Low grade dumped limestone sample having high silica of 8.1%, 36.8% CaO, and 3% Al2O3 has been studied with the aim to reduce the silica level to below 3% for its utilization in iron making. Beneficiation study of the...Low grade dumped limestone sample having high silica of 8.1%, 36.8% CaO, and 3% Al2O3 has been studied with the aim to reduce the silica level to below 3% for its utilization in iron making. Beneficiation study of the sample was initiated with desliming of the feed sample of -100 μm to remove the siliceous ultrafine particles and to improve the feed quality. Flotation study was carried out by column flotation technique varying the collector dosage, superficial air flow velocity and froth depth to assess their effect on silica reduction and CaO recovery. It was observed that increased collector dosage and superficial air velocity increases the recovery of CaO, and increase in the froth depth reduces the mass flow and silica content in the concentrate. The best result was found at 1.25 cm/sec superficial air velocity, 25 cm froth depth, 1.25 kgpt collector dosage and concentrate assayed 47.3% CaO, 2.8% silica with 72% CaO recovery.展开更多
In order to determine the effects of different mineral admixtures including fly ash （FA）, blast furnace slag （BFS） and metakaolin （MK） on hydration product phases from the nanoscale structure perspective, nanoin...In order to determine the effects of different mineral admixtures including fly ash （FA）, blast furnace slag （BFS） and metakaolin （MK） on hydration product phases from the nanoscale structure perspective, nanoindentation characteristics of the samples with similar 28-day strengths have been investigated. The results indicate that the volume fractions of porosity in po- rosity and hydration product phases of the samples with the same kind of mineral admixture are almost equal to each other, and are greater than that of the sample without mineral admixture. Mineral admixtures especially MK can decrease remarkably the volume fractions of CH in porosity and hydration product phases, and there exists a good linear relationship between the （AI＋Si）/Ca molar ratio of cementitious materials chemical compositions and the volume fraction of HD C-S-H gel in C-S-H gel. Therefore, it is possible to predict the volume fraction change of HD C-S-H gel in C-S-H gel by simply calculating the （AI＋Si）/Ca molar ratio of cementitious materials with similar 28-day strengths under the constant water-binder ratio.展开更多
This study investigates the values of pH,total dissolved solids(TDS),elevation,oxidative reduction potential(ORP),temperature,and depth,while the concentrations of Br,and potentially harmful metals(PHMs)such as Cr,Ni,...This study investigates the values of pH,total dissolved solids(TDS),elevation,oxidative reduction potential(ORP),temperature,and depth,while the concentrations of Br,and potentially harmful metals(PHMs)such as Cr,Ni,Cd,Mn,Cu,Pb,Co,Zn,and Fe in the groundwater samples.Moreover,geographic information system(GIS),XLSTAT,and IBM SPSS Statistics 20 software were used for spatial distribution modeling,principal component analysis(PCA),cluster analysis(CA),and Quantile-Quantile(Q-Q)plotting to determine groundwater pollution sources,similarity index,and normal distribution reference line for the selected parameters.The mean values of pH,TDS,elevation,ORP,temperature,depth,and Br were 7.2,322 mg/L,364 m,188 mV,29.6℃,70 m,0.20 mg/L,and PHMs like Cr,Ni,Cd,Mn,Cu,Pb,Co,Zn,and Fe were 0.38,0.26,0.08,0.27,0.36,0.22,0.04,0.43 and 0.86 mg/L,respectively.PHMs including Cr(89%),Cd(43%),Mn(23%),Pb(79%),Co(20%),and Fe(91%)exceeded the guideline values set by the world health organization(WHO).The significant R^(2)values of PCA for selected parameters were also determined(0.62,0.67,0.78,0.73,0.60,0.87,-0.50,0.69,0.70,0.74,-0.50,0.70,0.67,0.79,0.59,and-0.55,respectively).PCA revealed three geochemical processes such as geogenic,anthropogenic,and reducing conditions.The mineral phases of Cd(OH)_(2),Fe(OH)_(3),FeOOH,Mn_(3)O_(4),Fe_(2)O_(3),MnOOH,Pb(OH)_(2),Mn(OH)_(2),MnO_(2),and Zn(OH)_(2)(-3.7,3.75,9.7,-5.8,8.9,-3.6,2.2,-4.6,-7.7,-0.9,and 0.003,respectively)showed super-saturation and under-saturation conditions.Health risk assessment(HRA)values for PHMs were also calculated and the values of hazard quotient(HQ),and hazard indices(HI)for the entire study area were increased in the following order:Cd>Ni>Cu>Pb>Mn>Zn>Cr.Relatively higher HQ and HI values of Ni,Cd,Pb,and Cu were greater than one showing unsuitability of groundwater for domestic,agriculture,and drinking purposes.The long-term ingestion of groundwater could also cause severe health concerns such as kidney,brain dysfunction,liver,stomach problems,and even cancer.展开更多
Extracellular polymeric substances(EPS)are an importantmedium for communication and material exchange between iron-oxidizing bacteria and the external environment and could induce the iron(oxyhydr)oxides production wh...Extracellular polymeric substances(EPS)are an importantmedium for communication and material exchange between iron-oxidizing bacteria and the external environment and could induce the iron(oxyhydr)oxides production which reduced arsenic(As)availability.The main component of EPS secreted by iron-oxidizing bacteria(Ochrobactrum EEELCW01)was composed of polysaccharides(150.76-165.33 mg/g DW)followed by considerably smaller amounts of proteins(12.98–16.12 mg/g DW).Low concentrations of As(100 or 500μmol/L)promoted the amount of EPS secretion.FTIR results showed that EPS was composed of polysaccharides,proteins,and a miniscule amount of nucleic acids.The functional groups including-COOH,-OH,-NH,-C=O,and-C-O played an important role in the adsorption of As.XPS results showed that As was bound to EPS in the form of As3+.With increasing As concentration,the proportion of As3+adsorbed on EPS increased.Ferrihydrite with a weak crystalline state was only produced in the system at 6 hr during the mineralization process of Ochrobactrum sp.At day 8,the minerals were composed of goethite,galena,and siderite.With the increasing mineralization time,the main mineral phases were transformed from weakly crystalline hydrous iron ore into higher crystallinity siderite(FeCO_(3))or goethite(α-FeOOH),and the specific surface area and active sites of minerals were reduced.It can be seen from the distribution of As elements that As is preferentially adsorbed on the edges of iron minerals.This study is potential to understand the biomineralizationmechanism of iron-oxidizing bacteria and As remediation in the environment.展开更多
