Leaching

In order to develop an advanced polymer based package technology to obtain small and flexible medical implants, diffusion barriers are essential to protect electronic chips and components for corrosion caused by leaching of body fluids. These barriers need also to stop diffusion of harmful products such as Cu from the device into the body. Furthermore, the barrier layers need to be biocompatible, biostable, compatible with all process steps of the package fabrication and sterilization. Parylene is under investigation as candidate barrier material. WVTR tests are performed to characterize diffusion of water through the Parylene layer. Adhesion tests of Parylene-C on various substrates are performed and if needed adhesion promotion treatments are optimized, since good adhesion is crucial for corrosion prevention. Dedicated corrosion tests have shown that 5um Parylene-C is protecting Cu lines for corrosion at 70°C for at least 170 hours, more testing needs to be performed. Cell culture test have shown that Cu diffusion is not sufficiently stopped by 5um Parylene-C or-N, a thicker Parylene layer or a combination with other barriers might be essential. Also dedicated cell culture protocols with non-adherent cell types will have to be developed to perform reliable tests on these hydrophobic and cytophobic barrier layers.

The sequential extraction test, known as a BCR procedure, was used to assess a leachability of heavy metals (Zn, Cd, Pb, Cu) from the metallo-organic sorbent-iron humate-loaded with these metals. The sequential test allowed to discriminate between various fractions of heavy metals, namely the acid-extractable fraction, the fraction bound to Fe oxides, and the fraction bound to organic matter. It was proven that the heavy metals are bound mainly to Fe oxides and organic matter, and thus they may be relatively hardly liberated into the environment. The BCR sequential extraction test exhibited a very good repeatability, when it was applied to the loaded sorbent-relative standard deviations were typically lower than 10%.

Separation of the main metals contained in spent Li-ion batteries has been investigated using a treatment route consisting of the following steps: manual dismantling, acid leaching, precipitation with NH 4 OH and liquid-liquid extraction using Cyanex 272 [bis(2,4,4-trimethylpentyl) phosphinic acid] as the extractant agent. Aluminium, cobalt, lead and lithium were the main metal species identified in the residue. Lead was found solely in the anode of the battery, so this metal can be separated manually from the other metal species, which were found to predominate in the cathode. The following operational variables were investigated in the acid leaching step: temperature, solid/liquid ratio, H 2 SO 4 concentration and H 2 O 2 concentration which was used as the oxidizing agent. Around 55% of aluminium, 80% of cobalt and 95% of lithium were leached from the cathode when leaching solutions with H 2 O 2 were carried out. In the precipitation step, NH 4 OH was added to the leach liquor to raise the pH and aluminium was partially separated from cobalt and lithium at pH 5. After filtration, the aqueous solution was submitted to a purification step by liquid-liquid extraction with Cyanex 272 and around 85% of cobalt was separated.

Soils from many industrial sites in southeastern USA are contaminated with As because of the application of herbicide containing As2O3. Among those contaminated sites, two industrial sites, FW and BH, which are currently active and of most serious environmental concerns, were selected to characterize the occurrence of As in the contaminated soils and to evaluate its environmental leachability. The soils are both sandy loams with varying mineralogical and organic matter contents. Microwave-assisted acid digestion (EPA method 3051) of the contaminated soils indicated As levels of up to 325 mg/kg and 900 mg/kg (dry weight basis) for FW and BH soils, respectively. However, bulk X-ray powder diffraction (XRD) analysis failed to find any detectable As-bearing phases in either of the studied soil samples. Most of the soil As was observed by scanning electron microscopy, coupled with energy dispersive X-ray spectroscopy (SEM/EDX), to be disseminated on the surfaces of fine-grained soil particles in close association with Al and Fe. A few As-bearing particles were detected in BH soil using electron microprobe analysis (EMPA). Synchrotron micro-XRD and X-ray absorption near-edge structure (XANES) analyses indicated that these As-rich particles were possibly phaunouxite, a mineral similar to calcium arsenate, which could have been formed by natural weathering after the application of As2O3. However, the scarcity of those particles eliminated them from playing any important role in Assequestration.Synthetic acid rain sequential batch leaching experiments showed distinct As leaching behaviors of the two studied soil samples: BH soil, which has the higher As content, showed a slow, steady release of As, while FW soil, with a lower As content, showed a much quicker release and lower overall retention of As upon leaching. Sequential chemical extraction experiments were carried out using a simplified 4-step sequential chemical extraction procedure (SCEP) previously developed to characterize the fractionation of As and better understand the different leaching behaviors of the two studied soils. It was shown that only about 50 percent of the total extractable As was removed by the first two extraction steps, which represented the most weakly bonded and readily available As for environmental leaching. Compared with eScholarship provides open access, scholarly publishing services to the University of California and delivers a dynamic research platform to scholars worldwide. the sequential leaching experiments, it was further indicated that only half of the As associated with phases extracted by the second SCEP step was mobilized by SPLP leaching. Although microwave-assisted acid digestion results showed similar Al and Fe contents in both soils, the sequential chemical extraction experiments indicated that BH soil has a much higher content of amorphous Al and Fe phases and that a comparably higher portion of soil As was associated with those materials. The experimental results suggest that remediation efforts for the contaminated sites can be directed towards enhancing the formation of more stable As-bearing compounds in the soils to reduce the environmental leachability of As.

