Leaching characteristics of bottom ash from thermal power plants

The disposal of coal ash from thermal power plants in India is a challenging task. The objective of the present study was to investigate the leaching characteristics of the bottom ash disposed in ash pond of thermal power plants. A series of leaching experiments have been performed to analyze the tracing elements of metal at different liquid-to-solid ratios (L/S). L/S ratio varies from 20:1 to 80:1. From the experiment, it is observed that the elements Mn, Mg, Cr, Zn, and Cu are present in major concentrations while elements viz. Pb, Fe, Zn, and Co are present in minor concentrations. It is also observed that the leaching characteristics of the bottom ash are affected by the pH of extraction solution and L/S ratio. The minimum leachability of the solution was determined using an ASTM method, whereas the maximum leachability was determined using a TCLP method.     

Characterization of heavy metal trace elements in the fly ash from a thermal power plant

The disposal of fly ash in the thermal power plant is a challenging task. With the increase in the demand of the coal as fuel in thermal power plants, combustion products, such as coal ash, become a serious environmental problem due to their leaching characteristics. The objective of the present study was to investigate the leaching characteristics of the fly ash disposed in ash pond of thermal power plants. A series of leaching tests have been performed with different liquid-to-solid (L/S) ratio. The L/S ratio varies from 20:1 to 60:1. It is observed that the elements, such as Mn, Mg, Cr, Zn, Ni, Pb, Fe, and Cu, are most abundant elements, while Mo and Co are the least abundant elements. It is also observed that the leaching characteristics of the fly ash are affected by the pH of extraction solution and liquid-to-solid (L/S) ratio.     

The Bulalo geothermal field, Philippines: Reservoir characteristics and response to production

The Bulalo geothermal field has been operating since 1979, and currently has 330 MWe of installed capacity. The field is associated with a 0.5 Ma dacite dome on the southeastern flank of the Late Pliocene to Quaternary Mt. Makiling stratovolcano. The reservoir occurs within pre-Makiling andesite flows and pyroclastic rocks capped by the volcanic products of Mt. Makiling. Initially, the reservoir was liquid-dominated with a two-phase zone overlying the neutral-pH liquid. Exploitation has resulted in an enlargement of the two-phase zone, return to the reservoir of separated waste liquid that has been injected, scaling in the wellbores and rock formation, and influx of cooler groundwaters. Return of injected waters to the reservoir and scaling have been the major reservoir management concerns. These have been mitigated effectively by relocating injection wells farther away from the production area and by dissolving scale from wells with an acid treatment.     

Recovery of zinc and manganese from alkaline and zinc-carbon spent batteries

This paper concerns the recovery of zinc and manganese from alkaline and zinc-carbon spent batteries. The metals were dissolved by a reductive-acid leaching with sulphuric acid in the presence of oxalic acid as reductant. Leaching tests were realised according to a full factorial design, then simple regression equations for Mn, Zn and Fe extraction were determined from the experimental data as a function of pulp density, sulphuric acid concentration, temperature and oxalic acid concentration. The main effects and interactions were investigated by the analysis of variance (ANOVA). This analysis evidenced the best operating conditions of the reductive acid leaching: 70% of manganese and 100% of zinc were extracted after 5 h, at 80 °C with 20% of pulp density, 1.8 M sulphuric acid concentration and 59.4 g L⁻¹ of oxalic acid. Both manganese and zinc extraction yields higher than 96% were obtained by using two sequential leaching steps.     

