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In the work, the possibility of using microturbine plants to cover auxiliary needs in the electric and thermal energy of complexes for the processing of municipal solid waste, as well as in hydrogen production plants when oxidizing powdered aluminum with water. There were proposed basic thermal diagrams of power units. There were given justification for the choice of wet-steam microturbines, which provide a higher ratio between thermal and electric power, as well as the possibility of their separate regulation in comparison with gas turbine and gas piston units. There were analyzed the working process of a single-stage two-stream active centripetal steam microturbine with an electric power of 50 kW (600 kW - thermal), which was developed, manufactured and tested, both at idle and under load as part of energy technology complexes for the disposal of municipal and agricultural solid waste. Tests showed a reduced blade efficiency of the radial microturbine compared to the calculated one. There were carried out analysis of possible causes of discrepancy and measures were developed to achieve the declared characteristics by subsequent samples of turbogenerators. [ABSTRACT FROM AUTHOR]

High temperature thermal plasma gasification can treat non-homogeneous waste at increased conversion efficiency, compared to conventional gasification. A novel nitrogen plasma technology demonstration system is presented. The system can convert 20 kg/h of biomass to synthesis gas and is constructed inside a shipping container, which makes it mobile and suitable for application in remote rural areas of developing countries. An Aspen Plus model of the plasma gasification reactor was developed to enable energy and exergy analysis. The model gave good predictions of the real synthesis gas composition obtained during experimental runs. Simple gas and steam power cycles were also modelled to assess the feasibility of the system producing its own power. Based on typical composition of wood, it was found that the plasma torch power requirement is 20.7 kW. This amount of power can be generated using an open gas turbine cycle with compressor pressure ratio of 5 and turbine inlet temperature of 1007 °C. For a combined cycle case, using steam at 8 bar and 400 °C in a steam cycle, 14.6 kW of excess power becomes available. Alternatively, 68 kg/h of steam can be delivered, in addition to satisfying the torch requirement. • Plasma gasification can treat non-homogeneous waste at high conversion efficiency. • Plasma gasification requires significant power for the plasma torch. • A containerized nitrogen plasma system for small scale waste processing is presented. • The plasma torch power requirement can be satisfied by converting the syngas to power. • Exergy analysis identified non-avoidable and avoidable losses for future improvement. [ABSTRACT FROM AUTHOR]

Textile waste is a high-volume group of municipal waste that is difficult to dispose of due to synthetic additives and chemicals that give natural fibers the properties preferred by consumers. The paper presents a method of treating textile waste based on natural fibers (cotton and wool) with mineral acids and further biological conversion of obtained hydrolysates into biogas. It was found that the hydrolysates of cotton contain a pool of sugars (≥8 g/L of glucose), which are necessary for the growth of microorganism's consortium. The hydrolysates of the mixture of natural and synthetic fibers do not contain fermentation inhibitors (even when cotton was dotted with polyesters and polyamides), and the addition of an appropriate number of wool hydrolysates (up to 5 % v/v) favours the production of biogas. The results indicate that a moderate methane production from waste textiles composed of both cotton and synthetic materials can be achieved with no need of separation, which would significantly increase the cost of their processing. [ABSTRACT FROM AUTHOR]

• Origins of Al, Ca, Fe, Si, Ti, Mg, S, Na, K, and P are discussed using literature. • Ash contents and compositions of sorted SRF fractions are determined. • Contributions of material fractions to the recyclable share of SRF is investigated. • The main SRF fraction recycled in the cement kiln is the fine fraction. • The cement industry therefore offers a way to complement conventional recycling. Solid recovered fuel (SRF) ash consists of element oxides, which are valuable materials for cement manufacturers. When SRF is co-processed in the cement industry, its mineral content is incorporated into the clinker. Therefore, from a technical perspective, SRF ash is recycled. However, since recycling processes for materials that may be present in SRF exist, and since recycling goals are defined for different waste types, understanding the origin of these ash constituents and the contribution of different materials to the Recycling-index (R-index, i.e., the material-recyclable share of SRF) is important. In this work, the origins of Al, Ca, Fe, Si, Ti, Mg, Na, K, S, and P were first reviewed. Subsequently, ten SRF samples were sorted, and the ash content and composition of the sorting fractions (e.g., <10 mm, plastics, paper&cardboard) determined. Additionally, selected samples of polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), polyvinyl chloride (PVC), liquid packaging board (LPB), wood, and paper&cardboard (P&C) extracted from SRF were investigated. The results demonstrated that the materials that contributed most of the valuable oxides and ash content, and thereby to the R-index of SRF, are mixed or composite fractions, for example, the fine fraction, composites, and the sorting residues. Except for the composite LPB, no other material recovery options exist for most of these fractions. For this reason, the recycling of mixed and soiled materials or residues in the cement industry may be considered a complementary option to existing recycling processes. [ABSTRACT FROM AUTHOR]

