RESUMEN
This study assessed the effects of adding plastics and waste vegetable oil on the quality of coke in the coking process, on a pilot scale. A typical composition of the main plastics found in municipal solid waste was prepared using 33% HDPE, 5% LDPE, 10% PP, 21% PET, 24.8% PS, 5.2% PVC, 1% cellulose and also a 0.5% waste vegetable oil was added. The wastes were added to the coal blends in the proportions of 1%, 2% and 3% for plastics and 0.5% for vegetable oil. Two types of experiments were performed. The first was carried out in a hearth heating furnace (HHF) at temperatures of up to 900°C for a 7 h period. The second was a box test, which consists of heating coal blends in 18L cans using a pilot coking oven, for approximately 20 h at temperatures between 1050 and 1100°C. The quality parameters used for the assessment were the CSR (coke strength after reaction), CRI (coke reactivity index), ash, volatile matter and sulfur in order to identify the effect of plastic and vegetable oil on coke quality. Results for CSR in the HHF averaged 52.3%, and 56.63% in box test trials. The CRI results ranged from 26.6% to 35.7%. Among the different percentages of plastics used, 3% plastic blends provided the most stable CSR results. The industrial furnaces work at temperatures between 1100 and 1350°C and time coking 21-24h, compared to the test conditions achieved in the HHF and pilot furnace with box test. It was concluded that the results of CSR and CRI are consistent with the tests confirming the feasibility of using plastic in the steelmaking process.
Asunto(s)
Metalurgia/métodos , Aceites de Plantas , Plásticos , Reciclaje/métodos , Brasil , Carbón Mineral/análisis , Culinaria , Calor , Metalurgia/economía , Proyectos Piloto , Residuos Sólidos , AceroRESUMEN
Pyrolysis is the thermal degradation of organic material in oxygen-free or very lean oxygen atmosphere. This study evaluates the use of pyrolysis for conversion of leather wastes from chromium tanning processes into Carbonized Leather Residues (CLR), and the utilization of CLR in metallurgical processes through the production of iron ore pellets. CLR was used to replace mineral coal in proportions of 10% and 25% on fixed carbon basis content in the mixtures for pellets preparation. Experimental conversions were performed on a pilot scale pyrolysis plant and a pelletizing reactor of the "pot grate" type. The results demonstrated the technical feasibility of using the charcoal product from animal origin as an energy source, with recovery of up to 76.47% of chromium contained in CLR in the final produced of iron ore pellets. Pellets with 25% replacement of fixed carbon in the coal showed an enhanced compressive strength, with an average value of 344kgfpellet(-1), compared to 300kgfpellet(-1) for standard produced pellets.
Asunto(s)
Carbono/química , Cromo/química , Calor , Residuos Industriales/análisis , Metalurgia/métodos , Eliminación de Residuos/métodos , Curtiembre/métodos , Animales , Brasil , Carbón Orgánico , Carbón Mineral , Fuerza Compresiva , Monitoreo del Ambiente/métodos , Metales/química , Tamaño de la Partícula , Fósforo/química , Medición de Riesgo/métodos , Acero/química , Estrés Mecánico , Purificación del AguaRESUMEN
OBJECTIVE: To compare in vivo orthodontic mini-implants (MI) of smooth (machined) and rough (acid etched) surfaces, assessing primary and secondary stability. METHODS: Thirty-six (36) MI were inserted in the mandibles of six (6) dogs. Each animal received six (6) MI. In the right hemiarch, three (3) MI without surface treatment (smooth) were inserted, whereas in the left hemiarch, another three (3) MI with acid etched surfaces (rough) were inserted. The two distal MI in each hemiarch received an immediate load of 1.0 N for 16 weeks, whereas the MI in the mesial extremity was not subject to loading. Stability was measured by insertion and removal torque, initial and final mobility and by inter mini-implant distance. RESULTS: There was no statistical behavioral difference between smooth and rough MI. High insertion torque and reduced initial mobility were observed in all groups, as well as a reduction in removal torques in comparison with insertion torque. Rough MI presented higher removal torque and lower final mobility in comparison to smooth MI. MI did not remain static, with displacement of rough MI being smaller in comparison with smooth MI, but with no statistical difference. CONCLUSIONS: MI primary stability was greater than stability measured at removal. There was no difference in stability between smooth and rough MI when assessing mobility, displacement and insertion as well as removal torques.