Quantitative parameters of bed combustion, including the thickness of the combustion zone(TCZ), the maximum temperature of the combustion zone(MTCZ), and the bed shrinkage, were characterized through a series of sinte...Quantitative parameters of bed combustion, including the thickness of the combustion zone(TCZ), the maximum temperature of the combustion zone(MTCZ), and the bed shrinkage, were characterized through a series of sinter pot tests in transparent quartz pots. The results showed that TCZ first ascended and then descended as the sintering process proceeded. The sintering process was divided into four stages according to the variation rate of the TCZ. A "relative-coordinate" method was developed to obtain the actual reaction temperature of sinter along the height direction. With increasing the sintering temperature, the reactants transformed and entered into liquid phases. The mineral composition and microstructure of the sinter were characterized through X-ray diffraction and scanning electron microscopy–energy-dispersive X-ray spectroscopy. Liquid phases with greater Fe and Al contents were more likely to form acicular-like silico-ferrite of calcium and aluminum after crystallization because of the outward spread of Al, which led to a better fluidity of the liquid. An evolution mechanism of "solid-state reaction—liquid phases formation—crystallization" of the mineral phases is proposed.展开更多
Ceramic tiles were processed in this present work using clay mineral and steel slag. Steel slag in the range of 0-100wt % was added to kaolinite clay. The blended samples were hydraulic pressed into rectangular moulds...Ceramic tiles were processed in this present work using clay mineral and steel slag. Steel slag in the range of 0-100wt % was added to kaolinite clay. The blended samples were hydraulic pressed into rectangular moulds, oven dried and sintered to1200℃. Linear shrinkage, apparent porosity, water absorption, bulk density, and modulus of rupture of sintered specimens were examined. Phases present in the sintered products were identified using X-Ray Diffractometer (XRD), while the microstructural examination was conducted using Scanning Electron Microscopy (SEM). The elements present in the sintered products were identified using Energy Dispersive X-ray (EDX). Phases like quartz, wol-lastonite, anorthite and enstatite were identified in the sintered products. The SEM revealed crystals embedded in the glassy matrix. EDX studies detected Aluminum (Al), Silicon (Si), Magnesium (Mg) and Calcium (Ca) as the major metal ions. Results obtained showed that samples containing 20-60wt% steel slag have very good usable ceramic tile properties.展开更多
In Argentina, there are many sources of copper concentrates. Some of them are currently in operation, while others are in the exploration stage. All copper concentrates produced are exported to other countries for cop...In Argentina, there are many sources of copper concentrates. Some of them are currently in operation, while others are in the exploration stage. All copper concentrates produced are exported to other countries for copper refinement and to create various finished products. It is desirable that in the near future, these copper concentrates be processed in an Argentinean industrial plant. The aim of this paper was to present the results of a characterisation study carried out on five different copper concentrate samples. The thermal decomposition of the copper concentrates was determined by differential thermal analysis and thermogravimetry (DTA TG). The information was correlated with the chemical composition and the mineralogical phases of the samples identified by X-ray diffraction. A melting test at temperatures of up to 1300℃ was performed to complete the study of the concentrate’s behaviour during heating. After the test, all of the samples were observed by light and electronic scanning microscopy to identify the different phases generated under high-temperature conditions.展开更多
文摘Low grade dumped limestone sample having high silica of 8.1%, 36.8% CaO, and 3% Al2O3 has been studied with the aim to reduce the silica level to below 3% for its utilization in iron making. Beneficiation study of the sample was initiated with desliming of the feed sample of -100 μm to remove the siliceous ultrafine particles and to improve the feed quality. Flotation study was carried out by column flotation technique varying the collector dosage, superficial air flow velocity and froth depth to assess their effect on silica reduction and CaO recovery. It was observed that increased collector dosage and superficial air velocity increases the recovery of CaO, and increase in the froth depth reduces the mass flow and silica content in the concentrate. The best result was found at 1.25 cm/sec superficial air velocity, 25 cm froth depth, 1.25 kgpt collector dosage and concentrate assayed 47.3% CaO, 2.8% silica with 72% CaO recovery.
