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1.
Aust Vet J ; 98(9): 467-470, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32643193

RESUMO

The Mount Lofty Ranges koala (Phascolarctos cinereus) population in South Australia has a high prevalence of the renal disease oxalate nephrosis, for which an underlying genetic cause is suspected. South Australian koalas primarily originate from those in French Island, Victoria; however, oxalate nephrosis has not previously been reported in Victorian koalas. Examination of kidney tissue sections from 63 koalas across Victoria found that nine koalas were affected by oxalate nephrosis (14.3%). These included 2/5 koalas from French Island (40%), 4/14 koalas from the western regions (29%), 2/11 Raymond Island koalas (18%), and 1/13 Cape Otway koalas (8%). There were no cases of oxalate nephrosis identified in the Strzelecki koalas (n = 12). These findings suggest that oxalate nephrosis occurs in koalas from French Island and populations that have received significant influx of koalas from French Island, but not in the Strzelecki region, which has little to no French Island input. This lends support to the theory that an inherited abnormality of oxalate metabolism could underlie the high prevalence of oxalate nephrosis in the Mount Lofty Ranges koala population, and molecular investigations are currently underway to investigate a genetic cause.


Assuntos
Nefrose/veterinária , Phascolarctidae , Animais , Oxalatos , Austrália do Sul , Inquéritos e Questionários , Vitória
4.
Aust Vet J ; 98(6): 247-249, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32189333

RESUMO

Oxalate nephrosis is a prevalent renal disease in koalas (Phascolarctos cinereus) of the Mount Lofty Ranges population in South Australia. The symmetric dimethylarginine (SDMA) assay is widely used in companion animals to diagnose renal disease, particularly in the early stages. This study aimed to determine: (1) reference intervals for SDMA in koalas and (2) SDMA values of koalas with oxalate nephrosis. Blood samples were collected from 41 Mount Lofty Ranges koalas euthanased on welfare grounds. Koalas were necropsied and, based on renal histopathology, were classified as unaffected (n = 22) or affected (n = 19) by oxalate nephrosis. Serum or plasma samples were analysed for creatinine, urea and SDMA and urine samples for urine specific gravity (USG). The reference interval for SDMA in unaffected koalas was 2.4-22.9 µg/dL. In koalas with oxalate nephrosis, SDMA was elevated in 74% of cases above the upper limit of the confidence interval. SDMA was elevated in three affected koalas with normal creatinine values. A positive correlation was found between SDMA and creatinine (R = 0.775, P < 0.001) and SDMA and urea (R = 0.580, P < 0.001) and a negative correlation between SDMA and USG (R = -0.495, P = 0.027). In conclusion, SDMA correlates well with other commonly used tests of renal function in koalas and should be included as part of the standard diagnostic process to increase the accuracy of oxalate nephrosis diagnosis in koalas.


Assuntos
Nefrose/veterinária , Phascolarctidae , Animais , Arginina/análogos & derivados , Oxalatos , Austrália do Sul
5.
Clin Nephrol ; 93(5): 243-250, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32101518

RESUMO

AIMS: We aim to describe the clinical and histological findings in patients with the finding of any tubular oxalate deposits in kidney biopsy specimens. BACKGROUND: The prevalence, manifestation, and outcome of secondary oxalate nephropathy have not been extensively studied. MATERIALS AND METHODS: In this retrospective cohort study, we analyzed the clinical and histological findings in all patients with the finding of any tubular oxalate deposits in kidney biopsy specimens between July 1, 2017, and December 31, 2018, at Northwell Health Pathology Department (Manhasset, NY, USA). RESULTS: The prevalence of oxalate deposition on a kidney biopsy was 4.07% (25/615), and in 88% of cases was a major finding. Prior to biopsy, oxalate was anticipated in only 1 case. The etiology of oxalosis was clarified retrospectively in 14 cases, most commonly due to GI surgery (n = 10) and increased oxalate intake (n = 4). In 11 cases, etiology remained unknown, although at least 3 cases were exposed to antibiotics associated with secondary oxalosis. There was no significant clinical/pathological or survival difference between known vs. unknown cause groups. The overall 3-month renal survival rate was 76.0 ± 8.5%. Multivariate Cox regression showed that creatinine at the time of biopsy (HR: 1.79, 95% CI: 0.71 - 4.51), background histological chronicity change (HR: 1.82, 95% CI: 0.70 - 4.72) and oxalate density (HR: 2.27, 95% CI: 0.49 - 10.55) are associated with end-stage kidney disease. CONCLUSION: Oxalate deposition is common but rarely anticipated biopsy finding. Nephrologists need to consider surgical history and other secondary causes of oxalosis as causes of acute kidney injury and chronic kidney disease.