This article reports responses of two different forest ecosystems to 9 years (1988-96) of chronic nitrogen (N) additions at the Harvard Forest, Petersham, Massachusetts. Ammonium nitrate (NH 4 NO 3 ) was applied to a pine plantation and a native deciduous broad-leaved (hardwood) forest in six equal monthly doses (May-September) at four rates: control (no fertilizer addition), low N (5 g N m -2 y -1 ), high N (15 g N m -2 y -1 ), and low N ϩ sulfur (5 g N m -2 y -1 plus 7.4 g S m -2 y -1 ). Measurements were made of net N mineralization, net nitrification, N retention, wood production, foliar N content and litter production, soil C and N content, and concentrations of dissolved organic carbon (DOC) and nitrogen (DON) in soil water. In the pine stand, nitrate losses were measured after the first year of additions (1989) in the high N plot and increased again in 1995 and 1996. The hardwood stand showed no significant increases in nitrate leaching until 1995 (high N only), with further increases in 1996. Overall N retention efficiency (percentage of added N retained) over the 9-year period was 97-100% in the control and low N plots of both stands, 96% in the hardwood high N plot, and 85% in the pine high N plot. Storage in aboveground biomass, fine roots, and soil extractable pools accounted for only 16-32% of the added N retained in the amended plots, suggesting that the one major unmeasured pool, soil organic matter, contains the remaining 68-84%. Short-term redistribution of 15 N tracer at natural abundance levels showed similar division between plant and soil pools. Direct measurements of changes in total soil C and N pools were inconclusive due to high variation in both stands. Woody biomass production increased in the hardwood high N plot but was significantly reduced in the pine high N plot, relative to controls. A drought-induced increase in foliar litterfall in the pine stand in 1995 is one possible factor leading to a measured increase in N mineralization, nitrification, and nitrate loss in the pine high N plot in 1996.

The aim of this study is to investigate the utility of adding chelating agent during hydrochloric acid leaching of low-grade scheelite concentrates, obtained from Uludağ, Bursa (Türkiye). Examined parameters were as follows; leaching conditions, selective precipitation of tungsten salt from the acidic leach solution in which tungsten exists as hetero-poly-tungstate, the optimum precipitation conditions, the possibility of obtaining pure and nano-sized tungsten salt. Chelating agent leaching of scheelite concentrates in acidic solutions involves fewer process steps as compared to the classical methods. Furthermore, this route enables production of pure WO3 under prevalent conditions and without generating any spent liquor. The optimum leaching conditions were found to be 80°C, 2 M HCl, 1/10 solid/liquid ratio, stirring speed of 900 min−1 and W/PO43− weight ratio of 7/1. A tungsten leaching efficiency of 98% was reached under these conditions. It was also possible to selectively precipitate a pure (over 99%) tungstate salt, within minutes, from the poly-tungstate solution at 25°C by adding a `chelate breaking agent' at a NH4+/WO3 weight ratio of ≥1/4.

pH is one of the key parameters that determines heavy metal mobility in soils, sediments and waste materials. In many respects leaching behaviour as reflected by the pH stat leaching tests provide a better means of assessing environmental impact than analysis of total elemental composition. This paper discusses the use of pH stat leaching tests as a tool to assess the potential mobilisation of trace metals from soils, sediments and waste materials. The possibilities of pH stat leaching tests are illustrated by means of different examples.

In this study, the strength development and lechability aspects of metal-contaminated soil treated with ordinary portland cement (OPC) were investigated. The soil was collected from a scrap metal yard within the outskirts of Kuala Lumpur, Malaysia. Metal composition analysis indicated that the predominant metals present in the soil were iron (42,194 mg/kg), aluminium (8874 mg/kg), zinc (690 mg/kg), lead (428 mg/kg), copper (107 mg/kg) and chromium (52 mg/kg). The contaminated soil was treated with OPC using cement-to-dry soil (C/Sd) ratios of 0.5, 1 and 2. The effectiveness of the treatment was evaluated by performing unconfined compressive strength (UCS) as well as crushed and whole block leaching (WBL) tests on the treated soil. The treatment results were compared to the solidified waste acceptance criteria which were compiled based on the regulatory waste disposal limit at a disposal site in the United Kingdom and the maximum concentration of contaminants for toxicity characteristic of solid wastes from United States Environmental Protection Agency. Results indicated that chemical stabilization of metal-contaminated soils using OPC was effective for prevention of metal leaching from both disintegrated samples subsequent to years of weathering (crushed block) and intact samples (whole block) into the environment. © 2005 Elsevier Ltd. All rights reserved.