Asunto(s)
Implantación Dental Endoósea/instrumentación , Implantes Dentales de Diente Único , Oseointegración , Propiedades de Superficie , Aleaciones , Animales , Implantación Dental Endoósea/métodos , Fracaso de la Restauración Dental/estadística & datos numéricos , Análisis del Estrés Dental/métodos , Perros , Carga Inmediata del Implante Dental/instrumentación , Masculino , Metalurgia/métodos , Métodos de Anclaje en Ortodoncia/instrumentación , Métodos de Anclaje en Ortodoncia/métodos , Titanio , TorqueRESUMEN
Objective: To compare in vivo orthodontic mini-implants (MI) of smooth (machined) and rough (acid etched) surfaces, assessing primary and secondary stability.Methods:Thirty-six (36) MI were inserted in the mandibles of six (6) dogs. Each animal received six (6) MI. In the right hemiarch, three (3) MI without surface treatment (smooth) were inserted, whereas in the left hemiarch, another three (3) MI with acid etched surfaces (rough) were inserted. The two distal MI in each hemiarch received an immediate load of 1.0 N for 16 weeks, whereas the MI in the mesial extremity was not subject to loading. Stability was measured by insertion and removal torque, initial and final mobility and by inter mini-implant distance.Results:There was no statistical behavioral difference between smooth and rough MI. High insertion torque and reduced initial mobility were observed in all groups, as well as a reduction in removal torques in comparison with insertion torque. Rough MI presented higher removal torque and lower final mobility in comparison to smooth MI. MI did not remain static, with displacement of rough MI being smaller in comparison with smooth MI, but with no statistical difference.Conclusions:MI primary stability was greater than stability measured at removal. There was no difference in stability between smooth and rough MI when assessing mobility, displacement and insertion as well as removal torques.
Objetivo: comparar, in vivo, mini-implantes (MI) com superfície lisa (usinada) e porosa (tratada com ácido), avaliando sua estabilidade primária e secundária.Métodos:trinta e seis MI foram inseridos na mandíbula de seis cães, e cada animal recebeu seis MI. Na hemiarcada direita, foram inseridos três MI sem tratamento da superfície (liso); na esquerda, outros três com a superfície tratada com ácido (poroso). Os dois MI distais de cada hemiarcada receberam carga imediata de 1,0N durante dezesseis semanas, e o MI da extremidade mesial não recebeu carregamento. A estabilidade foi medida pelos torques de inserção e de remoção, pela mobilidade inicial e final, e pela distância inter-MI.Resultados:não houve diferença estatística do comportamento entre os MI lisos e porosos. No entanto, observou-se torque de inserção elevado e mobilidade inicial reduzida em todos os grupos. Para todos os grupos, houve redução dos torques de remoção, em relação ao de inserção. Os MI porosos apresentaram maior torque de remoção e menor mobilidade final, em relação aos MI lisos. Os MI não permaneceram estáticos, sendo o deslocamento dos MI porosos menor em relação aos MI lisos, mas sem diferença estatística.Conclusões:a estabilidade primária dos MI foi maior do que a estabilidade medida na sua remoção; não houve diferença na estabilidade entre os MI lisos e porosos ao avaliar-se a mobilidade, o deslocamento e os torques de inserção e remoção.
