scholarly journals Experimental study on acidification effect of tailing sand

2021 ◽  
Vol 248 ◽  
pp. 01048
Author(s):  
Wenzhao Chen ◽  
Kai Yang ◽  
Jiaqing Fan ◽  
Xiqi Liu ◽  
Xiaoqing Wei
Keyword(s):  
Fine Particles ◽  
Iron Concentration ◽  
Chemical Properties ◽  
Surface Friction ◽  
Friction Angle ◽  
Immersion Test ◽  
Coarse Particles ◽  
Natural Conditions ◽  
Lead Zinc ◽  
Reaction Processes

Sulfide minerals (mainly FeS2) contained in lead-zinc tailings are easy to be acidified in the air. The acidification mechanism is that the tailing sand generates sulfuric acid and sulfate under the catalysis of oxidant, water and oxygen. The acidic liquid generated by the reaction will continue to react with metal oxides to form an insoluble precipitate.In order to reveal the corresponding changes of chemical properties and physical properties of lead-zinc tailing sand during acidification, a series of reaction processes of tailings under natural conditions were simulated by immersion test in laboratory.It is found through the test that with the deepening of acidification, the coarse particles of tailing sand dissolve, resulting in the decrease of iron concentration in the compound, the increase of fine particles, the increase of specific surface area, the decrease of surface friction and occlusion friction between particles, resulting in the decrease of internal friction angle, and the decrease of the safety of tailings dam. words.

HREM image simulations for supported metal particle catalysts

1993 ◽  
Vol 51 ◽  
pp. 736-737 ◽  
Author(s):  
Ming-Hui Yao ◽  
David J. Smith
Keyword(s):  
Fine Particles ◽  
Amorphous Material ◽  
Chemical Properties ◽  
Morphological Features ◽  
Metal Particles ◽  
Plan View ◽  
Profile View ◽  
Imaging Conditions ◽  
Image Simulations ◽  
Supported Metal

The chemical properties of catalysts often depend on the size, shape and structure of the supported metal particles. To characterize these morphological features and relate them to catalysis is one of the main objectives for HREM study of catalysts. However, in plan view imaging, details of the shape and structure of ultra-fine supported particles (<2nm) are often obscured by the overlapping contrast from the support, and supported sub-nanometer particles are sometimes even invisible. Image simulations may help in the interpretation at HREM images of supported particles in particular to extract useful information about the size, shape and structure of the particles. It should also be a useful tool for evaluating the imaging conditions in terms of visibility of supported particles. P. L. Gai et al have studied contrast from metal particles supported on amorphous material using multislice simulations. In order to better understand the influence of a crystalline support on the visibility and apparent morphological features of supported fine particles, we have calculated images of Pt and Re particles supported on TiO2(rutile) in both plan view and profile view.

scholarly journals Contribution of Fine Particles to Air Emission at Different Phases of Biomass Burning

Atmosphere ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 278 ◽  
Author(s):  
Niloofar Ordou ◽  
Igor E. Agranovski
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Fine Particles ◽  
Combustion Process ◽  
Coarse Particles ◽  
Biomass Smoke ◽  
Smoke Particles ◽  
Air Emission ◽  
Entire Duration ◽  
Diffusion Properties

Particle size distribution in biomass smoke was observed for different burning phases, including flaming and smouldering, during the combustion of nine common Australian vegetation representatives. Smoke particles generated during the smouldering phase of combustions were found to be coarser as compared to flaming aerosols for all hard species. In contrast, for leafy species, this trend was inversed. In addition, the combustion process was investigated over the entire duration of burning by acquiring data with one second time resolution for all nine species. Particles were separately characterised in two categories: fine particles with dominating diffusion properties measurable with diffusion-based instruments (Dp < 200 nm), and coarse particles with dominating inertia (Dp > 200 nm). It was found that fine particles contribute to more than 90 percent of the total fresh smoke particles for all investigated species.

scholarly journals Ambient Particulate Matter Air Pollution in Mpererwe District, Kampala, Uganda: A Pilot Study

