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1.
Gastrointest Endosc ; 2020 Jan 03.
Artigo em Inglês | MEDLINE | ID: mdl-31911077

RESUMO

BACKGROUND AND AIMS: Prediction models for esophageal squamous cell carcinoma are not common, and no model targeting a clinical population has previously been developed and validated. We aimed to develop a prediction model for estimating the risk of high-grade esophageal lesions for application in clinical settings and to validate the performance of this model in an external population. METHODS: The model was developed based on the results of endoscopic evaluation of 5624 outpatients in one hospital in a high-risk region in northern China and was validated using 5765 outpatients who had undergone endoscopy in another hospital in a non-high-risk region in southern China. Predictors were selected with unconditional logistic regression analysis. The Akaike information criterion was used to determine the final structure of the model. Discrimination was estimated using the area under the receiver operating characteristic curve (AUC). Calibration was assessed using a calibration plot with an intercept and slope. RESULTS: The final prediction model contained 5 variables, including age, smoking, body mass index, dysphagia, and retrosternal pain. This model generated an AUC of 0.871 (95% confidence interval, 0.842-0.946) in the development set, with an AUC of 0.862 after bootstrapping. The 5-variable model was superior to a single age model. In the validation population, the AUC was 0.843 (95% confidence interval, 0.793-0.894). This model successfully stratified the clinical population into 3 risk groups and showed high ability for identifying concentrated groups of cases. CONCLUSIONS: Our model for esophageal high-grade lesions has a high predictive value. It has the potential for application in clinical opportunistic screening to aid decision making for both health care professionals and individuals.

2.
Environ Sci Technol ; 2019 Dec 17.
Artigo em Inglês | MEDLINE | ID: mdl-31790214

RESUMO

Partial nitritation providing a suitable effluent for subsequent anammox is a critical step in a two-stage autotrophic nitrogen removal system. This study demonstrates an innovative approach for attaining partial nitritation in an acidic bioreactor operating at a slightly low pH (i.e., 5-6). This approach is based on our hypothesis in this study that acid-tolerant ammonia-oxidizing bacteria (AOB) can produce nitrite and protons to self-sustain free nitrous acid (FNA, NO2- + H+ ↔ HNO2) at a parts per million level, as an inhibitor of nitrite-oxidizing bacteria (NOB). With influent nitrogen of about 200 mg/L and operating conditions of high dissolved oxygen, long sludge retention time, and moderate temperature, a lab-scale acidic bioreactor with FNA up to 2 mg of HNO2-N/L successfully established stable nitrite accumulation in the effluent for 200 days, with an average ratio [NO2-/(NO2- + NO3-)] exceeding 95%. A 16S rRNA amplicon sequencing analysis showed that Nitrosospira was the dominant AOB in the biomass of the bioreactor, while Nitrosomonas and Nitrospira, two typical nitrifying genera in neutral wastewater treatment, both disappeared after the startup of partial nitritation. Kinetic characterization revealed that Nitrosospira had a substrate affinity of 11.4-16.5 mg of total ammonia (NH4+ + NH3)/L. It also revealed that less than 3.5 mg of HNO2-N/L FNA did not inhibit AOB activity significantly. Acidic operation is economically attractive because it can be achieved via acidophilic ammonia oxidation without adding chemical acid. However, hazardous gas, nitric oxide (NO), should be removed from gas produced by acidic nitrifying bioreactors.

3.
Environ Geochem Health ; 41(4): 1767-1776, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28550602

RESUMO

The recovery of phosphate from human urine has been considered as one of the most attractive benefits of urine source separation because P is an essential but limited macronutrient. This study investigated the approach to modify wood waste biochar via metal oxides aiming to recover phosphate from human urine to produce a value-added biochar. Results showed the phosphate removal ability was enhanced for the modified biochar pre-treated in modification solutions of MgCl2, AlCl3, CaCl2 and FeCl3, respectively, while natural biochar released phosphate to urine. Among the tested biochar, Mg-biochar presented the best capacity for phosphate removal from the hydrolyzed urine, reaching 118 mgP g-1 at a MgCl2 concentration of 2.3 M. However, higher MgCl2 concentration would not further increase the adsorption capacity. Fitting of the adsorption kinetics and isotherms indicated that the phosphate removal process was probably controlled by multiple mechanisms. Both the experimental and fitting results confirmed that the content of Mg oxides was the key factor determining the adsorption rate and capacity of phosphate on Mg-biochar. pH ranges of 7-9 and the ammonium concentration higher than 108 mgN L-1 enhanced the phosphate adsorption capacity. As such, the Mg-biochar was more favored for the treatment of hydrolyzed urine rather than fresh urine with acidic pH and lower concentration of ammonium. Further calculations were carried out using the Langmuir model to evaluate the removal of phosphate and the product. Results indicate that it is an effective technique to use Mg-biochar for phosphate removal from hydrolyzed urine and it yields phosphate-enriched biochar products.


