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1.
Water Res ; 176: 115742, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32244104

RESUMO

The corrosion and scaling phenomenon have crucial impact on drinking water distribution systems (DWDS), which might lead to pipe blockage or leakage, colored water and other chemical stability issues. In this study, a simulating pipe system with continuous water flow was prepared to investigate the characteristics of corrosion and scaling on ductile iron pipe transporting ground water with sodium-hypochlorite (NaOCl) disinfection. Electrochemical assays, such as polarization curves and electrochemical impedance spectra were applied to monitor the corrosion and scaling process. Results showed the morphology and components of scale were closely related with the electrochemical analysis results. The corrosion current density decreased continuously as corrosion and scaling proceeded. The process could be divided into three stages. During Stage I (0-20 days), the corrosion current intensity of low NaOCl dosage experiments (1, 2 mg/L) were higher than those of high NaOCl dosage experiments (5, 10 mg/L). The difference could be explained by different oxidation potentials, pH and CaCO3 deposition. During Stage II (20-80 days), higher proportions of Fe3O4 in scale in experiments with no or low NaOCl dosages restrained the corrosion process and presented smaller corrosion current. Subsequently, the ductile iron surface became passivated and the difference of various NaOCl dosages affecting corrosion and scaling process turned to be negligible during Stage III (80-90 days). A negative linear relationship between the proportion of stable scale component and the corrosion current density was established. Besides the direct corrosion reaction with iron substrate, NaOCl dosing was accompanied by an increase in pH and calcium carbonate precipitation potential values, which affected the early period corrosion and scaling phenomenon greatly.


Assuntos
Água Subterrânea , Ferro , Corrosão , Desinfecção , Hipoclorito de Sódio , Abastecimento de Água
2.
Water Res ; 177: 115764, 2020 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-32305699

RESUMO

This study explored the ability of orthophosphate addition to limit lead release from lead service lines delivering high pH, low alkalinity water. We built pipe loop reactors with lead pipes harvested from Providence, RI, and we operated them with high pH and low alkalinity water of a composition similar to that in Providence. Orthophosphate addition decreased the release of both dissolved and particulate lead to the water. The most substantial decreases in total lead concentrations occurred after 15 weeks of orthophosphate addition, which was associated with the formation of calcium-lead-phosphorus (Ca-Pb-P) solids as part of the pipe scale. Pre-existing hydrocerussite (Pb3(CO3)2(OH)2(s)) in the scale of the lead pipe appeared to promote the formation of a Ca-Pb-P solid similar to phosphohedyphane (Ca2Pb3(PO4)3(Cl,F,OH)(s)). Continuous orthophosphate addition was also associated with the formation of a calcium phosphate solid with features like those of fluorapatite (Ca5(PO4)3F(s)) on the outermost layer of the scale. Through promoting the formation of these new solids within and on top of the scales, orthophosphate addition limited release of dissolved and particulate lead. These results demonstrate the ability of orthophosphate to control lead release at higher pH conditions than those for which it has typically been used. In addition to the formation of phosphate solids, PbO2(s), which was not present on the as-received pipes, was formed due to the constant supply of free chlorine in the laboratory-scale experiment.


Assuntos
Chumbo , Poluentes Químicos da Água , Cloro , Corrosão , Concentração de Íons de Hidrogênio , Fosfatos , Abastecimento de Água
3.
Chemosphere ; 250: 126230, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32234616

RESUMO

The Swiss disposal concept foresees that carbon-14 (14C) is predominantly released from irradiated steel disposed of in a cement-based repository for low- and intermediate-level radioactive waste. To predict how 14C migrates in the cementitious environment of the repository near field and subsequently in the host rock, knowledge about the carbon speciation during anoxic steel corrosion in alkaline conditions is therefore essential. To this end, batch-type corrosion experiments with carbon-containing zero-valent iron (ZVI) powders subject to oxidative pre-treatments were carried out in NaOH solution at pH 11 and 12.5. Alkanes and alkenes (C1-C7) were identified in the gas phase and produced on the iron surface by a Fischer-Tropsch type mechanism. The kind of oxidative pre-treatment has an effect on the production rate of hydrocarbons (HCs). In the liquid phase, carboxylic acids were identified and produced during the oxidative pre-treatment of the ZVI powders. They are released instantaneously from the oxide layer upon contact with the alkaline solution. The kind of oxidative treatment and the exposure time to oxic conditions directly influence the amount of carboxylic acids accommodated in the oxide layer.