Assuntos
Rim/metabolismo , Rim/patologia , Oxalatos/metabolismo , Idoso , Biópsia , Cristalização , Feminino , Humanos , Hiperoxalúria/complicações , Falência Renal Crônica/etiologia , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos
7.
J Environ Sci (China) ; 90: 385-394, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32081334

RESUMO

Nanometer-size zero-valent iron (NZVI) is an efficient reducing agent, but its surface is easily passivated with an oxide layer, leading to reaction inefficiency. In our study, oxalate (OA) was introduced into this heterogeneous system of NZVI, which could form ferrioxalate complexes with the NZVI surface-bound Fe3+ and dissolved Fe3+ in the solution. Photolysis of ferrioxalate complexes can facilitate the generation of Fe2+ from Fe3+ and CO2•- radical, both species have strong reduction capacity. Hence, a "photo-oxalate-Fe(0)" system through sunlight induction was established, which not only prohibited the formation of a surface passivation layer, but also displayed a synergetic mechanism of ferrioxalate photolysis to enhance reduction, exhibiting remarkably higher degradation activity (several times faster) toward the model pollutant Cr(VI) than the mechanism with NZVI alone. Factor tests suggested that both NZVI dosage and OA content markedly affected the reduction rate. Low pH was beneficial to the reduction efficiency. Moreover, recyclability experiment showed that the reduction rate decreased from 0.21706 to 0.03977 min-1 after three cycles of reuse due to the NZVI losing reaction activity generally, but the system still maintained considerable reduction capacity. Finally, a mechanism was revealed whereby NZVI would transform to Fe oxides after the exhaustion of its reductive power, and the photolysis of ferrioxalate to promote the cycling of iron species played the predominant role in providing extra reduction ability. These features confirm that introduction of OA into Cr(VI) reduction by NZVI through sunlight induction is advantageous and promising.


Assuntos
Cromo/química , Luz Solar , Poluentes Químicos da Água , Ferro , Oxalatos/química , Processos Fotoquímicos
9.
Chemosphere ; 249: 126201, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32086067

RESUMO

Photoreaction with the Fe(III)-oxalate complex has been reported to play an important role in various photochemical reactions in the natural atmospheric environment, and are applicable to treat various recalcitrant compounds in wastewater. We previously showed that a Fe(II) oxalate (FeOx) crystal can be recovered from the wastewater generated from soil washing, which can then be applied to the photoreaction for degradation of recalcitrant pollutants; however, photoreactions with FeOx compounds have not been fully reported yet. Therefore, this study aims to investigate the photoreaction characteristics of FeOx recovered from wastewater, to demonstrate the feasibility of its application to wastewater treatment. The physical and chemical properties of FeOx were characterized with X-ray diffraction, scanning electron microscopy/energy-dispersive X-ray spectrometry, and X-ray photoelectron spectroscopy analyses. The photoreaction of FeOx showed high methylene blue (MB) removal efficiencies similar to the reaction with TiO2, indicating that FeOx is applicable to the photoreaction for degradation of pollutants. Furthermore, the photodegradation of MB with FeOx was observed under visible light, as opposed to TiO2. MB could be removed by the photoreaction of FeOx under both basic and acidic pH conditions. Under basic pH conditions, MB could be removed by FeOx via both photoreaction and surface adsorption. The concentration of FeOx affected light penetration and Fe and oxalate levels in the solution, resulting in different MB removal kinetics. The photoreaction efficiency of FeOx could be affected by both photoreaction of Fe and oxalate in the solution and photoreaction and adsorption reaction of the FeOx surface.