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Cement stabilisation has been widely applied for the immobilisation of heavy metal ions before their disposal in landfills. This paper investigated the microstructure of cementitious wastes containing Pb, Cd, As, and Cr using an electron probe microanalyser and examined the implications of the microstructure on the leaching of the metal ions. From the microstructure analysis, it was proposed that Pb, As, and Cr ions were homogeneously dispersed in the calcium silicate hydrate (C-S-H) matrix by adsorption or precipitation with calcium or silicate compounds present in the cement. However, Cd formed discrete Cd(OH) 2 precipitates believed to be contained within the cement pores or adsorbed on the C-S-H matrix. The leaching of metals in the pH region of 6 to 8 decreased in the following order: Cr(VI)>Cd(II)>Pb(II) >As(V). This leaching trend was found to be influenced by the manner in which the metal ions were incorporated into the cement matrix. D

Cupels are generated by mines during the fire assaying of precious group metals. The cupels contain lead which is a known environmental hazard hence the need to recover it. This work illustrates how leaching and electrowinning processes can be combined to produce a hybrid lead recovery process. Bench scale tests were conducted for the hybrid leaching and electro winning process using Methane Sulfonic Acid (MSA) as a leaching solvent at a concentration of 200g MSA per litre of water. A glass electrowinning cell fitted with a 9cm × 4cm pure lead cathode and 9cm × 4cm graphite anode with inter electrode gap of 15cm and a magnetic stirrer bar was used. Lead laden cupels (containing 30g lead) were subjected to simultaneous leaching and electrowinning and lead recovery after a period of 80 minutes was found to be 98%. The hybrid process was found to require about 20% less solvent than that required for the convectional leaching process which requires multiple stages to reduce the concentr...

The eect of soaking, boiling and pressure cooking on the retention of folates in whole chickpeas (Cicer arietinum) and ®eld peas (Pisum sativum) was investigated. Pressure-cooking allowed signi®cantly higher (p<0.05) retention of folates compared to boiling in both the legumes. Retention of folates in chickpeas was greater than ®eld peas irrespective of the processing procedure used. Leaching into the cooking medium was identi®ed to be the major cause for losses of folates during soaking and cooking. Leaching losses were greater in ®eld peas compared to chickpeas.

For the determination of Cr(VI) concentrations with a potentiometric ion-selective electrode (ISE), ionophore-immobilized membranes were prepared by ultraviolet (UV)-induced graft polymerization followed by chemical treatment. Novel ionophores comprising various amine structures were immobilized onto poly(vinyl chloride) (PVC) matrixes, and these were examined to determine Cr(VI) selectively. Of the three ionophores examined in this study, the membranes with N,N,N,N-tetrakis(3-aminopropyl)-1,4-butanediamine (DABAm4) exhibited the highest Cr(VI) ion selectivity in both extraction and potentiometry experiments. The plasticizer in the membrane was optimized as 1.0 ml o-nitrophenyl octyl ether (NPOE)/g PVC to form diffusible channels. The potentiometric studies revealed that the performance of DABAm4immobilized PVC was equivalent to that of mobile ionophores in supported liquid membranes (SLMs). A reproducible response of Cr(VI) was attained within a response time of 1 s in the range of 2.16 × 10 −6 to 0.1 M, using the membrane prepared in this study. The selectivity for the Cr(VI) ion against the other interfering ions was compared reasonably between a solvent extraction and potentiometry. The long-term response of the Cr(VI) ISE showed slight deterioration over a continuous operation for 6 months, while the detection limit slightly decreased due to the leaching-out of the plasticizer. The ISE along with the DABAm4 immobilized membrane showed a higher Cr(VI) ion selectivity and more stable response under long-term usage than ISEs with typical SLMs.

By submitting this thesis electronically, I declare that the entirety of the work contained therein is my own, original work, that I am the sole author thereof (save to the extent explicitly otherwise stated), that reproduction and publication thereof by Stellenbosch University will not infringe any third party rights and that I have not previously in its entirety or in part submitted it for obtaining any qualification.

