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1.
Chemosphere ; 255: 126901, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32387904

RESUMO

Enhanced nitrate removal from the secondary effluent in municipal wastewater treatment plants (WWTPs) is essential for avoiding water eutrophication. To this end, a vertical baffled solid-phase denitrification reactor (VBSDR) was developed using a starch and polycaprolactone (PCL) blend plate (S-PCL) as a carbon source and biofilm carrier. In this study, we evaluated the denitrification performance and microbial diversity of the VBSDR. The results of the Fourier transform infrared spectroscopy (FTIR), carbon leaching experiment, and scanning electron microscopy (SEM) demonstrated that the S-PCL structure can be attached and degraded more rapidly. Furthermore, the denitrification performance under varied operational conditions, i.e., influent nitrate loading rate (NLR) and operating temperature, was also investigated. Herein, when treating low C/N ratio and low-strength wastewater, a high denitrification rate (DR) [0.33 gN/(L·d)] was achieved. The effect of temperature on DR can be described by the Arrhenius-type equation, which shows that low temperature has a negative influence on DR and nitrate removal efficiency. Furthermore, DR was simultaneously affected by the NLR and temperature. The microbial diversity and community structure were determined by Illumina high-throughput sequencing. The special carbon source led to Acidovorax (denitrifying bacteria) and Flavobacterium (hydrolysis acidifying bacteria) being the VBSDR biofilm's most predominant functional bacteria at the genus level.


Assuntos
Poliésteres/química , Eliminação de Resíduos Líquidos/métodos , Biofilmes , Reatores Biológicos/microbiologia , Carbono/química , Comamonadaceae , Desnitrificação , Nitratos/química , Nitrogênio/química , Amido/química , Temperatura , Águas Residuárias/química
2.
Chemosphere ; 250: 126223, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32113098

RESUMO

Air quality in large cities has worsened in recent years as a consequence people's health is directly affected. Among the toxic compounds released to environmental air are polycyclic aromatic hydrocarbons (PAHs), nitrated PAHs (nitro-PAHs), and oxygenated PAHs (oxy-PAHs). Performant methods to analyze these compounds is necessary to enable adequate monitoring of air quality. Thus, this manuscript presents the development of a highly sensitive method to analyze PAHs, nitro-PAHs, and oxy-PAHs collected from ambient air (PM2.5) and the gas phase for a period of one year in the urban area of Belo Horizonte, Brazil. PAHs and their derivatives were extracted by cold fiber solid phase microextraction (CF-SPME) and analyzed by gas chromatography coupled to mass spectrometry (GC/MS). The proposed method allows simultaneous analysis of 16 PAHs, nitro-PAHs and oxy-PAHs, presenting very good limits of detection and quantification, as well as appropriate precision and recovery. The results obtained for the period of one year allowed different studies. The compounds collected simultaneously from gas and particulate phase showed that total concentration of 16 PAHs were higher in the gas phase than in the particulate. On the other hand, nitro-PAHs and oxy-PAHs presented similar concentration in gas and particulate phases. The potential carcinogenicity of PAHs relative to benzo[a]pyrene showed benzo[a]pyrene equivalents of 0.49 ng m-3. The estimated risk of lifetime lung cancer was 5 × 10-5. Principal component analysis and diagnostic ratio was applied for source distribution indicating that burning of gasoline, diesel and biomass accounted for the PAHs profile in ambient air samples.


Assuntos
Poluentes Atmosféricos/análise , Poluição do Ar/estatística & dados numéricos , Monitoramento Ambiental , Hidrocarbonetos Policíclicos Aromáticos/análise , Poluição do Ar/análise , Benzo(a)pireno/análise , Brasil , Respiração Celular , Cidades , Poeira/análise , Cromatografia Gasosa-Espectrometria de Massas/métodos , Gasolina/análise , Humanos , Nitratos/química , Óxidos de Nitrogênio/análise , Oxigênio/química , Material Particulado/análise , Microextração em Fase Sólida
3.
Chemosphere ; 242: 125233, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31896207