This study assesses the viability of recycled expanded polystyrene (EPS) as an eco-friendly alternative for partially replacing sand in rendering mortars. Three mortars formulations were tested: one using 100% natural sand as a reference, and two with 30% volumetric substitution of natural sand by EPS (either virgin or recycled particles) in the total mortar volume. Two distinct mixing methods were employed for mortars incorporating EPS particles. The rheological behavior was assessed using a squeeze-flow test, and after 28 days, mechanical properties were evaluated, including compressive and flexural strength, and dynamic elastic modulus. Microstructural analysis via SEM-EDS and capillary water absorption tests were performed, along with an investigation into adhesive strength between concrete substrate and mortar. Mortars with EPS particles exhibited improved fluidity, with an initial mixing step enhancing particle homogenization. Notably, recycled EPS flakes outperformed virgin EPS beads in mechanical properties, particularly with mixing method B. Moreover, water absorption rates varied, and adhesive strength remained comparable to the reference mortar. • Partially replacing sand for EPS particles improves mortar flowability. • Recycled EPS flakes outperformed virgin EPS beads in mechanical properties. • Mortars with recycled EPS flakes exhibited strong adhesive strength. • Recycled EPS flakes offer a sustainable solution for reducing sand extraction. [ABSTRACT FROM AUTHOR]

Lignocellulosic material possesses a source of fermentable saccharides for biofuel production, however it must be supplemented with other nutrients for microbial growth. We have investigated the use of chicken feather as a source of amino acids and peptides. Alkaline hydrolysis of feather under mild conditions (80 °C, 0.6% NaOH) provided a highly solubilized preparation of assimilable nitrogen. Similar conditions were applicable for pre-treatment of wheat straw. The concentration of lignocellulose-derived inhibitors was low so washing or detoxification steps were unnecessary. Therefore, hydrolysis of both materials was carried out simultaneously, resulting in a cultivation medium that was suitable for direct use in biobutanol production. Thirteen strains of solventogenic clostridia were tested for their ability to produce butanol on this mixed hydrolysate; strains of Clostridium beijerinckii and Clostridium saccharoperbutylacetonicum produced the highest butanol concentrations. The proposed process of simultaneous hydrolysis followed by direct inoculation was then demonstrated by experimental production of butanol in a laboratory bioreactor, using C. beijerinckii strain NCIMB 8052 and producing 4.6 g/L of butanol. Although process optimization is still required, we have shown that feather and wheat straw could be co-processed, forming a convenient mixed substrate for biobutanol production. • Chicken feather was introduced as a source of nitrogen for production of butanol. • Mixed feather and wheat straw hydrolysate was used directly in butanol production. • Mild alkaline treatment was applied for both substrates - feather and straw. • No washing or detoxification step was necessary. [ABSTRACT FROM AUTHOR]

Anaerobic digestion (AD) is a widely used technology that allows for the reprocessing and reduction of waste biomass. A study was conducted to see if the AD technology might be used to process radioactively polluted agricultural biomass. For this purpose, laboratory tests were carried out with a 20-liter model biogas plant (BGP) with the radionuclide 134Cs and operational tests with the South Bohemian commercial biogas plant monitoring the radionuclide 137Cs. The activities of 134Cs in inputs, contaminated grass or maize silage and in emerging fractions were investigated in the model fermenter. The activity of 134Cs in the dry matter during the fermentation process increased by 46% on average, which corresponds to a reduction of dry matter by 43% due to the production of biogas. 137Cs activities were measured in commercial BGP maize, grass, and whole plant silage, wheat, digestate, biogas, and aerosol samples. The commercial BGP fermentation process was more efficient, with an 80% reduction in dry mass weight. Dry biomass (1.37 Bq/kg) had a 137Cs massic activity that was 4.4 times lower than the activity of dry digestate mass (6.01 Bq/kg). The activity of the 137Cs in biogas aerosol was 1.1 × 10−7 Bq/m3 or less, and the decontamination factor was 6.9 × 106 or greater. Most Cs remain in the digestate. No other ways of radioactivity leakage have been identified. [Display omitted] • A biogas plant can reprocess radionuclide-contaminated plant biomass. • Commercial fermenters significantly reduce organic mass in contaminated biomass. • Cesium is mostly transferred from biomass to digestate. • The cesium decontamination factor for biogas production is higher than 6900000. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Fly ash was successfully alkali activated at room temperature. • The use of expanded perlite and H 2 O 2 allowed obtaining lightweight mortars. • Numerical simulations predicted a satisfactory fire behaviour. • Alkali activated lightweight mortars were able to outperform cement-based ones. Abstract Alkali activated lightweight mortars, obtained by room temperature activation of coal fly ash, were studied as passive fire protection systems for steel elements. Physical, mechanical and thermal properties were investigated as a function of the compositional Si/Al molar ratio and of the amount of lightweight aggregate and foaming agent. Experimental findings were used as input data to assess their fire resistance by finite volume simulations. Results pointed out that the optimized alkali activated lightweight mortars are able to outperform alternative commercial cement-based mortars, thus representing a promising technology. [ABSTRACT FROM AUTHOR]