The Baccu Locci stream catchment (Sardinia, Italy) is affected by serious As contamination as a consequence of past mining. The presence of both point and widespread sources of contamination (waste-rock dumps and flotation tailings, respectively) strongly affects surface water chemistry, and produces high As concentrations (hundreds of mg l À1) in stream waters. Water chemistry of the Baccu Locci stream changes considerably over a distance of about 10 km as a consequence of various, locally concomitant, processes acting along the stream course: (1) mixing with metal-rich SO 4 waters; (2) dissolution/precipitation of metal-bearing phases; (3) mixing with HCO 3-dominated lake waters; (4) gypsum dissolution coupled with calcite precipitation; (5) mixing with dilute surface and/or ground waters. In contrast to metals (e.g. Pb, Cu, Zn and Cd), whose dissolved concentrations rapidly decrease downstream of the mined area through (co-)precipitation/adsorption mechanisms, As concentrations tend to gradually increase (up to 0.9 mg l À1) along the stream course as far as the alluvial plain, though significant variations are locally observed. This behaviour is mainly due to the higher mobility of As than metals under the near neutral-oxidative conditions occurring in the Baccu Locci stream waters. Results of a leaching test indicate that part of the As contained in the flotation tailings occurs as As(III), which is more mobile and less strongly sorbed than As(V). The As released to the waters by various mechanisms (i.e. release/desorption from the Fe(III)-hydroxides coatings of silicate grains, oxidation of residual arsenopyrite, decomposition of scorodite) tends to remain in solution and to be transported long distances. As a consequence of the widespread presence of highly As-contaminated flotation tailings all over the medium-lower Baccu Locci stream catchment, long-term As contamination is expected.

Oil-contaminated soil (OCS) results from leaking underground storage tanks, oil spills on clean soils, or soils surrounding petroleum refineries and crude oil wells. In Oman, Petroleum Development Oman (PDO) generates more than 50,000 ton/year of oil-contaminated soil. Recycling of OCS can be considered a viable solution to the disposal problem. This paper presents the results of investigating the permeability and leaching of asphalt concrete mixes containing OCS. Two types of soil were obtained from an asset area in northern Oman. Physical and chemical characterizations were performed on the OCS. The two soils were used as a replacement of fine aggregate in the asphalt concrete mix with percentages up to 40%, by total aggregate weight. Mixes were designed using the Marshall mix design method. Optimum asphalt contents were determined and samples were prepared at these asphalt contents and tested for permeability using a flexible-wall permeameter. Environmental assessment was performed by subjecting the mixes to the Toxicity Characteristic Leaching Procedure (TCLP) and analyzing the extract for heavy metals. The permeability was found to decrease with the addition of OCS. A significant decrease resulted when the percentage of OCS was increased to 30%. The leaching tests from the mix indicated that TCLP concentrations of the selected heavy metals were well below the TCLP regulatory limits for all OCS mixes.

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The determination of Al, B, Cu, Fe, Mn, Ni, P, Zn and Ca, K, Mg by inductively coupled plasma optical emission spectrometry (ICP-OES) and flame atomic absorption spectroscopy (FAAS), respectively, in digests and infusions of Hibiscus sabdariffa (petals), Rosa canina (receptacles), Ginkgo biloba (leaves), Cymbopogon citratus (leaves), Aloe vera (leaves) and Panax ginseng (roots) was carried out in this study. Particular attention has been given to Al and heavy metals for the identification of possible raw material contaminants, their transformation into the infusion and for predicting their eventual role in the human diet during daily consumption. Additionally, Ion Chromatography (IC) speciation of Al in the leachates was carried out.In dry herbs, hibiscus and ginkgo appeared to contain the greatest contents of Al, Fe, K, Mn, Ni, Zn and B, Mg, P, respectively. A. vera contained the highest amount of Ca and highest values of Cu and P were observed in ginseng. In infusions, the topmost concentrations of Al, B, Cu, Fe, P, K, Mn, Ni, Zn were detected in those prepared from hibiscus petals, Ca from aloe leaves and Mg from leaves of ginkgo. According to a possible daily consumption exceeding 1 L, hibiscus decoction was identified as potentially dietetically significant in the content of certain elements. It seems to be possibly one of the top contributors of B from food (up to 5.5 ± 0.2 mg/L). The Mg contained in the infusion (up to 106 ± 5 mg/L) may be a contributor in the attenuation of blood pressure. A high amount of accessible Mn (up to 17.4 ± 1.1 mg/L) can probably have an adverse effect in humans. The total Al allowance (up to 1.2 ± 0.1 mg/L) suggests that no more than 1 L of the hibiscus infusion should be consumed per day by sensitive individuals including pregnant women and should be completely excluded from the diet of children under 6 months of age and children with chronic renal failure.► Daily consumption of 1 L of infusion of H. sabdariffa may have an adverse effect in humans. ► Children under 6 months of age and children with chronic renal failure should avoid roselle infusion. ► Aluminium content in tea-like infusion may exceed generally recognized safety level. ► Hibiscus petals leachate could be significant source of manganese in human diet. ► Roselle decoction can possibly be one of the top boron contributors for humans.