基金supported by the National Basic Research Program of China("973"Program)(Grant No.2009CB623200)the Airport Building Research Program of Jiangsu Province China(Grant No.LKJC-11-KY-001)the Research and Application Program of China’s Ministry of Railways(Grant No.2010g004-h)
文摘In order to determine the effects of different mineral admixtures including fly ash （FA）, blast furnace slag （BFS） and metakaolin （MK） on hydration product phases from the nanoscale structure perspective, nanoindentation characteristics of the samples with similar 28-day strengths have been investigated. The results indicate that the volume fractions of porosity in po- rosity and hydration product phases of the samples with the same kind of mineral admixture are almost equal to each other, and are greater than that of the sample without mineral admixture. Mineral admixtures especially MK can decrease remarkably the volume fractions of CH in porosity and hydration product phases, and there exists a good linear relationship between the （AI＋Si）/Ca molar ratio of cementitious materials chemical compositions and the volume fraction of HD C-S-H gel in C-S-H gel. Therefore, it is possible to predict the volume fraction change of HD C-S-H gel in C-S-H gel by simply calculating the （AI＋Si）/Ca molar ratio of cementitious materials with similar 28-day strengths under the constant water-binder ratio.
基金financially supported National Natural Science Foundation of China(Grant Nos.41521001 and 41877204)the 111 Program(State Administration Foreign Experts Affairs&the Ministry of Education of China,Grant No.B18049)the China Postdoctoral Science Foundation(Grant No.2018M642944)。
文摘This study investigates the values of pH,total dissolved solids(TDS),elevation,oxidative reduction potential(ORP),temperature,and depth,while the concentrations of Br,and potentially harmful metals(PHMs)such as Cr,Ni,Cd,Mn,Cu,Pb,Co,Zn,and Fe in the groundwater samples.Moreover,geographic information system(GIS),XLSTAT,and IBM SPSS Statistics 20 software were used for spatial distribution modeling,principal component analysis(PCA),cluster analysis(CA),and Quantile-Quantile(Q-Q)plotting to determine groundwater pollution sources,similarity index,and normal distribution reference line for the selected parameters.The mean values of pH,TDS,elevation,ORP,temperature,depth,and Br were 7.2,322 mg/L,364 m,188 mV,29.6℃,70 m,0.20 mg/L,and PHMs like Cr,Ni,Cd,Mn,Cu,Pb,Co,Zn,and Fe were 0.38,0.26,0.08,0.27,0.36,0.22,0.04,0.43 and 0.86 mg/L,respectively.PHMs including Cr(89%),Cd(43%),Mn(23%),Pb(79%),Co(20%),and Fe(91%)exceeded the guideline values set by the world health organization(WHO).The significant R^(2)values of PCA for selected parameters were also determined(0.62,0.67,0.78,0.73,0.60,0.87,-0.50,0.69,0.70,0.74,-0.50,0.70,0.67,0.79,0.59,and-0.55,respectively).PCA revealed three geochemical processes such as geogenic,anthropogenic,and reducing conditions.The mineral phases of Cd(OH)_(2),Fe(OH)_(3),FeOOH,Mn_(3)O_(4),Fe_(2)O_(3),MnOOH,Pb(OH)_(2),Mn(OH)_(2),MnO_(2),and Zn(OH)_(2)(-3.7,3.75,9.7,-5.8,8.9,-3.6,2.2,-4.6,-7.7,-0.9,and 0.003,respectively)showed super-saturation and under-saturation conditions.Health risk assessment(HRA)values for PHMs were also calculated and the values of hazard quotient(HQ),and hazard indices(HI)for the entire study area were increased in the following order:Cd>Ni>Cu>Pb>Mn>Zn>Cr.Relatively higher HQ and HI values of Ni,Cd,Pb,and Cu were greater than one showing unsuitability of groundwater for domestic,agriculture,and drinking purposes.The long-term ingestion of groundwater could also cause severe health concerns such as kidney,brain dysfunction,liver,stomach problems,and even cancer.