Asunto(s)
Animales , Masculino , Perros , Propiedades de Superficie , Oseointegración , Implantes Dentales de Diente Único , Implantación Dental Endoósea/instrumentación , Titanio , Fracaso de la Restauración Dental/estadística & datos numéricos , Torque , Implantación Dental Endoósea/métodos , Análisis del Estrés Dental/métodos , Métodos de Anclaje en Ortodoncia/instrumentación , Métodos de Anclaje en Ortodoncia/métodos , Carga Inmediata del Implante Dental/instrumentación , Metalurgia/métodosRESUMEN
Metallurgical activities have been undertaken in northern South America (NSA) for millennia. However, it is still unknown how far atmospheric emissions from these activities have been transported. Since the timing of metallurgical activities is currently estimated from scarce archaeological discoveries, the availability of reliable and continuous records to refine the timing of past metal deposition in South America is essential, as it provides an alternative to discontinuous archives, as well as evidence for global trace metal transport. We show in a peat record from Tierra del Fuego that anthropogenic metals likely have been emitted into the atmosphere and transported from NSA to southern South America (SSA) over the last 4200 yrs. These findings are supported by modern time back-trajectories from NSA to SSA. We further show that apparent anthropogenic Cu and Sb emissions predate any archaeological evidence for metallurgical activities. Lead and Sn were also emitted into the atmosphere as by-products of Inca and Spanish metallurgy, whereas local coal-gold rushes and the industrial revolution contributed to local contamination. We suggest that the onset of pre-Hispanic metallurgical activities is earlier than previously reported from archaeological records and that atmospheric emissions of metals were transported from NSA to SSA.
Asunto(s)
Fósiles , Metalurgia/historia , Metales/análisis , Historia del Siglo XV , Historia Medieval , Metalurgia/métodos , Material Particulado/análisis , América del SurAsunto(s)
Adulto , Niño , Humanos , Contaminantes Ambientales , Mercurio , Minería , Metalurgia/métodos , Contaminantes Ocupacionales del Aire/efectos adversos , Biotransformación , Bacterias/metabolismo , Colombia , Ambiente , Política Ambiental , Contaminantes Ambientales/efectos adversos , Oro , Residuos Industriales/efectos adversos , Intoxicación por Mercurio/epidemiología , Intoxicación por Mercurio/etiología , Mercurio/metabolismo , Compuestos de Metilmercurio/metabolismo , Compuestos de Metilmercurio/envenenamiento , Compuestos de Metilmercurio/toxicidad , Minería/métodos , Enfermedades Profesionales/epidemiología , Enfermedades Profesionales/etiologíaRESUMEN
INTRODUCTION: The aim of this study was to assess the effect of nitrogen ion implantation on the flexibility of rotary nickel-titanium (NiTi) instruments as measured by the load required to bend implanted and nonimplanted instruments at a 30° angle. METHODS: Thirty K3 files, size #40, 0.02 taper and 25-mm length, were allocated into 2 groups as follows: group A, 15 files exposed to nitrogen ion implantation at a dose of 2.5 × 10(17) ions/cm(2), voltage 200 KeV, current density 1 µA/cm(2), temperature 130°C, and vacuum conditions of 10 × 10(-6) mm Hg for 6 hours; and group B, 15 nonimplanted files. One extra file was used for process control. All instruments were subjected to bend testing on a modified troptometer, with measurement of the load required for flexure to an angle of 30°. The Mann-Whitney U test was used for statistical analysis. Findings with P <.05 were considered significant. RESULTS: The mean load required to bend instruments at a 30° angle was 376.26 g for implanted instruments and 383.78 g for nonimplanted instruments. The difference was not statistically significant. CONCLUSIONS: Our findings show that nitrogen ion implantation has no appreciable effect on the flexibility of NiTi instruments.