lnorganic constituents of ash in biomass fuels are responsible for equipment failure and operating difficulties in thermochemical energy conversion facilities. Alkali metals, in the presence of chlorine and sulfur, are the leading contributors to this problem. Banagrass, a herbaceous species being considered for use as a dedicated energy crop, contains high levels of potassium and chlorine. Some inorganic elements are water soluble and the opportunity exists to remove them by mechanical dewatering and 16aching as part of the feedstock preparation process. Laboratory-scale equipment, representative of processes employed in the commercial extraction of sugar from cane, was used to prepare banagrass fuel treatments that included two degrees of comminution (coarse and fine) and two dew atering schemes (mechanical dewatering only, and a multi-step process consisting of initial mechanical dewatering followed by a water rinse and second dewatering). The treatment that included fine comminution and multi-step dewatering resulted in a fuel with substantial reductions in ash (45%), K (90%), CI (98%), S (55%), Na (68%), P (72%) and Mg (68%). The coarse comminution and multi-step dewatering scheme also resulted in reductions, but generally with 10-20% more of the initial constituent mass retained in the fuel. These two treatments produced fuels containing 0.11 and 0.23 kg (Na,_O + K_,O) GJ ~, respectively, with corresponding ash fusion temperature estimates of 1250 and 1075~C. By comparison, bagasse, the fibrous by-product of sugar cane, contains 0.06 kg (Na20 + K20) GJ ~ and has an estimated ash fusion temperature of roughly 1500c'C. Banagrass subjected to the most severe treatment, fine comminution with multi-step dewatering, should produce a boiler fuel with characteristics similar to those of bagasse.

Obtención de metales preciosos a partir de residuos sólidos mineros o relave RESUMEN Este estudio hace referencia a la recuperación de metales preciosos, como el oro y la plata presentes en los relaves sulfurados de los residuos mineros abandonados, mediante el empleo del Tratamiento Hidrometalúrgico, tal como lo constituye la lixiviación por cianuración por empozamiento. Este es un método de curado que involucra el empleo de cemento para aglomerar el oro y de esta manera recuperar valores de oro y plata, con la finalidad de darle un valor agregado al relave. El estudio involucra el análisis químico inicial de tres puntos de muestreo críticos in situ: P190, P192, P197, cuyas leyes iniciales son: 0.514 gr/TC, 0987 gr/TC, 0.719 gr/TC respectivamente, que posteriormente fueron sometidos a pruebas experimentales de Lixiviación por cianuración, con la finalidad de obtener la recuperación de metales valiosos de oro presente en los tres puntos mencionados.

Gold ore processing relies, among other criteria, on the efficient oxidation of not only the target metal, but also components inhibiting this crucial step, such as iron-and sulphur-based compounds. The associated oxygen mass requirements can be substantial and form a considerable part of the operational cost where this is the case. The Aachen High Shear Reactor TM , originally designed to enable efficient high-level oxygen mass transfer from gas to liquid phase in the treatment of refractory gold ores, has by now found many applications where substantial process optimization targets have to be met. With many of the easy-to-process reserves depleted, the remaining gold ores often have associated problems of cyanidable gold losses, slow leach kinetics, and high reagent consumptions. The endless pursuit of higher throughput to compensate for declining gold prices in recent times has only served to exacerbate these issues. The Maelgwyn Aachen technology has been developed and deployed successfully in a range of gold mining applications to address these problems and has now, in addition to its original application to refractory flotation concentrate, found significant industry uptake into normal oxide cyanidation circuits 1. This paper describes the journey from laboratory test work to full commercialization of Aachen reactors. Examples of work conducted to identify the envisaged level of shear, mass of oxygen, and general process conditions to maximize the potentials for a range of different ores and applications are provided. Early-stage economic evaluations include the identified benefits, which are then offset against the inputs of power, oxygen, and rental cost. A favourable balance typically leads to a trial phase on-site with a given scope of technology deployment. Data collection to support or validate the conclusions based on laboratory work forms part of final acceptance, and examples are provided. Finally, data from selected operational sites across Africa is presented demonstrating the ability of the Aachen reactor to assist with realizing hidden potentials in reagent savings, gold recovery, or throughput increases.

Prosperity in Qatar and the consequent stresses on water resources resulted in a sustainable increase in the bottled drinking water market. Reports on health concerns and possible migration of chemicals from the plastic material into the water have driven the current investigation. This study aims to address the extent of antimony (Sb) leaching from polyethylene terephthalate (PET) water bottles subject to temperature variations (24-50°C) due to Qatar's hot climate and improper storage conditions. A representative basket including 66 different imported and locally produced water bottles was considered. The concentrations of Sb in bottled water ranged from 0.168 to 2.263 μg/L at 24°C and from 0.240 to 6.110 μg/L at 50°C. Antimony concentrations in PET bottles at 24°C was significantly lower than those at 50°C (p = 0.0142), indicating that the temperature was a principal factor affecting the release of Sb from the plastic into the water. Although the detected Sb amounts were below the guidelines endorsed by WHO and Qatar (standard 5 μg/L) at 24°C, the concentration measured at 50°C was higher than the recommended WHO values (6.11 μg/L).

