technologyComment of iron ore beneficiation (IN): Milling and mechanical sorting. Average iron yield is 65% . The process so developed basically involves crushing, classification, processing of lumps, fines and slimes separately to produce concentrate suitable as lump and sinter fines and for pellet making. The quality is essentially defined as Fe contents, Level of SiO2 and Al2O3 contamination. The process aims at maximizing Fe recovery by subjecting the rejects/tailings generated from coarser size processing to fine size reduction and subsequent processing to recover iron values. technologyComment of iron ore beneficiation (RoW): Milling and mechanical sorting. Average iron yield is 84%. technologyComment of iron ore mine operation and beneficiation (CA-QC): Milling and mechanical sorting. Average iron yield is 75%. Specific data were collected on one of the two production site in Quebec. According to the documentation available, the technologies of the 2 mines seems similar. Uncertainity has been adjusted accordingly. technologyComment of niobium mine operation and beneficiation, from pyrochlore ore (BR, RoW): Open-pit mining is applied and hydraulic excavators are used to extract the ore with different grades, which is transported to stockpiles awaiting homogenization through earth-moving equipment in order to attain the same concentration. Conveyor belts (3.5 km) are utilized to transport the homogenized ore to the concentration unit. Initially, the ore passes through a jaw crusher and moves to the ball mills, where the pyrochlore grains (1 mm average diameter) are reduced to diameters less than 0.104 mm. In the ball mills, recycled water is added in order to i) granulate the concentrate and ii) remove the gas from the sintering unit. The granulated ore undergoes i) magnetic separation, where magnetite is removed and is sold as a coproduct and ii) desliming in order to remove fractions smaller than 5μm by utilizing cyclones. Then the ore enters the flotation process - last stage of the beneficiation process – where the pyrochlore particles come into contact with flotation chemicals (hydrochloric & fluorosilic acid, triethylamene and lime), thereby removing the solid fractions and producing pyrochlore concentrate and barite as a coproduct which is also sold. The produced concentrate contains 55% Nb2O5 and 11% water and moves to the sintering unit, via tubes or is transported in bags while the separated and unused minerals enter the tailings dam. In the sintering unit, the pyrochlore concentrate undergoes pelletizing, sintering, crushing and classification. These units not only accumulate the material but are also responsible for removing sulfur and water from the concentrate. Then the concentrate enters the dephosphorization unit, where phosphorus and lead are removed from the concentrate. The removal of sulphur and phosphorus have to be executed because of the local pyrochlore ore composition. Then the concentrate undergoes a carbothermic reduction by using charcoal and petroleum coke, producing a refined concentrate, 63% Nb2O5 and tailings with high lead content that are disposed in the tailings dam again. technologyComment of rare earth element mine operation and beneficiation, bastnaesite and monazite ore (CN-NM): Firstly, open pit, mining (drilling and blasting) is performed in order to obtain the iron ore and a minor quantity of rare earth ores (5−6 % rare earth oxide equivalent). Then, a two-step beneficiation process is applied to produce the REO concentrate. In the first step, ball milling and magnetic separation is used for the isolation of the iron ore. In the second step, the resulting REO tailing (containing monazite and bastnasite), is processed to get a 50% REO equivalent concentrate via flotation. technologyComment of rare earth oxides production, from rare earth oxide concentrate, 70% REO (CN-SC): This dataset refers to the separation (hydrochloric acid leaching) and refining (metallothermic reduction) process used in order to produce high-purity rare earth oxides (REO) from REO concentrate, 70% beneficiated. ''The concentrate is calcined at temperatures up to 600ºC to oxidize carbonaceous material. Then HCl leaching, alkaline treatment, and second HCl leaching is performed to produce a relatively pure rare earth chloride (95% REO). Hydrochloric acid leaching in Sichuan is capable of separating and recovering the majority of cerium oxide (CeO) in a short process. For this dataset, the entire quantity of Ce (50% cerium dioxide [CeO2]/REO) is assumed to be produced here as CeO2 with a grade of 98% REO. Foreground carbon dioxide CO2 emissions were calculated from chemical reactions of calcining beneficiated ores. Then metallothermic reduction produces the purest rare earth metals (99.99%) and is most common for heavy rare earths. The metals volatilize, are collected, and then condensed at temperatures of 300 to 400°C (Chinese Ministryof Environmental Protection 2009).'' Source: Lee, J. C. K., & Wen, Z. (2017). Rare Earths from Mines to Metals: Comparing Environmental Impacts from China's Main Production Pathways. Journal of Industrial Ecology, 21(5), 1277-1290. doi:10.1111/jiec.12491 technologyComment of scandium oxide production, from rare earth tailings (CN-NM): See general comment. technologyComment of vanadium-titanomagnetite mine operation and beneficiation (CN): Natural rutile resources are scarce in China. For that reason, the production of titanium stems from high-grade titanium slag, the production of which includes 2 processes: i) ore mining & dressing process and ii) titanium slag smelting process. During the ore mining and dressing process, ilmenite concentrate (47.82% TiO2) is produced through high-intensity magnetic separation of the middling ore, which is previously produced as a byproduct during the magnetic separation sub-process of the vanadium titano-magnetite ore. During the titanium slag smelting process, the produced ilmenite concentrate from the ore mining & dressing process is mixed with petroleum coke as the reducing agent and pitch as the bonding agent. Afterwards it enters the electric arc furnace, where it is smelted, separating iron from the ilmenite concentrate and obtaining high-grade titanium slag.