Assuntos
Compostos Férricos/química , Processos Fotoquímicos , Poluentes Químicos da Água/química , Adsorção , Compostos Férricos/análise , Compostos de Ferro , Cinética , Luz , Azul de Metileno/química , Oxalatos , Fotólise , Águas Residuárias/análise , Águas Residuárias/química , Poluentes Químicos da Água/análise , Difração de Raios X
10.
Curr Opin Nephrol Hypertens ; 29(2): 237-242, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31972597

RESUMO

PURPOSE OF REVIEW: Both chronic kidney disease (CKD) and kidney stones are major public health problems, which are closely interrelated. Recurrent kidney stones predispose to CKD although CKD seems to decrease risk of further kidney stone formation. Herein, we review new information of this interrelationship. RECENT FINDINGS: Several epidemiological studies in the past have shown an association between history of kidney stones and risk for CKD and CKD progression. Recent literature supports this concept and it is reviewed in this article. The issue of whether CKD protects against new kidney stone formation remains unsettled and there is no recent literature addressing it. In relation to stone risk factors in CKD, there are several interesting new articles that discuss mechanisms of hypocitraturia in early CKD before overt metabolic acidosis. Since hypocitraturia is an important risk factor for kidney stone formation we addressed these new data in detail. There are also new data supporting urinary oxalate excretion as a predictor of CKD progression. SUMMARY: It seems clear that recurrent kidney stones should be avoided not only because of their immediate clinical manifestations but also because of their long-term predisposition to CKD progression. Mechanisms leading to hypocitraturia in early CKD still remain controversial.


Assuntos
Cálculos Renais/complicações , Insuficiência Renal Crônica/etiologia , Ácido Cítrico/urina , Humanos , Oxalatos/urina
11.
J Med Microbiol ; 69(3): 339-346, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31961786

RESUMO

Metabolism is the foundation of all living organisms and is at the core of numerous if not all biological processes. The ability of an organism to modulate its metabolism is a central characteristic needed to proliferate, to be dormant and to survive any assault. Pseudomonas fluorescens is bestowed with a uniquely versatile metabolic framework that enables the microbe to adapt to a wide range of conditions including disparate nutrients and toxins. In this mini-review we elaborate on the various metabolic reconfigurations evoked by this microbial system to combat reactive oxygen/nitrogen species and metal stress. The fine-tuning of the NADH/NADPH homeostasis coupled with the production of α-keto-acids and ATP allows for the maintenance of a reductive intracellular milieu. The metabolic networks propelling the synthesis of metabolites like oxalate and aspartate are critical to keep toxic metals at bay. The biochemical processes resulting from these defensive mechanisms provide molecular clues to thwart infectious microbes and reveal elegant pathways to generate value-added products.


Assuntos
Redes e Vias Metabólicas , Metais/toxicidade , Estresse Oxidativo , Pseudomonas fluorescens/fisiologia , Trifosfato de Adenosina/metabolismo , Ácido Aspártico/metabolismo , Homeostase , NAD/metabolismo , NADP/metabolismo , Oxalatos/metabolismo , Oxirredução , Espécies Reativas de Oxigênio/efeitos adversos , Estresse Fisiológico
12.
J Sci Food Agric ; 100(4): 1702-1710, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31803935

RESUMO

BACKGROUND: The presence of insoluble calcium oxalate druse crystals (CaOx) in sweet potato (Ipomoea batatas) can negatively affect its nutritional quality. Photosynthesis, starch, and protein composition are linked with oxalate synthesis and tuber quality under water scarcity. Our main objective was the oxalate quantitation of sweet potato tubers and shoots and also to assess how drought changes their nutritional value. Eight sweet potato accessions from Madeira, the Canaries and Guinea-Bissau were analyzed for their response to drought stress. Tubers and shoots were analyzed for total (T-Ox), soluble (S-Ox) and insoluble (CaOx) oxalates, protein, chlorophyll content index (CCI), soluble starch, starch swelling power, and starch solubility in water. RESULTS: The S-Ox and CaOx content was higher in shoots. Six accessions were above maximum CaOx levels for raw consumption. Accessions with more favorable responses to drought had decreased CaOx with S-Ox increase content for osmoregulation. They also presented slightly decreased CCI and protein contents. These accessions also had an increased shoot starch content, for further tuber storage starch hydrolysis, and maintained the quality and functional properties of the tuber starch grain. Those with a less favorable response to drought had a higher T-Ox and CaOx content in both organs, hindering water absorption. They also had decreased protein and CCI, with a slight increase in tuber starch hydrolysis. CONCLUSION: Oxalate content was significantly related to carbohydrate metabolism, CCI, and protein synthesis. This study significantly contributed to the screening of the sweet potato stress response to drought, to adapt this crop to climatic change through breeding programs. © 2019 Society of Chemical Industry.