Assuntos
Carvão Vegetal/química , Óxido de Magnésio/química , Fosfatos/isolamento & purificação , Urina/química , Madeira/química , Adsorção , Humanos , Concentração de Íons de Hidrogênio , Hidrólise , Cinética , Metais/química , Modelos Teóricos , Óxidos/química , Fosfatos/química , Resíduos
4.
ACS Appl Mater Interfaces ; 10(35): 29965-29971, 2018 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-30084629

RESUMO

Inexpensive, active, stable, and CO-tolerant nonplatinum catalysts for efficient methanol electro-oxidation are highly desirable to direct methanol fuel cell (DMFC) technology; however, it is still challenging. In this study, we report palladium and cobalt nanowires with jagged appearance (Pd-Co J-NWs), synthesized via first anodic-aluminum-oxide template-confined electrodeposition of Pd-Co regular nanowires, followed by a wet-chemical transformation. Benefiting from the "jagged" appearance and Co dopants, the mass and specific activities of Pd-Co J-NWs for methanol electro-oxidation are evaluated ∼3.2 times and ∼2.1 times as high as those of Pd/C catalysts, respectively. After chronoamperometric measurements for 2000 s, the catalytic stability of Pd-Co J-NWs is ∼5.4 times higher compared to that of commercial Pd/C. Moreover, the onset potential of CO-stripping of Pd-Co J-NWs (0.5 V) is lower than that of Pd/C (0.7 V), suggesting CO antipoisoning. Our approach to Pd-Co J-NWs catalysts provides an experimental guideline for designing other high-performance nonplatinum catalysts, which is promising for future DMFC industry.

5.
Water Sci Technol ; 77(9-10): 2341-2347, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29757186

RESUMO

Ultrasonic treatment for enhancing biological processes has recently attracted considerable attention in wastewater treatment. In this study, we systematically investigated the mixed liquor properties of activated sludge under ultrasonic treatment. The sludge samples were collected from the aerobic tank of a full-scale membrane bioreactor (MBR) treating municipal wastewater, and the volatile suspended solids (VSS) concentration was approximately 6.0 g/L. The results showed that ultrasonic treatment induced floc disintegration, organics release, temperature increase, microbial activity and pH variation. The maximum mg soluble chemical oxygen demand (COD) per mg VSS released was estimated to be 0.147 using the Monod equation. The exponential increase in the concentration of dissolved organic matter is related to the loss of relative heterotrophic bacterial activity. A sonolysis-cryptic growth model was demonstrated to be capable of describing ultrasonic sludge reduction, which would support the further development of ultrasonic treatment technology in activated sludge systems.


Assuntos
Reatores Biológicos , Esgotos/química , Eliminação de Resíduos Líquidos/métodos , Análise da Demanda Biológica de Oxigênio , Ultrassom , Águas Residuárias/química , Poluentes Químicos da Água
6.
Sci Total Environ ; 635: 1507-1519, 2018 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-29710672

RESUMO

Recycle domestic greywater for on-site non-potable uses can lessen the demand on potable water and the burden on wastewater treatment plants. However, lack of studies to assess health risk associated with such practices has hindered their popularity. A Quantitative Microbial Risk Assessment was conducted to estimate the public health risks for two greywater reuse scenarios: toilet flushing and food-crop irrigation. Household greywater quality from three sources (bathroom, laundry and kitchen) was analyzed. Mathematical exposure rates of different scenarios were established based on human behavior using Monte-Carlo simulation. The results showed that, greywater from all three household sources could be safely used for toilet flushing after a simple treatment of microfiltration. The median range of annual infection risk was 8.8 × 10-15-8.3 × 10-11 per-person-per-year (pppy); and the median range of disease burden was 7.6 × 10-19-7.3 × 10-15 disability-adjusted life years (DALYs) pppy. In food-crop irrigation scenario, the annual infection risks and disease burdens of treated greywater from bathroom and laundry (2.8 × 10-8, 4.9 × 10-8 pppy; 2.3 × 10-12-4.2 × 10-12 DALYs pppy) were within the acceptable levels of U.S. EPA annual infection risk (≤10-4 pppy) and WHO disease burden (≤10-6 DALYs pppy) benchmarks, while kitchen greywater was not suitable for food-crop irrigation (4.9 × 10-6 pppy; 4.3 × 10-10 DALYs pppy) based on these benchmarks. The model uncertainties were discussed, which suggests that a more accurate risk estimation requires improvements on data collection and model refinement.