Based on the variety of existing nanomaterials with numerous modifications, the effort of investigating environmental fate and effects will be tremendous. Hence, it will be necessary to group nanomaterials which feature similar environmental fate and effects. Therefore, the project objective was to correlate physical-chemical data with ecotoxicological effects for selected nanomaterials and to define reference values which can serve as a basis for grouping. The report presents the development of concepts for grouping of nanomaterials with regard to their ecotoxicological effects with focus on aquatic ecotoxicity. The project was structured into five steps. First, fourteen nanomaterials were selected according to pre-defined criteria. The selected NMs were different subtypes of Ag, ZnO, TiO2, CeO2 and Cu. In a second step, their physico-chemical properties were determined in water and in all test media. Based on the results hypotheses regarding the expected ecotoxicity were formulated (third step). In a fourth step, the hypotheses were verified by testing the selected NMs in three ecotoxicological tests (acute aquatic toxicity with algae, daphnia and fish embryo according to the OECD Test Guidelines No. 201, 202 and 236). Finally, step five consisted of the compilation of a grouping concept based on nanomaterials physico-chemical parameters which were identified as relevant for the emergence of a toxic effect in aquatic organisms. Veröffentlicht in Texte | 102/2017.
Im Rahmen des UFOPLAN 2008 wurde eine Literaturstudie vom Umweltbundesamt - FKZ 3708 61 300 - in Auftrag gegeben, die den jetzigen Stand des Wissens und den Forschungsbedarf im Bereich der Emission von nanoskaligen Partikeln aus Produkten im Verlauf ihres Lebenszyklus und ihre mögliche ökologische Relevanz zusammenfassen soll. Hierfür wurden Informationen zu nanoskaligem Silber, nanoskaligem Titandioxid, nanoskaligem Carbon Black, nanoskaligem Ceroxid - speziell für Wischtücher, Außenwandfarben, Füllstoff in Reifen und Additive im Kraftstoff - zusammengetragen und bewertet. Veröffentlicht in Texte | 52/2010.