RESUMO

Acid/base/oxidant pretreatment influenced subsequent quaternary ammonium epoxide compounds modified carbon (QAE-AC) and hence PFOA and nitrate removal. This work discerned that the most favorable QAE-AC protocol for PFOA removal was achieved when the wood carbon pretreated with HNO3 to adjust the carbon's slurry pH to 4.77, and tailored with the QUAB188. For nitrate removal, the most favorable when the carbon was pretreated with NaOH to raise the carbon's slurry pH to 9.34, and then loaded with the QUAB360. Based on experimentally results and molecular model, we found that pore volume, phenolic groups and the surface charge were the main factors affecting the PFOA removal, while the only factor affecting nitrate removal was surface charge. The QUAB's epoxide functionalities have cross-linked with phenolics along the activated carbon's graphene edge sites. QAE is preferentially reacted with the phenolic in the micropores and mesopores of carbon, and some QAE molecules form new "pore-like structures" outside the pores with the graphene planes or other QAE molecules. This pore-like structure hosted adsorption capacity by the quaternary ammonium. The favorable PFOA adsorption sites were in smaller mesopores via both hydrophobic interaction and electrostatic interaction; and nitrate sorption was occurring in the smaller micropores via anion exchange. Therefore, it can be considered that QAE-AC can simultaneously adsorb PFOA and nitrate in water.


Assuntos
Caprilatos/química , Fluorcarbonetos/química , Modelos Químicos , Nitratos/química , Compostos de Amônio Quaternário/química , Poluentes Químicos da Água/química , Adsorção , Compostos de Amônio/química , Ânions , Carvão Vegetal/química , Compostos de Epóxi , Oxidantes , Água
4.
Environ Sci Pollut Res Int ; 27(9): 9274-9287, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31916171

RESUMO

Nitrate pollution in rivers, lakes, shallow groundwater, and even deep groundwater occurs in many parts of the world. And, it's essential to assessing the relationship between nitrate pollution and human health, which is called human health risk assessment (HHRA). In this paper, groundwater samples were collected for their nitrate content in a typical karst hydrogeological unit in East China during the wet and dry seasons. Then, a human health risk assessment was conducted using the four-step risk assessment process developed by the US Environmental Protection Agency (USEPA), which aimed to determine the potential risk posed to human health by nitrate in the groundwater. To make the assessment more authentic and objective, the drinking water and dermal contact exposure pathways were considered, and the people were divided into four groups, including infants (0~6 months), children (7 months~17 years old), females (18 years and older), and males (18 years and older), in the wet and dry seasons to determine the impacts of the exposure pathway, age, sex, and precipitation period. The results indicated that more than half of the groundwater samples exceeded 10 mg/L (measured as nitrogen), which is the drinking water standard of China. The children and infants had greater health risks than the adults at the same groundwater nitrate concentration, and those two groups need to be paid more attention; the adult females had a greater health risk than the adult males in the two precipitation periods, which shows that the order of the health risk was infants ˃ children ˃ adult females ˃ adult males. In addition, the value of the hazard quotient (HQ) and the area of the adverse effects were both higher in the wet season than in the dry season, which explains that precipitation can affect the human health risk as well. The HQ caused by the drinking water exposure pathway was much higher than that caused by the dermal contact exposure pathway. This study can provide information for more effective and reasonable decisions to city managers for groundwater nitrate pollution prevention.


Assuntos
Água Subterrânea , Nitratos/química , Poluentes Químicos da Água , Adulto , Criança , China , Cidades , Feminino , Humanos , Lactente , Masculino , Medição de Risco
5.
Chemosphere ; 241: 125115, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31683419

RESUMO

In this study, a novel and highly reactive Sn-Pd catalyst supported by environmentally benign kaolinite (Sn-Pd-kaolinite) was developed and evaluated for stability for effective nitrate (NO3-) reduction in batch and continuous mode. Complete NO3- removal with fast reduction kinetics (k = 18.16 × 10-2 min-1) and 71% selectivity toward N2 were achieved by the Sn-Pd-kaolinite catalyst during batch reactions. During continuous tests, 100% NO3- removal and 80% N2 was achieved for 60 h. However, NO3- removal efficiency gradually decreased to 80% in170 h. The catalyst was then successfully regenerated in the system by increasing H2 flow which achieved a complete NO3- removal again. The metal leaching from catalyst surface was negligible (Sn 0.01% and Pd 0.006%) and the structure was stable during the continuous test, confirming that the Sn-Pd-Kaolinite catalyst had a superior reaction kinetics and operational durability.