Purpose The objective of this study was to investigate the bioleaching of Cr, Cu, Pb, and Zn from sewage sludge using iron-oxidizing microorganisms. These conditions include the solid concentration, initial pH, ferrous iron concentration, inoculum concentration as well as the kinetics of solubilization of metals from sewage sludge to determine whether they impact on bioleaching efficiency. Materials and methods The sludge sample containing bacteria used in this study was collected from Fuzhou Jingshan sewage treatment plant. Indigenous iron-oxidizing bacteria were enriched from the sludge. Conditions affecting the bioleaching and application were conducted using batch experiments. The analysis of Cr, Cu, Pb, and Zn was carried out with an atomic absorption spectrophotometer, and the pH and ORP were measured using pH meter and ORP meter.

Limonene is present in orange peel wastes and is known as an antimicrobial agent, which impedes biogas production when digesting the peels. In this work, pretreatment of the peels to remove limonene under mild condition was proposed by leaching of limonene using hexane as solvent. The pretreatments were carried out with homogenized or chopped orange peel at 20-40 ∘ C with orange peel waste and hexane ratio (w/v) ranging from 1 : 2 to 1 : 12 for 10 to 300 min. The pretreated peels were then digested in batch reactors for 33 days. The highest biogas production was achieved by treating chopped orange peel waste and hexane ratio of 12 : 1 at 20 ∘ C for 10 min corresponding to more than threefold increase of biogas production from 0.061 to 0.217 m 3 methane/kg VS. The solvent recovery was 90% using vacuum filtration and needs further separation using evaporation. The hexane residue in the peel had a negative impact on biogas production as shown by 28.6% reduction of methane and lower methane production of pretreated orange peel waste in semicontinuous digestion system compared to that of untreated peel.

Electric Arc Furnace dusts are considered hazardous waste due to their high heavy metals content (zinc, lead, etc.). The Waelz process is one of the most efficient technologies, in terms of capacity and quality, able to recover nearly the 90% of zinc contained in such EAF dusts. Unfortunately, the resulting slag still has eco-compatibility problems, although its mechanical and chemical properties are suitable for civil engineering applications. Stabilization tests, by quartz addition, were performed on EAF dusts in a laboratory furnace. Temperature, treatment time and cooling rate were varied in order to define the best conditions for regulating the formation of a stable microstructure able to hinder the release of substances. Microstructural characterization was carried-out using SEM and XRD analysis. Leaching tests were performed according to EN 12457-2 standards and water analyses were performed using ICP-OES. The best chemical stability was achieved when dust powders were mixed with 20% of silica and water-cooled.

Laboratory analyses a b s t r a c t Membrane and glass fiber filters are widely used in laboratory water and wastewater analyses. During sample filtration, some filters release organic compounds, which may interfere with organic analyses. This research investigated the interferences due to organic leaching in the determinations of dissolved organic carbon (DOC), biodegradable dissolved organic carbon (BDOC), soluble biochemical oxygen demand (BOD), and soluble chemical oxygen demand (COD) and the appropriate cleaning method for the filters. Nineteen filters studied included 16 membrane filters and 3 glass fiber filters. A wide variation was observed on the amount and characteristics of organics leaching from the filters. Some filters showed no organic leaching while some others had very high organic leaching. Soaking the filters in deionized distilled water (DDW) resulted in more leachable organics from the filters compared with filtering DDW through them. Certain filters should be avoided for use in the above analyses and soaking in DDW is a more suitable cleaning method than discarding initial filtration volumes for most filters.

The disposal of fly ash as a byproduct of thermic power stations, results in significant environmental problems. The leaching of coal fly ash during disposal is of concern for possible contamination, especially for the aquatic environment when ash is in contact with water. The aim of this study was to investigate the leaching behaviour of fly ashes currently disposed in Kemerkoy Power Plant (Turkey) fly-ash-holding pond. The studies were conducted with fly ashes from the electrostatic precipitators (fresh fly ash) and from the fly ash pond (pre-leached fly ash). The fly ashes has alkaline in nature and pH ranges between 11.9 to 12.2. The pre-leached fly ash exhibited lower EC values (7,400 µS) than the fresh fly ash (10,300 µS). In contrast to Fe and Pb, the elements such as Cr, Cd, Cu and Co did not leach from the fly ash. The Ca and Mn concentrations decreased with increasing temperature whereas, Na and K concentrations increased. The results showed that the most important effects of fly ash leaching were pH, Na, Ca, K, Fe, Mg, Mn and Pb.

