Comparative Study: Impacts of Ca and Mg Salts on Iron Oxygen Carriers in Chemical Looping Combustion of Biomass.

Chemical looping combustion (CLC) is one of the most promising methods for carbon capture and storage (CCS). An oxygen carrier, i.e., a mineral that can be oxidized and reduced, is used to convert the fuel in the process. The produced CO2 is inherently separated from the air components that enables easier CCS. The use of biomass-based fuels is desirable since it can lead to negative CO2 emissions. On the other hand, alkali compounds from the biomass may interact with the oxygen carrier causing problems, such as deactivation of the oxygen carrier. The most common oxygen carriers contain iron, since iron-based ores and industrial waste materials are readily available and cost-efficient. Therefore, the interaction between the iron oxygen carriers and the biomass ash-forming compounds needs to be investigated. Since Ca/Mg are abundant in biomass, it is important to clarify how their compounds interact with the oxygen carrier. In this study, the effect of Ca/Mg carbonates, chlorides, nitrates, sulfates, and phosphates along with synthetic biomass-derived ash on iron oxides was investigated. Redox reactions were investigated at 950 °C during 5 h under both oxidizing and reducing atmospheres. The results showed that the effect of Ca/Mg salts on the oxygen carrier varied depending on the anion of the salt. Generally, the nitrate- and phosphate-based salts of both Ca and Mg showed the harshest effect regarding agglomeration of the oxygen carriers. It was shown that the Ca/Mg-based compounds interacted differently with iron oxides, which was an unexpected result.

Comprehensive treatments of tungsten slags in China: A critical review.

As a critical and strategic metal, tungsten is widely used in the fields of machinery, mining and military industry. With most of the tungsten resources reserves in the world, China is the largest producer and exporter of tungsten. This has resulted in the generation of a huge amount of tungsten slag (slag) stored in China. This slag always contains not only valuable elements, such as tungsten (W), scandium (Sc), tin (Sn), niobium (Nb) and tantalum (Ta), but also toxic elements, such as arsenic (As), lead (Pb), chromium (Cr) and mercury (Hg). Due to a lack of developed technologies, most of these slags cannot be treated safely, which results in a waste of resources and serious environmental and ecological risks. In this review we briefly describe the distribution and proportion of tungsten deposits in China, the tungsten extraction process and the properties of tungsten slag. We also mainly discuss the comprehensive treatments for the valuable and toxic slag, including the amounts of valuable metal elements that can be recovered and the stabilization of toxic elements. These aspects are summarized in a comparison of their advantages and disadvantages. In particular, we focus on the efforts to analyze the relationship between the existing processes and attempts to establish a comprehensive technology to treat tungsten slag and also suggest areas for future research.

Incineration of EV Lithium-ion batteries as a pretreatment for recycling - Determination of the potential formation of hazardous by-products and effects on metal compounds.

In several industrial Lithium-ion batteries recycling processes, a thermal treatment with oxidative atmosphere is used to separate the battery components and to remove the organic components. This method is often combined with hydrometallurgical processes with the aim to increase the metal recovery rate or to improve the efficiency of the existing processes. Despite such efforts, the effects of a thermal treatment in an oxidative atmosphere on the microstructure and composition on cathode and anode materials has not been explored. In this manuscript, spent batteries which cathode active material has the composition Li(NixMnyCoz)Oz, i.e. NMC-LiBs, were subjected to thermal treatment at 400˚, 500˚, 600˚, and 700 °C for 30, 60, and 90 min. The microstructure and the composition were studied using XRD and ICP-OES. Thermodynamic calculations were performed to forecast the trend of the carbothermic reduction of active materials. It was observed the formation of gas and organic oil by-products from the decomposition of the polypropylene separator and the polyvinylidene fluoride binder. The identification of the composition of these by-products has great importance since they have a corrosive and toxic behavior. It was observed the fluorine behavior during the thermal treatment and its presence in the oil by-products.

Controlling the Composition and Magnetic Properties of Nano-SrFe12O19 Powder Synthesized from Oily Cold Mill Sludge by the Citrate Precursor Method.