Investigation of Cu leaching from municipal solid waste incinerator bottom ash with a comprehensive approach

Municipal solid waste incinerator (MSWI) bottom ash is often reused as a secondary construction material. This study used a comprehensive approach to characterize the leaching behavior of copper (Cu) from the MSWI bottom ash. The batch titration procedure was used to determine the acid neutralizing capacity and Cu leaching as a function of pH. The sequential extraction procedure (SEP) was adopted to analyze the speciation of Cu in the MSWI bottom ash. The metal speciation equilibrium model for surface and ground water (Visual MINTEQ) was used to evaluate the equilibrium of the leachates with the relative minerals, and to determine the speciation of the aqueous Cu in the leachates. Based on the multi-analysis of the results, Cu would be significantly released from the MSWI bottom ash when it is acidic. The Cu leaching pattern was not only affected by dissolved organic carbon, it was also limited by its speciation in the MSWI bottom ash. Furthermore, almost 100% of the aqueous Cu in the leachate was bound to organic matter in basic and neutral conditions, but mostly existed as Cu²⁺ in an acidic condition. These findings provide an important insight into predicting the leaching behavior of Cu from the MSWI bottom ash, as well as its impact on the environment.     

Characterization of used alkaline batteries powder and analysis of zinc recovery by acid leaching

This paper discusses the spent alkaline batteries characterization and leaching stage experiments results with sulfuric acid as leachant, as part of a complex system, involving purification and electrolytic stages, aiming the Zn recovery. After dismantling batteries by mineral processing techniques, the black powder sample produced was submitted to X-ray diffraction and atomic absorption spectrophotometry in order to identify its composition. Batch laboratory experiments were conducted for acid leaching procedure to determine appropriate leaching conditions from the viewpoint of maximum zinc extraction. On these tests an amount of dry powder was added to sulfuric acid at different conditions and after leaching and filtration, the aqueous solutions were submitted to atomic absorption spectrophotometry analysis to verify the Zn content.     

Physiochemical and leaching characteristics of fly and bottom ash

Bottom ash and fly ash are the by-products of coal in thermal power plants. They are the combustion wastes and contain many elements that may harmful to the environment. The present study investigates the physiochemical, mineral, and leaching characteristics of an Indian coal ash (bottom ash and fly ash). From the characterization of bottom ash and fly ash, it is found that the ash samples are enriched predominantly in silica, alumina, and iron oxides. A series of leaching experiments have been performed to analyze the tracing elements of metal at the different liquid to solid ratio (L/S). The L/S varies from 20:1 to 80:1. From the leaching results of the fly ash and bottom ash data, it is observed that the tracing elements of Mn, Mg, Cr, Zn, Ni, Pb, Fe, and Cu are the most abundant elements, while Hg, Mo, and Co are the least abundant elements.     

苏州河重金属污染特征及风险评价

沿苏州河水流方向设置 13个采样点进行3次采样,分析苏州河中As、Cd、Cr、Cu、Pb、Zn的分布,采用主成因分析和冗余分析,评价了苏州河水相及沉积相中微生物的稳定性以及重金属对微生物的影响。通过计算健康风险指数、内罗梅指数、地累积指数和重金属分配系数,评价了地表水中重金属对暴露人群存在的风险以及流域的生态危害。结果表明,水相中主要为Zn、Pb、Cu,沉积相中Zn质量浓度最高;研究流域的物种丰富度变化甚微;As和Cr对成人和儿童均存在不同程度的致癌风险,Cd的潜在生态危害最大。     

空煤比对煤气化过程中痕量元素迁移规律的影响

采用氢化物发生器和原子荧光光谱法联用(HG-AFS)和电感耦合等离子发射光谱法(ICP-AES),测定了常压流化床煤气化产物中As、Cd、Co、Cr、Cu、Mn、Mg、Ni、Hg、Pb、V、Se、Sr、Zn 14种痕量元素含量,分析了空煤比对痕量元素在气化产物中迁移规律的影响。结果表明：在旋风高温焦中,CA、Ni富集,As、Co、Cu、V、Se、Hg耗散;空煤比对Mn、Sr、Hg、Se、As影响不大;随着空煤比增加,Pb、Zn、Cu、Co、Ni的相时富集系数(REs)略微增加,Cd、Mg的REs减少;V、Cr在低空煤比条件下有较高的REs。在布袋低温焦中,Cd、As、Cu、Cr、Ni、Pb、Zn富集,Co、V、Se、Hg耗散;随着空煤比增加,Pb、Cu、Ni的REs增加;Cd、As、Cr、Se的REs减少。底渣中的Mn和Sr相对于高、低温焦而言有轻微的富集。随着空煤比增加,Cu、Zn在煤气中含量增加,Cr、Co、As、Hg在煤气中含量减小。     