Assuntos
Carbono/química , Ferro/química , Poluentes Químicos da Água/química , Radioisótopos de Carbono , Corrosão , Compostos Orgânicos , Oxirredução , Aço/química
4.
Ultrasonics ; 104: 106110, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32146383

RESUMO

Surface mechanical attrition treatment (SMAT) of metallic biomaterials has gained significant importance due to its ability to develop nano structure in the surface region. In the present study, the microstructural changes and corrosion behavior of the commercially pure titanium (cp-Ti), following different durations of ultrasonic shot peening (USSP) has been investigated. cp-Ti was shot peened for different durations from 0 to 120 s and the treated samples were examined for microstructural changes in the surface region, cell viability and corrosion behavior. Cell viability was considerably increased after USSP for 60-120 s, exhibiting maximum for the 90 s of USSP. The passivation tendency was also improved with peening duration up to 90 s, however, it declined for longer duration of USSP. The beneficial effects of USSP may be attributed to nano structuring in the surface region and development of higher positive potentials at the USSP treated surface. Transmission Electron Microscope (TEM) examination of the USSPed surface revealed dislocation entanglement and substructure. Also, higher surface volta potential was observed over the USSPed sample exhibiting better cell proliferation. The present work is corollary to previous work of the group and mainly discusses the role of USSP duration, as a process parameter, on the cell viability and corrosion resistance of cp-Ti.


Assuntos
Células-Tronco Mesenquimais/fisiologia , Nanoestruturas/química , Titânio/química , Ultrassom/métodos , Proliferação de Células , Sobrevivência Celular , Corrosão , Técnicas Eletroquímicas , Humanos , Teste de Materiais , Microscopia de Força Atômica , Microscopia Eletrônica , Propriedades de Superfície , Difração de Raios X
5.
Water Res ; 175: 115675, 2020 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-32155486

RESUMO

The release of potentially toxic metal ions from corrosion scales formed on pipe surfaces is of great concern for water quality in drinking water distribution systems (DWDS). This study examined the effects of alkalinity, chloride, and sulfate on metal release from corrosion scales sampled from a corroded iron pipe. Jar tests and recirculation pipe systems were used to investigate the metal-release potential during stagnant and active flow conditions. The experimental data show that both the ambient water chemistry and hydraulic conditions exerted complex influences on metal release from the exposed corrosion scales. Fe, Mn, and Ni were more labile to be released during a 132-h period of stagnation, while the release of Al, Zn, and Cu was an order of magnitude higher under flow conditions compared to stagnant conditions. Increasing concentrations of chloride (from 5 mg/L to 60 mg/L) and sulfate (from 20 mg/L to 100 mg/L) resulted in the increased release of Fe, Al, and Zn, especially under active flow conditions. This effect could be effectively mitigated by increasing alkalinity from 50 mg/L to 200 mg/L as CaCO3. While increasing alkalinity suppressed the release of Fe and stimulated the release of Al and Cu under stagnant conditions, this contradictory effect was not observed under active flow conditions.


Assuntos
Água Potável , Poluentes Químicos da Água , Corrosão , Ferro , Metais , Qualidade da Água , Abastecimento de Água
6.
Water Res ; 173: 115525, 2020 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-32036289

RESUMO

In order to prevent corrosion damage, steel structures need to be protected. Coating systems achieve this by the isolation of the steel from its environment. Common binding agents are epoxide and polyurethane resins which harden by polyaddition reactions. In contact with water, various organic substances might be leached out and released into the aquatic environment potentially causing adverse effects. So far, no legal requirements are mandatory for the environmental sustainability of coating systems. To characterize emissions from steel coatings, recommendations for the ecotoxicological assessment of construction products were utilized. Seven different coating systems based on epoxide or polyurethane resins were leached in 8 steps (6 h-64 d), followed by the testing of acute toxic effects on bacteria and algae as well as estrogen-like and mutagenic effects. In addition, chemical analysis by GC-MS was performed to identify potentially toxic compounds released from the coating systems. Two systems tested did not show any significant effects in the bioassays. One coating system caused significant algal toxicity, none was found to cause mutagenic effects. The other coating systems mainly showed estrogenic effects and bacterial toxicity. The effects increased with increasing leaching time. 4-tert-butylphenol, which is used in epoxy resins as a hardener, was identified as the main contributor to acute and estrogenic effects in two coatings. The release mechanism of 4-tert-butylphenol was characterized by two different modelling approaches. It was found that the release from the most toxic coating is not explainable by an elevated content of 4-tert-butylphenol but more likely by the release mechanism that - in contrast to the less toxic coating - is controlled not only by diffusion. This finding might indicate a sub-optimal formulation of this coating system resulting in a less stable layer and thus an increased release of toxic compounds.


