Strong Acid Leaching Research Articles

Characteristic pollutants risk assessment of modified manganese residue utilization in sintered product.

The resource disposal of electrolytic manganese residue can effectively solve the problem of environmental pollution caused by it, among which the problem of heavy metal pollution is the most prominent. In this study, a new type of eco-friendly brick mixed with electrolytic manganese residue was designed. The influence of the content of electrolytic manganese residue on its macroscopic properties, microscopic properties, and leaching characteristics was analyzed by test methods such as compressive strength test, radioactivity test, XRF, XRD, FTIR, and ICP test of bricks. The results showed that the manganese content in the EMR leachate was 8120mg/L, which exceeded the Chinese standard. The leaching experiment of ordinary aqueous solution of sintered bricks mixed with 20% EMR showed that the content of heavy metals was far lower than the Chinese national standard. There was no non-carcinogenic risk of heavy metals in the strong acid leaching solution of sintered bricks mixed with 20% EMR. Only the carcinogenic risk values of Cr for adults and children were 4.21 × 10-4 and 9.82 × 10-4 respectively, both exceeding the USEPA limit, but the application scene of sintered bricks was difficult to achieve strong acidity, so it was judged that it had no carcinogenic risk to the human body. Characteristic heavy metals such as Mn, Cr, and As existed stably in sintered bricks through substitution and encapsulation. In addition, the compressive strength and radioactivity of EMR sintered bricks met the requirements of the Chinese national standard "Fired Ordinary Bricks." This product can be used as national standard MU20 grade brick. This study provided an efficient method for the safe and environmentally friendly disposal of EMR in a sustainable control system.

Staged leaching behavior of red mud during dealkalization with mild acid

Dealkalization is a major limiting factor for the comprehensive utilization of red mud, and acid leaching is considered an effective and promising way to achieve it. Most studies have focused on the recovery of metals in this extreme alkaline waste by strong acid leaching, ignoring the dealkalization and stabilization of red mud with low concentrations of acid. In this study, the leaching behavior of the major elements in red mud was carefully investigated by the treatment with a range of H+ concentrations from 10−6 to 1.8 mol/L. Analysis of both leachate and residue confirmed a stepwise sequential leaching behavior of Na, Al, and Ca, which was important for dealkalization of red mud. Treatment with an acidic solution at pH 1 removed 17.84% of Na, but almost no other metals. Greater than 60% Na was leached by an acidic solution with H+ concentration of 0.5 mol/L, but the dissolution efficiencies of Al, Si, and Ca were less than 10%, resulting in a relatively simple leaching liquid treatment process. And the pH of the leaching residue was 8.5 which slightly alkaline so the residual RM could be used as soil aggregates. When using an acidic solution with an H+ concentration of 1.6 mol/L, the dissolution efficiency of Na reached at 94.70%, leaving only 0.47% Na in the residue, which makes it possible to meet the demand of application for construction materials. From the results of the phase analysis, it was found that the sequential leaching behavior was due to the dissolution, decomposition, and transformation of the particles containing the main elements, and was compatible with the SEM-EDS inspection. Based on these results, a new multi-stage acid leaching dealkalization process has been proposed to provide an effective and economical way to dealkalize red mud.

Chemical Composition Simplification of the Seydişehir (Konya, Turkey) Alumina Plant Waste

Red mud, a residue of alumina production from bauxite refining, contains oxides of valuable metals such as Fe, Al, Ti, Si, Na, Ca, etc. The presence of these numerous metal oxides does not allow introducing the highly basic raw red mud within any industrial process, which leads to its storage over a wide land area. In order to simplify the chemical composition of this waste, the effects of weak acid leaching (citric acid) and strong acid leaching (hydrochloric acid) are studied. The treatment efficiency is discussed based on scanning electron microscope and X-ray diffraction analysis of solid product and inductively coupled plasma spectrometry analysis of acidic solutions. The effects of temperature and acid concentration on metals dissolution are estimated by rough kinetic considerations which present results comparable to those in the literature. More than 50% of Al and 50% of Ca detected by inductively coupled plasma mass spectrometry were separated via the organic acid process, while during leaching with HCl whole Ca, Fe, and more than 60% Ti and 80% of Al similarly determined were recovered. This confirms that within the red mud, metals behave differently under several forms with different reactivity toward acidic medium. Therefore, an eventual combination of both acids can be an efficient way to prepare them ready and suitable for possible industrial applications.