Influence of preparation methods and Zr and Y promoters on Cu/ZnO catalysts used for methanol steam reforming

Binary Cu/ZnO catalysts were prepared using three different methods (coprecipitation, sequential precipitation and homogeneous precipitation) and tested in a methanol steam reforming reaction. Zirconium and yttrium were tested as promoters, and their effects were evaluated in the same reaction. The studied preparation methods influenced the surface area of the Cu-based catalysts and consequently their catalytic activity; however, we verified that surface area was not the only factor influencing activity. Different structural changes in the aurichalcite precursor resulted from the different preparation methods used, and these differences were also observed in the reduced catalysts. An expansion of the Cu lattice with an increase in microstrain were identified and attributed to the formation of a Cu–Zn alloy. Based on the correlation found between these structural changes and the catalytic activity, the Cu–Zn alloy was proposed as active site. We concluded that the preparation methods used influenced Cu dispersion and overall catalyst structure, and Cu–Zn alloy formation resulted from the incorporation of Zn atoms into the Cu lattice. This influence was more pronounced in the catalysts prepared by homogeneous precipitation and coprecipitation. The yttrium promoter did not provide textural or structural advantages. In contrast, the incorporation of Zr promoted both greater Cu dispersion and structural changes in the Cu lattice.     

Elemental composition of biogas residues: Variability and alteration during anaerobic digestion

Biogas production and the amount of thereby incurred digestates increased remarkably in the last decade. Digestates should be used as soil fertilizers to close nutrient cycles. However, knowledge about the elemental composition of digestates from biogas production and element losses or accumulations during fermentation process is insufficient so far. Intending to enlarge the database for the elemental composition of digestates and to investigate element in- and outputs of biogas fermenters, we measured the concentrations of C, N, P, K, S, Ca, Mg, Fe, Mn, Zn, Cu, Pb, Cd, Ni, Mo and Se of digestates and feedstock (ingestates) of four full-scale biogas plants in Germany monthly over a one year period. Ingestates were sewage sludge, fat and mash (SEW1), sewage sludge and fat (SEW2), pig slurry, treacle and food residues (SL) and maize silage (M). We developed a statistical method to calculate the number of required sampling dates which have to be integrated for the calculation of reliable element budgets between ingestates and digestates for the case when information about the amount and composition of the produced biogas is not available. Our results suggest that two (SEW2), five (SEW1, M) and 10 (SL) sampling dates had to be integrated for reliable balances. All fermenters revealed losses of N, most likely due to volatilization of NH₃. Losses of S (probably H₂S), Mg (precipitation of struvite), Cd and Zn (precipitation of sulfides) could be detected in some cases. Iron and Mn accumulations can be attributed to attrition of the stirrer.     

Electrocatalysis property of CuZn electrode with Pt and Ru decoration

Electrocatalysis properties strongly depend on the interaction of metallic particles and this interaction enables to change the electronic structure of alloys which enhances the catalytic activity. This property is the key factor in the developing of cost-effective and efficient Hydrogen Evolution Reaction (HER) electrocatalysts for sustainable hydrogen production. In this study, novel electrocatalysts which are decorated with Pt and Ru have been developed for HER electrocatalysis. Microscopic analysis such as scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD) and atomic force microscopy (AFM) are performed to determine the morphological and compositional structures. Electrocatalysis properties are evaluated by cathodic current-potential curves, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) in 1.0 M KOH solution. Chronoamperometry (CA) and cycle tests are used for stability/durability of electrocatalysts. Results show that a small onset potential of the porous Cu/Ni/CuZn–Pt is obtained for HER. Exchange current density and polarization resistance are found to be 5.39 mA cm^?2 and 2.0 Ω cm² at overpotential of ?100 mV for porous Cu/Ni/CuZn–Pt, respectively, indicating that Cu/Ni/CuZn–Pt is higher electrocatalytic properties than the others. Moreover, very low overpotentials at 10 and 40 mA cm^?2 are obtained on porous Cu/Ni/CuZn–Pt compared with porous Cu/Ni/CuZn–Ru and Cu/Ni/CuZn. Porous Cu/Ni/CuZn–Pt also displays excellent stability/durability in test solution. The remarkable electrocatalysis properties of porous Cu/Ni/CuZn–Pt can be explained due to high porous structure, leaching of Zn from the deposit, intrinsic activity of Pt as well as changing in the electronic structure. It should be considered that porous Cu/Ni/CuZn–Pt is of high corrosion resistance in test solution for 120 h, which makes it good candidate for HER.     