Assuntos
Poluentes Químicos da Água , Água , Corrosão , Ecotoxicologia , Aço
7.
Sci Total Environ ; 718: 136679, 2020 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-32092508

RESUMO

At present, the researches on the corrosion of mixed microorganisms pay more attention to iron-oxidizing bacteria (IOB) and sulfate-reducing bacteria (SRB) in tap water or seawater. Pseudomonas fluorescens and Escherichia coli are two common microorganisms in reclaimed water, but there are few studies about their interaction on metal interface and about their influence on metal corrosion behavior. The corrosion behavior of carbon steel under mixed microorganisms of Escherichia coli and Pseudomonas fluorescens was studied by corrosion weight loss, electrochemistry, scanning electron microscopy (SEM) and X-ray diffraction (XRD) in this paper. The dominant bacteria under mixed bacteria conditions determined the final result of corrosion reaction in reclaimed water. On the first three days, the dominant strain was Escherichia coli, which produced acid on the surface of carbon steel and deteriorated corrosion. After the 3rd day, the dominant strain was Pseudomonas fluorescens, which inhibited the growth of Escherichia coli and slowed down corrosion. When the extracellular polymeric substances (EPS) concentration of Pseudomonas fluorescens reached 400 mg/L, it would inhibit the growth and reproduction of Escherichia coli. On the contrary, Escherichia coli EPS acted as a nutrient for Pseudomonas fluorescens, promoting the growth and reproduction of Pseudomonas fluorescens.


Assuntos
Aço , Bactérias , Biofilmes , Carbono , Corrosão , Água
8.
Chemosphere ; 248: 125912, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32006826

RESUMO

Novel meso-zero valent iron (mZVI) was investigated for treating complex wastewater containing toxic heavy metal Cr6+ and organic compound phenol. This study is first of its kind illustrating coupled removal in single-step with H2O2 playing a major role as an oxidant and reductant. The mechanism involved was electron transfer from Fe0/2+ to Cr6+ resulting in Fe2+/3+ which in turn was consumed for phenol oxidation returning as Fe2+ into the system for further Cr6+ reduction. While comparing, single-step simultaneous removal of Cr6+ and phenol showed better performance in terms of pollutant removal, Fe2+/3+ recurrent reaction and precipitation generation, double-tep sequential removal performed better in iron active-corrosion time. It was also observed that the entire redox cycle of Cr6+-Cr3+-Cr6+ was reusable for co-contaminant phenol degradation at all pH with the recurrence of Fe2+-Fe3+-Fe2+. The proposed technique was checked for its viability in a single batch reactor and the complex chemistry of the reactions are unfolded by conducting chemical speciation and mass balance study at every stage of reaction. The unique functioning of mZVI was proven with micro-analysis of ZVI's surface and compared with granular ZVI, cZVI. The results obtained from this study open the door for a safer and cleaner single treatment system in removing both toxic heavy metals and organic compounds from contaminated surface water, groundwater and many such industrial effluents.


Assuntos
Cromo/química , Fenol/química , Eliminação de Resíduos Líquidos , Poluentes Químicos da Água/química , Corrosão , Água Subterrânea/química , Peróxido de Hidrogênio/química , Ferro/química , Oxidantes/química , Oxirredução , Fenóis/análise , Águas Residuárias/química , Poluentes Químicos da Água/análise
9.
Chemosphere ; 249: 126130, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32058134