Assuntos
Temperatura Alta , Caulim/química , Nitratos/química , Compostos de Estanho/química , Catálise , Cinética , Oxirredução , Paládio/química
6.
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
7.
Ecotoxicol Environ Saf ; 191: 110001, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31812281

RESUMO

The interference of toxic heavy metals in the process of microbial aerobic denitrification is a hot issue in industry wastewater treatment in recent years. In this study, a multifunctional aerobic denitrifying bacterium - Pseudomonas aeruginosa G12 isolated from sewage sludge was used to explore the simultaneous removal ability to NO3--N and Cr(VI) in wastewater by a series of batch experiments. The results showed that G12 could effectively remove NO3--N (500 mg L-1) and Cr(VI) (10 mg L-1) by 98% and 93%, respectively. Meanwhile, the study found that the strain G12 had the potential to adapt to the complex external environment, including different carbon resources, nitrogen sources, and the coexisting heavy metals (Mn2+ and Cu2+). The strain G12 also had the considerable tolerance to initial NO3--N (100-700 mg L-1) and Cr(VI) (1-20 mg L-1) concentrations. The instrument analysis methods-Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD), from the molecular level, further confirmed that the strain G12 could remove NO3--N by aerobic denitrification, and the reduced functional groups (amino group, amide group, hydroxyl group and carboxyl group) on the surface of bacteria could transform Cr(VI) to Cr(III) (mainly CrCl3). This study will offer a promising new microbial resource for nitrogen and Cr(VI) removal in industry wastewater treatment.


Assuntos
Cromo/metabolismo , Nitratos/metabolismo , Pseudomonas aeruginosa/metabolismo , Águas Residuárias/química , Poluentes Químicos da Água/metabolismo , Desnitrificação , Metais Pesados/metabolismo , Nitratos/química , Óxidos de Nitrogênio/metabolismo , Esgotos/microbiologia
8.
Environ Sci Pollut Res Int ; 27(1): 1112-1117, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31820236

RESUMO

The present work designs a low-cost biological treatment strategy consisting of constructed wetlands (CWs) followed by entrapped algae (EA) for removing nutrients (PO43-, NO3-, and NH4+) and organic matters from high-strength wastewater. The CWs are efficient means for organic pollutant removal but face challenges in nutrient removal. Algae have a high growth rate and nutrient uptake capabilities from wastewater. The severe challenge that limits the use of algae for nutrient removal from wastewater is its post-treatment separation from wastewater. This work presents a strategy to address the described problems of CWs and algae-based system. It also assesses the performance of the system using synthetic wastewater. A combined system of CW followed by EA (CW-EA) was able to treat 86.0% of phosphate, 95.0% of nitrate, 74.0% of ammonium, and 87.0% of chemical oxygen demand (COD) from high-strength wastewater.


Assuntos
Nitrogênio/análise , Águas Residuárias/análise , Purificação da Água/métodos , Análise da Demanda Biológica de Oxigênio , Nitratos/química , Nitrogênio/química , Nutrientes , Fosfatos/química , Plantas , Eliminação de Resíduos Líquidos/métodos , Áreas Alagadas
9.
Environ Sci Pollut Res Int ; 27(2): 1956-1968, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31768960

RESUMO

Membrane separation processes are being currently applied to produce drinking water from water contaminated with nitrate. The overall process generates a brine with high nitrate/nitrite concentration that is usually send back to a conventional wastewater treatment plant. Catalytic processes to nitrate reduction are being studied, but the main goal of achieving a high selectivity to nitrogen production is still a matter of research. In this work, a two-step process was evaluated, aiming to verify the best combination of operational parameters to efficiently reduce nitrate to nitrogen. In the first step, the nitrate was reduced to nitrite by electroreduction, applying a copper electrode and different cell potentials. A second step of the process was carried out by reducing the generated nitrite with a catalytic process by hydrogenation. The results showed that the highest nitrate reduction (89%) occurred when a cell potential of 11 V was applied. In this condition, the nitrite ion was generated with all experimental conditions evaluated. Then, to reduce the nitrite ion formed by catalytic reduction, activated carbon fibers (ACF) and powder γ-alumina (γ-Al2O3) were tested as supports for palladium (Pd). With both catalysts, the total nitrite conversion was obtained, being the selectivity to gaseous compounds 94% and 97% for Pd/Al2O3 and Pd/ACF, respectively. Considering the results obtained, a two-stage treatment setup to brine denitrification may be proposed. With electrochemistry, an operating condition was achieved in which ammonium production can be controlled to very low values, but the reduction is predominant to nitrite. With the second step, all nitrite is converted to nitrogen gas and just 3% of ammonium is produced with the most selective catalyst. The main novelty of this work is associated to the use of a two-stage process enabling 89% of nitrate reduction and 100% of nitrite reduction.