Assuntos
Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/microbiologia , Microbiologia da Água , Reciclagem , Medição de Risco
7.
Nanoscale ; 9(26): 8918-8924, 2017 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-28642953

RESUMO

We have developed "crack-tips" and "superlattice" enriched Pt-Cu nanoflakes (NFs), benefiting from the synergetic effects of "crack-tips" and "superlattice crystals"; the Pt-Cu NFs exhibit 4 times higher mass activity, 6 times higher specific activity and 6 times higher stability than those of the commercial Pt/C catalyst, respectively. Meanwhile, the Pt-Cu NFs show more enhanced CO tolerance than the commercial Pt/C catalyst.

8.
Water Sci Technol ; 75(1-2): 155-164, 2017 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-28067655

RESUMO

This study investigated the recovery of N, P and K from source-separated urine in laboratory-scale combined processes of air stripping and precipitation. Two operation scenarios were carried out to recover N/P (named partial scenario) and N/P/K (named complete scenario). Most of the nutrients were recovered (>70%) by optimising the operation parameters including the increase of air flow rate and more dosages of the sources of Mg and P. Absorbent rich in ammonium sulphate and solid precipitates including struvite, struvite-K, and struvite-Na was produced. The simultaneous recovery of P and K was the key process to determine the substance input. The ratio of substance input to nutrient recovered (P2O5 and K2O) was 4.14 in the partial scenario, whereas it increased to 10.61 in the complete scenario. The inevitable co-precipitation of struvite-Na mainly responded for the lower economic efficiency of the complete scenario.


Assuntos
Amônia , Nitrogênio/química , Potássio/química , Estruvita , Urina/química , Humanos , Fosfatos , Eliminação de Resíduos Líquidos , Poluentes Químicos da Água
9.
ISA Trans ; 67: 455-465, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28108002

RESUMO

Hydraulic servomechanism is the typical mechanical/hydraulic double-dynamics coupling system with the high stiffness control and mismatched uncertainties input problems, which hinder direct applications of many advanced control approaches in the hydraulic servo fields. In this paper, by introducing the singular value perturbation theory, the original double-dynamics coupling model of the hydraulic servomechanism was reduced to a integral chain system. So that, the popular ADRC (active disturbance rejection control) technology could be directly applied to the reduced system. In addition, the high stiffness control and mismatched uncertainties input problems are avoided. The validity of the simplified model is analyzed and proven theoretically. The standard linear ADRC algorithm is then developed based on the obtained reduced-order model. Extensive comparative co-simulations and experiments are carried out to illustrate the effectiveness of the proposed method.

10.
Environ Sci Technol ; 50(2): 864-71, 2016 Jan 19.
Artigo em Inglês | MEDLINE | ID: mdl-26678011

RESUMO

Oxidation of ammonia to nitrite rather than nitrate is critical for nitritation process for wastewater treatment. We proposed a promising approach by using controlled ultrasonic treatment to enhance the activity of ammonia-oxidizing bacteria (AOB) and suppress that of nitrite-oxidizing bacteria (NOB). Batch activity assays indicated that when ultrasound was applied, AOB activity reached a peak level and then declined but NOB activity deteriorated continuously as the power intensity of ultrasound increased. Kinetic analysis of relative microbial activity versus ultrasonic energy density was performed to investigate the effect of operational factors (power, sludge concentration, and aeration) on AOB and NOB activities and the test parameters were selected for reactor tests. Laboratory sequential batch reactor (SBR) was further used to test the ultrasonic stimulus with 8 h per day operational cycle and synthetic waste urine as influent. With specific ultrasonic energy density of 0.09 kJ/mg VSS and continuously fed influent containing above 200 mg NH3-N/L, high AOB reproductive activity was achieved and nearly complete conversion of ammonia-N to nitrite was maintained. Microbial structure analysis confirmed that the treatment changed community of AOB, NOB, and heterotrophs. Known AOB Nitrosomonas genus remained at similar level in the biomass while typical NOB Nitrospira genus disappeared in the SBR under ultrasonic treatment and after the treatment was off for 30 days.