RESUMO

In this study, the effect of ball milling on pyrite (FeS2) promoting arsenic (As) removal by zero-valent iron (Fe0) was investigated. The influences of different mass ratios of ball-milled FeS2/Fe0, the dosage of ball-milled FeS2/Fe0 used and initial pH value were evaluated by batch experiments. The results showed that the ball-milled FeS2/Fe0 system had a higher total As removal efficiency than the mixed FeS2-Fe0 system, ball-milled FeS2 and ball-milled Fe0 systems in equal mass. Higher As removal efficiency in ball-milled FeS2/Fe0 system was primarily related to the accelerated corrosion of Fe0, which was supported by the determination of total Fe2+ release and electrochemical experiments. SEM-EDS and XPS characterizations revealed that there were iron sulfides (Fe(II)-S and Fe(III)-S) produced on the surface of Fe0 in ball-milled FeS2/Fe0, which could facilitate the electron transfer of Fe0 and enhanced the corrosion of it. BET test also indicated that ball-milled FeS2/Fe0 possessed a higher specific surface area than ball-milled Fe0. In addition, the results also showed the optimum mass ratio of FeS2 and Fe0 in ball-milled FeS2/Fe0 to remove As ([As(III)] = 2 mg/L) was 1:1, and the optimum dosage was 0.5 g/L, thereby indicating the optimal As:Fe0 molar ratio was about 1:168. And the removal rate of As by ball-milled FeS2/Fe0 was faster in acidic condition than that in alkaline condition. These findings suggest that Fe0-based arsenic removal efficiency can be enhanced by ball-milling with FeS2, making it more feasible for remediation of arsenic-polluted water.


Assuntos
Arsênico/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Arsênico/análise , Corrosão , Compostos Férricos , Compostos Ferrosos , Ferro/química , Sulfetos/química , Água , Poluentes Químicos da Água/análise
10.
Water Res ; 172: 115470, 2020 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-31951947

RESUMO

Microbially influenced corrosion (MIC) is the main cause of metal corrosion in anoxic environments. Biocides are often dosed to the corrosive media to inhibit and kill the microbes which cause MIC. In this study, intermittent dosages of free nitrous acid (FNA), which was previously found to be a biocide, were applied to a simulated water injection system containing carbon steel coupons with mature biofilm, to study the effect of FNA on mitigation of metal corrosion. In each treatment, 0.49 mg-N/L FNA was dosed using 200 mg-N/L nitrite at pH 6 for 24 h. The corrosion properties were monitored by open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), 3D optical profiling, and direct weight measurement. The biofilm viability was monitored by measuring cellular ATP level. The general corrosion rate (calculated by weight-loss measurement) was decreased by up to 31%, which was supported by LPR tests and reduced ATP levels of the corrosion-inducing biofilm. The 3D optical profiling results showed that FNA decreased the average pitting corrosion rate by 59%, with 2 intermittent treatments and 82-day interval over 304 days. Intermittent dosing of FNA has strong potential to be an effective and efficient strategy for controlling MIC in oil recovery infrastructure.


Assuntos
Ácido Nitroso , Água , Biofilmes , Corrosão , Aço
11.
Environ Sci Technol ; 54(4): 2192-2201, 2020 02 18.
Artigo em Inglês | MEDLINE | ID: mdl-31961665

RESUMO

Access to clean and safe drinking water is a perpetual concern in Arctic communities because of challenging climatic conditions, limited options for the transportation of equipment and process chemicals, and the ongoing effects of colonialism. Water samples were gathered from multiple locations in a decentralized trucked drinking water system in Nunavut, Canada, over the course of one year. The results indicate that point of use drinking water quality was impacted by conditions in the source water and in individual buildings and strongly suggest that lead and copper measured at the tap were related to corrosion of onsite premise plumbing components. Humic-like substances were the dominant organic fraction in all samples, as determined by regional integration of fluorescence data. Iron and manganese levels in the source water and throughout the water system were higher in the winter and lower in the summer months. Elevated concentrations of copper (>2000 µg L-1) and lead (>5 µg L-1) were detected in tap water from some buildings. Field flow fractionation coupled with inductively coupled plasma mass spectrometry and ultraviolet-visible spectrometry was used to demonstrate the link between source water characteristics (high organics, iron and manganese) and lead and copper in point of use drinking water.