Assuntos
Ipomoea batatas/metabolismo , Oxalatos/química , Tubérculos/química , Água/metabolismo , Metabolismo dos Carboidratos , Secas , Ipomoea batatas/química , Oxalatos/metabolismo , Fotossíntese , Brotos de Planta/química , Brotos de Planta/metabolismo , Tubérculos/metabolismo , Amido/análise , Amido/metabolismo , Água/análise
13.
Am J Physiol Cell Physiol ; 318(2): C372-C379, 2020 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-31825656

RESUMO

Most kidney stones are composed of calcium oxalate, and small increases in urine oxalate enhance the stone risk. The mammalian intestine plays a crucial role in oxalate homeostasis, and we had recently reported that Oxalobacter-derived factors stimulate oxalate transport by human intestinal Caco2-BBE (C2) cells through PKA activation. We therefore evaluated whether intestinal oxalate transport is directly regulated by activation of the PKA signaling pathway. To this end, PKA was activated with forskolin and IBMX (F/I). F/I significantly stimulated (3.7-fold) [14C]oxalate transport by C2 cells [≥49% of which is mediated by the oxalate transporter SLC26A6 (A6)], an effect completely blocked by the PKA inhibitor H89, indicating that it is PKA dependent. PKA stimulation of intestinal oxalate transport is not cell line specific, since F/I similarly stimulated oxalate transport by the human intestinal T84 cells. F/I significantly increased (2.5-fold) A6 surface protein expression by use of immunocytochemistry. Assessing [14C]oxalate transport as a function of increasing [14C]oxalate concentration in the flux medium showed that the observed stimulation is due to a F/I-induced increase (1.8-fold) in Vmax and reduction (2-fold) in Km. siRNA knockdown studies showed that significant components of the observed stimulation are mediated by A6 and SLC26A2 (A2). Besides enhancing A6 surface protein expression, it is also possible that the observed stimulation is due to PKA-induced enhanced A6 and/or A2 transport activity in view of the reduced Km. We conclude that PKA activation positively regulates oxalate transport by intestinal epithelial cells and that PKA agonists might therapeutically impact hyperoxalemia, hyperoxaluria, and related kidney stones.


Assuntos
Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Mucosa Intestinal/metabolismo , Oxalatos/metabolismo , Transdução de Sinais/fisiologia , Animais , Células CACO-2 , Linhagem Celular Tumoral , Células Epiteliais/efeitos dos fármacos , Células Epiteliais/metabolismo , Humanos , Hiperoxalúria/metabolismo , Mucosa Intestinal/efeitos dos fármacos , Peptídeos e Proteínas de Sinalização Intracelular/farmacologia , Transporte de Íons/fisiologia , Cálculos Renais/metabolismo , Transdução de Sinais/efeitos dos fármacos
14.
Int J Clin Pharmacol Ther ; 58(2): 121-127, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31699211

RESUMO

BACKGROUND AND OBJECTIVE: Varenicline is an effective drug for smoking cessation. The aim of the present study was to compare the pharmacokinetics and safety profiles of two different varenicline formulations (varenicline tartrate (reference) and varenicline oxalate (test)), each containing 1 mg varenicline base in humans. MATERIALS AND METHODS: A randomized, open-label, two-sequence, two-period, single-dose crossover study with a 2-week washout period was conducted with 30 healthy male participants. Blood samples for the pharmacokinetic analysis of varenicline were collected up to 96 hours following the administration of each drug. Pharmacokinetic parameters were also calculated, including the peak plasma concentration (Cmax), area under the plasma concentration-time curve (AUC) from time zero to the time of the last measurable concentration (AUClast) as well as AUC from time zero to infinity (AUCinf). ANOVA for pharmacokinetic equivalence was assessed using log-transformed Cmax and AUC values, and the geometric mean ratios (GMRs) and their 90% confidence intervals (CIs) were assessed as well. The safety profiles were also assessed. RESULTS: 27 participants completed the study. No significant differences were found for any pharmacokinetic parameters of varenicline between the two formulations. The observed average values of Cmax, AUClast, and AUCinf were 4.46 ng/mL, 97.68 ng×h/mL, and 101.60 ng×h/mL for reference and 4.54 ng/mL, 97.10 ng×h/mL, and 100.97 ng×h/mL for test, respectively. The GMRs and 90% CIs for Cmax, AUClast, and AUCinf were 1.0106 (0.9626 - 1.0610), 0.9904 (0.9540 - 1.0282), and 0.9885 (0.9517 - 1.0268), respectively. No clinically relevant changes were observed in the physical, biochemical, hematologic, electrocardiographic, or urinalysis findings during the study, and no serious adverse events were found. CONCLUSION: The results of the present study reveal that varenicline oxalate and varenicline tartrate have similar pharmacokinetic characteristics as varenicline, and that these two formulations exhibit pharmacokinetic equivalence to meet the regulatory criteria. Both varenicline formulations were generally well tolerated.