Assuntos
Amônia/metabolismo , Consórcios Microbianos/efeitos da radiação , Ultrassom/métodos , Purificação da Água/métodos , Bactérias , Betaproteobacteria , Biomassa , Reatores Biológicos/microbiologia , Cinética , Nitratos , Nitritos , Nitrosomonas/efeitos da radiação , Oxirredução , Esgotos , Águas Residuárias/microbiologia
11.
ISA Trans ; 59: 280-9, 2015 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-26519219

RESUMO

This paper investigates on the high performance torque control of electro-hydraulic load simulator (EHLS). In order to suppress actuator's motion disturbance, a nonlinear robust dual-loop control scheme is developed, which consists of a open-loop nonlinear velocity feed-forward compensator and a closed-loop nonlinear deterministic robust torque controller. The main function of the open-loop compensator is to decouple actuator's active motion disturbance, whereas the torque loop controller aims at guaranteeing the dynamics performance of tracking torque reference. Besides actuator's motion disturbance, both the nonlinearity characteristics and friction problem of the EHLS system are taken into consideration in this paper. The effectiveness of the developed method are verified through comparative co-simulations and experiments.

12.
Water Res ; 80: 71-9, 2015 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-25996754

RESUMO

Nutrients recovery from urine to close the nutrient loop is one of the most attractive benefits of source separation in wastewater management. The current study presents an investigation of the thermodynamic modeling of the recovery of P and K from synthetic urine via the precipitation of magnesium potassium phosphate hexahydrate (MPP). Experimental results show that maximum recovery efficiencies of P and K reached 99% and 33%, respectively, when the precipitation process was initiated only through adding dissolvable Mg compound source. pH level and molar ratio of Mg:P were key factors determining the nutrient recovery efficiencies. Precipitation equilibrium of MPP and magnesium sodium phosphate heptahydrate (MSP) was confirmed via precipitates analysis using a Scanning Electron Microscope/Energy Dispersive Spectrometer and an X-ray Diffractometer. Then, the standard solubility products of MPP and MSP in the synthetic urine were estimated to be 10(-12.2 ± 0.0.253) and 10(-11.6 ± 0.253), respectively. The thermodynamic model formulated on chemical software PHREEQC could well fit the experimental results via comparing the simulated and measured concentrations of K and P in equilibrium. Precipitation potentials of three struvite-type compounds were calculated through thermodynamic modeling. Magnesium ammonium phosphate hexahydrate (MAP) has a much higher tendency to precipitate than MPP and MSP in normal urine while MSP was the main inhibitor of MPP in ammonium-removed urine. To optimize the K recovery, ammonium should be removed prior as much as possible and an alternative alkaline compound should be explored for pH adjustment rather than NaOH.


Assuntos
Precipitação Química , Compostos de Magnésio/química , Fosfatos/química , Fósforo/química , Compostos de Potássio/química , Potássio/química , Urina/química , Algoritmos , Concentração de Íons de Hidrogênio , Cinética , Microscopia Eletrônica de Varredura , Modelos Químicos , Fosfatos/fisiologia , Reprodutibilidade dos Testes , Solubilidade , Espectrometria por Raios X , Termodinâmica , Eliminação de Resíduos Líquidos/métodos , Difração de Raios X
13.
BMC Musculoskelet Disord ; 15: 239, 2014 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-25027542