technologyComment of cobalt production (GLO): Cobalt, as a co-product of nickel and copper production, is obtained using a wide range of technologies. The initial life cycle stage covers the mining of the ore through underground or open cast methods. The ore is further processed in beneficiation to produce a concentrate and/or raffinate solution. Metal selection and further concentration is initiated in primary extraction, which may involve calcining, smelting, high pressure leaching, and other processes. The final product is obtained through further refining, which may involve processes such as re-leaching, selective solvent / solution extraction, selective precipitation, electrowinning, and other treatments. Transport is reported separately and consists of only the internal movements of materials / intermediates, and not the movement of final product. Due to its intrinsic value, cobalt has a high recycling rate. However, much of this recycling takes place downstream through the recycling of alloy scrap into new alloy, or goes into the cobalt chemical sector as an intermediate requiring additional refinement. Secondary production, ie production from the recycling of cobalt-containing wastes, is considered in this study in so far as it occurs as part of the participating companies’ production. This was shown to be of very limited significance (less than 1% of cobalt inputs). The secondary materials used for producing cobalt are modelled as entering the system free of environmental burden. technologyComment of natural gas production (CA-AB): Canadian data completed with german data. The uncertainty has been adjusted accordingly. Data used in original data contains no information on technology. technologyComment of natural gas production (DE): Data in environmental report contains no information on technology. technologyComment of natural gas production (RoW): The data describes an average onshore technology for natural gas to 13% out of combined oil gas production. Natural gas is assumed to 20% sour. Leakage in exploitation is estimated at 0.38% and production 0.12%. It is further assumed that about 30% of the produced water is discharged in surface water. Water emissions are differentiated between combined oil and gas production and gas production. technologyComment of natural gas production (RU): The data describes an average onshore technology for natural gas with a share of 4% out of combined oil gas production and 96% from mere natural gas production. Natural gas is assumed to 20% sour. It is assumed that about 30% of the produced water is discharged in surface water. Water emissions are differentiated between combined oil and gas production and gas production. technologyComment of natural gas production (US): US data (NREL) for emissions completed with german data. Emissions from NREL include combined production (petroleumm and gas) and off-shore production. The uncertainty has been adjusted accordingly. Data used in original data contains no information on technology. technologyComment of petroleum refinery operation (CH): Average data for the used technology. technologyComment of primary zinc production from concentrate (RoW): The technological representativeness of this dataset is considered to be high as smelting methods for zinc are consistent in all regions. Refined zinc produced pyro-metallurgically represents less than 5% of global zinc production and less than 2% of this dataset. Electrometallurgical Smelting The main unit processes for electrometallurgical zinc smelting are roasting, leaching, purification, electrolysis, and melting. In both electrometallurgical and pyro-metallurgical zinc production routes, the first step is to remove the sulfur from the concentrate. Roasting or sintering achieves this. The concentrate is heated in a furnace with operating temperature above 900 °C (exothermic, autogenous process) to convert the zinc sulfide to calcine (zinc oxide). Simultaneously, sulfur reacts with oxygen to produce sulfur dioxide, which is subsequently converted to sulfuric acid in acid plants, usually located with zinc-smelting facilities. During the leaching process, the calcine is dissolved in dilute sulfuric acid solution (re-circulated back from the electrolysis cells) to produce aqueous zinc sulfate solution. The iron impurities dissolve as well and are precipitated out as jarosite or goethite in the presence of calcine and possibly ammonia. Jarosite and goethite are usually disposed of in tailing ponds. Adding zinc dust to the zinc sulfate solution facilitates purification. The purification of leachate leads to precipitation of cadmium, copper, and cobalt as metals. In electrolysis, the purified solution is electrolyzed between lead alloy anodes and aluminum cathodes. The high-purity zinc deposited on aluminum cathodes is stripped off, dried, melted, and cast into SHG zinc ingots (99.99 % zinc). Pyro-metallurgical Smelting The pyro-metallurgical smelting process is based on the reduction of zinc and lead oxides into metal with carbon in an imperial smelting furnace. The sinter, along with pre-heated coke, is charged from the top of the furnace and injected from below with pre-heated air. This ensures that temperature in the center of the furnace remains in the range of 1000-1500 °C. The coke is converted to carbon monoxide, and zinc and lead oxides are reduced to metallic zinc and lead. The liquid lead bullion is collected at the bottom of the furnace along with other metal impurities (copper, silver, and gold). Zinc in vapor form is collected from the top of the furnace along with other gases. Zinc vapor is then condensed into liquid