Distributions of environmentally hazardous elements in the Tertiary oil shale deposits from NW Anatolia,Turkey: A statistical analysis

The environmentally hazardous element concentrations (As, Cd, Cr, Cu, Hg, Mn, Pb, S, and Zn) and element–organic matter relations of the oil shale deposits in six different fields in NW Anatolia, Turkey, were investigated and the characteristics of fields were compared. The enrichment factor (EF) for most of the trace elements in the studied oil shales generally show enrichment patterns for all the fields. Only Cr, Hg, and Pb for oil shale samples from the Bahçecik field samples and Hg for oil shale samples from the Gölpazar? field samples are depleted. Arsenic in the Bahçecik field samples and Hg in the Himmeto?lu field samples are neither depleted nor enriched. The lowest and highest element enrichments in these fields are determined to be Hg and S, respectively. In general, all elements have high concentrations in the Beypazar? and Seyitömer fields and low concentrations in the Himmeto?lu, Bahçecik, and Gölpazar? (except for As) fields. A positive correlation at significance level of p ≤ 0.05 was observed for total organic carbon content with Cd in four of the fields, with Cu and S in two fields and with Cr, Mn, and Zn in only one field.     

Effects of synthesis methods on performance of CuZn/MCM-41 catalysts in methanol steam reforming

CuZn-based catalysts are active in production of hydrogen by methanol steam reforming. However, there is a need to have further insight on their physico-chemical properties to improve selectivity to hydrogen. Therefore, a series of CuZn/MCM-41 catalysts was synthesized by four different routes; one pot hydrothermal synthesis (OPMCM), co-impregnation (COMCM), serial impregnation (SRMCM) and copper impregnated on Zn-MCM-41 (ZNMCM). Samples of catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), inductively coupled plasma (ICP) emission spectrometry, Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). XRD revealed disruption in the ordered pore network typical in MCM-41 for all catalysts synthesized and also showed that the one pot synthesis catalyst had wide spread dispersion of Cu and Zn. SEM micrographs captured irregularly shaped particles of different sizes. While XPS showed that different Cu and Zn species were formed within the catalyst matrix. XPS also confirmed that there was wide spread dispersion and interaction of Cu and Zn with MCM-41 matrix in the OPMCM catalyst. COMCM and OPMCM demonstrated the highest activity with 88 and 65% methanol conversion with corresponding H₂ selectivity of 91 and 86% respectively. They are better than SRMCM and ZNMCM which had average H₂ selectivity of 19% and 31% respectively. CO selectivity was less than 1.8% for the COMCM and OPMCM catalysts. While SRMCM and ZNMCM had CO selectivity's as high as 8.9% and 7.2% respectively. The data generated shows that catalytic activity is largely affected by the nature of Cu species within the catalyst matrix.     

Recent progress in scaling up highly efficient Zn(S,O)/Cu-chalcopyrite thin film solar cells and modules at HZB

In the present contribution we report on recent work covering Zn(S,O) buffer as heterojunction partner layer applied to pilot line low-gap Cu(In,Ga)(SSe)₂ (CIGSSe, E_g = 1.03 eV) and production scale wide-gap CuInS₂ (CIS, E_g = 1.54 eV). We highlight the crucial role that the processing control of the Zn(S,O) plays for the fabrication of Cu-chalcopyrite solar cells and modules. The analytical information obtained by the correlation with state-of-the art high resolution Transmission electron microscopy, X-ray photoemission and Auger spectroscopy (XPS and XAES) as well as L-edge XAS are discussed. A large number of efficient laboratory-scale solar cells and monolithically interconnected prototype CIGSSe and CIS modules are produced. The efficiencies are comparable to the CdS base line references or even higher. The electrical, electronic properties and the emerging phenomena in Cd-free devices such as light soaking are discussed.     