Assuntos
Oxalatos/farmacocinética , Vareniclina/farmacocinética , Área Sob a Curva , Disponibilidade Biológica , Estudos Cross-Over , Humanos , Masculino , Comprimidos , Equivalência Terapêutica
15.
Life Sci ; 241: 117108, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31786192

RESUMO

AIMS: Telmisartan (TLM), a highly selective angiotensin II type 1 receptor blocker (ARB) and partial PPAR-γ agonist, has versatile beneficial effects against oxidative stress, apoptosis, inflammatory responses and epithelial-mesenchymal transition (EMT). However, its underlying mechanism of inhibiting oxalate and calcium oxalate (CaOx) crystal-induced EMT by activating the PPAR-γ pathway remains unclear. MAIN METHODS: CCK-8 assays were used to evaluate the effects of TLM on cell viability. In addition, intracellular reactive oxygen species (ROS) levels were measured by the cell-permeable fluorogenic probe 2,7-dichlorofluorescein diacetate (DCFH-DA). Wound-healing and Transwell assays were used to evaluate the migration ability of HK2 cells exposed to oxalate. Moreover, immunofluorescence, immunohistochemistry and western blotting were used to examine the expression of E-cadherin, N-cadherin, vimentin and α-SMA and explore the underlying molecular mechanisms in HK2 cells and a stone-forming rat model. KEY FINDINGS: Our results showed that TLM treatment could protect HK2 cells from oxalate-induced cytotoxicity and oxidative stress injury. Additionally, TLM prevented EMT induction by oxalate and CaOx crystals via the PPAR-γ-AKT/STAT3/p38 MAPK-Snail pathway in vitro and in vivo. However, knockdown of PPAR-γ with small interfering RNA or the PPAR-γ-specific antagonist GW9662 abrogated these protective effects of TLM. SIGNIFICANCE: As a PPAR-γ agonist, TLM can ameliorate oxalate and CaOx crystal-induced EMT by exerting an antioxidant effect through the PPAR-γ-AKT/STAT3/p38 MAPK-Snail signaling pathway. Therefore, TLM can block EMT progression and could be a potential therapeutic agent for preventing and treating calcium oxalate urolithiasis formation and recurrence.


Assuntos
Transição Epitelial-Mesenquimal/efeitos dos fármacos , Oxalatos/toxicidade , PPAR gama/metabolismo , Telmisartan/farmacologia , Animais , Oxalato de Cálcio/toxicidade , Linhagem Celular , Transição Epitelial-Mesenquimal/fisiologia , Humanos , Túbulos Renais/citologia , Masculino , Estresse Oxidativo/efeitos dos fármacos , PPAR gama/genética , Proteínas Proto-Oncogênicas c-akt/metabolismo , Ratos Sprague-Dawley , Fator de Transcrição STAT3/metabolismo , Fatores de Transcrição da Família Snail/metabolismo , Fator de Crescimento Transformador beta1/toxicidade , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismo
16.
GM Crops Food ; 11(1): 54-66, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31668117

RESUMO

Chicory (Cichorium intybus L.) is a medicinal and industrial plant from the Asteraceae family that produces a variety of sesquiterpene lactones (STLs), most importantly bitter guaianolides: lactucin, lactucopicrin and 8-deoxylactucin as well as their modified forms such as oxalates. These compounds have medicinal properties; however, they also hamper the extraction of inulin - a very important food industry product from chicory roots. The first step in guaianolide biosynthesis is catalyzed by germacrene A synthase (GAS) which in chicory exists in two isoforms - GAS long (encoded by CiGASlo) and GAS short (encoded by CiGASsh). AmiRNA silencing was used to obtain plants with reduced GAS gene expression and level of downstream metabolites, guaianolide-15-oxalates, as the major STLs in chicory. This approach could be beneficial for engineering new chicory varieties with varying STL content, and especially varieties with reduced bitter compounds more suitable for inulin production.