A bio-hydrometallurgical approach towards leaching of lanthanum from the spent fluid catalytic cracking catalyst using Aspergillus niger

Spent fluid catalytic cracking catalysts (SFCCC) are the wastes generated from oil refineries, which accounts for 700,000–900,000 metric ton/year worldwide. Lanthanum, a short-term near critical element is the key component of SFCCC and accounts for 8170 mg/Kg. The current research intends to recover lanthanum from SFCCC by Aspergillus niger and compare the results with strong organic and inorganic acid leaching. Batch studies of one-step bioleaching (OSB) at 1, 3 and 5% pulp densities yielded 63%, 52%, and 33% lanthanum recovery, respectively. The decrease in leaching efficiency with an increase in pulp density may be attributed to the inhibition effect of SFCCC on A. niger. Citric acid was the main lixiviant produced by A. niger, whose production was triggered by SFCCC at ≤1% pulp density. Acidic pH of the leaching medium suggested acidolysis as the key mechanism. Cell-free spent medium bioleaching (cfSMB) resulted in 30.8% leaching recovery, which was significantly less than the OSB. In chemical leaching, sulfuric and nitric acid showed 38% efficiency whereas oxalic acid showed 5% recovery. Hydrochloric, citric and gluconic acids resulted in 68%, 65%, and 64% leaching recoveries, respectively, which is nearly the same as that offered by OSB. OSB being the greener process, suggested for lanthanum leaching from SFCCC over other processes.

A Cost-Effective Lithium-Ion Battery Direct Recycling Process

Lithium-ion batteries have dominated the power source market for consumer electronics (W⋅h scale) and are becoming the dominant battery technology for electrified vehicles (EV, kW⋅h scale) and grid-scale electrochemical energy storage systems (MW⋅h scale) [1,2]. The growing ubiquity of lithium-ion batteries also brings a rapid growth in hazardous battery waste from manufacturing processes and end-of-life (EOL) disposal [3,4]. In the EV sector alone, approximately 50-100 million lithium-ion cells in the US and China will reach their EOL by 2020, thus generating large amounts of hazardous waste [5]. However, conventional pyrometallurgical and hydrometallurgical battery recycling processes require high temperature, strong acid leaching and extensive gas treatment, which lead to prohibitive cost, high energy consumption, water contamination and recycled materials with low resale value [6,7]. Since the cathode materials account for 30-40% of the overall battery cost, a cost-effective and eco-friendly direct recycling process that yields reusable battery-grade cathode materials can lower the energy consumption and battery materials cost. In this talk, we will demonstrate a scalable and cost-effective direct recycling process for EOL lithium-ion batteries to yield battery-grade cathodes. The recycled cathodes retain the microstructure and show equivalent electrochemical performance compared to the pristine cathode materials. We will also present life cycle analysis for several cathode materials widely used in current state-of-the-art electrified vehicles and compare the energy consumptions of different recycling approaches. Reference [1] M.S. Whittingham, Lithium Batteries and Cathode Materials, Chem. Rev. 104 (2004) 4271–4302. doi:10.1021/cr020731c. [2] M.S. Whittingham, Ultimate Limits to Intercalation Reactions for Lithium Batteries, Chem. Rev. 114 (2014) 11414–11443. doi:10.1021/cr5003003. [3] E. Gies, Recycling: Lazarus batteries, Nature. 526 (2015) 526S100a. doi:10.1038/526S100a. [4] L. Gaines, To recycle, or not to recycle, that is the question: Insights from life-cycle analysis, MRS Bull. 37 (2012) 333–338. doi:10.1557/mrs.2012.40. [5] Estimated based on the EV sales volume of US and China from 2011-2015, n.d. [6] J.B. Dunn, L. Gaines, J.C. Kelly, K.G. Gallagher, Life Cycle Analysis Summary for Automotive Lithiumion Battery Production and Recycling, in: Rewas 2016 Mater. Resour. Sustain., John Wiley & Sons, Inc., 2016: pp. 73–79. doi:10.1002/9781119275039.ch11. [7] L. Gaines, The future of automotive lithium-ion battery recycling: Charting a sustainable course, Sustain. Mater. Technol. 1–2 (2014) 2–7. doi:10.1016/j.susmat.2014.10.001.