Asunto(s)
Aleaciones Dentales/química , Técnicas Electroquímicas/métodos , Níquel/química , Nitrógeno/química , Preparación del Conducto Radicular/instrumentación , Titanio/química , Diseño de Equipo , Humanos , Ensayo de Materiales , Metalurgia/métodos , Docilidad , Rotación , Estrés Mecánico , Propiedades de Superficie , Temperatura , Factores de Tiempo , VacioAsunto(s)
Contaminantes Ambientales , Mercurio , Metalurgia/métodos , Minería , Adulto , Contaminantes Ocupacionales del Aire/efectos adversos , Bacterias/metabolismo , Biotransformación , Niño , Colombia , Ambiente , Política Ambiental , Contaminantes Ambientales/efectos adversos , Oro , Humanos , Residuos Industriales/efectos adversos , Mercurio/metabolismo , Intoxicación por Mercurio/epidemiología , Intoxicación por Mercurio/etiología , Compuestos de Metilmercurio/metabolismo , Compuestos de Metilmercurio/envenenamiento , Compuestos de Metilmercurio/toxicidad , Minería/métodos , Enfermedades Profesionales/epidemiología , Enfermedades Profesionales/etiologíaRESUMEN
The popularization of mobile phones, combined with a technological evolution, means a large number of scrap and obsolete equipment are discarded every year, thereby causing economic losses and environmental pollution. In the present study, the printed wiring boards scrap of mobile phones were characterized in order to recycle some of the device components, using techniques of mechanical processing, hydrometallurgy and electrometallurgy. The use of the techniques of mechanical processing (milling, particle size classification, magnetic and electrostatic separation) was an efficient alternative to obtain a concentrated fraction (mainly iron in the magnetic fraction and copper in the conductive fraction) and another fraction containing polymers and ceramics. At the end of mechanical processing, a concentrated fraction of metals could be obtained with an average concentration of 60% copper. This concentrated fraction in metals was dissolved in aqua regia and sent to electrowinning to recover 92% of the dissolved copper. The obtained cathodes have a copper content above 95%, which demonstrates the technical feasibility of recovery of copper using the techniques of mechanical processing, hydrometallurgy and electrometallurgy.
Asunto(s)
Teléfono Celular/instrumentación , Cobre/aislamiento & purificación , Instalación Eléctrica , Reciclaje/métodos , Ácido Clorhídrico , Magnetismo , Metalurgia/métodos , Ácido Nítrico , Electricidad EstáticaRESUMEN
STATEMENT OF PROBLEM: A new short-cycle, spinel-based investment was developed to minimize the long heating cycle generally required for conventional investments for titanium castings, but the quality of castings made using this material has yet to be evaluated. PURPOSE: The purpose of this study was to compare the Vickers hardness, castability, surface roughness, in vitro marginal misfit, and internal porosity of castings made using silica phosphate-based and spinel-based investments. MATERIAL AND METHODS: The specimens were commercially pure titanium cast using silica phosphate-based investment, Rematitan Plus (RP), and spinel-based investments, Rematitan Ultra (RU) or short-heat-cycle Trinell (TR). Disc-shaped patterns (6 × 3 mm) were cast, and Vickers hardness was measured at the surface, and 50, 100, 150, and 200 µm beneath the surface (n=10). Microstructure was analyzed by optical microscopy (×100). Mesh patterns (14 × 14 × 0.5 mm) were used for castability testing (n=10). Surface roughness (Ra) was measured on disc-shaped patterns (13 × 3 mm) with a profilometer (n=8). Wax copings were cast, screwed to implant abutments, and the marginal misfit was measured using image analysis software (n=10). Internal porosity of the copings was evaluated by density comparisons (n=10). Hardness data were analyzed by 2-way ANOVA and the Tukey HSD test. Castability, surface roughness, and marginal misfit were analyzed by 1-way ANOVA and the Tukey HSD test, and internal porosity by Kruskal-Wallis and Student-Newman-Keuls tests (α=.05). RESULTS: RP had the highest hardness values at the surface and 50 µm beneath, but the hardness values of TR, RU, and RP were statistically equivalent at 100, 150, and 200 µm. Significant differences were seen when comparing RU and TR with RP for castability (P<.001), surface roughness (P<.001), and marginal misfit (P<.001). No significant differences were seen for internal porosity. CONCLUSIONS: The quality of castings made from the new investment, TR, was similar to the quality of those made using the conventional spinel-based investment, RU, and superior to those made using RP.