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Stephan Schwander ◽  
Clement D. Okello ◽  
Juergen Freers ◽  
Judith C. Chow ◽  
John G. Watson ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Air Quality ◽  
Pilot Study ◽  
Fine Particles ◽  
Airborne Particulate Matter ◽  
Personal Exposure ◽  
Ambient Air ◽  
Combustion Products ◽  
Carbonaceous Aerosol ◽  
Coarse Particles

Air quality in Kampala, the capital of Uganda, has deteriorated significantly in the past two decades. We made spot measurements in Mpererwe district for airborne particulate matter PM2.5(fine particles) and coarse particles. PM was collected on Teflon-membrane filters and analyzed for mass, 51 elements, 3 anions, and 5 cations. Both fine and coarse particle concentrations were above 100 µg/m3in all the samples collected. Markers for crustal/soil (e.g., Si and Al) were the most abundant in the PM2.5fraction, followed by primary combustion products from biomass burning and incinerator emissions (e.g., K and Cl). Over 90% of the measured PM2.5mass can be explained by crustal species (41% and 59%) and carbonaceous aerosol (33%–55%). Crustal elements dominated the coarse particles collected from Kampala. The results of this pilot study are indicative of unhealthy air and suggest that exposure to ambient air in Kampala may increase the burden of environmentally induced cardiovascular, metabolic, and respiratory diseases including infections. Greater awareness and more extensive research are required to confirm our findings, to identify personal exposure and pollution sources, and to develop air quality management plans and policies to protect public health.

scholarly journals Characteristics of atmospheric mercury deposition and size-fractionated particulate mercury in urban Nanjing, China

2014 ◽  
Vol 14 (5) ◽  
pp. 2233-2244 ◽  
Author(s):  
J. Zhu ◽  
T. Wang ◽  
R. Talbot ◽  
H. Mao ◽  
X. Yang ◽  
...  
Keyword(s):  
Dry Deposition ◽  
Wet Deposition ◽  
Fine Particles ◽  
Unit Area ◽  
Atmospheric Mercury ◽  
Anthropogenic Sources ◽  
Deposition Flux ◽  
Coarse Particles ◽  
Mercury Deposition ◽  
Particulate Mercury

Abstract. A comprehensive measurement study of mercury wet deposition and size-fractionated particulate mercury (HgP) concurrent with meteorological variables was conducted from June 2011 to February 2012 to evaluate the characteristics of mercury deposition and particulate mercury in urban Nanjing, China. The volume-weighted mean (VWM) concentration of mercury in rainwater was 52.9 ng L−1 with a range of 46.3–63.6 ng L−1. The wet deposition per unit area was averaged 56.5 μg m−2 over 9 months, which was lower than that in most Chinese cities, but much higher than annual deposition in urban North America and Japan. The wet deposition flux exhibited obvious seasonal variation strongly linked with the amount of precipitation. Wet deposition in summer contributed more than 80% to the total amount. A part of contribution to wet deposition of mercury from anthropogenic sources was evidenced by the association between wet deposition and sulfates, as well as nitrates in rainwater. The ions correlated most significantly with mercury were formate, calcium, and potassium, which suggested that natural sources including vegetation and resuspended soil should be considered as an important factor to affect the wet deposition of mercury in Nanjing. The average HgP concentration was 1.10 ± 0.57 ng m−3. A distinct seasonal distribution of HgP concentrations was found to be higher in winter as a result of an increase in the PM10 concentration. Overall, more than half of the HgP existed in the particle size range less than 2.1 μm. The highest concentration of HgP in coarse particles was observed in summer, while HgP in fine particles dominated in fall and winter. The size distribution of averaged mercury content in particulates was bimodal, with two peaks in the bins of < 0.7 μm and 4.7–5.8 μm. Dry deposition per unit area of HgP was estimated to be 47.2 μg m−2 using meteorological conditions and a size-resolved particle dry deposition model. This was 16.5% less than mercury wet deposition. Compared to HgP in fine particles, HgP in coarse particles contributed more to the total dry deposition due to higher deposition velocities. Negative correlation between precipitation and the HgP concentration reflected the effect of scavenging of HgP by precipitation.

scholarly journals Physico-chemical properties and heavy metal contents of a tropical estuarine ecosystem, Nigeria