Lead leaching from lead-based paint (LBP) was examined using standardized laboratory protocols and tests with leachate from actual and simulated landfill environments. Two different LBP samples were tested; leaching solutions included leachates from three municipal solid waste (MSW) landfills and three construction and demolition (C&D) debris landfills. The toxicity characteristic leaching procedure (TCLP) and the synthetic precipitation leaching procedure (SPLP) were also performed. Lead concentrations were many times higher using the TCLP compared to the SPLP and the landfill leachates. No significant difference (α = 0.05) was observed in leached lead concentrations from the MSW landfill and C&D debris landfill leachates. The impact of other building materials present in LBP debris on lead leaching was examined by testing mixtures of LBP (2%) and different building materials (98%; steel, wood, drywall, concrete). The type of substrate present impacted lead leaching results, with concrete demonstrating the most dramatic impact; the lowest lead concentrations were measured in the presence of concrete under both TCLP and SPLP extractions.

Thirty-three samples of construction and demolition waste collected at 11 recycling facilities in Denmark were characterised in terms of total content and leaching of inorganic elements and presence of the persistent organic pollutants PCBs and PAHs. Samples included (i) &quot;clean&quot; (i.e. unmixed) concrete waste, (ii) mixed masonry and concrete, (iii) asphalt and (iv) freshly cast concrete cores; both old and newly generated construction and demolition waste was included. PCBs and PAHs were detected in all samples, generally in non-critical concentrations. Overall, PAHs were comparable to background levels in urban environments. &quot;Old&quot; and &quot;new&quot; concrete samples indicated different PCB congener profiles and the presence of PCB even in new concrete suggested that background levels in raw materials may be an issue. Significant variability in total content of trace elements, even more pronounced for leaching, was observed indicating that the number of analysed ...

The mechanochemical processing of bauxite with lime has been investigated. The milling of bauxite and lime mixtures in an attritor mill resulted in the formation of an iron rich hydrogarnet phase in bauxite/lime slurries containing greater than 9% CaO. Up to 90% of the quartz contained in the bauxite was found to have been removed by the hydrogarnet reaction. The hydrogarnet compound was stable during the high temperature alumina extraction step, resulting in a 30% drop in caustic soda consumption. Alumina extraction was not influenced by the mechanochemical processing. Ó

Wood has been known for a long time to contain nitrogen and mineral elements like potassium, calcium, sodium and magnesium. These elements are found as carbonates in the ash when wood is burnt. 7he finding that the ash of cocoa husk contains a higher than average percentage of potassium carbonate has been reported repeatedly in the fiterarare. A carbonate content of 40-60% and 3-5% based on the ash and dried husk, respectively, confirmed the reported vahws. The objective of this work was to obtain the ashing and leaching parameters which would optimize the extraction from the ash of potassium carbonate, which could be used directly in soap manufacture.

Ilmenite occurs in black sand at the mouth of great rivers as in India, or as massive deposits like in Quebec Province in Canada. It is unsuitable for processing into pigment or for metal production because of its high iron content and its low grade. Pyrometallurgical and hydrometallurgical methods have been developed to cope with this problem which resulted in the production of two commercial products that became known as synthetic rutile and Sorelslag. Attempts are also underway to produce TiO 2 pigment directly from ilmenite. This report presents a newly developed process called the Magpie process, which enables the production of high-grade synthetic rutile (over 95% TiO 2 ) from low grade ilmenite (10-12% TiO 2 ). Naturally, if such process is applied for low-grade ore it can be applied with advantage to high grade material as well.

Методические указания составлены на основании типовых и рабочих программ по курсу «Теория гидрометаллургических процессов». Данное методическое указания написан на основе предмета "Теория  гидрометаллургических процессов" и содержит в своем составе текст лекций, практических занятий и других материалов. В нем рассматриваются такие темы как, общие сведения о термодинамике электролитных растворов, термодинамика простого выщелачивания, термодинамика процессов химического выщелачивания, кинетика и механизм процессов выщелачивания, методы ускорения процессов выщелачивания, кинетика и механизм процессов выщелачивания самородков, оксидов и сульфидов металлов, основы процессов экстракции, основы ионообменных процессов, а также основы выделения металлов и их соединений из водных растворов.

