoma , Nail Diseases , Skin Neoplasms , Adolescent , Child , Cohort Studies , Humans , Melanoma/pathology , Nail Diseases/diagnosis , Nail Diseases/epidemiology , Nail Diseases/pathology , Republic of Korea/epidemiology , Retrospective Studies , Skin Neoplasms/pathology
12.
Dermatology ; 238(5): 837-845, 2022.
Article in English | MEDLINE | ID: mdl-35078198

ABSTRACT

BACKGROUND: The inflammatory lesions of acne leave scars which greatly affect patients' quality of life. Treatment options targeting both acne and acne scars are still lacking. OBJECTIVES: To evaluate the clinical efficacy of epidermal growth factor ointment (EGFO) on acne and acne scars. METHODS: The study design was 12-week, prospective, split-face, single-blinded. The 36 patients with mild to moderate acne vulgaris applied EGFO on one side of the face and the vehicle ointment on the other side twice daily. The patients were assessed every 4 weeks by acne lesion and scar counts, investigator's global assessment for acne (IGA) and scar (SGA), and the ECCA scar grading scale. Biopsies were performed before and after treatment. RESULTS: Acne and acne scars were significantly improved on EGFO-treated sides, while control sides were not. Acne lesion and scar counts were significantly reduced after 4 weeks, while IGA, SGA, and ECCA grade significantly decreased after 8 weeks. Immunohistochemistry showed decreased expression of keratin 16, NF-κB p65, IL-1α, and IL-8, and increased expression of TGF-ß1, elastin, and collagen type 1, 3 after treatment. CONCLUSIONS: EGFO can be a treatment option targeting acne and acne scars.


Subject(s)
Acne Vulgaris , Cicatrix , Acne Vulgaris/complications , Acne Vulgaris/drug therapy , Acne Vulgaris/pathology , Cicatrix/drug therapy , Cicatrix/etiology , Cicatrix/pathology , Epidermal Growth Factor/therapeutic use , Humans , Immunoglobulin A/therapeutic use , Ointments/therapeutic use , Prospective Studies , Quality of Life , Treatment Outcome
14.
J Hazard Mater ; 372: 121-128, 2019 06 15.
Article in English | MEDLINE | ID: mdl-29631752

ABSTRACT

The sustained oxidation of aqueous organic pollutants using hydroxyl radicals (HO) generated in the UV-irradiated solution of ferric ions was investigated in the presence of Cr(VI). The synergistic effect of simultaneous 4-chlorophenol (4-CP) oxidation and Cr(VI) reduction is explained in terms of the various roles of OH radical, degradation intermediates, and Fe3+/Fe2+ redox cycle. The photolysis of FeIII(OH)2+ generates OH radical which degrades the organic substrate. The reduction of Cr(VI) was inhibited by the OH radical-induced re-oxidation of Cr(III) in the absence of 4-CP. The complete removal of Cr(VI) was achieved only in the presence of phenolic substrates which not only reacts with OH radical (hence inhibiting the reoxidation of Cr(III)) but also generates reducing intermediates which effectively reduce Cr(VI). Fe2+ also converted Cr(VI) to Cr(III) with regenerating Fe3+, which makes the overall process photocatalytic. The photocatalytic activity for the simultaneous removal of 4-CP and Cr(VI) was largely maintained up to five cycles. Such simultaneous and synergic photoactivity was also observed for other phenolic compounds (4-bromophenol, 4-nitrophenol, phenol). The simultaneous and synergic removal of phenolic compounds and Cr(VI) can be enabled through the redox couple of Fe3+/Fe2+ working as a homogeneous photocatalyst.