The sensitivity of water chemistry to climate in a forested, nitrogen-saturated catchment recovering from acidification

Fluxes of major ions and nutrients were measured in the N-saturated mountain forest catchment-lake system of Čertovo Lake (Czech Republic) from 1998 to 2014. The lake has been rapidly recovering from atmospheric acidification due to a 90% decrease in sulphate (SO42−) deposition since the late 1980s and nitrate (NO3−) contribution to the pool of strong acid anion and leaching of dissolved organic carbon (DOC) have increased. Present concentrations of base cations, phosphorus (P), total organic N (TON), and ionic (Ali) and organically bound (Alo) aluminium in tributaries are thus predominantly governed by NO3− and DOC leaching. Despite a continuing recovery lasting 25 years, the Čertovo catchment is still a net source of protons (H+), producing 44mmolm−2yr−1 H+ on a catchment-area basis (corresponding to 35μmolL−1 on a concentration basis). Retention of the deposited inorganic N in the catchment averages 20%, and ammonium consumption (51mmolm−2yr−1) and net NO3− production (28molm−2yr−1) are together the dominant terrestrial H+ generating processes. In contrast, the importance of SO42− release from the soils on terrestrial H+ production is continuously decreasing, with an average of 47mmolm−2yr−1 during the study. The in-lake biogeochemical processes reduce the incoming acidity by ∼40%, neutralizing 23μmolL−1 H+ (i.e., 225mmolm−2yr−1 on a lake-area basis). Denitrification and photochemical and microbial decomposition of DOC are the most important in-lake H+ consuming processes (50 and 39%, respectively), while hydrolysis of Ali (from tributaries and photochemically liberated from Alo) is the dominant in-lake H+ generating process. Because the trends in water chemistry and H+ balance in the catchment-lake system are increasingly related to variability in NO3− and DOC leaching, they have become sensitive to climate-related factors (drought, elevated runoff) and forest damage that significantly modify the leaching of these anions. During the study period, increased exports of NO3− (accompanied by Ali and base cations) from the Čertovo catchment occurred after a dry and hot summer, after forest damage, and during elevated winter runoff. Increasing DOC export due to decreasing acid deposition was further elevated during years with higher runoff (and especially during events with lateral flow), and was accompanied by P, TON, and Alo leaching. The climate-related processes, which originally “only” confounded chemical trends in waters recovering from acidification, may soon become the dominant variables controlling water composition in N-saturated catchments.

Removal of tin and extraction of indium from acid-dissolved solution of waste indium-tin targets

The recovery of indium from waste indium tin oxide (ITO) target has great significance for the economy and environment. Based on our previous study on the optimization of acid leaching technique, the present study focuses on tin removal via zinc substitution and indium recovery from a tin-free leach solution. The results show that when the amount of added zinc powder and reaction time increase, the tin removal effect can be improved. The optimal conditions obtained are as follows: additional content of zinc powder from 20 g/L to 25 g/L, reaction temperature of 60 °C, and reaction time from 3 h to 4 h. Under this condition, the tin removal rate exceeds 98%, and the tin content in the tin removal solution is lower than 0.05 g/L. After tin removal, the substitution time could be reduced from 3–5 d to 1–2 d by neutralizing the residual acid by using alkaline residue and maintaining the pH value less than 2. The indium recovery rate is also improved when this condition is used. The indium content in the tin residue is reduced to lower than 0.1% and the acid-insoluble β-SnO2 could be obtained via the strong nitric acid leaching of the indium-containing tin residue. Indium could be recovered from ITO with a high purity of 99.995% via electrorefining.