This paper proposes a new method for producing nano-SrFe12O19 powder by the citrate precursor route using solid waste as a source of iron. This solid iron-containing waste, which exists in the form of an oily sludge, is produced by a cold rolling mill. This sludge was first subjected to a process, including sulfuric acid leaching, oxidation, precipitation, and nitric acid leaching, to obtain an iron nitrate (Fe(NO3)3) solution. Next, the Fe(NO3)3 solution was mixed with a strontium nitrate (Sr(NO3)2) solution obtained by subjecting strontium carbonate to nitric acid leaching. Subsequently, citric acid, as chelating agent, and ammonia water, as precipitating agent, were added to the mixed solution to form a gel. The gel was dried and spontaneously combusted, then annealed at different temperatures for 2 h in flowing air. The effects of the Fe3+/Sr2+ molar ratio and annealing temperature on the formation, morphology, and magnetic properties of SrFe12O19 were investigated. The results showed that single-phase SrFe12O19 powder was obtained by decreasing the Fe3+/Sr2+ molar ratio from the stoichiometric value of 12 to 11.6 and increasing the annealing temperature to 1000 °C for 2 h. Adjustment of the Fe/Sr molar ratio to 12 and the annealing temperature to 900 °C enabled the magnetic properties to be optimized, including saturation magnetization (Ms) 80.2 emu/g, remanence magnetization (Mr) 39.8 emu/g, and coercive force (Hc) 6318 Oe.

Recovery of industrial valuable metals from household battery waste.

The modern community is dependent on electronic devices such as remote controls, alarm clocks, electric shavers, phones and computers, all of which are powered by household batteries. Alkaline, zinc-carbon (Zn-C), nickel metal hydride, lithium and lithium-ion batteries are the most common types of household energy storage technologies in the primary and secondary battery markets. Primary batteries, especially alkaline and Zn-C batteries, are the main constituents of the collected spent battery stream due to their short lifetimes. In this research, the recycling of main battery components, which are steel shells, zinc (Zn) and manganese oxides, was investigated. Household batteries were collected in Gothenburg, Sweden and mechanically pretreated by a company, Renova AB. The steel shells from spent batteries were industrially separated from the batteries themselves and the battery black mass obtained. A laboratory-scale pyrolysis method was applied to recover the Zn content via carbothermic reduction. First, the carbothermic reaction of the battery black mass was theoretically studied by HSC Chemistry 9.2 software. The effect of the amount of carbon on the Zn recovery was then examined by the designed process at 950°C. The recovery efficiency of Zn from battery black mass was over 99%, and the metal was collected as metallic Zn particles in a submicron particle size range. The pyrolysis residue was composed of mainly MnO2with some minor impurities such as iron and potassium. The suggested recycling process is a promising route not only for the effective extraction of secondary resources, but also for the utilization of recovered products in advanced technology applications.

Source analysis of municipal solid waste in a mega-city (Guangzhou): Challenges or opportunities?

Rapid economic development accelerates the generation of municipal solid waste (MSW), and thereby calls for an effective and reliable waste management strategy. In the present work, we systematically investigated the status of MSW management in a mega-city of China (Guangzhou). The data were collected from literatures, government statistics and field sampling work. It can be found that a combination of waste sorting by individual residents and a necessary quantity of sanitation workers is one of the most feasible strategies to achieve a sustainable waste management. With implementation of that integrated strategy, approximately 0.03 million tons of metal, 0.24 million tons of paper, as well as 0.46 million tons of plastics can be recycled/recovered for further processing. A cost reduction of 70 million US$ is achieved in comparison with the un-optimized system due to the sale revenue of recyclable materials and the saving from waste disposal fees. The values of environmental assessment were expressed as environmental load units. The developed scenarios could decrease the environmental cost, namely, 0.66 million US$. Based on the studies, waste sorting is urgently needed in Guangzhou. However, to make the proposed strategy to be more economically feasible, the sorting should be performed individually as well as with public participation. The establishment of a win-win situation for all stakeholders is an effective path for the improvement of the integrated waste management system.

Assessment of copper and zinc recovery from MSWI fly ash in Guangzhou based on a hydrometallurgical process.

