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1.
The hydrolyzed titania residue with mainly precipitated hydrated TiO2 is prepared from mechanically activated Panzhihua ilmenite leached by hydrochloric acid. We use H2O2 as a coordination agent to leach Ti from the hydrolyzed titania residue. The effects of H2O2 to-hydrolyzed titania residue mass ratio, leaching pH value, leaching temperature, leaching time, and H2O2 concentration on leaching of hydrolyzed titania residue by H2O2 are investigated. The recovery of Ti is above 98% under the optimal conditions. XRD shows that the peroxo-titania powder prepared by boiling the aqueous titanium peroxide solution is crystalline anatase phase. A well-crystallized anatase TiO2 and rutile TiO2 can be obtained through calcining at the temperature of 800 and 1000 °C, respectively. EDS shows that the impurities including silicon are enriched in the leaching slag. Little Si is detected as the only impurity in the synthetic TiO2 due to the weak alkaline condition of leaching.  相似文献   

2.
刘敬勇  常向阳 《地球化学》2009,38(3):251-261
利用元素总量和Pb同位素示踪技术对广东云浮硫酸厂含Tl黄铁矿冶炼堆渣场周围土壤中Tl的污染程度和迁移行为进行了研究。研究发现堆渣场周围土壤中Tl污染物主要集中于表层土壤约16．5cm深度内,并且表现出沿垂直方向向下迅速下降的特点。堆渣场周围土壤中Tl与Pb呈显著线性相关,表明自然条件下田与Pb在土壤中的迁移相似性,并且都以横向迁移为主。堆渣场固结层周围土壤至少44cm范围已经受到废渣中Tl释放的影响,Tl污染物平均下渗速率达到2．75cm／a。酸性雨水的淋滤作用及废渣自身不断酸化的特性是废渣中．Tl迁移释放入土壤的主要因素,土壤铁氧化物胶体及有机质是土壤对Tl产生吸附的主要载体。  相似文献   

3.
Arsenic in groundwater is a serious environmental problem. The contamination of groundwater with arsenic has been of utmost concern worldwide. Steel slag is a solid waste generated from steel production. Although steel slags have been used for arsenic removal from water, this process has not been systematically or integratively researched. In this study, the arsenic removal capacity and mechanism were investigated for carbon steel slag, stainless steel slag and Fe-modified stainless steel slag based on an in-depth study. The study also evaluated the potential utilization of different steel slag for regeneration. The maximum adsorption of arsenic on carbon steel slag, stainless steel slag and Fe-modified stainless steel slag was 12.20, 3.17 and 12.82 mg g?1 at 25 °C, respectively. The modification of stainless steel slag by FeC13 can generate more pore structures and larger surface areas, and 300 °C treatment produces the best regeneration efficiency. The ΔG values were negative for all of the steel slags, indicating the spontaneous nature of the adsorption process. The solution pH was a critical parameter for the removal of arsenic for steel slags. Under highly alkaline solution conditions, the mechanism of arsenic removal by carbon steel slag and stainless steel slag can be attributed to chemisorption, including chemical precipitation and coordination reactions, and under weakly alkaline solution conditions, electrostatic interaction and specific adsorption are the arsenic removal mechanisms by Fe-modified stainless steel slag. Regeneration of the Fe-modified stainless steel slag was better achieved than that of the other steel slags in the application of high-temperature treatment.  相似文献   

4.
The accumulation of electrolytic manganese residue (EMR) has become a serious problem and its recycling will be of great benefit to protect the environment and assist sustainable development. The reusing method was conducted by leaching EMR with sulfuric acid and the optimal leaching condition was 1:3 (g/g) as the ratio of solid to liquid with 20% (g/g) H2SO4 , heating at 90 ℃ for 3 hours, which aims at extracting Mn in a sulfuric acid medium. The produced MnSO4 solution was precipitated by adding alkali and oxidized in aqueous phase. The oxidized products were characterized by various techniques, including X-ray powder diffraction (XRD), Fourier transform infrared (IR) spectrometry, vibrating sample magnetometry (VSM), with Brunauer-Emmett-Teller (BET) specific surface area instrument and laser particle size analyzer. The final products were confirmed to be a single-phase Mn3O4 .  相似文献   