RESUMO

BACKGROUND: Glucocorticoid has been used extensively in clinical applications, because of its several pharmacologic actions, which include immunosuppression, anti-inflammation, anti-shock, and relief of asthma. However, the long-term or high-dose application of glucocorticoid can induce adverse effects such as osteoporosis, which is known in this case as glucocorticoid-induced osteoporosis (GIOP). It is a secondary osteoporosis that results in easy fracturing, and even disability. Therefore it became a thorny issue. METHODS: The rat model of glucocorticoid-induced osteoporosis (GIOP) was replicated to isolate BMSCs. Rats were assigned into four groups: normal, normal induction, GIOP, and GIOP induction. The growth cycle was monitored by using flow cytometry. Osteogenic differentiation was compared by using alkaline phosphatase (ALP) staining with a modified calcium cobalt method. The quantitative detection of osteoprotegerin and the receptor activator of nuclear factor kappa-B ligand (RANKL) was conducted by using enzyme-linked immunoassay. Finally, renal Klotho mRNA expression was assessed by using RT-PCR. RESULTS: BMSC proliferation was reduced in GIOP rats. The ALP-positive expression of normal BMSCs to the osteogenic induction solution was stronger than that of BMSCs from GIOP rats (P < 0.01). Osteoprotegerin expression was significantly higher in the normal induction group than in the normal, GIOP (P < 0.01), and GIOP induction groups (P < 0.05). RANKL expression was significantly higher in the normal induction group than in the other groups (P < 0.01) and significantly higher in the normal group than in the GIOP and GIOP induction groups (P < 0.01). RT-PCR analysis showed that renal Klotho mRNA expression was significantly reduced in the GIOP group compared with the normal group (P < 0.01). CONCLUSION: BMSC proliferation, osteogenic differentiation, and reactive activity to an osteogenic inductor were reduced in GIOP rats. Klotho mRNA expression decreased during GIOP induction.


Assuntos
Células da Medula Óssea/patologia , Diferenciação Celular , Dexametasona , Glucocorticoides , Células-Tronco Mesenquimais/patologia , Osteogênese , Osteoporose/patologia , Fosfatase Alcalina/metabolismo , Animais , Biomarcadores/metabolismo , Células da Medula Óssea/metabolismo , Ciclo Celular , Células Cultivadas , Modelos Animais de Doenças , Feminino , Glucuronidase/genética , Glucuronidase/metabolismo , Masculino , Células-Tronco Mesenquimais/metabolismo , Osteoporose/induzido quimicamente , Osteoporose/genética , Osteoporose/metabolismo , Osteoprotegerina/metabolismo , Ligante RANK/metabolismo , Ratos Sprague-Dawley
14.
Chemosphere ; 93(11): 2669-74, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-24034894

RESUMO

Particulate organic matter (POM) in wastewater is a potential denitrification carbon source, while the optimal operational mode using denitrification mechanism with POM is still unclear in wastewater treatment plants. In this work, we investigated the denitrification rates (DNRs) in a full-scale membrane bioreactor (MBR) coupled with two-stage pre-anoxic (pre-AN), and then evaluated the POM denitrification efficiency using mechanism modeling. The results indicate that POM related fraction accounted for the majority of the obtained specific DNR of 1.39±0.46mgNg(-1) MLVSS h(-1) in the second pre-AN without available soluble carbon source. The modeling approaches with calibration and validation procedures estimated a high residual POM concentration of 0.17g COD g(-1) MLVSS in the activated sludge, which provided specific DNR of 1.14mgNg(-1) MLVSS h(-1). High POM retention time in the reactor was the result of high solid retention time used in the MBR. In particular, post-AN of high biomass concentration could provide the highest POM denitrification efficiency in MBR. The MBR process combined with additional sludge reduction technology could further enhance denitrification by POM.


Assuntos
Reatores Biológicos , Desnitrificação , Modelos Químicos , Material Particulado/análise , Águas Residuárias/química , Membranas Artificiais , Eliminação de Resíduos Líquidos/métodos
15.
Bioresour Technol ; 146: 537-542, 2013 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-23973972

RESUMO

Low frequency and density ultrasound has attracted considerable attention in enhancing wastewater treatment performance, particularly in the removal of nitrogen. In the present study, two sequencing batch reactors were operated to confirm the effects of ultrasound at the frequency of 40 kHz and density of 0.027 W/mL on partial nitrification and simultaneous nitrification and denitrification (SND). At the optimal irradiation time of 2.0 h, the obtained nitrite accumulation ratio and SND efficiency at full aerobic were 73.9% and 72.8%, respectively. Nitrite accumulation was the result of increased NH4(+)-N removal and improved ammonia oxidizing bacteria (AOB) activity with simultaneous inhibition of nitrite oxidizing bacteria (NOB) activity. Ultrasonic treatment could provide suitable conditions in temperature and pH for AOB growth, and destroy the NOB community structure. Moreover, organic matters were released and offered an additional carbon source for denitrification apart from the negative effects on sludge properties.