Fly ash commonly accumulates a significant amount of heavy metals and most of these heavy metals are toxic and easily leached out to the environment, posing risks to human health. Thus, fly ash has been classified as a type of hazardous waste and requires proper treatment before disposal in specific landfill sites for hazardous waste. In this study, a hydrometallurgical process developed to recover copper and zinc performed in pilot scale close to industrial scale followed by a landfill compliance leaching test of the ash residue is evaluated. LIX860N-I and Cyanex 572 gave high selectively for extractions, a yield efficiency of 95% and 61% was achieved for copper and zinc respectively. Results of pilot experiments reveals that the combining metal recovery/recycling and landfill disposal of the ash residue in a local regular landfill was demonstrated to be a technically and economically effective strategy. Specifically, the economic and environmental aspects of a scenario, in which the fly ash generated in Guangzhou is processed were systematically assessed. the assessment results show that a 7.15 million US$ of total expense reduction, a less energy cost of 19k GJ as well as 2100 tons less CO2 emissions could be achieved annually comparing to the current alternative, direct disposal of the fly ash as hazardous waste. The results reveal that the hydrometallurgical process has industrial application potential on both economic and environmental aspects and further optimization of the process can give more accurate assessment of the cost and environment effect. In addition, leaching tests and evaluation of solid residue according to the regulations specific to the country should be studied in future.

Recovery of phosphorous from industrial waste water by oxidation and precipitation.

This paper describes the development of a method for recovery of phosphorous from one of the waste waters at an Akzo Nobel chemical plant in Ale close to Göteborg. It was found that it is possible to transform the phosphorous in the waste water to a saleable product, i.e. a slowly dissolving fertilizer. The developed process includes oxidation of phosphite to phosphate with hydrogen peroxide and heat. The phosphate is then precipitated as crystalline struvite (ammonium magnesium phosphate) by the addition of magnesium chloride. The environmental impacts of the new method were compared with those of the current method using life cycle assessment. It was found that the methodology developed in this project was an improvement compared with the current practice regarding element resource depletion and eutrophication. However, the effect on global warming would be greater with the new method. There could however be several ways to decrease the global warming effect. Since most of the carbon dioxide emissions come from the production of magnesium chloride from carbonates, changing to utilization of a magnesium chloride from desalination of seawater or from recycling of PVC would decrease the carbon footprint significantly.

Crystal structure and identification of resonance forms of diethyl 2-(3-oxoiso-1,3-di-hydro-benzo-furan-1-yl-idene)malonate.

The reaction of diethyl malonate with phthaloyl chloride in aceto-nitrile in the presence of tri-ethyl-amine and magnesium chloride results in the formation of the title compound, diethyl 2-(3-oxo-1,3-di-hydro-2-benzo-furan-1-yl-idene)propane-dioate, C15H14O6. One of the ester groups of the diethyl malonate fragment is almost coplanar with the isobenzo-furan unit, while the plane of the other group is perpendicular to it [dihedral angles = 5.45 (3) and 83.30 (3)°, respectively]. The C-C and C-O distances both in the heterocyclic furan ring and the diethyl malonate fragment are indicative of the dipolar delocalization occurring within the isobenzo-furan unit. This delocalization is likely to be responsible for the unusual inter-molecular O⋯O contact [2.756 (2) Å], established between the O atom of the furan ring and the carbonyl O atom of the diethyl malonate fragment. In the crystal, weak C-H⋯O inter-actions are observed, which link the mol-ecules into [100] chains.

Investigation of zinc recovery by hydrogen reduction assisted pyrolysis of alkaline and zinc-carbon battery waste.