5.
The kinetics of spent nickel oxide catalyst (NiO/Al2O3) leaching in sulphuric acid solutions was investigated. The effects of sulphuric acid concentration, temperature, stirring speed, and particle size on the rate of nickel leaching were studied. In addition, the reaction residues at various levels of nickel extraction were examined by SEM, X-ray diffraction, electron microprobe, and chemical analysis. The results of the kinetic analysis of the leaching data for various experimental conditions indicated that the reaction is controlled by diffusion through the catalyst network with the activation energy of 16.6 ± 0.9 kJ/mol. A linear relationship between the rate constant and the inverse square of the initial particle diameter is also characteristic for a diffusion-controlled process.  相似文献   

6.
Metal leaching from metallurgical wastes (slags) by means of environmentally friendly approaches is promising for practical applications. The goal of this study was to compare the feasibility of metal bioleaching from Cu slags by means of Pseudomonas fluorescens and Acidithiobacillus thiooxidans. Two size particles (<0.3 mm and 1–2 mm) of two types of Cu slags (massive crystalline slag and granulated amorphous slag) were used to study metal (Cu, Zn and Fe) bioleaching. The 40-days bioleaching experiments with P. fluorescens began at circumneutral pH (7.0), whereas the experiments with A. thiooxidans were started under acidic (pH 2.5) conditions. The results demonstrated that A. thiooxidans catalyzes metal leaching from both slag types investigated. After 21 days of incubation, optimal leaching was achieved and up to 79% Cu, 76% Zn and 45% Fe could be extracted from crystalline slag under conditions of 1 wt.% pulp density and particle size <0.3 mm. The optimal efficiency achieved with amorphous slag was 81% Cu, 79% Zn and 22% Fe when 1% pulp density and 1–2 mm particle size were used. The use of P. fluorescens resulted in poor leaching efficiencies as compared to the performance of A. thiooxidans, presumably due to the higher pH conditions maintained during the P. fluorescens incubations. The maximum metal leaching efficiencies with P. fluorescens were achieved at 1% pulp density and particle size <0.3 mm and did not exceed 10% Cu, 4% Zn, 0.3% Fe for crystalline slag and 4% Cu, 3% Zn, 0.7% Fe for amorphous slag. Both slags exhibited a good potential for bioleaching with A. thiooxidans, however; further optimization of the process parameters (e.g. pulp density, particle size and pH) is needed to improve the efficiency.  相似文献   

7.
《Applied Geochemistry》2004,19(7):1039-1064
Slag collected from smelter sites associated with historic base-metal mines contains elevated concentrations of trace elements such as Cu, Zn and Pb. Weathering of slag piles, many of which were deposited along stream banks, potentially may release these trace elements into the environment. Slags were sampled from the Ely and Elizabeth mines in the Vermont copper belt, from the copper Basin mining district at Ducktown, Tennessee and from the Clayton silver mine in the Bayhorse mining district, Idaho, in the USA. Primary phases in the slags include: olivine-group minerals, glass, spinels, sulfide minerals and native metals for Vermont samples; glass, sulfide minerals and native metals for the Ducktown sample; and olivine-group minerals, clinopyroxenes, spinels, sulfide minerals, native metals and other unidentified metallic compounds for Clayton slag. Olivine-group minerals and pyroxenes are dominantly fayalitic and hedenbergitic in composition, respectively and contain up to 1.25 wt.% ZnO. Spinel minerals range between magnetite and hercynite in composition and contain Zn (up to 2.07 wt.% ZnO), Ti (up to 4.25 wt.% TiO2) and Cr (up to 1.39 wt.% Cr2O3). Cobalt, Ni, Cu, As, Ag, Sb and Pb occur in the glass phase, sulfides, metallic phases and unidentified metallic compounds. Bulk slag trace-element chemistry shows that the metals of the Vermont and Tennessee slags are dominated by Cu (1900–13,500 mg/kg) and Zn (2310–10,200 mg/kg), whereas the Clayton slag is dominated by Pb (63,000 mg/kg), Zn (19,700 mg/kg), Cu (7550 mg/kg), As (555 mg/kg), Sn (363 mg/kg) and Ag (200 mg/kg). Laboratory-based leach tests indicate metals can be released under simulated natural conditions. Leachates from most slags were found to contain elevated concentrations of Cu and Zn (up to 1800 and 470 μg/l, respectively), well in excess of the acute toxicity guidelines for aquatic life. For the Idaho slag, the concentration of Pb in the leachate (11,000 μg/l) is also in excess of the acute toxicity guideline. Geochemical modeling of the leachate chemistry suggests that leachates from the Vermont, Tennessee and Clayton slags are saturated with amorphous silica and Al hydroxide. Therefore, the dissolution of silicate and oxide phases, the oxidation of sulfide phases, as well as the precipitation of secondary phases may control the composition of leachate from slags. The presence of secondary minerals on slag deposits in the field is evidence that these materials are reactive. The petrographic data and results of leaching tests from this study indicate slag may be a source of potentially toxic metals at abandoned mine sites.  相似文献   