基金supported by the National Natural Science Foundation of China(No.42177392)the Dean’s Research Fund 2020/21(No.04626)of the Education University of Hong Kong.
文摘Extracellular polymeric substances(EPS)are an importantmedium for communication and material exchange between iron-oxidizing bacteria and the external environment and could induce the iron(oxyhydr)oxides production which reduced arsenic(As)availability.The main component of EPS secreted by iron-oxidizing bacteria(Ochrobactrum EEELCW01)was composed of polysaccharides(150.76-165.33 mg/g DW)followed by considerably smaller amounts of proteins(12.98–16.12 mg/g DW).Low concentrations of As(100 or 500μmol/L)promoted the amount of EPS secretion.FTIR results showed that EPS was composed of polysaccharides,proteins,and a miniscule amount of nucleic acids.The functional groups including-COOH,-OH,-NH,-C=O,and-C-O played an important role in the adsorption of As.XPS results showed that As was bound to EPS in the form of As3+.With increasing As concentration,the proportion of As3+adsorbed on EPS increased.Ferrihydrite with a weak crystalline state was only produced in the system at 6 hr during the mineralization process of Ochrobactrum sp.At day 8,the minerals were composed of goethite,galena,and siderite.With the increasing mineralization time,the main mineral phases were transformed from weakly crystalline hydrous iron ore into higher crystallinity siderite(FeCO_(3))or goethite(α-FeOOH),and the specific surface area and active sites of minerals were reduced.It can be seen from the distribution of As elements that As is preferentially adsorbed on the edges of iron minerals.This study is potential to understand the biomineralizationmechanism of iron-oxidizing bacteria and As remediation in the environment.
基金financially supported by the National Science Foundation for Young Scientists of China (No.51304014)
文摘Quantitative parameters of bed combustion, including the thickness of the combustion zone(TCZ), the maximum temperature of the combustion zone(MTCZ), and the bed shrinkage, were characterized through a series of sinter pot tests in transparent quartz pots. The results showed that TCZ first ascended and then descended as the sintering process proceeded. The sintering process was divided into four stages according to the variation rate of the TCZ. A "relative-coordinate" method was developed to obtain the actual reaction temperature of sinter along the height direction. With increasing the sintering temperature, the reactants transformed and entered into liquid phases. The mineral composition and microstructure of the sinter were characterized through X-ray diffraction and scanning electron microscopy–energy-dispersive X-ray spectroscopy. Liquid phases with greater Fe and Al contents were more likely to form acicular-like silico-ferrite of calcium and aluminum after crystallization because of the outward spread of Al, which led to a better fluidity of the liquid. An evolution mechanism of "solid-state reaction—liquid phases formation—crystallization" of the mineral phases is proposed.
文摘Ceramic tiles were processed in this present work using clay mineral and steel slag. Steel slag in the range of 0-100wt % was added to kaolinite clay. The blended samples were hydraulic pressed into rectangular moulds, oven dried and sintered to1200℃. Linear shrinkage, apparent porosity, water absorption, bulk density, and modulus of rupture of sintered specimens were examined. Phases present in the sintered products were identified using X-Ray Diffractometer (XRD), while the microstructural examination was conducted using Scanning Electron Microscopy (SEM). The elements present in the sintered products were identified using Energy Dispersive X-ray (EDX). Phases like quartz, wol-lastonite, anorthite and enstatite were identified in the sintered products. The SEM revealed crystals embedded in the glassy matrix. EDX studies detected Aluminum (Al), Silicon (Si), Magnesium (Mg) and Calcium (Ca) as the major metal ions. Results obtained showed that samples containing 20-60wt% steel slag have very good usable ceramic tile properties.
文摘In Argentina, there are many sources of copper concentrates. Some of them are currently in operation, while others are in the exploration stage. All copper concentrates produced are exported to other countries for copper refinement and to create various finished products. It is desirable that in the near future, these copper concentrates be processed in an Argentinean industrial plant. The aim of this paper was to present the results of a characterisation study carried out on five different copper concentrate samples. The thermal decomposition of the copper concentrates was determined by differential thermal analysis and thermogravimetry (DTA TG). The information was correlated with the chemical composition and the mineralogical phases of the samples identified by X-ray diffraction. A melting test at temperatures of up to 1300℃ was performed to complete the study of the concentrate’s behaviour during heating. After the test, all of the samples were observed by light and electronic scanning microscopy to identify the different phases generated under high-temperature conditions.