Extraction of Silica from Palm Ash Using Organic Acid Leaching Treatment

Agricultural wastes such as palm ash and rice husk have a possibility to be used as a usefully renewable source for production of energy and silica (SiO2). Extensive researches have been carried out to extract silica from agricultural wastes such as rice husk, due to silica as a useful raw material for industrial application. In the previous studies, the strong acid leaching treatment was carried out to remove metallic impurities and organics contained in rice husk. A strong acid leaching treatment, however, is significantly hazardous to the environment and people [. In this study, the environmentally benign and economically effective process to produce SiO2 materials from palm ash has been established by using citric acid leaching, not the conventional strong acids. Results showed that silica can be extracted from palm ash using citric acid leaching treatment under the optimum extracting conditions with 70°C of solution temperature, 60 minutes of reaction time and concentration of citric acid of more than 2%. The purity of silica extracted is more than 90%.

Extraction of Silica from Palm Ash Using Citric Acid Leaching Treatment: Preliminary Result

Large quantities of agricultural wastes such as palm ash and rice husk are found throughout Malaysia, have a possibility to be used as a usefully renewable source for production of energy and silica (SiO2). Extensive researches have been carried out to extract silica from agricultural wastes such as rice husk, due to silica as a useful raw material for industrial application. In the previous studies, the strong acid leaching treatment was carried out to remove metallic impurities and organics contained in rice husk. Since leaching treatment is a proper route to extract the silica, sulphuric acid (H2SO4), hydrochloric acid (HCl) and nitric acid (HNO3) solutions are currently used in leaching treatment to prepare silica materials [. A strong acid leaching treatment, however, is significantly hazardous to the environment and people. In this study, the weaker acid, citric acid solutions were used to replace strong acid in leaching processes. Preliminary results showed that silica can be extracted from palm ash using citric acid leaching treatment under the optimum extracting conditions with 70°C of solution temperature, 60 minutes of reaction time and concentration of citric acid of more than 2%. The purity of silica extracted is more than 90%.

Review of Extraction of Silica from Agricultural Wastes Using Acid Leaching Treatment

Large quantities of agricultural wastes such as palm ash and rice husk are found in Malaysia, have a large possibility to be employed as usefully renewable to produce energy and silica (SiO2). Extensive researches have been carried out to extract silica from agricultural wastes such rice husk, because silica is useful raw material for industrial application. In the previous studies, the strong acid leaching treatment was carried out on rice husk to remove metallic impurities and organics contained in them. Leaching treatment is a proper route to extract the silica. Sulphuric acid (H2SO4), hydrochloric acid (HCl) and nitric acid (HNO3) solutions are conventionally used in leaching treatment to prepare silica materials [. A strong acid leaching treatment, however, is significantly hazardous to the environment and humans. This paper reviews the common extraction method used and the latest research trends in extraction of silica.

Energy conservation, CO2, and other greenhouse gas reduction

To read more about them, turn to page 10. To join TMS, visit www.tms.org/Society/Membership.aspx. Energy conservation as well as CO 2 and other greenhouse gas reduction present long-term challenges to our society, and the problems are exacerbated by the rapid consumption of materials and energy and signifi cant emissions of greenhouse gas and toxic gases. By 2050 the world’s oil production will be half of what it is today. Capping CO 2 in the atmosphere at 450 ppmv will require its sequestration. Metallurgical industries and transportation systems are the main energy users and the main producers of greenhouse gas. Production of renewable energy and saving energy in metallurgical processing are two keys to energy conservation. As an example, solar cell energy is a well known renewable energy and it is claimed as a green energy by most people. However, if the feedstock, especially for multi-crystalline silicon, is included, solar cell energy is not a green energy since during the production of the high purity silicon, signifi cant energy is consumed, much CO 2 is emitted, and several non-green processes, such as strong acid leaching, are included. Furthermore, during the wafer slicing process of a high-purity silicon ingot, over 50% becomes slurry wastes and there are no successful industrial processes to recycle these valuable wastes. In order to save energy, traditional industrial processes should be optimized. Furthermore, reuse, recycling, and recovery of metals and materials should be emphasized since these processes usually use less energy than the primary production processes. The control of CO 2 and other greenEnergy Conservation, CO2, and Other Greenhouse Gas Reduction