8.
The removal of Cu(II) and Pb(II) was studied on two types of slags (blast furnace and steelmaking slag) and their modifications prepared by leaching with demineralized water (with contact time 24 and 48 h) and 0.001 mol L?1 HCl solution. The slags and their modifications were characterized by x-ray fluorescence spectroscopy, x-ray diffraction, infrared spectroscopy, and the specific surface area was measured. Environmental scanning electron microscope was used to study the microscopic changes of the slags. The highest removal amounts of Cu(II) were found on the blast furnace slag leached for 48 h. This fact can be explained by the higher specific surface area of the leached blast furnace slag; the removal of Cu(II) is supposed to take place by co-precipitation of its hydroxides or hydroxo-complexes on the slag surface. On the contrary, the modified steelmaking slags exhibit no improvement of the removal properties. The used treatment of the slags decreased the sorption capacities for Pb(II). The original steelmaking slag showed to be the best adsorbent for both metal cations.  相似文献   

9.
The raw sands from Hohenbocka (Germany) containing iron essentially in pyrite form is used for glass grade sands processing by dump leaching for several weeks followed by attrition and two-stage classification. The analysis of the sands by means of X-Ray Fluorescence Analysis (RFA) showed an average of about 420 ppm Fe. The objective of this investigation was to reduce the processing time and the total iron content below 105 ppm in the sand product for special glass applications. Due to the presence of sulfide and oxide iron at different ratios in raw sands, a combination of chemical and physical methods was investigated. Leaching was carried out at different acid concentrations, followed by surface cleaning by neutral and alkaline attrition, and gravity separation. Additionally, the effect of continuous addition of H2O2 during leaching to remove iron from sands was investigated. Only two days of leaching was required at the initial acid concentration to 25 g/L. After attrition and tabling of leached sands, a product with 84 ppm of iron was achieved. The continuous removal of dissolved metals by adsorption with active carbon could make it possible to reuse the regenerated sulphuric acid for leaching. With recirculation, the quantity of fresh sulphuric acid required was 0.4 kg/t of quartz sand.  相似文献   

10.
With different properties, zinc is one of the most important non-ferrous metals and it is used in various application areas, especially as an anti-corrosion agent. In Turkey, zinc production was based on zinc carbonate ores (ZnCO3), at Çinkur plant from establishment to 1997 due to high reserves of zinc carbonate. After that, zinc concentrate coming from Iran was used in this plant over the last two decades. Thus, two different leach residues called as Turkish leach residue (TLR) and Iranian leach residue (ILR) were accumulated more than one million ton in Çinkur stock piles. In this study, it is aimed to investigate zinc recovery for each leach residue by use of sulphuric acid (H2SO4) and to compare the TLR and the ILR. Initially, detailed chemical, mineralogical and thermal analyses of these different leach residues were carried out. In order to investigate the effect of acid concentration and reaction duration on zinc recovery, leaching experiments were carried out at following conditions: 95 °C, 100 g/L pulp density and 600 rpm stirring rate. According to the characterization results, the chemical compositions for both residues are nearly similar; however, experimental results show that zinc recovery per cent of the ILR was higher than that of TLR for all experimental durations and acid concentrations. This may be due to the presence of Zn-containing compounds in the both residues at different percentages.  相似文献   