zinc. The lead and cadmium impurities in zinc bullion are removed through a distillation process. The imperial smelting process is an energy-intensive process and produces zinc of lower purity than the electrometallurgical process. technologyComment of rare earth oxides production, from rare earth oxide concentrate, 70% REO (CN-SC): This dataset refers to the separation (hydrochloric acid leaching) and refining (metallothermic reduction) process used in order to produce high-purity rare earth oxides (REO) from REO concentrate, 70% beneficiated. ''The concentrate is calcined at temperatures up to 600ºC to oxidize carbonaceous material. Then HCl leaching, alkaline treatment, and second HCl leaching is performed to produce a relatively pure rare earth chloride (95% REO). Hydrochloric acid leaching in Sichuan is capable of separating and recovering the majority of cerium oxide (CeO) in a short process. For this dataset, the entire quantity of Ce (50% cerium dioxide [CeO2]/REO) is assumed to be produced here as CeO2 with a grade of 98% REO. Foreground carbon dioxide CO2 emissions were calculated from chemical reactions of calcining beneficiated ores. Then metallothermic reduction produces the purest rare earth metals (99.99%) and is most common for heavy rare earths. The metals volatilize, are collected, and then condensed at temperatures of 300 to 400°C (Chinese Ministryof Environmental Protection 2009).'' Source: Lee, J. C. K., & Wen, Z. (2017). Rare Earths from Mines to Metals: Comparing Environmental Impacts from China's Main Production Pathways. Journal of Industrial Ecology, 21(5), 1277-1290. doi:10.1111/jiec.12491 technologyComment of scandium oxide production, from rare earth tailings (CN-NM): See general comment. technologyComment of sulfur production, petroleum refinery operation (Europe without Switzerland): The technology level in Europe applied here represents a weighted average of BREF types II (62%), III (29%), IV (9%) refineries; API 35; sulfur content 1.03%. technologyComment of sulfur production, petroleum refinery operation (PE): The technology represents BREF type II refinery; API 25; sulfur content 0.51% technologyComment of sulfur production, petroleum refinery operation (BR): The technology represents BREF type II refinery; API 25; sulfur content 0.57% technologyComment of sulfur production, petroleum refinery operation (ZA): The technology represents a weighted average of BREF types II and III refineries; API 35; sulfur content 0.7% technologyComment of sulfur production, petroleum refinery operation (CO): The technology represents a weighted average of BREF types II and IV refineries; API 35; sulfur content 0.56% technologyComment of sulfur production, petroleum refinery operation (IN): The technology represents a weighted average of BREF types II and IV refineries; API 35; sulfur content 1.39% technologyComment of sulfur production, petroleum refinery operation (RoW): This dataset represents the prevailing technology level in Europe, this is a weighted average of BREF complexity types II (62%), III (29%), IV (9%) refineries (see BREF document, European Commission, 2015); API 35; sulfur content 1.03%. Reference(s): European Commission (2015) Best Available Techniques (BAT) Reference Document (BREF) for the Refining of Mineral Oil and Gas, Industrial Emissions Directive 2010/75/EU Integrated Pollution Prevention and control, accessible online at http://eippcb.jrc.ec.europa.eu/reference/BREF/REF_BREF_2015.pdf, February 2019 technologyComment of synthetic fuel production, from coal, high temperature Fisher-Tropsch operations (ZA): SECUNDA SYNFUEL OPERATIONS: Secunda Synfuels Operations operates the world’s only commercial coal-based synthetic fuels manufacturing facility of its kind, producing synthesis gas (syngas) through coal gasification and natural gas reforming. They make use of their proprietary technology to convert syngas into synthetic fuel components, pipeline gas and chemical feedstock for the downstream production of solvents, polymers, comonomers and other chemicals. Primary internal customers are Sasol Chemicals Operations, Sasol Exploration and Production International and other chemical companies. Carbon is produced for the recarburiser, aluminium, electrode and cathodic production markets. Secunda Synfuels Operations receives coal from five mines in Mpumalanga (see figure attached). After being crushed, the coal is blended to obtain an even quality distribution. Electricity is generated by both steam and gas and used to gasify the coal at a temperature of 1300°C. This produces syngas from which two types of reactor - circulating fluidised bed and Sasol Advanced SynthoTM reactors – produce components for making synthetic fuels as well as a number of downstream chemicals. Gas water and tar oil streams emanating from the gasification process are refined to produce ammonia and various grades of coke respectively. imageUrlTagReplacea79dc0c2-0dda-47ec-94e0-6f076bc8cdb6 SECUNDA CHEMICAL OPERATIONS: The Secunda Chemicals Operations hub forms part of the Southern African Operations and is the consolidation of all the chemical operating facilities in Secunda, along with Site Services activities. The Secunda Chemicals hub produces a diverse range of products that include industrial explosives, fertilisers; polypropylene, ethylene and propylene; solvents (acetone, methyl ethyl ketone (MEK), ethanol, n-Propanol, iso-propanol, SABUTOL-TM, PROPYLOL-TM, mixed C3 and C4 alcohols, mixed C5 and C6 alcohols, High Purity Ethanol, and Ethyl Acetate) as well as the co-monomers, 1-hexene, 1-pentene and 1-octene and detergent alcohol (SafolTM).