Assessing the bleaching capacity of some Cameroonian clays on vegetable oils

Four Cameroonian clays, constituted mainly of smectites associated to minor amounts of kaolinite and quartz, have been used to bleach palm oil, cottonseed oil and maize germ oil. Kinetic studies show that the best temperature and contact time for optimum bleaching of vegetable oil varied with the type of oil; these are: 95 °C and 2.5 h for palm oil, 85 °C and 0.25 h for cottonseed oil, and 85 °C and 0.5 h for maize germ oil. The bleaching ability of natural clays was poor when compared with that of industrial adsorbents. Acid activation of Cameroonian clays with 1N sulphuric acid solution increased tremendously their adsorptive capacity, which therefore matches those of the industrial adsorbents. Further increase of the concentration of the acid solution used for clay activation did not induce a noticeable increase in the bleaching power of the adsorbents. This was attributed to the fact that the increase in the surface area is due to the formation of silica but the surface area of H-clays remains almost constant over strong acid leaching and silica has very poor bleaching power of vegetable oils. FT-IR spectroscopy studies of the adsorbents after bleaching suggest strong interactions between the clays and adsorbent surface. Acid and iodine values of bleached oils reveal that oils are not deteriorated by clays during the bleaching process. The overall results lead to the conclusion that Cameroonian clays can be converted into potent adsorbents for bleaching vegetable oils.

The Bioaccessibility of Lead (Pb) from Vacuumed House Dust on Carpets in Urban Residences

Risk assessments for toxicants in environmental media via oral exposure often rely on measurements of total concentration in a collected sample. However, the human digestive system cannot dissolute all of a toxicant present in the binding matrix, and cannot absorb it with nearly 100% efficiency. In vitro bioaccessibility has been developed as a method to estimate oral bioavailability of a toxicant using a physiologically-based extraction procedure. Bioaccessibility measurements are more physiologically relevant than strong acid leaching measurements of concentration. A method for measuring bioaccessible lead in house dust was derived from the bioaccessibility method currently used for heavy metals in contaminated soils. House dust was collected from carpets in typical urban residences. Bioaccessible lead was measured in house dust (<75 microm) from the homes of 15 participants. The bioaccessibility ranged from 52.4% to 77.2% in gastric fluid, and 4.9% to 32.1% in intestinal fluid. House dust samples from five homes were analyzed to assess the relationship among lead bioaccessibility of three particle size fractions (<75, 75-150, and 150-250 microm). Changes in lead bioaccessibility as a function of particle size fraction were not significant for gastric fluid (p= 0.7019); however they were significant for intestinal fluid (p= 0.0067). This decrease of bioaccessibility may result from the readsorption of dissolved lead onto the dust particles or precipitation of lead with phosphates in a high-pH environment. The bioaccessibility data obtained for two biofluids were applied to the IEUBK model, and results for intestinal bioaccessibility of lead provide support for the model default value of 30% lead bioavailability of dust as a reasonable population indicator for dose, but the higher values for gastric bioaccessibility of lead appeared to provide an upper bound that approached actual blood lead levels in the children living in the studied homes. This upper bound seemed to overcome some of the limitations of the model when it lacks child-specific activity data and characterization of all exposure routes.