Zinc (Zn) recovery from alkaline and zinc-carbon (Zn-C) battery waste were studied by a laboratory scale pyrolysis process at a reaction temperature of 950°C for 15-60min residence time using 5%H2(g)-N2(g) mixture at 1.0L/min gas flow rate. The effect of different cooling rates on the properties of pyrolysis residue, manganese oxide particles, were also investigated. Morphological and structural characterization of the produced Zn particles were performed. The battery black mass was characterized with respect to the properties and chemical composition of the waste battery particles. The thermodynamics of the pyrolysis process was studied using the HSC Chemistry 5.11 software. A hydrogen reduction reaction of the battery black mass (washed with Milli-Q water) takes place at the chosen temperature and makes it possible to produce fine Zn particles by rapid condensation following the evaporation of Zn from the pyrolysis batch. The amount of Zn that can be separated from the black mass increases by extending the residence time. Recovery of 99.8% of the Zn was achieved at 950°C for 60min residence time using 1.0L/min gas flow rate. The pyrolysis residue contains MnO and Mn2O3 compounds, and the oxidation state of manganese can be controlled by cooling rate and atmosphere. The Zn particles exhibit spherical and hexagonal particle morphology with a particle size varying between 200nm and 3µm. However the particles were formed by aggregation of nanoparticles which are primarily nucleated from the gas phase.

Production of zinc and manganese oxide particles by pyrolysis of alkaline and Zn-C battery waste.

Production of zinc and manganese oxide particles from alkaline and zinc-carbon battery black mass was studied by a pyrolysis process at 850-950°C with various residence times under 1L/minN2(g) flow rate conditions without using any additive. The particular and chemical properties of the battery waste were characterized to investigate the possible reactions and effects on the properties of the reaction products. The thermodynamics of the pyrolysis process were studied using the HSC Chemistry 5.11 software. The carbothermic reduction reaction of battery black mass takes place and makes it possible to produce fine zinc particles by a rapid condensation, after the evaporation of zinc from a pyrolysis batch. The amount of zinc that can be separated from the black mass is increased by both pyrolysis temperature and residence time. Zinc recovery of 97% was achieved at 950°C and 1h residence time using the proposed alkaline battery recycling process. The pyrolysis residue is mainly MnO powder with a low amount of zinc, iron and potassium impurities and has an average particle size of 2.9µm. The obtained zinc particles have an average particle size of about 860nm and consist of hexagonal crystals around 110nm in size. The morphology of the zinc particles changes from a hexagonal shape to s spherical morphology by elevating the pyrolysis temperature.

Leaching optimization of municipal solid waste incineration ash for resource recovery: A case study of Cu, Zn, Pb and Cd.

Ash from municipal solid waste incineration (MSWI) may be quite cumbersome to handle. Some ash fractions contain organic pollutants, such as dioxins, as well as toxic metals. Additionally, some of the metals have a high value and are considered as critical to the industry. Recovery of copper, zinc and lead from MSWI ashes, for example, will not only provide valuable metals that would otherwise be landfilled but also give an ash residue with lower concentrations of toxic metals. In this work, fly ash and bottom ash from an MSWI facility was used for the study and optimization of metal leaching using different solutions (nitric acid, hydrochloric acid and sulfuric acid) and parameters (temperature, controlled pH value, leaching time, and liquid/solid ratio). It was found that hydrochloric acid is relatively efficient in solubilizing copper (68.2±6.3%) and zinc (80.8±5.3%) from the fly ash in less than 24h at 20°C. Efficient leaching of cadmium and lead (over 92% and 90% respectively) was also achieved. Bottom ash from the same combustion unit was also characterized and leached using acid. The metal yields were moderate and the leachates had a tendency to form a gelatinous precipitate, which indicates that the solutions were actually over-saturated with respect to some components. This gel formation will cause problems for further metal purification processes, e.g. solvent extraction.

Investigations into Recycling Zinc from Used Metal Oxide Varistors via pH Selective Leaching: Characterization, Leaching, and Residue Analysis.

Metal oxide varistors (MOVs) are a type of resistor with significantly nonlinear current-voltage characteristics commonly used in power lines to protect against overvoltages. If a proper recycling plan is developed MOVs can be an excellent source of secondary zinc because they contain over 90 weight percent zinc oxide. The oxides of antimony, bismuth, and to a lesser degree cobalt, manganese, and nickel are also present in varistors. Characterization of the MOV showed that cobalt, nickel, and manganese were not present in the varistor material at concentrations greater than one weight percent. This investigation determined whether a pH selective dissolution (leaching) process can be utilized as a starting point for hydrometallurgical recycling of the zinc in MOVs. This investigation showed it was possible to selectively leach zinc from the MOV without coleaching of bismuth and antimony by selecting a suitable pH, mainly higher than 3 for acids investigated. It was not possible to leach zinc without coleaching of manganese, cobalt, and nickel. It can be concluded from results obtained with the acids used, acetic, hydrochloric, nitric, and sulfuric, that sulfate leaching produced the most desirable results with respect to zinc leaching and it is also used extensively in industrial zinc production.