Assuntos
Água Potável , Poluentes Químicos da Água , Canadá , Corrosão , Nunavut , Qualidade da Água , Abastecimento de Água
12.
Environ Sci Technol ; 54(4): 2344-2352, 2020 02 18.
Artigo em Inglês | MEDLINE | ID: mdl-31971374

RESUMO

Reinforced cementitious structures in nuclear waste repositories will act as barriers that limit the mobility of radionuclides (RNs) in case of eventual leakage. CEM-V/A cement, a ternary blended cement with blast furnace slag (BFS) and fly ash (FA), could be qualified and used in nuclear waste disposal. Chemical interactions between the cement and RNs are critical but not completely understood. Here, we combined wet chemistry methods, synchrotron-based X-ray techniques, and thermodynamic modeling to explore redox interactions and nonredox sorption processes in simulated steel-reinforced CEM-V/A hydration systems using selenite as a molecular probe. Among all of the steel corrosion products analyzed, only the addition of Fe0 can obviously enhance the reducing ability of cement toward selenite. In comparison, steel corrosion products showed stronger reducing power in the absence of cement hydrates. Selenium K-edge X-ray absorption spectroscopy (XAS) revealed that selenite immobilization mechanisms included nonredox inner-/outer-sphere complexations and reductive precipitations of FeSe and/or Se(0). Importantly, the hydrated pristine cement showed a good reducing ability, driven by ferrous phases and (bi)sulfides (as shown by sulfur K-edge XAS) originated from BFS and FA. The overall redox potential imposed by hydrated CEM-V/A was determined, hinting to a redox shift in underground cementitious structures.


Assuntos
Materiais de Construção , Aço , Corrosão , Oxirredução , Ácido Selenioso
13.
Environ Sci Technol ; 54(4): 2323-2333, 2020 02 18.
Artigo em Inglês | MEDLINE | ID: mdl-31977201

RESUMO

Microbially induced concrete corrosion is a major deterioration process in sewers, causing a huge economic burden, and improved mitigating technologies are required. This study reports a novel and promising effective solution to attenuate the corrosion in sewers using calcium nitrite-admixed concrete. This strategy aims to suppress the development and activity of corrosion-inducing microorganisms with the antimicrobial free nitrous acid, which is generated in situ from calcium nitrite that is added to the concrete. Concrete coupons with calcium nitrite as an admixture were exposed in a sewer manhole, together with control coupons that had no nitrite admixture, for 18 months. The corrosion process was monitored by measuring the surface pH, corrosion product composition, concrete corrosion loss, and the microbial community on the corrosion layer. During the exposure, the corrosion loss of the admixed concrete coupons was 30% lower than that of the control coupons. The sulfide uptake rate of the admixed concrete was also 30% lower, leading to a higher surface pH (0.5-0.6 unit), in comparison to that of the control coupons. A negative correlation between the calcium nitrite admixture in concrete and the abundance of sulfide-oxidizing microorganisms was determined by DNA sequencing. The results obtained in this field study demonstrated that this novel use of calcium nitrite as an admixture in concrete is a promising strategy to mitigate the microbially induced corrosion in sewers.


Assuntos
Nitritos , Esgotos , Corrosão , Ácido Nitroso , Sulfetos
14.
Dent Mater ; 36(3): 431-441, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-31992484

RESUMO

OBJECTIVE: The Ti-6Al-4V (TAV) alloy is commercially used as a dental implant material. This work seeks to elucidates the origins of degradation of Ti-6Al-4V (TAV) implant alloys that result in peri-implant bone loss. 
Methods: In this work, a combination of microstructure, surface, and solution analyses was utilized to study the corrosion mechanism of the TAV alloy in oral environments. The corrosion of TAV alloys in the F--enriched environment of a crevice was evaluated through nanoscale surface analysis. And, the findings were further rationalized via electrochemical means. 
 RESULTS: Our results suggest the bone loss was caused by crevice corrosion and the consequential release of by-products, and the crevice corrosion was potentially induced by the buildup of corrosive species such as fluorides, which are common additives in dental products. In turn, the corrosion properties of the TAV alloy were evaluated in fluoride enriched environments. Nanoscale analysis of corroded surfaces, carried out using vertical scanning interferometry (VSI) showed that the corrosion susceptibility of the constituent phases dictates the corrosion product species. In specific, the aluminum-rich α phase preferentially dissolves under potential-free conditions and promotes the formation of insoluble Al-Ti oxides. Notably, under conditions of applied potential, oxidative dissolution of the vanadium-rich ß phase is favored, and the vanadium release is promoted. 
 SIGNIFICANCE: These findings elucidate the origins of degradation of TAV-implants that result in the release of corrosion by-products into the local biological environment. More important, they offer guidelines for materials design and improvement to prevent this nature of degradation of dental implants.