Spatial and Temporal Distribution of Trace Metals in Sediments from the Scheldt Estuary, South-west Netherlands

The spatial and temporal distribution of trace metals has been studied in sediments of the Scheldt estuary, in order to identify trends in space and time. Sediment trace metal data, obtained by 11 laboratories, were considered for the period 1959–90. It was found that trace metal data obtained by complete sample digestion (e.g. HClO 4-HF) were incomparable to those obtained by strong acid leaching (e.g. HNO 3-HCl). However, various strong acid leaches were found to yield comparable results for sediment trace metals, except for chromium. Hence, trace metal data obtained by strong acid digestion could be merged into a comprehensive database (except for chromium), which was analysed by an ANOVA procedure. Sediment trace metal contents were normalized against a common standard, based on their grain size fraction and organic matter content. Spatial variations were investigated for four areas encompassing the entire Scheldt estuary within the periods 1978–85 and 1986–90. For one specific area, mid-estuary, trace metal data were studied from 1959 to 1987. For each area and period considered, the sediment trace metal content was calculated at the average percentage <16 μm and organic matter content of the whole data set. The results showed that: (1) The upper Scheldt estuary is strongly polluted by trace metals, especially cadmium; (2) Viewed in historic perspective, pollution of the Scheldt estuary by trace metals was maximal at the end of the 1950s but decreased considerably through the 1970s and again in the 1980s. Monitoring data of suspended matter composition and trace metal profiles in a radiodated sediment core tend to confirm this pollution history; (3) The trace metal content of the sediments decreases in the downstream direction due to mixing of metal-rich fluvial sediments and metal-poor marine sediments; (4) Although physical mixing is the most important process that controls the trace metal content of the sediments, evidence is presented for mobilization of cadmium with increasing salinity, whilst this is suggested for arsenic.

Geochemical mapping and databases in Finland

Regional geochemical maps in Finland have been produced from many different programmes. The scale of sampling, the material collected and the analytical methods used varied according to the aim of the study. The entire country was covered at a reconnaissance scale using glacial till, groundwater, surface water and organic stream sediments as sampling media. Glacial till was sampled throughout the country at a regional scale. Local scale mapping and detailed geochemical studies are carried out in selected areas. The main analytical methods have been ICP-AES and ICP-MS, but other methods were used when necessary. In assaying solid material, both total decomposition and strong acid (aqua regia) leaching were used. The results are stored in ALKEMIA, a database developed in the geochemistry department of the Geological Survey of Finland. The data are available as tabulated ASCII files and as digital image files on diskettes, or as various types of symbol and colour maps from desired areas or map sheets. Two examples of the application of geochemical mapping data in prospecting and in environmental research are presented. Indications of the presence of gold and multiple-sulphide ore deposits have been the most useful results obtained from a prospecting standpoint. On the environmental side, reconnaissance scale geochemical mapping data gave more reliable information on the base cation concentration than bedrock maps, making them particularly valuable in devising an acidification assessment model.

A hydrometallurgical process to treat carbon steel electric arc furnace dust

A process is described for the treatment of carbon steel electric arc furnace dust to remove zinc, lead, copper and cadmium as sulphides, potentially saleable to a zinc plant, followed by recycling of the iron oxide residue to the steel producing furnace. Clean gypsum, expected to be saleable, is a by-product. The process uses a strong acetic acid leach to dissolve most of the heavy metals and calcium. hydrogen sulphide to precipitate the heavy metal sulphides, and sulphuric acid to precipitate calcium as gypsum. The regenerated acetic acid is treated by ion exchange to remove impurities. The acetic acid is reconcentrated by distillation or other means for recycle to strong acid leaching.

Amorphization levels, nature and localization of the extraframework phases of dealuminated Y zeolites

Acid-leached and unleached Y zeolites dealuminated by steam calcination have been characterized by spectroscopic techniques and chemical analysis. Measurement of the free volumes of the supercages has been carried out by benzene adsorption. The experimental results are mathematically conclusive, and it appears that the amorphous phase obtained after dealumination is quasi-aluminous (SiO 2 < 5%) of which 65% is localized in the supercages. The zeolitic framework is conserved during partial dissolution of the extralattice aluminous fraction, but 10% of it is destroyed during strong acid leaching and the silica is then exposed. The same technique can be used to localize a solid additive obtained after impregnation of the Y zeolites.