Investigation of an Electrochemical Method for Separation of Copper, Indium, and Gallium from Pretreated CIGS Solar Cell Waste Materials.

Recycling of the semiconductor material copper indium gallium diselenide (CIGS) is important to ensure a future supply of indium and gallium, which are relatively rare and therefore expensive elements. As a continuation of our previous work, where we recycled high purity selenium from CIGS waste materials, we now show that copper and indium can be recycled by electrodeposition from hydrochloric acid solutions of dissolved selenium-depleted material. Suitable potentials for the reduction of copper and indium were determined to be -0.5 V and -0.9 V (versus the Ag/AgCl reference electrode), respectively, using cyclic voltammetry. Electrodeposition of first copper and then indium from a solution containing the dissolved residue from the selenium separation and ammonium chloride in 1 M HCl gave a copper yield of 100.1 ± 0.5% and an indium yield of 98.1 ± 2.5%. The separated copper and indium fractions contained no significant contamination of the other elements. Gallium remained in solution together with a small amount of indium after the separation of copper and indium and has to be recovered by an alternative method since electrowinning from the chloride-rich acid solution was not effective.

Solvent extraction separation of copper and zinc from MSWI fly ash leachates.

Fly ash from combustion of municipal solid waste (MSW) contains significant amounts of metals, some of which are valuable and some of which are potentially toxic. This type of ash is most often stabilized and landfilled which means that the metals will be difficult to reclaim at a later stage. In recent years efforts have been made to develop feasible methods to recover selected metals, such as Zn, from MSW fly ash. If this would be possible, a significant amount of valuable metals could be re-inserted in the industrial material loops. This paper describes the development and evaluation of a process for recovery of Cu and Zn from MSW combustion fly ash based on hydrochloric acid leaching followed by two solvent extraction processes, one for each metal. The separation of Cu from the acid leachate was done using an aldoxime extractant, LIX860N-I, in kerosene and a mixture of phosphine oxides, Cyanex 923, also in kerosene, was used for extraction of Zn from the Cu-depleted aqueous phase. The extraction of Cu was selective, but a significant amount of other metals, such as Fe and Pb, were co-extracted together with Zn. It was shown that it is possible to decrease the contamination of Fe by using a suitable concentration of nitric acid solution for stripping or by removing the contaminating metals through cementation. The suggested process was tested for two MSW combustion fly ashes in laboratory scale experiments and gave Cu yields of 69-87% and Zn yields of 75-80% based on the contents in the ash.

Leaching for recovery of copper from municipal solid waste incineration fly ash: influence of ash properties and metal speciation.

Recovery of metals occurring in significant amounts in municipal solid waste incineration fly ash, such as copper, could offer several advantages: a decreased amount of potentially mobile metal compounds going to landfill, saving of natural resources and a monetary value. A combination of leaching and solvent extraction may constitute a feasible recovery path for metals from municipal solid waste incineration fly ash. However, it has been shown that the initial dissolution and leaching is a limiting step in such a recovery process. The work described in this article was focused on elucidating physical and chemical differences between two ash samples with the aim of explaining the differences in copper release from these samples in two leaching methods. The results showed that the chemical speciation is an important factor affecting the release of copper. The occurrence of copper as phosphate or silicate will hinder leaching, while sulphate and chloride will facilitate leaching.

Initial studies of the recovery of Cu from MSWI fly ash leachates using solvent extraction.

Large volumes of ash from combustion of municipal solid waste are produced and most of it is landfilled. As this type of ash contains significant amounts of metal compounds the landfilling strategy is not optimal when considered from a resource conservation perspective. A better situation would be created if metals were recovered from the ash. In the present study leaching and solvent extraction was applied for release and separation of copper from municipal solid waste combustion fly ashes. The results showed promising results with Cu yields of 50-95%. The yield was heavily dependent on the efficiency of the initial leaching of Cu from the ash.