15.
Environ Sci Technol ; 51(7): 3973-3981, 2017 04 04.
Article in English | MEDLINE | ID: mdl-28277657

ABSTRACT

We investigated a sequential photocatalysis-dark reaction, wherein organic pollutants were degraded on Ag/TiO2 under UV irradiation and the dark reduction of hexavalent chromium (Cr(VI)) was subsequently followed. The photocatalytic oxidation of 4-chlorophenol (4-CP), a test organic substrate, induced the generation of degradation intermediates and the storage of electrons in Ag/TiO2 which were then utilized for reducing Cr(VI) in the postirradiation period. The dark reduction efficiency of Cr(VI) was much higher with Ag/TiO2 (87%), compared with bare TiO2 (27%) and Pt/TiO2 (22%). The Cr(VI) removal by Ag/TiO2 (87%) was contributed by adsorption (31%), chemical reduction by intermediates of 4-CP degradation (26%), and reduction by electrons stored in Ag (30%). When formic acid, humic acid or ethanol was used as an alternative organic substrate, the electron storage effect was also observed. The postirradiation removal of Cr(VI) on Ag/TiO2 continued for hours, which is consistent with the observation that a residual potential persisted on the Ag/TiO2 electrode in the dark whereas little residual potential was observed on bare TiO2 and Pt/TiO2 electrodes. The stored electrons in Ag/TiO2 and their transfer to Cr(VI) were also indicated by the UV-visible absorption spectral change. Moreover, the electrons stored in the preirradiated Ag/TiO2 reacted with O2 with showing a sign of low-level OH radical generation in the dark period.


Subject(s)
Environmental Pollutants , Adsorption , Catalysis , Chromium , Environmental Pollutants/chemistry , Environmental Pollutants/radiation effects , Humic Substances , Oxidation-Reduction , Titanium , Ultraviolet Rays
16.
Environ Sci Technol ; 49(6): 3506-13, 2015 Mar 17.
Article in English | MEDLINE | ID: mdl-25695481

ABSTRACT

The oxidation of As(III) (arsenite) to As(V) (arsenate), a critical pretreatment process for total arsenic removal, is easily achieved using chemical oxidation methods. Hydrogen peroxide (H2O2) is widely used as an environmentally benign oxidant but its practical use for the arsenite oxidation is limited by the strong pH dependence and slow oxidation kinetics. This study demonstrated that H2O2-induced oxidation of As(III) can be markedly enhanced in the presence of nonferrous metal oxides (e.g., WO3, TiO2, ZrO2) as a heterogeneous catalyst working over a wide pH range in ambient reaction conditions. In particular, TiO2 is an ideal catalyst because it is not only active and stable but also easily available and inexpensive. Although the photocatalytic oxidation of As(III) on TiO2 was intensively studied, the thermal catalytic activities of TiO2 and other nonferrous metal oxides for the arsenic oxidation have been little investigated. The heterogeneous oxidation rate increased with increasing the TiO2 surface area and [H2O2] and weakly depended on pH whereas the homogeneous oxidation by H2O2 alone was favored only at alkaline condition. The oxidation rate in the TiO2/H2O2 system was not reduced at all in the absence of dioxygen. It was not retarded at all by OH radical scavengers but markedly inhibited by hydroperoxyl radical scavengers. It is proposed that the surface complexation of H2O2 on TiO2 induces the generation of the surface hydroperoxyl radical through an inner-sphere electron transfer, which subsequently reacts with As(III). The catalytic activity of TiO2 was maintained without showing any sign of deactivation. The heterogeneous catalytic oxidation is proposed as a viable method for the preoxidation treatment of As(III)-contaminated water under ambient conditions.


Subject(s)
Arsenites/chemistry , Hydrogen Peroxide/chemistry , Metals/chemistry , Oxides/chemistry , Water Pollutants, Chemical/chemistry , Water Purification/methods , Catalysis , Hydrogen-Ion Concentration , Kinetics , Oxidation-Reduction
17.
Environ Sci Technol ; 48(7): 4030-7, 2014 Apr 01.
Article in English | MEDLINE | ID: mdl-24617811