Assuntos
Desnitrificação , Nitratos/química , Nitritos/química , Sais/química , Catálise , Nitrogênio , Oxirredução
10.
Carbohydr Polym ; 227: 115367, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31590884

RESUMO

In this study, functionalized hydrogel bioadsorbents were produced from gum tragacanth (GT) carbohydrate and quaternary ammonium salt (TMSQA) as a crosslinker. The prepared bioadsorbents were used for the removal of NO3- ions from water through the electrostatic and ion exchange mechanism and antibacterial activity. The effect of quaternary ammonium content on the adsorption capacity was studied. The bioadsorbents were characterized by using FE-SEM, energy dispersive X-Ray (EDX), FT-IR, and TGA techniques. The equilibrium time and the most effective pH value for maximum NO3- removal (20 mg g-1) were 21 min and 7, respectively. A series of isotherms and kinetics models were undertaken and the obtained data were fitted well to the Langmuir isotherm and pseudo-second-order rate kinetic. The thermodynamic study confirmed the suitability of NO3- removal by the as-prepared bioadsorbent at room temperature, and also the negative value of ΔGº = -89.1 kJ mol-1 demonstrating the spontaneous nature of adsorption.


Assuntos
Hidrogéis/química , Nitratos/química , Compostos de Amônio Quaternário/química , Tragacanto/química , Poluentes Químicos da Água/química , Adsorção , Bacillus subtilis/efeitos dos fármacos , Bacillus subtilis/crescimento & desenvolvimento , Escherichia coli/efeitos dos fármacos , Escherichia coli/crescimento & desenvolvimento , Hidrogéis/farmacologia , Concentração de Íons de Hidrogênio , Compostos de Amônio Quaternário/farmacologia , Temperatura , Tragacanto/farmacologia , Purificação da Água/métodos
11.
Chemosphere ; 239: 124792, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31526998

RESUMO

We systematically investigated the surface characteristics of polystyrene microplastic particles (PSMPs) prepared by ball milling to impart a porous surface structure and special surface characteristics, and studied the mechanism of adsorption of As(III) onto PSMPs. The sizes of the PSMPs prepared by ball milling for 2, 4, and 8 h were in the ranges of 0.1-1, 1-10, and 10-100 µm, respectively. That is, the longer the milling time is, the larger the specific surface area of the particles is. Moreover, the higher the point of zero charge is, the higher the adsorbed amount of As(III) is. The highest adsorption rate of As(III) onto PSMPs was found to be 1.12 mg g-1. After 1200 min, the adsorption reached equilibrium, and a pseudo-second-order model better fitted the As(III) adsorption kinetics. The Langmuir and Freundlich models could well describe the adsorption isotherms. Furthermore, hydrogen bonds between As(III) and PSMPs were broken at high temperatures, resulting in a decrease in As(III) adsorption onto PSMP, which indicated that the adsorption process was exothermic. Increases in the pH and concentrations of interfering nitrate and phosphate ions in the solution led to inhibited As(III) adsorption of PSMPs. The electrostatic potential of most areas of the PSMP surface was positive, and the H atom on the carboxyl group exhibited a very large positive potential (+56.6 kcal/mol), and thus attracted arsenic oxyanions. Thus, it was determined that As(III) adsorbed to the surface of PSMPs through hydrogen bonding with the carboxyl group. Electrostatic forces and non-covalent interactions are the key mechanisms affecting the adsorption of As(III) onto PSMPs. This work provides a clear theoretical basis for the behavior of the PSMP as an arsenic carrier and might aid to improve the environmental toxicity of arsenic.