Assuntos
Amônia/química , Carbono/química , Nitritos/química , Esgotos/química , Ultrassom , Eliminação de Resíduos Líquidos/métodos , Purificação da Água/métodos , Reatores Biológicos , Desnitrificação , Concentração de Íons de Hidrogênio , Nitrificação , Nitrogênio , Oxigênio/química , Temperatura Ambiente , Fatores de Tempo , Ultrassonografia , Águas Residuárias
16.
J Hazard Mater ; 229-230: 115-21, 2012 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-22749970

RESUMO

The electro-Fenton (E-Fenton) treatment of landfill leachate concentrates was investigated in this study. The concentrates were generated from nanofiltration of biologically pretreated landfill leachate, and contained high concentrations of refractory organics and inorganic salts. During the E-Fenton treatment, H(2)O(2) was electrochemically produced at a carbon-polytetrafluorethylene (PTFE) cathode with oxygen feeding. The in situ generated H(2)O(2) then reacted with Fe(2+) that was added into the concentrates to bring about Fenton oxidation of the refractory organics in the concentrates. The effectiveness of the E-Fenton treatment of the concentrates was appraised in terms of its removal efficiency of total organic carbon (TOC) of the concentrates. The effects of FeSO(4) dosage, current density, initial pH of the solution, and cathode area on the process performance were also evaluated. Under optimal reaction conditions that included a current density of 30 mA cm(-2), FeSO(4) dosage of 10mM, initial pH of 3, and cathode area of 20 cm(2), the TOC and total nitrogen (TN) removal efficiencies were 82% and 51% after 6h of the E-Fenton treatment. The results indicated that the E-Fenton technology could produce sufficient amounts of advanced oxidants in situ to effectively degrade the refractory organic pollutants in high-strength leachate concentrates.


Assuntos
Poluentes Químicos da Água/química , Purificação da Água/métodos , Carbono/química , Eletrodos , Compostos Ferrosos/química , Peróxido de Hidrogênio/química , Politetrafluoretileno/química , Ultrafiltração
17.
Chemosphere ; 88(2): 219-23, 2012 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-22445958

RESUMO

The simultaneous removal of K and P from urine for nutrient recycling by crystallization of magnesium potassium phosphate hexahydrate (MPP) in a laboratory-scale draft tube and baffle reactor (DTBR) is investigated. Results show that mixing speed and hydraulic retention time are important operating factors that influence crystallization and crystal settlement. Slurry should be discharged at a crystal retention time of 11 h to maintain fluidity in the reactor. Further applications of the DTBR using real urine (pretreated by ammonia stripping and diluted five times) showed that 76% K and 68% P were recycled to multi-nutrient products. The crystals collected were characterized and confirmed mainly as a mixture of magnesium ammonium phosphate hexahydrate, MPP, and magnesium sodium phosphate heptahydrate. Results indicate that the DTBR effectively achieved the simultaneous recycling of K and P from urine to multi-nutrient products through MPP crystallization.


Assuntos
Compostos de Magnésio/química , Urina/química , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química , Precipitação Química , Magnésio/química , Fosfatos/química , Fósforo/química , Potássio/química , Reciclagem , Estruvita
18.
Environ Sci Technol ; 45(15): 6539-44, 2011 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-21714543

RESUMO

Analytical pyrolysis was conducted to evaluate the major hazardous air pollutant (HAP) emissions from pyrolysis of bituminous coal and a furan binder, which are the two most commonly used casting materials for making green sand and furan no-bake molds in Chinese foundries. These two materials were flash pyrolyzed in a Curie-point pyrolyzer at 920 °C and slowly pyrolyzed in a thermogravimetric analyzer (TGA) from ambient temperature to 1000 °C with a heating rate of 30 °C/min. The emissions from Curie-point and TGA pyrolysis were analyzed with gas chromatography-mass spectrometer/flame ionization detector. Thirteen HAP species were identified and quantified in the pyrolysis emissions of the two materials. The prominent HAP emissions were cresols, benzene, toluene, phenol, and naphthalene for the bituminous coal, whereas they were m,p,o-xylenes for the furan binder. Xylenesulfonic acid, the acidic catalyst in furan binder, was found to be the major source of xylene emissions. Thermogravimetry-mass spectrometer monitored the evolution of HAP emissions during TGA pyrolysis. For both of the casting materials, most of the emissions were released in the temperature range of 350-700 °C.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental , Substâncias Perigosas/análise , Metalurgia , Metais/química , Temperatura Ambiente , China , Carvão Mineral , Ionização de Chama , Furanos/química , Cromatografia Gasosa-Espectrometria de Massas , Peso Molecular , Termogravimetria
19.
Chemosphere ; 84(2): 207-12, 2011 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-21596418