2018 ◽  
Vol 5 (11) ◽  
pp. 781-797
Author(s):  
Paul Chinedu Echi ◽  
Daberechi Ndudim Okpechi ◽  
Janet Azu Urum ◽  
Izuchukwu Samson Arukwe
Keyword(s):  
Heavy Metal ◽  
Chemical Properties ◽  
Oxygen Demand ◽  
International Standards ◽  
Anthropogenic Pressure ◽  
Estuarine Ecosystem ◽  
Metal Concentrations ◽  
Metal Contents ◽  
Zinc Cadmium ◽  
Lead Zinc

Ibaka Estuarine in Mbo, Nigeria, has little or no information on its basic properties, therefore its water samples were studied from March to June 2018 in three different stations and compared with International Standards to evaluate its physic-chemical properties as well as heavy metal contents. The physic-chemical properties studied include pH, salinity (g/L), EC (μs/cm), turbidity (NTU), total suspended solids (mg/L), total dissolved solids (mg/L), dissolved oxygen (mg/L), BOD5 (mg/L), and chemical oxygen demand (mg/L). In addition, some metal concentrations of manganese, iron, copper, lead, zinc, cadmium, chloride and magnesium were determined by atomic absorption spectroscopy (AAS). The range of metal concentrations manganese (0.08-0.12 mg/L), copper (0.05-0.09 mg/L), lead (0.01-0.03 mg/L), iron (1.86-4.66 mg/L), zinc (0.68-1.16 mg/L), cadmium (0.04-0.08 mg/L), chloride (675.0-791.25 mg/L), magnesium (10.66-14.30 mg/L). The study infers that anthropogenic pressure plays damaging role to its properties in addition to general health implication of high values for Fe, Zn, Cd, Cl and Mg which exceeded international standard.

scholarly journals The Friction Angle of the Leiyang Marble Surface after Exposure to High Temperature

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Meng Hong Peng ◽  
Man Huang
Keyword(s):  
Surface Condition ◽  
Surface Friction ◽  
Friction Angle ◽  
Effect Of Temperature ◽  
Tilt Test ◽  
Rock Surface ◽  
Sliding Angle ◽  
Normal Loading ◽  
Basic Friction Angle ◽  
Marble Surface

There is a lack of information about the temperature-dependent nature of the rock surface, which is one of the essential parameters to predict the surface friction. In the present study, we experimentally study the effect of temperature on the basic friction angle of the marble surface through the direct shear test under the low normal loading condition and tilting test (Stimpson/disk tilt test). The basic friction angle gradually decreases with the increase in temperature from 20°C to 600°C for the two kinds of the tilting test. The results indicate that the Stimpson test on samples with the length-to-diameter ratio of 2 can be more reliable to estimate the basic friction angle of the rock surface after exposure to high temperatures. The results illustrate that the sliding angle depends on the surface condition. With the increase in the repetitive measurements, the sliding angle decreases as the marble surface is cleaned, and the parameter increases as the marble surface is not cleaned.

A Study of Airborne Wear Particles Generated From a Sliding Contact

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Ulf Olofsson ◽  
Lars Olander ◽  
Anders Jansson
Keyword(s):  
Ultrafine Particles ◽  
Fine Particles ◽  
Urban Environments ◽  
Airborne Particles ◽  
Wear Particles ◽  
Coarse Particles ◽  
Sliding Velocity ◽  
Airborne Particle ◽  
Particle Generation ◽  
Pin On Disk

Recently, much attention has been paid to the influence of airborne particles in the atmosphere on human health. Sliding contacts are a significant source of airborne particles in urban environments. In this study airborne particles generated from a sliding steel-on-steel combination are studied using a pin-on-disk tribometer equipped with airborne-particle counting instrumentation. The instrumentation measured particles in size intervals from 0.01μm to 32μm. The result shows three particle size regimes with distinct number peaks: ultrafine particles with a size distribution peak around 0.08μm, fine particles with a peak around 0.35μm, and coarse particles with a peak around 2 or 4μm. Both the particle generation rate and the wear rate increase with increasing sliding velocity and contact pressure.

scholarly journals Morphological, chemical and optical absorbing characterization of aerosols in the urban atmosphere of Valladolid