Assuntos
Arsênico/química , Microplásticos/química , Poliestirenos/química , Adsorção , Ligação de Hidrogênio , Concentração de Íons de Hidrogênio , Cinética , Nitratos/química , Tamanho da Partícula , Fosfatos/química , Salinidade , Eletricidade Estática , Propriedades de Superfície , Temperatura , Poluentes Químicos da Água/química
12.
Chemosphere ; 239: 124803, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31520973

RESUMO

Nitrogen biogeochemistry occupies a central role in nitrogen cycles and exerts a significant influence on primary productivity and global carbon cycles. In order to better understand the nitrogen biogeochemistry in coastal regions, spatiotemporal nitrogen fixation, denitrification and anammox were investigated in the coastal regions of northern Beibu Gulf (NBG), South China Sea (SCS). Nitrogen fixation was mainly detected in the water column of outer bays, attributed to the low nitrate concentration and low N/P (N/P < 16). Comparisons of the nitrogen fixation rates between unicellular (<10 mm) and the filamentous diazotrophs (>10 mm) indicated that the contribution of unicellular diazotrophs was more important than filamentous diazotrophs. Besides, field investigation revealed that Richelia was the dominant species in filamentous diazotrophs. On the other hand, both denitrification and anammox were found in the surface sediment and denitrification dominated the nitrogen loss process. Denitrification was mainly related to the nitrate concentration in pore water and organic matter in the sediment, while anammox was mainly regulated by the concentration of nitrate and nitrite in pore water. Additionally, temperature, dissolved oxygen (DO) and salinity also had an impact on denitrification and anammox. The net areal yield of nitrogen biogeochemical processes was estimated to be -1079t/a, as an important pathway of nitrogen removal. This study adds to the knowledge of nitrogen biogeochemistry in the nutrient-replete coastal region and highlights its significance in such an environment.


Assuntos
Baías/química , Ciclo do Nitrogênio , Nitrogênio/química , Baías/microbiologia , Ciclo do Carbono , China , Cianobactérias/metabolismo , Desnitrificação , Nitratos/química , Nitritos/química , Nitrogênio/análise , Fixação de Nitrogênio , Oxigênio/química , Salinidade , Análise Espaço-Temporal
13.
Chemosphere ; 240: 124868, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31542583

RESUMO

Multi-soil-layering (MSL) system with brick-wall pattern structure and gravitational flow can be used for decentralized rural domestic sewage treatment. The capability of soil for contaminant removal is maximized within soil mixture blocks (SMBs). However, the performance of removing nitrate was still not ideal during operation. To improve its performance in MSL system, the relationship between biophysiological characteristics of denitrifying species and operating conditions was studied. Microbial species diversity of activated sludge and soil samples were analyzed. The significant effects of independent factors and their interactions on microbial species diversity and denitrifying species abundance were revealed on the basis of factorial analysis. The results indicated activated sludge in SMBs played a key role in increasing the richness of denitrifying species in MSL system. Slow-release poly (butylene succinate) (PBS) had the most dominant positive effect on increasing denitrifying species abundance. Submersion had significantly positive effect on species richness in SMBs. These three factors, including activated sludge, PBS in SMBs, and submersion condition had different significant effects on microbial responses. They were favorable for denitrification and ensuring a better removal efficiency of nitrate and total nitrogen. The porous zeolites were served as the habitats for most of aerobic bacteria to form biofilms, which could promote the oxygen consumption in both sewage and system to improve denitrification in SMBs. The results could help on the enhancement of denitrification in MSL system from biophysiological insights. It can provide a sound strategy for using MSL system with great performance on contaminant removal.


Assuntos
Nitratos/química , Esgotos/química , Solo/química
14.
Chemosphere ; 240: 124872, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31550589

RESUMO

Batch experiments were conducted using two biochar materials produced from different feedstocks to examine the behavior of solution-borne nitrate in the presence and absence of three model low-molecular weight organic acids (LMWOAs). The results showed that the biochar materials alone were not able to remove the solution-borne nitrate. LMWOAs caused protonation of the biochar surfaces and consequently enabled the biochar materials to adsorb nitrate from the solution. Different types of LMWOA had different capacities to immobilize solution-borne nitrate. Over 80% of the solution-borne nitrate could be removed within 72 h in the presence of citric acid or malic acid. By comparison, removal rate of nitrate was lower in the presence of oxalic acid, possibly due to competition of oxalate ion with nitrate for the available adsorption sites on the biochar surfaces. Nitrate adsorption onto the MSP700 biochar in the presence of all three-LMWOAs followed first order and second order kinetics, suggesting that the immobilization of nitrate involved complex interplay of physisorption and chemisorption. Nitrate adsorption onto RH700 biochar in citric and malic acid treatment systems followed second order kinetics. In the presence of oxalic acid for both biochar materials, nitrate adsorption showed perfect correlation R2 = 1 for both models.