Removal of hazardous metals from MSW fly ash--an evaluation of ash leaching methods.

Incineration is a commonly applied management method for municipal solid waste (MSW). However, significant amounts of potentially hazardous metal species are present in the resulting ash, and these may be leached into the environment. A common idea for cleaning the ash is to use enhanced leaching with strong mineral acids. However, due to the alkalinity of the ash, large amounts of acid are needed and this is a drawback. Therefore, this work was undertaken in order to investigate some alternative leaching media (EDTA, ammonium nitrate, ammonium chloride and a number of organic acids) and to compare them with the usual mineral acids and water. All leaching methods gave a significant increase in ash specific surface area due to removal of soluble bulk (matrix) compounds, such as CaCO(3) and alkali metal chlorides. The use of mineral acids and EDTA mobilised many elements, especially Cu, Zn and Pb, whereas the organic acids generally were not very effective as leaching agents for metals. Leaching using NH(4)NO(3) was especially effective for the release of Cu. The results show that washing of MSW filter ash with alternative leaching agents is a possible way to remove hazardous metals from MSW fly ash.

Alternative materials for adsorption of heavy metals and petroleum hydrocarbons from contaminated leachates.

In the present work, waste products from forest industries (sawdust, pine bark and fibre sludge ash), as well as some biological materials (peat, shrimp shells and seaweed), have been investigated with respect to their capacities to adsorb metals and hydrocarbons from contaminated waters. Batch and column experiments were carried out with artificial metal ion solutions and contaminated leachates from an industrial landfill. The fibre sludge ash and the Sphagnum peat showed the highest sorption capacities for metals among the materials studied in batch experiments with single-metal solutions. The uptake of metals by the fibre ash for the metals studied was: Cu and Pb 112 microg g(-1), Zn 115 microg g(-1) and Cr 97 microg g(-1). For peat the uptake was: Pb 109 microg g(-1), Cu 105 microg g(-1), Zn 100 microg g(-1) and Cr 99 microg g(-1). These materials were also effective in adsorption of diesel oil, and the n-alkanes C16 and C12. Peat and ash adsorbed respectively 36.6 and 36.4 mg g(-1) of C12, 1.84 and 1.94 mg g(-1) of C16 and for both 0.98 mg g(-1) of diesel oil. Bark adsorbed diesel oil to 0.83 mg g(-1). In the column experiments, the removal of metals from a contaminated landfill leachate by ash and peat was lower than from artificial solutions with only a few metals. The results suggest interference from other components in the leachates, such as competition of ions for the same active sites. It is quite clear that laboratory tests can overestimate the performance of adsorbents and that experiments should be specific for the intended application. For most of the metals studied in columns, peat appeared to be the best adsorbent, with respect to both sorption capacity and service time. The addition of 10% by weight of fibre ash to the peat gave higher adsorption capacities for Cd, Ni and Pb but lower for the Cu and Zn.

Adsorption of Cd, Cu, Ni, Pb and Zn on Sphagnum peat from solutions with low metal concentrations.

This work investigates adsorption of metal ions on Sphagnum peat from solutions with environmentally relevant concentrations of metals. The peat moss is intended as an alternative, low-cost filter material for contaminated waters. Adsorption of Cd, Cu, Ni, Pb and Zn was studied in batch tests, and adsorption isotherms were determined. The kinetics of adsorption was analyzed using a second-order model and rate constants were calculated. An empirical model for predicting adsorption of metal ions at a given time was derived from these constants. Metal ions were removed in the descending order Pb>Cu>Ni>Cd>Zn. Relationship between the affinities of the metals to the peat active sites with chemical properties for the metals were indicated by the results. In addition, equilibration studies were performed at constant pH and ionic strength. The experimental data fitted the Freundlich equation. Both the uptake of metals and the Freundlich constants increased in line with increasing pH. The Freundlich exponent declined with higher initial concentrations, suggesting adsorption to sites with lower activity.