Mass Balance of Major and Trace Elements in a Coal-Fired Power Plant

The Soma power plant in western Turkey consists of six 165-MW units (B1–4 and B5–6), of which the first four units (B1–4) burn Early-Middle Miocene feed coals from the lower seam in central mines (southern Soma village), and later, two units (B5–6) use Early-Middle Miocene and Upper Miocene feed coals from the lower and upper seams in Denis mines (northern Soma village). A total of 48 samples, feed coals (FCs), fly ashes (FAs) and bottom ashes (BAs), which were systematically collected once a week over an eight-week period from both group boiler units, B1–4 with 660 MW and B5–6 with 330 MW capacity from Soma power plant, have been evaluated for major and trace elements (Al, Ca, Fe, K, Mg, Mn, Na, Ti, S, As, B, Ba, Be, Bi, Cd, Co, Cr, Cu, Cs, Ga, Ge, Hf, Hg, Li, Mo, Nb, Ni, P, Pb, Rb, Sb, Sc, Se, Sn, Sr, Ta, Th, Tl, U, V, Y, Zn, Zr, and REEs) to get information on behavior during coal combustion. This study indicates that some elements such as Hg, Bi, Cd, As, Pb, Ge, Tl, Sn, Zn, Sb, B show enrichments in FAs relative to the BAs in both group boiler units. In addition to these, Cs, Lu, Tm, and Ga in Units B1–4 and S in Units B5–6 also have enrichments in FAs. Elements showing enrichments in BAs in both group boiler units are Ta, Mn, Nb. In addition to these, Se, Ca, Mg, Na, Fe in Units B1–4 and Cu in Units B5–6 also have enrichments in BAs. The remaining elements investigated in this study have no clear segregation between FAs and BAs. Mass balance calculations with the two methods show that some elements, S, Ta, Hg, Se, Zn, Na, Ca in Units B1–4, and Hg, S, Ta, Se, P in Units B5–6, have volatile behavior during coal combustion in the Soma power plant. This study also implies that some elements, Sb and Tb in Units B1–4 and Sb in Units B5–6, have relatively high retention effects in the combustion residues from the Soma power plant.     

部分痕量元素在油页岩中的富集特性及挥发行为

选取吉林桦甸、广东茂名、吉林汪清、辽宁大平4个矿区的油页岩为研究对象,用电感耦合等离子发射光谱技术和原子荧光技术对油页岩中14种痕量元素的含量进行了测定.结果表明,油页岩中的痕量元素含量明显高于中国煤中对应元素的平均含量,特别是Mn、P、Ti.与国外煤相比,痕量元素As、Mn、Zn、V、Cu和Cr在我国桦甸油页岩中表现出高含量特性.与地壳丰度相比,油页岩中痕量元素具有比较明显的富集亲硫元素、贫亲铁和亲石元素的特征.同时,研究了燃烧温度对油页岩中痕量元素的挥发行为的影响.结果表明:所研究元素的挥发性均随燃烧温度的升高而增大,其中As、Pb和Zn表现出较强的挥发行为,茂名油页岩中的痕量元素在燃烧过程中表现出较高的稳定性.     