11.
The enthalpies of solution in molten 2PbO · B2O3 of phases synthesized at one atmosphere in the system MgGa2O4-Mg2GeO4 have been measured. A spinel solid solution, which is stable at 1400 °C from the MgGa2O4 end-member to 27 mole percent Mg2GeO4, shows endothermic heats of mixing of up to 10 kJ/mole at the solubility limit. The spinelloid phase, Mg3Ga2GeO8, is energetically less stable than a mixture of terminal spinel solid solutions (0.73 MgGa2O4·0.27 Mg2GeO4(sp)+Mg2GeO4(sp)), by 3.63±3.64 kJ/mole. This indicates that the spinelloid is a high-entropy phase.The volume of the spinel solid solution, MgGa2O4-Mg2GeO4, shows a positive deviation from Vegard's Law. Modeling of the cation distribution in the solid solution indicates that this V is due to a change in the spinel type from inverse towards normal as the Mg2GeO4 content increases.  相似文献   

12.
High pressure phase relation of the system Fe2SiO4–Fe3O4 was investigated by synthesis experiments using multi-anvil high pressure apparatus. A complete solid solution with spinel structure along Fe2SiO4–Fe3O4 join occurs above 9 GPa at 1200 °C. Lattice constants of the solid solution show almost linear variation with composition. A spinelloid phase is stable for intermediate compositions in the pressure range from 3 to 9 GPa. the synthesized spinelloid phase is successfully indexed assuming nickel aluminosilicate V type structure. Received: October 16, 1995 / Revised, accepted: March 19, 1997  相似文献   

13.
微波酸溶消解方法是测定固体废物中金属元素最主要的前处理方法,消解时使用不同的酸体系对测定结果有较大的影响。本文以国家土壤标准样品、固体废物标准样品和固体废物实际样品为材料,比较了在硝酸-盐酸、硝酸-氢氟酸、硝酸-盐酸-双氧水、硝酸-盐酸-氢氟酸-双氧水4种酸体系下,16种金属元素测定结果的差异以及在硝酸-盐酸和硝酸-盐酸-氢氟酸-双氧水酸体系下各元素的精密度和准确度。研究表明:一些土壤基体中加入氢氟酸能使Mo和Sb的回收率提高40%左右,固体废物样品中只有Sb的回收率能提高33%~50%。对于含氢氟酸的酸消解体系,改变硝酸和盐酸的比例,其测定结果没有明显差异;对于元素含量相差悬殊的铬渣样品,由于空间电荷效应,高浓度的Cr对V的测定有抑制作用。从方法的准确度和精密度来看,硝酸-氢氟酸-盐酸-双氧水的消解效果最好。  相似文献   

14.
The Hopewell Furnace National Historic Site in southeastern Pennsylvania, which features an Fe smelter that was operational in the 18th and 19th centuries, is dominated by three slag piles. Pile 1 slag, from the Hopewell Furnace, and pile 2 slag, likely from the nearby Cornwall Furnace, were both produced in cold-blast charcoal-fired smelters. In contrast, pile 3 slag was produced in an anthracite furnace. Ore samples from the nearby Jones and Hopewell mines that fed the smelter are mainly magnetite-rich with some sulfides (pyrite, chalcopyrite, sphalerite) and accessory silicates (quartz, garnet, feldspar, and clay minerals). Slag piles 1 and 2 are similar mineralogically containing predominantly skeletal and dendritic aluminian diopside and augite, skeletal forsteritic olivine, glass, rounded blebs of metallic Fe, and exotic quartz. Olivine is a major phase in all samples from pile 2, whereas it occurs in only a few samples from pile 1. Samples of the <2 mm-size fraction of surface composite slag material or crushed slag from at depth in piles 1 and 2 are mineralogically similar to the large surface slag fragments from those piles with the addition of phases such as feldspars, Fe oxides, and clay minerals that are either secondary weathering products or entrained from the underlying bedrock. Pile 3 slag contains mostly skeletal forsteritic olivine and Ti-bearing aluminian diopside, dendritic or fine-grained subhedral melilite, glass, euhedral spinel, metallic Fe, alabandite–oldhamite solid solution, as well as a sparse Ti carbonitride phase. The bulk chemistry of the slag is dominated by Al2O3 (8.5–16.2 wt.%), CaO (8.2–26.2 wt.%), MgO (4.2–24.7 wt.%), and SiO2 (36.4–59.8 wt.%), constituting between 81% and 97% of the mass of the samples. Piles 1 and 2 are chemically similar; pile 1 slag overall contains the highest Fe2O3, K2O and MnO, and the lowest MgO concentrations. Pile 3 slag is high in Al2O3, CaO and S, and low in Fe2O3, K2O and SiO2 compared to the other piles. In general, piles 1 and 2 are chemically similar to each other, whereas pile 3 is distinct – a conclusion that reflects their mineralogy. The similarities and differences among piles in terms of mineralogy and major element chemistry result from the different smelting conditions under which the slag formed and include the fuel source, the composition of the ore and flux, the type of blast (cold versus hot), which affects the furnace temperature, and other beneficiation methods.  相似文献   