Atmospheric leaching of a sphalerite concentrate in sulphate and chloride media was performed and the effect of several variables, such as solid/liquid ratio and oxidant (Fe(III)) concentration were investigated. The behaviour of minor elements, such as Cu, In, As, Sb, Bi, Sn and Pb, was also studied under different conditions. The results showed that using a solid/liquid ratio of 5% (w/v) it was possible to leach 95% of zinc after 2 h, with a solution of 0.5 M H 2 SO 4 and Fe 2 (SO 4 ) 3 at 80°C. The minor elements As, Sb and Bi were also completely leached whereas copper leaching was favoured by the use of chloride medium. The oxidation of Fe(II) during the leaching tests was studied and an improvement of 20% zinc extraction was observed in an oxygenated system. Cross-current leach tests using two/three stages and a solid/ liquid ratio of 10% (w/v) were performed to achieve 90% of zinc extraction. The electron microprobe analysis of the leaching residues showed no change on the sphalerite composition after the leaching, which indicates that the leaching of sphalerite involves the break down of the sulphide structure.

Delayed ettringite formation (DEF) can damage concrete that has experienced a temperature above about 70°C. Claims that slow release of sulfate from the clinker can have a similar effect in concrete not thus heated are unsupported. Chemical and microstructural aspects of DEF are reviewed. Expansion results from formation of ettringite crystals of submicrometre size in the paste, the larger crystals readily observed in cracks and voids being recrystallisation products. The rate and ultimate extent of expansion are influenced by factors of three types: chemistry, which determines how much ettringite can be formed; paste microstructure, which determines the stresses produced by its formation; and concrete or mortar microstructure, which determines the response of the material to those stresses. Alkali present before the end of the heat treatment can increase expansion, but when present subsequently, it decreases expansion by inhibiting ettringite formation. Leaching therefore promotes expansion.

This review aims at considering the use of REEs to trace pedogenetic processes, in order to quantify the respective contribution of the successive processes on pedogenesis. We first consider the origins and contents of REEs in soils, to assess their natural occurrence, and tackle the common data treatment used to interpret their concentrations. We review subsequently the impact of the different pedogenetic processes on the fate of REEs in soils: from their release into a soil solution by primary mineral (heavy minerals, phosphates, silicates and carbonates) dissolution during weathering, to their fixation on-or into main REE-bearing secondary minerals (clay minerals, Fe-Mn-oxides and carbonates), then their mobilization by plant recycling and organic matter, and finally the impact of argilluviation and redox processes on their fractionation. We conclude that REEs, much more than other trace elements, can interestingly trace the considered processes that are encountered in a large diversity of non-polluted soils arising from diverse parent materials. Weathering generally fractionates REEs and accounts for a significant part of the variation in the initial REE stock of the soils. Plant recycling induces a weak mobilization of REEs and their accumulation in topsoil. Argilluviation can be traced using the MREE-enrichment and the Eu-anomaly of the clay minerals. Redox processes can be traced by the Ce-anomaly caused by the precipitation of cerium on Mn-oxides. To use REEs as tracers of pedogenetic processes, we recommend to: (i) precisely characterize the REE-bearing minerals, (ii) adapt the choice of reference(s) for normalization and (iii) perform mass balance calculations.

Altın zenginleştirme, gümüş zenginleştirme, bakır zenginleştirme, demir zenginleştirme, antimuan zenginleştirme, molibden zenginleştirme, Alüminyum zenginleştirme, nikel zenginleştirme, otoklav liçi, tank liçi, yığın liçi, gravite ile zenginleştirme, sallantılı masa, kromit zenginleştirme tesisi,

The combined process developed using Ion Exchange, Solvent Extraction and ElectroWinning (IX-SX-EW), is described. This method is excellent for processing of pregnant leach solutions both from spent and new copper heaps and dumps, acid mine drainage and other industrial streams. The process produces high grade, marketable cathode copper. The effluents produced from the process totally meet stringent environmental standards. The Buchim Copper Project in Macedonia for heap and dump leaching and copper recovery unit operations of the proposed flow sheet is described. Key findings of the process and comparison between conventional SX-EW process and novel process are also presented.

Biocompatibility or tissue compatibility describes the ability of a material to perform with an appropriate host response when applied as intended. Poly-methylmethacrylate (PMMA) based resins are most widely used resins in dentistry, especially in fabrication of dentures and orthodontic appliances. They are considered cytotoxic on account of leaching of various potential toxic substances, most common being residual monomer. Various in vitro and in vivo experiments and cell based studies conducted on acrylic based resins or their leached components have shown them to have cytotoxic effects. They can cause mucosal irritation and tissue sensitization. These studies are not only important to evaluate the long term clinical effect of these materials, but also help in further development of alternate resins. This article reviews information from scientific full articles, reviews, or abstracts published in dental literature, associated with biocompatibility of PMMA resins and it is leached out components. Published materials were searched in dental literature using general and specialist databases, like the PubMED database. V C 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B:

... 43 (1995) 61-72 Leaching of chalcopyrite concentrate with ferric chloride Tom Havl&#x27;k a, Milan ~krobian a, Peter Bal b, Roland ... Zevgolis and Cooke (1975 ) observed a 200 to 400% difference in the electroleaching rates of five different chalcopyrite samples serving as anodes. ...