ABSTRACT

This study demonstrates that the production of reactive oxidizing species (e.g., hydroxyl radical (•OH)) during the photolysis of nitrite (NO2(-)) or nitrate (NO3(-)) leads to the oxidative conversion of arsenite (As(III)) to arsenate (As(V)). While the direct UV photolytic oxidation of As(III) was absent, nitrite (20 or 200 µM) addition markedly accelerated the oxidation of As(III) under UV irradiation (λ > 295 nm), which implies a role of NO2(-) as a photosensitizer for As(III) oxidation. Nitrate-mediated photooxidation of As(III) revealed an initial lag phase during which NO3(-) is converted into NO2(-). UV-Photosensitized oxidation of As(III) was kinetically enhanced under acidic pH condition where nitrous acid (HNO2) with a high quantum yield for •OH production is a predominant form of nitrite. On the other hand, alkaline pH that favors the photoinduced transformation of NO3(-) to NO2(-) significantly facilitated the catalytic reduction/oxidation cycling, which enabled the complete oxidation of As(III) at the condition of [As(III)]/[NO2(-)] ≫ 1 and markedly accelerated NO3(-)-sensitized oxidation of As(III). The presence of O2 and N2O as electron scavengers enhanced the photochemical dissociation of NO2(-) via intermolecular electron transfer, initiating the oxidative As(III) conversion route probably involving NO2• and superoxide radical anion (O2•(-)) as alternative oxidants. The outdoor experiment demonstrated the capability of NO2(-) for the photosensitized production of oxidizing species and the subsequent oxidation of As(III) into As(V) under solar irradiation.


Subject(s)
Arsenites/chemistry , Nitrates/radiation effects , Nitrites/radiation effects , Photolysis/radiation effects , Ultraviolet Rays , Hydrogen-Ion Concentration/radiation effects , Nitrites/chemistry , Oxidants/chemistry , Oxidation-Reduction/radiation effects , Spectrophotometry, Ultraviolet , Umbelliferones/chemistry
18.
Environ Sci Technol ; 47(16): 9381-7, 2013 Aug 20.
Article in English | MEDLINE | ID: mdl-23879475

ABSTRACT

Arsenite (As(III)) in water was demonstrated to be efficiently oxidized to arsenate (As(V)) under 254 nm UV irradiation without needing any chemical reagents. Although the molar absorption coefficient of As(III) at 254 nm is very low (2.49 ± 0.1 M(-1)cm(-1)), the photooxidation proceeded with a quantum yield over 1.0, which implies a chain of propagating oxidation cycles. The rate of As(III) photooxidation was highly enhanced in the presence of dissolved oxygen, which can be ascribed to its dual role as an electron acceptor of photoexcited As(III) and a precursor of oxidizing radicals. The in situ production of H2O2 was observed during the photooxidation of As(III) and its subsequent photolysis under UV irradiation produced OH radicals. The addition of tert-butyl alcohol as OH radical scavenger significantly reduced (but not completely inhibited) the oxidation rate, which indicates that OH radicals as well as superoxide serve as an oxidant of As(III). Superoxide, H2O2, and OH radicals were all in situ generated from the irradiated solution of As(III) in the presence of dissolved O2 and their subsequent reactions with As(III) induce the regeneration of some oxidants, which makes the overall quantum yield higher than 1. The homogeneous photolysis of arsenite under 254 nm irradiation can be also proposed as a new method of generating OH radicals.


Subject(s)
Arsenites/radiation effects , Arsenites/chemistry , Oxidation-Reduction , Oxygen/chemistry
19.
J Hazard Mater ; 192(2): 928-31, 2011 Aug 30.
Article in English | MEDLINE | ID: mdl-21689884

ABSTRACT

The magnetic field (MF) effect on the zero valent iron (ZVI) induced oxidative reaction was investigated for the first time. The degradation of 4-chlorophenol (4-CP) in the ZVI system was employed as the test oxidative reaction. MF markedly enhanced the degradation of 4-CP with the concurrent production of chlorides. The consumption of dissolved O(2) by ZVI reaction was also enhanced in the presence of MF whereas the competing reaction of H(2) production from proton reduction was retarded. Since the ZVI-induced oxidation is mainly driven by the in situ generated hydroxyl radicals, the production of OH radicals was monitored by the spin trap method using electron spin resonance (ESR) spectroscopy. It was confirmed that the concentration of trapped OH radicals was enhanced in the presence of MF. Since both O(2) and Fe(0) are paramagnetic, the diffusion of O(2) onto the iron surface might be accelerated under MF. The magnetized iron can attract oxygen on itself, which makes the mass transfer process faster. As a result, the surface electrochemical reaction between Fe(0) and O(2) can be accelerated with the enhanced production of OH radicals. MF might retard the recombination of OH radicals as well.


Subject(s)
Iron/chemistry , Magnetics , Oxidation-Reduction
SELECTION OF CITATIONS
SEARCH DETAIL
...