15.
In this study, the release of elements and in particular U from five Austrian orthogneiss and granite samples into a CO2-bearing solution was investigated to describe the initial phase (24 h) of leaching focusing on the impact of ferrous (hydro)oxide formation. Experiments were conducted at ambient temperature by flushing CO2:N2 gas through the reactive solution (pHinitial?~?4.3) at a liquid:solid ratio of 10:1 with and without a reducing agent. The chemical evolution of the leaching solution was dominated by incongruent dissolution of silicates showing a parabolic kinetic behavior due to protective surface formation most likely caused by precipitation of amorphous FeIII/Al hydroxides. However, the relative distribution of Ca, Mg and Sr in the leaching solution excellently traced the individual bulk rock composition. The mobilization of U was highly prevented under oxidizing conditions by sorption onto ferrous (hydro)oxides, which were precipitating through ongoing silicate leaching. Therefore, the leaching behavior of individual U-bearing minerals was less relevant for U release. At reducing conditions, the above elements were accumulated in the solution, although an oversaturation regarding UIVO2 was calculated. This indicates its inhibited formation within the experimental run time. The composition of experimental leaching solutions did not reflect analyzed groundwater compositions from investigated local rock-type aquifers indicating that reaction rate constants of siliceous rocks significantly differ between values found in nature and in the laboratory. Change in active mineral surface areas with ongoing weathering, accumulation of secondary precipitates, leached layer formation and given reaction time are key factors for distinct elemental release.  相似文献   

16.
矿渣磷酸镁水泥的力学性能和水化机理   总被引：1，自引：0，他引：1  
以高炉矿渣作为磷酸镁水泥(MPC)的活性混合材料,研究了MPC的凝固时间、力学性能、物相组成和显微结构,并探讨了矿渣MPC的作用机理。实验固定磷镁比为25%,硼镁比为7.5%,矿渣掺量分别为磷镁总质量的0%、10%、20%、30%和40%。结果表明,矿渣参与了水化反应并提高了MPC的胶凝性能,随着矿渣掺量增大,矿渣MPC的抗压强度提高,但矿渣水化产生的膨胀应力会破坏MPC的内部结构,因此其抗折强度随矿渣掺量增大而降低。矿渣MPC的主要水化产物为六水合磷酸镁铵(MgNH4PO4.6H2O),矿渣的掺入使凝胶相增加,并有部分Ca2+进入MgNH4PO4.6H2O晶格,使水化产物的形貌、大小发生变化。样品中剩余较多死烧镁和矿渣颗粒,可起骨料作用。  相似文献   

17.
A thermochemical data base for phases in the system Fe-Mg-Si-O at high pressures up to 300 kbar is established by supplementing the available calorimetric data with data calculated from experimental high pressure synthesis studies. Phases included in the data base are the SiO2 polymorphs, rock salt solid solutions (Fe-Mg-O), Fe2O3, Fe3O4, (Mg, Fe)2SiO4 olivine, spinel, modified spinel and (Mg, Fe)SiO3 perovskite and pyroxene. Phases not included are the MgSiO3-ilmenite and -garnet. Fe-Mg solution properties of olivine, spinel, perovskite and wustite (rock salt) are estimated. The wüstite solid solution has been modeled as a nonideal solution of three end members; FeO, FeO1.5 and MgO. The new data base is made consistent with most of the available information on high pressure phase studies. The data base is useful in generating phase diagrams of various different compositions for the purpose of planning new experiments and analysing existing phase synthesis data.  相似文献   