2005 ◽  
Vol 5 (10) ◽  
pp. 2739-2748 ◽  
Author(s):  
S. Mogo ◽  
V. E. Cachorro ◽  
A. M. de Frutos
Keyword(s):  
Mass Fraction ◽  
Fine Particles ◽  
Aerosol Particles ◽  
Cascade Impactor ◽  
Urban Atmosphere ◽  
Coarse Particles ◽  
X Ray ◽  
Illumination System ◽  
Inverse Power Law

Abstract. Samples of atmospheric aerosol particles were collected in Valladolid, Spain, during the winter of 2003-2004. The measurements were made with a Dekati PM10 cascade impactor with four size stages: greater than 10 µm, between 2.5 to 10 µm, 1 to 2.5 µm and less than 1 µm. The size and shape of the particles were analyzed with a scanning electron microscope (SEM) and elemental analysis was done with an energy dispersive x-ray analysis (EDX). We present an evaluation by size, shape and composition of the major particulate species in the Valladolid urban atmosphere. The total aerosol concentration is very variable, ranging from 39.86 µg·m-3 to 184.88 µg·m-3 with the coarse particles as the dominant mass fraction. Emphasis was given to fine particles (<1 µm), for which the visible (400 nm to 650 nm) light absorption coefficients were measured using the integrating plate technique. We have made some enhancements in the illumination system of this measurement system. The absorption coefficient, σa, is highly variable and ranges from 7.33×10-6 m-1 to 1.01×10-4 m-1 at a wavelength of 550 nm. There is an inverse power law relationship between σa and wavelength, with an average exponent of -0.8.

scholarly journals INVESTIGATION OF INFLUENCE OF LAPES LANDFILL LEACHATE ON GROUND AND SURFACE WATER POLLUTION WITH HEAVY METALS/LAPIŲ SĄVARTYNO FILTRATO ĮTAKOS APLINKOS PAVIRŠINIŲ IR POŽEMINIŲ VANDENŲ UŽTERŠTUMUI SUNKIAISIAIS METALAIS TYRIMAI/ ИССЛЕДОВАНИЕ ЗАГРЯЗНЕНИЯ ПОВЕРХНОСТНЫХ И ПОДЗЕМНЫХ ВОД ТЯЖЕЛЫМИ МЕТАЛЛАМИ ИЗ ФИЛЬТРАТА СВАЛКИ В ЛАПЕС

2009 ◽  
Vol 17 (3) ◽  
pp. 131-139 ◽  
Author(s):  
Bronius Jaskelevičius ◽  
Vaida Lynikienė
Keyword(s):  
Heavy Metals ◽  
Heavy Metal ◽  
Waste Disposal ◽  
Industrial Waste ◽  
Iron Concentration ◽  
Chemical Properties ◽  
Biological Interactions ◽  
Paper Properties ◽  
Toxic Compounds ◽  
The Third