RESUMO

This study investigated the simultaneous removal of P and K from synthetic urine through the precipitation of magnesium potassium phosphate hexahydrate (MPP, MgKPO(4)·6H(2)O) in bench-scale experiments. Results show that the removal efficiencies of P and K are mainly determined by the solution pH and the molar ratio of Mg:K:P. Co-precipitation of struvite-type compounds, i.e., magnesium ammonium phosphate hexahydrate (MAP, MgNH(4)PO(4)·6H(2)O), magnesium sodium phosphate heptahydrate (MSP, MgNaPO(4)·7H(2)O), and MPP, was confirmed by analysis of the solid precipitates using a Scanning Electron Microscope/Energy Dispersive X-ray Apparatus and an X-ray Diffractometer. The co-precipitation significantly influenced the removal of K. As much ammonium as possible should be removed prior to MPP precipitation because MAP had higher tendency to form than MPP. The inevitable co-precipitation of MPP and MSP resulted in the addition of more MgCl(2)·6H(2)O and Na(2)HPO(4)·12H(2)O to obtain the high removal of K. In total, the removal efficiencies of P and K were 77% and 98%, respectively, in the absence of ammonium when pH was 10 and the molar ratio of Mg:K:P was 2:1:2. The results indicate that the MPP precipitation is an efficient method for the simultaneous removal of P and K to yield multi-nutrient products.


Assuntos
Fosfatos/metabolismo , Fósforo/urina , Potássio/urina , Urina/química , Precipitação Química , Modelos Biológicos , Modelos Químicos , Fosfatos/química , Fósforo/química , Potássio/química , Eliminação de Resíduos Líquidos/métodos
20.
Waste Manag ; 31(2): 311-7, 2011 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-20609574

RESUMO

The present research explored the role played by water-wash on geopolymerization for the immobilization and solidification of municipal solid waste incineration (MSWI) fly ash. The water-wash pretreatment substantially promoted the early strength of geopolymer and resulted in a higher ultimate strength compared to the counterpart without water-wash. XRD pattern of water-washed fly ash (WFA) revealed that NaCl and KCl were nearly eliminated in the WFA. Aside from geopolymer, ettringite (Ca(6)Al(2)(SO(4))(3)(OH)(12)·26H(2)O) was formed in MSWI fly ash-based geopolymer (Geo-FA). Meanwhile, calcium aluminate hydrate (Ca(2)Al(OH)(7)·3H(2)O), not ettringite, appeared in geopolymer that was synthesized with water-washed fly ash (Geo-WFA). Leached Geo-WFA (Geo-WFA-L) did not exhibit any signs of deterioration, while there was visual cracking on the surface of leached Geo-FA (Geo-FA-L). The crack may be caused by the migration of K(+), Na(+), and Cl(-) ions outside Geo-FA and the negative effect from crystallization of expansive compounds can not be excluded. Furthermore, transformation of calcium aluminate hydrate in Geo-WFA to ettringite in Geo-WFA-L allowed the reduction of the pore size of the specimen. IR spectrums suggested that Geo-WFA can supply more stable chemical encapsulation for heavy metals. Static monolithic leaching tests were conducted for geopolymers to estimate the immobilization efficiency. Heavy metal leaching was elucidated using the first-order reaction/diffusion model. Combined with the results from compressive strength and microstructure of samples, the effects of water-wash on immobilization were inferred in this study.


Assuntos
Carbono/química , Incineração , Material Particulado/química , Eliminação de Resíduos , Poluentes Químicos da Água/análise , Água/química , Compostos de Alumínio/química , Compostos de Cálcio/química , China , Cinza de Carvão , Força Compressiva , Cinética , Metais Pesados/análise , Minerais/química , Polimerização , Difração de Raios X
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