Assuntos
Implantes Dentários , Ligas , Corrosão , Ligas Dentárias , Teste de Materiais , Saliva Artificial , Propriedades de Superfície , Titânio
15.
J Environ Sci (China) ; 89: 218-226, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31892393

RESUMO

The current study analyzes the contribution of 10 water quality parameters (including pH, turbidity, conductivity, total dissolved solids (TDS), hardness, total organic carbon (TOC), alkalinity, calcium ions, chlorides and sulfates) to corrosion extent of stainless steel valves taken from different locations in a reverse osmosis system of a reclaimed water plant. The valves were in service for 5 years. Raman spectroscopy and X-ray photoelectron spectroscopy analyses are conducted to quantify corrosion products on different valves under various water quality conditions. On that basis, bivariate and multivariate regression analyses between the 10 water quality parameters and the corrosion extent of valve specimens (represented by metal loss percentage (MLP) values) are carried out to check the contribution of those water quality parameters to MLP. The results indicate that the proportions of metal oxides as corrosion products vary according to the corrosion extent of the valves. Although no linear correlation is found, all 10 water quality parameters except for pH show a significant positive correlation with the MLP values of the valve specimens. Moreover, results of multivariate regression suggest that the variation of MLP can be explained by turbidity, TDS, TOC and sulfates. A positive contribution of turbidity, TDS and TOC to MLP is observed, whereas the contribution of sulfates is negative. The results from the current work help to identify the reasons for water quality-induced failure of stainless steel equipment in RO systems.


Assuntos
Aço Inoxidável , Purificação da Água , Qualidade da Água , Corrosão , Osmose , Abastecimento de Água
16.
Dent Mater J ; 39(1): 148-153, 2020 Jan 31.
Artigo em Inglês | MEDLINE | ID: mdl-31666486

RESUMO

Many ß-Ti alloys have been developed for, and used in, medical devices because of the corrosion resistance, biocompatibility, and exceptionally low Young's modulus. The aim of the present study was to investigate the histomorphometric aspects of peri-implant bone around Ti-Nb-Sn alloy implants and compare them with those in the case of commercially pure Ti (Ti). Fluorescent morphological observations of ST-2 cells on the substrate were performed and bone morphogenesis around implants in rat femur was evaluated. There was no difference between the cell morphology on Ti and those on the Ti-Nb-Sn alloy during observation for 24 h. A comparison of the Ti-Nb-Sn alloy implant and the Ti implant showed no significant differences between the bone-to-implant contact ratios or the bone fractions. These results suggest that the biological adaptations with Ti-Nb-Sn implants during a healing period are similar to those with Ti. Ti-Nb-Sn is therefore suitable for use in dental implants.


Assuntos
Ligas , Titânio , Animais , Materiais Biocompatíveis , Osso e Ossos , Corrosão , Módulo de Elasticidade , Ratos
17.
J Biosci Bioeng ; 129(2): 199-205, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31587942

RESUMO

The corrosive issues are comprehensively caused in oilfield rejection system, in which sulfide is one of (bio-)chemical factors leading to high corrosive rate and blocking problem. Generally, aerobic treatment is a well-established and cost-effective unit for sulfide removal before oilfield wastewater reinjection. However, the residual dissolved oxygen (DO), which causes chemical, biological and electrochemical corrosion to water injection pipeline equipment, is still high after multi-stage filtration of DO removal. Here, a novel system to achieve quick and efficient DO removal through a three-electrode (cathode-anode-cathode)-upflow bioelectrochemical reactor (RCAC) was constructed before wastewater reinjection. Bioelectrodes were well established by utilizing organic matters of oilfield wastewater and conducted extracellular electron transport to achieve a steady DO removal from ∼5 mg/L to 0.01 mg/L (HRT 6 h), the DO removal efficiency reached approximately 100%, and the downside biocathode made the largest contribution for DO removal. In the treated wastewater, the corrosion rate of stainless steel N80 ultimately declined over 30 days testing. As a result of DO removal and ammonia conversion to nitrate by bioelectrodes, the corrosive microorganisms were substantially changed. Especially, sulfate-reducing bacteria (SRB) on the surface of N80 immersed in treated wastewater were decreased in abundance; while nitrate-reducing bacteria (NRB) enriched more, which can compete with SRB to prevent biological corrosion.