Projektziel war die Entwicklung eines Konzeptes, um Nanomaterialien (NM) hinsichtlich ihrer Ökotoxizitat für Algen, Daphnien, und den Fischembryo zu gruppieren. Dabei wurden fünf Arbeitsschritte durchlaufen: (i) Auswahl von insgesamt 14 NM, die sich auf die Materialtypen Ag, ZnO, TiO2, CeO2, und Cu aufteilten; (ii) umfassende physikalischĄ-chemische Charakterisierung aller Materialien in Wasser und den drei Testmedien; (iii) Entwicklung von Hypothesen zur erwarteten Ökotoxizitat; (iv) ökotoxikologische Testung aller NM in den drei ausgewählten Testsystemen; (v) Erprobung verschiedener Gruppierungsänsatze auf Basis der physikalischĄ-chemischen Parameter (PCParameter), die als relevant für die aquatische Ökotoxizitat identifiziert worden waren. Als relevant wurden Morphologie, Stabilität (Ionenfreisetzung, Kristallstruktur) und die Ökotoxizitat der chemischen Verbindung identifiziert und darauf basierend ein Schema zur Gruppierung vorgeschlagen. Es ist jedoch nicht auszuschließen, dass weitere Parameter zu berücksichtigen sind. Es zeigte sich weiterhin, dass keine sinnvolle Gruppierungshypothese auf einem einzelnen PCĄ-Parameter beruhen kann. Für eine sinnvolle Gruppierung ist ein Set von Parametern notwendig. Um das vorgeschlagene Gruppierungskonzept im Hinblick auf die regulatorische Anwendung zukünftig weiterzuentwickeln sind folgende Aspekte zu berücksichtigen: (i) gezielte Berücksichtigung von Oberflächenmodifikationen, die bewusst bei dem Projekt ausgeschlossen worden waren; (ii) Ersatz des Fischembryotests aufgrund seiner geringen Sensitivität; (iii) Anpassung der Methoden zur Bestimmung der Oberflächenreaktivitat, da keine Übereinstimmung zwischen den entsprechenden Messwerten und der Ökotoxizitat ermittelt wurde; (iv) die Kinetik ausgewählter PCĄ-Parameter (Agglomerationsverhalten; ZetaĄ-Potential, Reaktivität, Löslichkeit) im Test. Ferner wird eine größere Anzahl an ECĄ-Werten benötigt, um die Aussagekraft der Statistik zu erhöhen. Quelle: Forschungsbericht
Projektziel war die Entwicklung eines Konzeptes, um Nanomaterialien (NM) hinsichtlich ihrer Ökotoxizitat für Algen, Daphnien, und den Fischembryo zu gruppieren. Dabei wurden fünf Arbeitsschritte durchlaufen: (i) Auswahl von insgesamt 14 NM, die sich auf die Materialtypen Ag, ZnO, TiO2, CeO2, und Cu aufteilten; (ii) umfassende physikalischĄ-chemische Charakterisierung aller Materialien in Wasser und den drei Testmedien; (iii) Entwicklung von Hypothesen zur erwarteten Ökotoxizitat; (iv) ökotoxikologische Testung aller NM in den drei ausgewählten Testsystemen; (v) Erprobung verschiedener Gruppierungsänsatze auf Basis der physikalischĄ-chemischen Parameter (PCParameter), die als relevant für die aquatische Ökotoxizitat identifiziert worden waren. Als relevant wurden Morphologie, Stabilität (Ionenfreisetzung, Kristallstruktur) und die Ökotoxizitat der chemischen Verbindung identifiziert und darauf basierend ein Schema zur Gruppierung vorgeschlagen. Es ist jedoch nicht auszuschließen, dass weitere Parameter zu berücksichtigen sind. Es zeigte sich weiterhin, dass keine sinnvolle Gruppierungshypothese auf einem einzelnen PCĄ-Parameter beruhen kann. Für eine sinnvolle Gruppierung ist ein Set von Parametern notwendig. Um das vorgeschlagene Gruppierungskonzept im Hinblick auf die regulatorische Anwendung zukünftig weiterzuentwickeln sind folgende Aspekte zu berücksichtigen: (i) gezielte Berücksichtigung von Oberflächenmodifikationen, die bewusst bei dem Projekt ausgeschlossen worden waren; (ii) Ersatz des Fischembryotests aufgrund seiner geringen Sensitivität; (iii) Anpassung der Methoden zur Bestimmung der Oberflächenreaktivitat, da keine Übereinstimmung zwischen den entsprechenden Messwerten und der Ökotoxizitat ermittelt wurde; (iv) die Kinetik ausgewählter PCĄ-Parameter (Agglomerationsverhalten; ZetaĄ-Potential, Reaktivität, Löslichkeit) im Test. Ferner wird eine größere Anzahl an ECĄ-Werten benötigt, um die Aussagekraft der Statistik zu erhöhen. Quelle: Forschungsbericht