Assuntos
Chicória , Oxalatos , Sesquiterpenos de Germacrano
17.
Food Chem Toxicol ; 135: 110915, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31669600

RESUMO

Fibrogenesis is a common feature for all types of chronic kidney disease (CKD). Epithelial-to-mesenchymal transition (EMT) of renal tubular epithelial cells is one of the main processes involving renal fibrosis and its inhibition is considered as a preventive/therapeutic strategy for CKD. Trigonelline (TRIG), a plant alkaloid commonly found in herbs, coffee bean, soy bean and other edible food plants, has several beneficial effects on human health and has been proposed to reduce renal fibrosis but with unclear mechanisms. This study thus addressed cellular mechanism underlying the anti-fibrogenic effects of TRIG in renal tubular epithelial cells grown in vitro. EMT was successfully induced by oxalate treatment as indicated by morphological changes into spindle-shape cells, increased expression of mesenchymal proteins (fibronectin, vimentin and α-smooth muscle actin (α-SMA)), decreased expression of epithelial proteins (E-cadherin and zonula occludens-1 (ZO-1)) and increased activity of a profibrotic factor (matrix metalloproteinase-9 (MMP-9)). Interestingly, these oxalate-induced EMT features could be attenuated by TRIG pretreatment. Moreover, TRIG also prevented oxalate-induced cell migration, reactive oxygen species (ROS) overproduction, and down-regulation of Nrf-2 signaling molecule. These data indicated that TRIG could attenuate the effects of oxalate-induced EMT and thus may serve as the anti-fibrotic compound for prevention and/or treatment of CKD.


Assuntos
Alcaloides/farmacologia , Células Epiteliais/efeitos dos fármacos , Transição Epitelial-Mesenquimal/efeitos dos fármacos , Oxalatos/efeitos adversos , Substâncias Protetoras/farmacologia , Actinas/metabolismo , Animais , Caderinas/metabolismo , Movimento Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Cães , Células Epiteliais/metabolismo , Fibronectinas/metabolismo , Células Madin Darby de Rim Canino , Fator 2 Relacionado a NF-E2/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Vimentina/metabolismo , Proteína da Zônula de Oclusão-1/metabolismo
20.
Chemosphere ; 239: 124612, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31499301

RESUMO

The degradation of carboxylic acid has been identified as one of the rate-determining steps in the mineralization of organic pollutants by ozonation. In this study, Ce(III)-doped graphitic carbon nitride (Ce-CN) composites with different Ce(III) contents were synthesized and used as catalysts for the ozonation of oxalate. The morphology and structure of the Ce-CN were comprehensively characterized using various techniques such as SEM, XRD, FTIR, and XPS. The results show that the structure of g-C3N4 provided an ideal site for the accommodation of Ce(III) and thus facilitated the formation of surface hydroxyl groups. With 2.5%Ce-CN as a catalyst, the degradation efficiency of oxalate was increased by 47.1% after reaction for 30 min. The decomposition of ozone was accelerated in the presence of Ce-CN. Hydroxyl radicals were recorded by electron spin resonance and identified as the major actives species. Under the catalysis of 2.5%Ce-CN, the production of hydroxyl radicals was increased by 40%. The Ce(III) and surface hydroxyl groups that distributed uniformly on the surface of Ce-CN were speculated as the dual catalytic sites for the complexation of oxalate and activation of ozone, respectively. Ce-CN had a high stability and reutilization capability. It is proposed that a complex was formed between surface Ce(III) and oxalate, and this complex could be more easily attacked by the surrounding ozone and hydroxyl radicals than free oxalate. As oxalate is a typical recalcitrant carboxylic acid, the findings from this study are expected to promote the application of ozonation in the removal of organic pollutants.


Assuntos
Cério/química , Grafite/química , Compostos de Nitrogênio/química , Oxalatos/química , Ozônio/química , Poluentes Químicos da Água/química , Catálise , Radical Hidroxila/química , Compostos Orgânicos
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