As a result of global and intense production the waste disposal problems become more and more urgent. Waste processing, utilization and recycling is to a certain extent limited by many economic, organisational and technological factors, and this inevitably encourages waste disposal in landfills. Physical, chemical and biological interactions in landfill cell result in formation of landfill gas and harmful leachate. Because of lack of control, together with usual communal waste, industrial waste was also dumped to landfills, therefore gas and leachate produced include large amounts of toxic compounds. Once hazardous waste materials occured in landfills, later they vastly expanded the whole spectrum of toxic materials and compounds. In the landfill environment chemical properties of surface and ground water and concentration of separate components are governed by seepage of leachate and industrial solutants into soil and ground layers and their transport by subsurface waters. Influence on the environment exerted by heavy metals contained in the leachate of Lapes Landfill is discussed in this paper. Properties of industrial waste material influenced order of the main pollutants: the most important elements in this case are Cu, Ni, Zn, Pb, Mn, Cr and other ions, the sulphides of these metals and other toxic compounds. The First Landfill field is more polluted with heavy metal polutants than the Third field. In all the samples iron concentration is the greatest exceeding even 200 times the admissible value allowed (Norm HN 24:2003). Sources (springs) S11 and S17 are least contaminated with heavy metals. The greatest groundwater pollution was found in monitoring bore G13s. The leachate processed in purification devices is released to the Third stream. Heavy metal concentrations in waters of this stream are low and they further decrease downstream because the pollutants are diluted. Santrauka Masiškai gaminant produkciją, ją vartojant, vis opesnė tampa atliekų problema. Atliekų perdirbimą, utilizavimą iš dalies ribojantys ekonominiai, organizaciniai bei technologiniai veiksniai neišvengiamai skatina atliekas šalinti į sąvartynus. Dėl sąvartyno tūryje vykstančių fizinių, cheminių bei biologinių reakcijų susidaro sąvartyno dujos ir kenksmingas filtratas. Kadangi dėl nepakankamos kontrolės į sąvartynus kartu su buitinėmis, komunalinėmis atliekomis buvo šalinamos pramonės atliekos, susidarančiose dujose bei filtrate yra daug toksiškų junginių. Šią toksinių medžiagų bei junginių įvairovę dar labiau papildo į sąvartynus patenkančios pavojingos atliekos. Gruntinio ir paviršinio upelių vandens cheminę sudėtį ir kai kurių komponentų koncentraciją sąvartyno aplinkoje lemia filtrato ir pramoninių tirpalų įsisunkimo į gruntą mastas bei požeminių tėkmių pernašos. Straipsnyje nagrinėjama Lapių sąvartyno filtrate aptiktų sunkiųjų metalų įtaka aplinkai. Pramonės atliekos lėmė, kad filtrato pagrindiniai teršiantieji elementai yra Cu, Ni, Zn, Pb, Mn, Cr ir kt. jonai, šių metalų sulfidai ir kiti toksiniai junginiai. Pirmasis kaupimosi laukas yra labiau užterštas sunkiaisiais metalais nei trečiasis laukas. Visuose mėginiuose didžiausia yra geležies koncentracija. Ji net iki 200 kartų viršija HN 24:2003 leidžiamąją normą. Mažiausiai sunkiaisiais metalais užteršti šaltiniai (S11 ir S17 postai). Požeminis vanduo labiausiai užterštas G13s gręžinyje. Iš valymo įrenginių išvalytas filtratas yra išleidžiamas į upelį. Šio upelio vandenyje rastų sunkiųjų metalų koncentracijos yra nedidelės, o upeliui tekant tolyn teršalai atskiedžiami, ir metalų koncentracijos mažėja. Резюме Массовое производство продукции, пользование ею все более обостряют проблему отходов. Процессы переработки и утилизации отходов, в определенной степени ограничивающие экономические, организационные и технологические факторы, неизбежно способствуют интенсификации удаления отходов на свалки. На свалках отходов в результате протекающих физических, химических и биологических реакций образуются газы и токсичный фильтрат. Поскольку из-за недостаточного контроля на свалку вместе с бытовыми, коммунальными отходами удалялись и промышленные отходы, в составе образующихся газов и фильтрата имеется много токсичных соединений. Опасные отходы еще более увеличили спектр токсичных материалов и соединений в газах и фильтрате свалки. Химический состав и концентрация отдельных компонентов грунтовых и поверхностных вод в районе свалки определяют проникновение фильтрата и промышленных растворов в грунт и их перенос подземными течениями. В статье изучается влияние тяжелых металлов из фильтрата свалки в Лапес на состояние вод в районе свалки. Промышленные отходы способствовали появлению в фильтрате ионов основных загрязняющих элементов Cu, Ni, Zn, Pb, Mn, Cr, сульфидов этих металлов и других токсичных соединений. Первое поле накопления отходов в большей степени загрязнено тяжелыми металлами, чем третье поле. Во всех опытных образцах воды отмечена самая большая концентрация ионов железа, почти в 200 раз превышающая допустимую норму HN 24:2003. Наименьшее загрязнение тяжелыми металлами отмечено в подземной воде источников (посты S11 и S17). Грунтовые воды больше всего загрязнены в скважине G13s. Поверхностные воды ручьев, в которые проникает фильтрат, а также сливается очищенный фильтрат, содержат небольшие концентрации тяжелых металлов, которые разбавляются течением и уменьшаются.

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