technologyComment of rare earth oxides production, from rare earth oxide concentrate, 70% REO (CN-SC): This dataset refers to the separation (hydrochloric acid leaching) and refining (metallothermic reduction) process used in order to produce high-purity rare earth oxides (REO) from REO concentrate, 70% beneficiated. ''The concentrate is calcined at temperatures up to 600ºC to oxidize carbonaceous material. Then HCl leaching, alkaline treatment, and second HCl leaching is performed to produce a relatively pure rare earth chloride (95% REO). Hydrochloric acid leaching in Sichuan is capable of separating and recovering the majority of cerium oxide (CeO) in a short process. For this dataset, the entire quantity of Ce (50% cerium dioxide [CeO2]/REO) is assumed to be produced here as CeO2 with a grade of 98% REO. Foreground carbon dioxide CO2 emissions were calculated from chemical reactions of calcining beneficiated ores. Then metallothermic reduction produces the purest rare earth metals (99.99%) and is most common for heavy rare earths. The metals volatilize, are collected, and then condensed at temperatures of 300 to 400°C (Chinese Ministryof Environmental Protection 2009).'' Source: Lee, J. C. K., & Wen, Z. (2017). Rare Earths from Mines to Metals: Comparing Environmental Impacts from China's Main Production Pathways. Journal of Industrial Ecology, 21(5), 1277-1290. doi:10.1111/jiec.12491 technologyComment of sodium chloride production, powder (RER, RoW): For the production of dry salt, three different types of sodium chloride production methods can be distinguished namely, underground mining of halite deposits, solution mining with mechanical evaporation and solar evaporation. Their respective products are rock salt, evaporated salt and solar salt: - Underground mining: The main characteristic of this technique is the fact that salt is not dissolved during the whole process. Instead underground halite deposits are mined with traditional techniques like undercutting, drilling and blasting or with huge mining machines with cutting heads. In a second step, the salt is crushed and screened to the desired size and then hoisted to the surface. - Solution mining and mechanical evaporation: In this case, water is injected in a salt deposit, usually in about 150 to 500 m depth. The dissolution of the halite or salt deposits forms a cavern filled with brine. This brine is then pumped from the cavern back to the surface and transported to either an evaporation plant for the production of evaporated salt or transported directly to a chemical processing plant, e.g. a chlor-alkali plant. - Solar evaporation: In this case salt is produced with the aid of the sun and wind out of seawater or natural brine in lakes. Within a chain of ponds, water is evaporated by sun until salt crystallizes on the floor of the ponds. Due to their natural process drivers, such plants must be located in areas with only small amounts of rain and high evaporation rates - e.g. in the Mediterranean area where the rate between evaporation and rainfall is 3:1, or in Australia, where even a ratio up to 15:1 can be found. There are some impurities due to the fact that seawater contains not only sodium chloride. That leads to impurities of calcium and magnesium sulfate as well as magnesium chloride. With the aid of clean brine from dissolved fine salt, these impurities are washed out. As a fourth form on the market, the so-called 'salt in brine' may be found, which is especially used for the production of different chemicals. In this case, the solution mining technique without an evaporation step afterwards is used. This dataset represents the production of dry sodium chloride by underground mining (51%) and by solution mining (49%) with modern solution mining technology (thermo compressing technology). References: Althaus H.-J., Chudacoff M., Hischier R., Jungbluth N., Osses M. and Primas A. (2007) Life Cycle Inventories of Chemicals. ecoinvent report No. 8, v2.0. EMPA Dübendorf, Swiss Centre for Life Cycle Inventories, Dübendorf, CH.
technologyComment of magnesium sulfate production (RER, RoW): Data approximated with data from lime mining, crushing and milling. technologyComment of rare earth oxides production, from rare earth oxide concentrate, 50% REO (CN-NM): At first, the 50% REO concentrate undergoes acid roasting, where it is heated to 550 °C with the addition of 93% sulfuric acid to produce rare earth sulfates (approximatelly 50% RE sulfate present). In the following water leaching & chlorine conversion process, the produced RE sulfates are leached and converted to 92% mixed RE chlorides, with a conversion efficiency of 97%. Afterwards, solvent extraction is applied to the mixed RE chlo-rides by mixing them with an organic extractant such as di(2-ethylhexyl) phosphoric acid, with the small differences in basicity of the different RE metals serving as the driving agent of the separation process. The products of the solvent extraction process are aqueous solutions of individual RE ions high purity (99%). The generated RE ions are then precipitated in the aqueous solutions to produce RE carbonates. Calcination of the RE carbonates at 750−800 °C with natural gas as the heat source is the final step to form the individual REOs (lanthanum oxide, cerium oxide, neodymium oxide and a mixed samarium-europium gadolinium concentrate).