Assuntos
Carvão Vegetal/química , Nitratos/química , Compostos Orgânicos/química , Peso Molecular
15.
Chemosphere ; 238: 124543, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31450109

RESUMO

Nano micro-electrolysis materials (nMETs) have been used to degrade refractory pollutants in batch experiments. The reasonable formation mechanism of nMETs was given through DMXY digital biomicroscopy. Based on the kinetic data of Chlortetracycline (CTC) removal by nMETs in batch experiments, combined with the binomial distribution equation of CTC reduction by nano materials an experimental-scale fluidized bed (ESFB) was designed. The effects of CTC removal performance, pH and iron ion concentration were investigated. Under pure CTC solution environment, the experimental data showed that the average removal rates of CTC by nMET and nano micro-electrolysis material with loading copper (Cu-nMET) are 90.0% and 95.7% in ESFB, respectively. In the presence of nitrate, although the consumption of two kinds of nano-materials increased, their removal efficiencies of pollutants have 2.2%, 0.2% increase compared with the nitrate-free ESFB. At the same time, the CTC degradation pathway and the enhanced removal mechanism by Cu-nMET was proposed. Through microelectrolysis reaction, complexation reaction and the active substances produced, the intermediate products can be degraded completely to NH4+, CO2, H2O and so on. This study aims to provide a theoretical basis for the environmental application of nMETs.


Assuntos
Clortetraciclina/isolamento & purificação , Cobre/química , Eletrólise/métodos , Ferro/química , Nitratos/química , Poluentes Químicos da Água/isolamento & purificação , Clortetraciclina/análise , Clortetraciclina/química , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/química
16.
Food Chem ; 305: 125456, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31525594

RESUMO

This work developed a new technique and an application of an existing approach to determine sodium in food sauces, involving enthalpimetric reactions in the infrared. Infrared Thermometric Titration (TT-IR) was utilized, with simple analyzers and low-cost measurement instruments for the acquisition of the surface temperature generated in the sodium precipitation reaction and development of software for the acquisition and processing of data using Raspberry Pi. The sodium was also quantified by Thermal Infrared Enthalpimetry (TIE), a recently developed technique. The rapid and simple quantification of sodium by the TT-IR and TIE showed the possibility of a selective reaction for sodium, using aluminum nitrate, potassium and ammonium fluoride in an acid medium, with reduction of the reagents and without the digestion step in the sample preparation. The results acquired through TT-IR and TIE corroborated the Flame Atomic Emission Spectrometry (FAES) with 96 to 103% and 95 to 102%, respectively.


Assuntos
Análise de Alimentos/métodos , Raios Infravermelhos , Sódio/análise , Produtos Vegetais/análise , Compostos de Alumínio/química , Limite de Detecção , Nitratos/química , Sódio/química , Espectrofotometria Atômica , Temperatura , Termometria/métodos
17.
Chemosphere ; 238: 124654, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31524611

RESUMO

Nitrate is a byproduct of the anaerobic ammonium oxidation (anammox) process and is related to its electron transfer. However, little is known about the influence of nitrate on the anammox process. In this work, the biphasic effect of exogenous nitrate on the anammox process was investigated in an upflow biofilter (UBF) reactor with ammonium as the sole electron donor. The responses of anammox to increased nitrate were analyzed by one-way ANOVA test and found to be significantly different under a constant and decreased nitrite condition (p < 0.01). With a single increase in nitrate and constant ammonium and nitrite in the influent, the total nitrogen removal rate (TNRR) of anammox was uninhibited, but stoichiometry deviated and nitrate production always showed a linear decrease. In contrast, anammox exhibited a range of activity with constant ammonium and simultaneously increased nitrate and decreased nitrite in the influent, including a continuous reduction of TNRR, a nonpersistent ammonium overconsumption and a pronounced nonlinear response of nitrate production. Correlation analysis shows that the lack of ammonium overconsumption was accompanied by the disappearance of nitrate underproduction. Kinetic models of product formation were effectively used to explore the nitrate production behavior of anammox subjected to increased nitrate, and the metabolite of nitrate was divided into a growth negative coupling type and growth (partial) coupling type under a constant and decreased nitrite condition, respectively. These findings collectively suggest that nitrate has a biphasic effect on the anammox process and is correlated with the availability of nitrite.