Thorium-uranium disequilibrium dating of Late Quaternary ferruginous concretions and rinds

Radioactive ferruginous nodules from the Alligator Rivers Uranium Province, Northern Territory, Australia, were systematically examined by optical microscopy, XRD, alpha- and fission-track autoradiography, and analysed for U, Th, Ra and major stable elements. Correlation of autoradiographs with microscopic structure and analyses of selective extractions confirmed that U and Th were strongly associated with Fe oxides. Fission-track autoradiography showed no concentration gradient evidence for postdepositional leaching of uranium. Strong acid leaching studies showed that irreversibly adsorbed U, and authigenic 234U and 230Th, but not 226Ra, are quantitatively retained by accumulated oxide/oxyhydroxide. Correlation of the groundwater activity ratio with oxidic 234U/ 238U activity ratios indicated the latter was radiogenically consistent with oxidic 230Th/ 234U activity ratios < 1. Dense, accumulated Fe/Mn oxide matrices are apparently capable of forming radiogenic closed systems in respect of the 230U → 234U → 230Th decay set. 234U/ 238U and 230Th/ 234U activity ratios were used to derive similar mean ages of rinds for four nodules in the same horizon. Th/U ages were also determined, using a Th-index detrital correction method previously used for impure carbonates, of pedogenic Fe/Mn accumulations having background concentrations of U and Th from other locations in Australia. These ages were compared with TL and 14C ages of the-host sediments. The comparisions suggest that Th/U dating could be used to age indurated layers of Fe/Mn oxides in soil horizons < 350 ka old.

Tributyltin determination in marine sediments: A comparative study of methods

AbstractTwo independent speciation methods have been applied to the determination of tributyltin (TBT) in marine sediments: (1) acetic acid leaching/hydride generation/cold trapping/GC/quartz furnace AA; and (2) toluene–tropolone extraction/HPLC/GFAA. TBT determines in a typically moderately polluted sediment (Porto Vecchio Bay, Corsica, France) are in very good agreement, as also are the determination of total recoverable tin by the first method and by a direct one using strong acid leaching followed by GFAA. These cross‐verifications lead one to conclude that both speciation methods are convenient and allow for valid determination of TBT in marine sediments, with no loss of TBT. Method‐induced modification of tin speciation has not been observed.

Strontium, neodymium and lead isotope characteristics of the Granadilla Pumice, Tenerife: a study of the causes of strontium isotope disequilibrium in felsic pyroclastic deposits

Summary The Granadilla Pumice deposit, the product of a single explosive eruption of phonolitic magma, exhibits stratigraphically systematic internal compositional variations interpreted as the result of fractionation of the observed phenocryst assemblage in the pre-eruptive magma body. Whole-rock 87 Sr/ 86 Sr data exhibit a consistent profile, with the most differentiated compositions having the most radiogenic strontium. The resultant 87 Sr/ 86 Sr versus 1/Sr mixing line has a positive slope, suggesting the addition of a relatively radiogenic strontium component to the existing strontium concentration profile. There is no significant systematic variation, however, in neodymium or lead isotopes. Separated alkali feldspar phenocrysts have 87 Sr/ 86 Sr values of 0.7031–0.7032, identical with Tenerife mafic magmas; the strontium isotopic variation is restricted to the complementary glasses. The more radiogenic component in the glasses is only partially removed by acid leaching and has a strontium isotope ratio of about 0.707, deduced from analysis of the leachant. Strong acid leaching, accompanied by up to 25% sample dissolution, results in greater, but not complete, loss of the more radiogenic component, with a good correlation between pre- and post-leaching glass isotopic compositions. These relationships cannot be easily explained by either post-eruptive alteration or contamination of the magma chamber with high- 87 Sr/ 86 Sr country rock. The data are instead consistent with a model of interaction between vesiculating magma and hydrothermal fluids with high 87 Sr/ 86 Sr, immediately before and/or during explosive eruption, involving limited diffusion of strontium from the fluid into bubble walls before quenching of the magma to form glassy pumice. This process may be common during large explosive eruptions, and we suggest that whole-rock strontium isotope variations found in strontium-poor felsic pyroclastic deposits may not reflect purely magmatic processes, even though they closely mimic plausible magmatic variations.