Engineered nanomaterials (ENM) such as nano-sized cerium dioxide (CeO2) are increasingly applied. Meanwhile, concerns on their environmental fate are rising. Understanding the fate of ENM within and between environmental compartments such as surface water and groundwater is crucial for the protection of drinking water resources. Therefore, the colloidal stability of CeO2 ENM (2 mg L-1) was assessed with various surface coatings featuring different physico-chemical properties such as weakly anionic polyvinyl alcohol (PVA), strongly anionic polyacrylic acid (PAA) or complex natural organic matter (NOM) at various water compositions in batch experiments (pH 2 - 12, ionic strength 0-5 mM KCl or CaCl2). While uncoated CeO2 ENM aggregate in the range of pH 4-8 in 1 mM KCl solution, the results show that PAA, PVA and NOM surface coatings stabilize CeO2-ENM at neutral and alkaline pH in 1 mM KCl solution. Stabilization by PAA and NOM is associated with strongly negative zeta potentials below -20 mV, suggesting electrostatic repulsion as stabilization mechanism. No aggregation was detected up to 5 mM KCl for PAA- and NOM-coated CeO2 ENM. In contrast, CaCl2 induced aggregation at >2.2 mM CaCl2 for PAA and NOM-coated CeO2 ENM respectively. PVA-coated ENM showed zeta potentials of -15 mV to -5 mV in the presence of 0-5 mM ionic strength, suggesting steric effects as stabilization mechanism. The hydrodynamic diameter of PVA-coated ENM was larger compared to PAA and NOM at low ionic strength, but the size did not increase with ionic strength of the suspensions. The effect of ionic strength and counter ion valency (pH 7) on the colloidal stability of ENM depends on the prevailing stabilization mechanism of the organic coating. NOM can be similarly effective in colloidal stabilization of CeO2-ENM as PAA. Our results suggest natural Ca-rich waters will lead to ENM agglomeration even of coated CeO2-ENM. © 2018 The Authors. Published by Elsevier B.V.
Where surface-functionalized engineered nanoparticles (NP) occur in drinking water catchments, understanding their transport within and between environmental compartments such as surface water and groundwater is crucial for risk assessment of drinking water resources. The transport of NP is mainly controlled by (i) their surface properties, (ii) water chemistry, and (iii) surface properties of the stationary phase. Therefore, functionalization of NP surfaces by organic coatings may change their fate in the environment. In laboratory columns, we compared the mobility of CeO2 NP coated by the synthetic polymer polyacrylic acid (PAA) with CeO2 NP coated by natural organic matter (NOM) and humic acid (HA), respectively. The effect of ionic strength on transport in sand columns was investigated using deionized (DI) water and natural surface water with 2.2 mM Ca2+ (soft) and 4.5 mM Ca2+ (hard), respectively. Furthermore, the relevance of these findings was validated in a near-natural bank filtration experiment using HA-CeO2 NP. PAA-CeO2 NP were mobile under all tested water conditions, showing a breakthrough of 60% irrespective of the Ca2+ concentration. In contrast, NOM-CeO2 NP showed a lower mobility with a breakthrough of 27% in DI and < 10% in soft surface water. In hard surface water, NOM-CeO2 NP were completely retained in the first 2 cm of the column. The transport of HA-CeO2 NP in laboratory columns in soft surface water was lower compared to NOM-CeO2 NP with a strong accumulation of CeO2 NP in the first few centimeters of the column. Natural coatings were generally less stabilizing and more susceptible to increasing Ca2+ concentrations than the synthetic coating. The outdoor column experiment confirmed the low mobility of HA-CeO2 NP under more complex environmental conditions. From our experiments, we conclude that the synthetic polymer is more efficient in facilitating NP transport than natural coatings and hence, CeO2 NP mobility may vary significantly depending on the surface coating. © The Author(s) 2019
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