Assuntos
Compostos de Amônio/química , Anaerobiose/efeitos dos fármacos , Nitratos/farmacologia , Reatores Biológicos , Desnitrificação , Cinética , Nitratos/química , Nitritos/química , Nitrogênio/química , Oxirredução
18.
Environ Sci Pollut Res Int ; 27(7): 7504-7514, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31884534

RESUMO

Sediment is an endogenous pollution source, which often leads water systems to eutrophication due to the release of nutrients, especially phosphorus (P). Calcium nitrate (CN) was dosed to the water systems under different modes to control P release from the sediments in this study. A 63-day static laboratory test was conducted to explore the effects of intermittent dosing and one-time dosing modes of CN on P locking in the sediment and the concentrations of nitrogen (N) and P in waters. Results showed that 89% total phosphorus (TP) in the overlying water and 91% TP in the interstitial water of sediment were reduced in the intermittent dosing reactor, which were 4% and 13% higher than those in the one-time dosing reactor, respectively. Thus, the concentration of TP in the overlying water of the dosing reactors was both below 0.1 mg/L during the whole experiment. Meanwhile, the mean values of oxidation-reduction potential (ORP) in the sediment increased to - 110.7 ± 42.02 mV when CN was added intermittently, which were significantly higher than those of the one-time dosing reactor (- 158.3 ± 44.61 mV) and control reactor (- 320.7 ± 0.05 mV). Compared with one-time dosing mode, the intermittent dosing not only reduced the maximum concentrations of NO2--N from 9.21 to 1.79 mg/L and NO3--N from 92.42 to 27.58 mg/L but also shorten their retention time in the overlying water, which might depress the toxic threats to aquatic animals in water environments. Therefore, the intermittent dosing of CN could not only improve the P locking effect but also minimize the risks to aquatic animals in water environments under the premise of reasonable dosage selected. In a word, this research provided an effective operation mode for locking P with CN in the heavily polluted water bodies, which is also advantageous to avoid toxic threats to aquatic animals in water environment.


Assuntos
Compostos de Cálcio/química , Sedimentos Geológicos , Nitratos/química , Fósforo/química , Poluentes Químicos da Água , Eutrofização , Nitrogênio/química , Nutrientes/química
19.
Environ Sci Pollut Res Int ; 27(6): 5890-5900, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31863374

RESUMO

Mg-Fe layered double hydroxide intercalated with chloride (Mg-Fe-Cl LDH) was synthetized, characterized, and evaluated as adsorbent to remove nitrate from aqueous solution. The pH, initial nitrate concentration, adsorbent dosage, and particle size were investigated. Kinetic data was best represented by pseudo-second order model indicating that the rate limiting step was chemisorption. Intraparticle diffusion model indicates that adsorption kinetic is limited by external and intraparticle diffusion. Sips model was selected, based on R2, ARE, and AIC, to adequately represent the adsorption isotherms, which permits to affirm that the adsorption occurs in heterogeneous surface, obtaining the maximum adsorption capacity of 18.17 mg.g-1 at 30 oC. Thermodynamics parameters indicate that the adsorption was spontaneous, exothermic, and with structural modification. These findings come up with Mg-Fe-Cl LDH as a suitable adsorbent for nitrate and could contribute to its removal from the water and wastewater.


Assuntos
Cloretos/química , Hidróxidos/química , Ferro/química , Magnésio/química , Nitratos/química , Poluentes Químicos da Água , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Nitratos/análise
20.
Molecules ; 24(22)2019 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-31718040

RESUMO

This article presents an ecologically safe aqueous two-phase system based on poly(ethylene oxide) with a molecular weight of 1500, designed for complex extraction of Ni(II), Co(II), Fe(III), Mn(II), Zn(II), Cu(II), and Al(III) from nitrate solutions. A kinetic dependence has been investigated for a distribution ratio for the metals examined. The influence of pH-values, temperature, initial metal concentration, and nitric acid content have on the extraction of a wide range of metals in the heterogeneous poly(ethylene oxide) 1500-NaNO3-H2O system has been discovered. As a result, the complex extraction of metals (EMe > 60%) was achieved in one step of extraction without introducing additional chemicals into the system.


Assuntos
Extração Líquido-Líquido , Metais/química , Metais/isolamento & purificação , Nitratos/química , Polietilenoglicóis/química , Algoritmos , Concentração de Íons de Hidrogênio , Modelos Teóricos , Temperatura
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