Asunto(s)
Revestimiento para Colado Dental/química , Técnica de Colado Dental , Materiales Dentales/química , Dureza , Titanio/química , Análisis de Varianza , Adaptación Marginal Dental , Calor , Humanos , Metalurgia/métodos , Estadísticas no Paramétricas , Propiedades de SuperficieRESUMEN
Pure Mg has been proposed as a potential degradable biomaterial to avoid both the disadvantages of non-degradable internal fixation implants and the use of alloying elements that may be toxic. However, it shows excessively high corrosion rate and insufficient yield strength. The effects of reinforcing Mg by a powder metallurgy (PM) route and the application of biocompatible corrosion inhibitors (immersion in 0.1 and 1M KF solution treatments, 0.1M FST and 1M FST, respectively) were analyzed in order to improve Mg mechanical and corrosion resistance, respectively. Open circuit potential measurements, polarization techniques (PT), scanning electrochemical microscopy (SECM) and electrochemical impedance spectroscopy (EIS) were performed to evaluate its corrosion behavior. SECM showed that the local current of attacked areas decreased during the F(-) treatments. The corrosion inhibitory action of 0.1M FST and 1M FST in phosphate buffered solution was assessed by PT and EIS. Under the experimental conditions assayed, 0.1M FST revealed better performance. X-ray photoelectron spectroscopy, energy dispersive X-ray and X-ray diffraction analyses of Mg(PM) with 0.1M FST showed the presence of KMgF(3) crystals on the surface while a MgF(2) film was detected for 1M FST. After fluoride inhibition treatments, promising results were observed for Mg(PM) as degradable metallic biomaterial due to its higher yield strength and lower initial corrosion rate than untreated Mg, as well as a progressive loss of the protective characteristics of the F(-)-containing film which ensures the gradual degradation process.
Asunto(s)
Fluoruros/farmacología , Magnesio/química , Metalurgia/métodos , Tampones (Química) , Materiales Biocompatibles Revestidos/farmacología , Corrosión , Impedancia Eléctrica , Electricidad , Electrodos , Microscopía Electrónica de Rastreo , Espectroscopía de Fotoelectrones , Potenciometría , Polvos , Espectrometría por Rayos X , Propiedades de Superficie/efectos de los fármacos , Resistencia a la Tracción/efectos de los fármacos , Termodinámica , Difracción de Rayos XRESUMEN
A study on laboratory scale to evaluate the environmental compatibility of electric arc furnace dust (EAFD) is reported in this article. EAFD, a waste by-product of the steel-making process, was generated on a steel plant located in Brazil. Different leaching tests, NBR10005 (Brazilian), AFNORX31-210 (French), JST-13 (Japanese), DIN38414-S4 (German), TCLP (American), and NEN 7343 (Netherland) were conducted. These leaching procedures are batch tests and are columns conducted in a way that an equilibrium condition should be achieved. The pH of the medium showed a crucial parameter governing the release of metals from the solid phase into solution. As the pH of the medium varies with the leachant used, this determines the dissolution of the elements. Zn, Pb, Mn, Cd, and Cu presented high leachability at NBR10005 procedures (acid pH). Except Pb and Cr, the leachability of all others metals in leaching tests with alkaline pH decreases with the increase of the pH. NBR10005 classifies the EAFD as a hazardous waste due to high concentration of Pb and Cd in leachate. The column tests are presented in the following order of leaching: Pb>Cr>Zn>Mn>Cu>Cd.