Analysis of a hydrometallurgical route to recover base metals from spent rechargeable batteries by liquid–liquid extraction with Cyanex 272

A hydrometallurgical route is proposed to recover zinc and manganese from spent alkaline batteries in order to separate base metals such as nickel, copper, aluminium, cadmium, lithium and cobalt which constitute the main metallic species of spent NiCd, NiMH and Li-ion rechargeable batteries. The route comprises the following main steps: (1) sorting batteries by type, (2) battery dismantling to separate the spent battery dust from plastic, iron scrap and paper, (3) leaching of the dust with sulphuric acid and (4) metal separation by a liquid–liquid extraction using Cyanex 272 (bis-2,4,4-trimethylpentyl phosphinic acid) as extractant. The metal content of NiCd, NiMH and Li-ion batteries from three distinct manufacturers has been evaluated. A factorial design of experiments was used to investigate the leaching step using operational variables such as temperature, H₂SO₄ concentration, S/L ratio and H₂O₂ concentration. Analysis of metal separation by the liquid–liquid extraction with Cyanex 272 identified a pH_1/2 2.5–3.0 for zinc and aluminium, pH_1/2 4.0–4.5 for manganese, cadmium, copper and cobalt, pH_1/2 6.5 for nickel and pH_1/2 8.0 for lithium. These results indicate that batteries must be previously sorted by type and treated separately. In addition, data fitting to an equilibrium model proposed for the reactive test system by the European Federation of Chemical Engineering (EFChE) have indicated that MR₂(RH)₂ and MR₂ complexes (where M = Zn, Mn, Co, Cd and Cu) co-exist in the organic phase with Cyanex 272 depending on the loading conditions. The route has been found technically viable to separate the main metallic species of all batteries considered in this study.     

XPS, TEM and NRA investigations of Zn(Se,OH)/Zn(OH)2 films on Cu(In,Ga)(S,Se)2 substrates for highly efficient solar cells

Structural and compositional properties of Zn(Se,OH)/Zn(OH)₂ buffer layers deposited by chemical bath deposition(CBD) on Cu(In,Ga)(S,Se)₂ (CIGSS) absorbers are investigated. Due to the aqueous nature of the CBD process, oxygen and hydrogen were incorporated into the ‘ZnSe’ buffer layer mainly in the form of Zn(OH)₂ as is shown by X-ray photoelectron spectroscopy and nuclear reaction analysis (NRA) measurements leading to the nomenclature ‘Zn(Se,OH)’. Prior to the deposition of Zn(Se,OH), a zinc treatment of the absorber was performed. During that treatment a layer mainly consisting of Zn(OH)₂ grew to a thickness of several nanometer. The whole buffer layer therefore consists of a Zn(Se,OH)/Zn(OH)₂ structure on CIGSS. Part of the Zn(OH)₂ in both layers (i.e. the Zn(Se,OH) and the Zn(OH)₂ layer) might be converted into ZnO during measurements or storage. Scanning electron microscopy pictures showed that a complete coverage of the absorber with the buffer layer was achieved. Transmission electron microscopy revealed the different regions of the buffer layer: An amorphous area (possibly Zn(OH)₂) and a partly nanocrystalline area, where lattice planes of ZnSe could be identified. Solar cell efficiencies of ZnO/Zn(Se,OH)/Zn(OH)₂/CIGSS devices exceed 14% (total area).     

Analysis of oil content in drying petroleum sludge of tank bottom

In this paper, the oil content and corresponding components were analyzed in the samples of drying tank bottom petroleum sludges from Sinochem Xingzhong Oil Staging (Zhoushan) Co. Ltd. The composition of the oily sludge was determined by using organic solvent extraction gravimetric method (organic solvent is selected as petroleum ether, benzene, and toluene, respectively) and calcining-gravimetric method. It was found that measurement errors by using petroleum ether extraction gravimetric method and direct weight-loss method were bigger than those errors by using benzene or toluene extraction gravimetric method. During the measurement, it was also found that toluene should be recommended instead of benzene due to its lower toxicity. The measurement results show that water content, oil content and solid content by mass in the sludge were 9.8%, 25.8% (the asphaltene is accounted for 22.7% of the oil content in the sludge) and 64.4%, respectively. Also, chemical composition of the solids in the sludge was analyzed by using organic solvent extraction gravimetric method and XRD structure analysis method, then it was shown that Fe(OH)O·H₂O is the main solid component in the sludge.