Assuntos
Campos de Petróleo e Gás , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química , Amônia/química , Amônia/metabolismo , Fenômenos Bioquímicos , Reatores Biológicos , Corrosão , Técnicas Eletroquímicas , Filtração , Nitratos/química , Nitratos/metabolismo , Sulfetos/química , Eliminação de Resíduos Líquidos/instrumentação
18.
Bioelectrochemistry ; 132: 107406, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31812086

RESUMO

Investigation of carbon steel corrosion influenced by in-situ microbial communities can provide reliable information about microbiologically influenced corrosion (MIC) in the oil and gas field. Here, we investigated the 90-day corrosion behavior of Q235 carbon steel influenced by interior deposit microflora of an in-service pipeline using open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS). Linear sweep voltammetry (LSV), 16S rRNA gene sequencing, and surface analysis were used to comprehensively analyze the corrosion mechanisms. The results indicated that OCP was decreased while the charge transfer resistance (Rct) was increased, and that steel corrosion was inhibited during the first 45 days. Subsequently, OCP was significantly increased while Rct was rapidly decreased, and steel corrosion was enhanced. After 90-day immersion, severe pitting corrosion with a maximum pit depth of 89.6 µm occurred on the steel surface. Viable microbes in the final biofilm significantly increased the cathodic current. Iron carbonate, chukanovite and cementite were identified as the main corrosion products on the steel surface. Methanobacterium dominated the final biofilm community. These observations indicate that the corrosion mechanism of the final biofilm can be explained by extracellular electron transfer MIC in which microbes corrode steel by direct electron uptake.


Assuntos
Biofilmes , Carbono/química , Corrosão , Aço/química , Eletrodos , Microbiota/genética , RNA Ribossômico 16S/genética
19.
Bioelectrochemistry ; 132: 107408, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31816577

RESUMO

Metallic materials can be easily corroded in marine environments, in which pitting corrosion is very common. In this study, we investigated the effect of Bacillus subtilis, isolated from the South China Sea on the corrosion behavior of 2A14 aluminum alloy in seawater. Surface analysis of the alloy in the presence of the bacteria was used to observe corrosion morphology and the corrosion products studied. Electrochemical method was used to analyze the corrosion susceptibility of the alloy in seawater in the presence of the bacteria. Surface analysis suggested that a protective film with CaMg(CO3)2 was gradually formed on the surface of the alloy in the presence of the bacteria. The electrochemical results showed that the radius of the impedance arc of the alloy immersed in seawater with bacteria increased gradually with time. The bacteria promoted the formation of the CaMg(CO3)2 film, which blocked seawater from the alloy and consequently, inhibited pitting corrosion.


Assuntos
Ligas/farmacologia , Alumínio/farmacologia , Bacillus subtilis/efeitos dos fármacos , Biofilmes , Corrosão , Água do Mar , Ligas/química , Alumínio/química , Microscopia Eletrônica de Varredura , Espectrometria por Raios X , Difração de Raios X
20.
Bioelectrochemistry ; 132: 107413, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31816578

RESUMO

Microbiologically influenced corrosion (MIC) of bare and silane-TiO2 sol-gel coated stainless steel (SS) was studied in treated urban wastewater (TUWW). Combining the electrochemical impedance spectroscopy (EIS) and the scanning vibrating electrode technique (SVET) showed that SS surface colonization occurs, at earlier stages, by iron-oxidizing bacteria (IOB), and later by sulphate-reducing bacteria (SRB). The SVET results showed that chemical corrosion process and bacterial respiration led to the depletion of dissolved oxygen, creating a differential aeration cell and thus a localized corrosion phenomenon. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) showed that the growth of a bacterial biofilm on 304L SS was a dynamic process, stimulating the localized oxidation of SS. To improve corrosion protection, a silane-TiO2 sol-gel coating for SS is proposed. SEM showed that the coating reduced bacterial adhesion and EIS study demonstrated that the coating improved the barrier properties and corrosion resistance of 304L SS in TUWW over a short period of immersion.


Assuntos
Bactérias/metabolismo , Corrosão , Silanos/química , Aço Inoxidável , Titânio/química , Águas Residuárias , Aderência Bacteriana , Microbiologia da Água
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