18.
Detailed phase relations have been determined within the systems Fe2O3-MgO-TiO2 and FeO-MgO-TiO2. Experiments were performed over the temperature interval 1173–1473 K by equilibrating pelletized, fine-grained oxide mixtures in either inert calcia-stabilized zirconia pots (Fe2O3-MgO-TiO2 system) or evacuated silica tubes (FeO-MgO-TiO2 system). Equilibrium phase assemblages were determined by combined optical microscope, X-ray diffraction and EMP examination. Phase relations in the Fe2O3-MgO-TiO2 ternary are dominated by the instability of the M2O3 solid solution relative to the phase assemblage M3O4 + M3O5. A miscibility gap along the M2O3 binary also gives rise to two, 3-phase fields (α-M2O3 + M3O5 + M3O4 and α′-M2O3 + M3O5 + M3O4) separated by the M3O4 + M3O5 phase field. Phase relations in the FeO-MgO-TiO2 ternary were divided into two sub-systems. For the FeTiO3-MgTiO3-TiO2 sub-ternary, there is complete solid solution along the M2O3 and M3O5 binary joins at high temperature. At low temperatures (T < 1373 K) the M3O5 pseudobrookite solid solution decomposes to M2O3 + TiO2. Increasing the concentration of MgO in M3O5 phase results in a decrease in the temperature at which M3O5 becomes unstable and compositional tie lines linking M2O3 and TiO2 fan out, before the appearance of a three-phase region where M2O3, M3O5, and TiO2 coexist. Within the expanded FeO-MgO-TiO2 system, at temperatures above ∼1273 K there is a continuous solid solution along the M3O4 binary. At low temperatures (T < 1273 K) the Mg2TiO4 end-member breaks down to MgO and MgTiO3. The M3O4 phase shows significant non-stoichiometry, down to at least 1173 K. Fe2+-Mg partitioning data were obtained for coexisting M2O3-M3O5 and M2O3-M3O4 pairs in the FeO-MgO-TiO2 ternary. Assuming a regular solution mixing model for all phases, the M2O3 and M3O4 solid solutions were both found to exhibit moderate positive deviations from ideality (∼2600 J/mol), whereas the data for the M3O5 binary suggest close to ideal behaviour. Received: 22 May 1998 / Accepted: 3 November 1998  相似文献   

19.
The aim of this research was to evaluate the feasibility of using the vitrification process as an alternative solution to the disposal of a coal fly ash and metallurgical slags in landfills. The starting wastes were characterised in terms of chemical, granulometric, mineralogical, and microstructural analysis. A selected batch composition composed by 58.5% fly ash, 31.5% metallurgical slag and 10.0 Na2O% (wt%) was melted at 1450 °C and poured to obtain monolithic glass samples. The environmental behaviour of the starting wastes and the resulting glass was evaluated by standard leaching tests, which shows that vitrification leads to a stabilisation process in which the inorganic components of the wastes are immobilised throughout their incorporation into the glass structure. Moreover, vitrification transforms those hazardous wastes into a new non-hazardous glass. A preliminary study shows that the new glass is suitable for developing glass–ceramic tiles appropriate for floor pavement and wall covering.  相似文献   

20.
Stabilities of hexagonal new aluminous (NAL) phase and Ca-ferrite-type (CF) phase were investigated on the join NaAlSiO4-MgAl2O4 in a pressure range from 23 to 58 GPa at approximately constant temperature of 1,850 K, on the basis of in situ synchrotron X-ray diffraction measurements in a laser-heated diamond-anvil cell. The results show that NAL is formed as a single phase up to 34 GPa, NAL + CF between 34 and 43 GPa, and only CF at higher pressures in 40%NaAlSiO4-60%MgAl2O4 bulk composition. On the other hand, both NAL and CF coexist below 38 and 36 GPa, and only CF was obtained at higher pressures in 60%NaAlSiO4-40%MgAl2O4 and 20%NaAlSiO4-80%MgAl2O4 composition, respectively. These results indicate that NAL appears only up to 46 GPa at 1,850 K, and CF forms continuous solid solution at higher pressures on the join NaAlSiO4-MgAl2O4. NAL has limited stability in subducted mid-oceanic ridge basalt crust in the Earth’s lower mantle and undergoes a phase transition to CF in deeper levels.  相似文献   

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