Suez-ResourceCo in Adelaide is a Construction & Demolition and Commercial & Industrial waste processing facility that produces alternative fuel for the local cement kiln operation. In recent years, Australia has seen an increase in energy cost and the state of South Australia has experienced a significant rise: approximately 29% increase in wholesale electricity price (2015/16 to 2016/17). Although the facility has been monitoring energy consumption at the gate level, the highly variable profile and many assets in operation have motivated the facility to conduct an energy flow analysis. The study identifies key assets for sub-metering to understand their energy profile and validate overall energy flow of the facility. The result outlines how the design paradigm of the waste industry has led to vastly over-sized plant leading to low efficiencies and power factors. Hence, potential energy and GHG saving is quantified through proposed efficiency gains. [ABSTRACT FROM AUTHOR]

The environmental legacies of metal mining are often dominated by large waste facilities, which can be sources of acid and metalliferous drainage, resulting in both local pollution and irreversible loss of some of the soluble minerals. Whether a material is treated as waste or ore depends on a wide variety of factors and circumstances. Three critical aspects – time, the extractive strategy and the economic context - are discussed in this paper. The authors argue that the fine line between waste and ore requires a mine waste management (MWM) hierarchy that properly considers waste as a potential future resource. This hierarchy exhibits four main levels: reduce, reprocess & stockpile, downcycle and dispose, which are illustrated by a review of both academic research and public data on industrial practices. The authors conclude that to generate the most successful outcomes the hierarchy must operate across all levels and is a core component of an overall mine sustainability framework. [ABSTRACT FROM AUTHOR]

Bioleaching of copper from pure granular shots and from a “pre-consumer” secondary resource from automotive industry (Brake Pads Powder, “BPP”) was carried out in a comparative study with conventional planktonic and PVA-encapsulated micro-organisms using a mixed culture of iron oxidizing bacteria: A. ferrooxidans , L. ferrooxidans and L. ferriphilum . The global process is characterized as “sequential” since a preliminary acid leaching is performed for ferrous iron extraction from the BPP material before the copper bioleaching itself. Prior to bioleaching experiments, resistance to dissolved copper has been quantified at various concentrations to assess a potential protective effect of the biomass by the PVA-matrix. PVA-encapsulated bacteria showed a better resistance to dissolved copper with a linear progression in the ferrous iron oxidation kinetic up to 40 gCu 2+ /L concentrations while planktonic cells presented a drastic decrease in this kinetic between 10 and 40 gCu 2+ /l, resulting in a 2 to 3-fold kinetic increase for the encapsulated bacteria depending on the strain. Bioleaching of elemental granular copper in 9 K medium (Fe 2+ : 10 g/L) showed significant enhancement of copper leaching kinetic with encapsulated biomass (1.9 · 10 −1 gCu 2+ /L h) in comparison with the planktonic mode (8.2 · 10 −2 gCu 2+ /L h). These tests demonstrated thereby the role of ferrous iron bio-oxidation and acid consumption values close to the stoichiometric ratio. Finally, the bioleaching with encapsulated bacteria was applied to copper extraction from BPP and showed a 150% enhanced kinetic in comparison with equivalent planktonic system and a 300% increase vs abiotic mode with respective leaching rates of 4.43 · 10 −2 ; 2.9 · 10 −2 and 1.48 · 10 −2 gCu 2+ /L h. Cell immobilization offers complementary benefits as continuous process and permanent bacteria acclimation. This technology presents an interesting alternative to conventional planktonic and “two-step” processes. [ABSTRACT FROM AUTHOR]

The problem of proper organization of waste management systems is becoming more and more significant these days. In Poland, regulations requiring municipalities to achieve by 2020, 50% recovery of weight fractions such as paper, metal, plastic and glass are the main factor contributing to the need to undertake new activities in the field of waste management. Waste processing takes place in complex technical systems. Modern waste processing systems are characterized by low efficiency. Currently, it is estimated that the efficiency of installations dealing with the sorting of waste does not exceed 35%. In 2015, the authors of the article carried out waste morphology in the city of Wroclaw (only selectively collected waste). On its basis, the authors established that fractions suitable for re-use accounted for 77% of the total weight of waste sent to processing plants. Despite the significant development of systems for automatic identification and sorting of waste in recent years, systems using mainly human labour are still very common. The main goal of this article is to analyse the impact of changes in the type of waste picked up on consecutive workstations on the value of indicators used to evaluate the process of manual waste sorting. [ABSTRACT FROM AUTHOR]

Three different batches of waste solutions of sodium sulphate from the manufacture of cyclohexanone (COD = 32.86, 104 and 107 g O 2 /dm 3 ) were processed by electro-electrodialysis (EED) to convert the waste salt into NaOH and H 2 SO 4 solutions for re-use within a production plant. A laboratory installation equipped with Ultrex AMI 7001S and Nafion N–423 ion-exchange membranes was used. The applied current density was 7.5 A/dm 2 . It was found that the current efficiencies of the EED products were the same as those of EED processing of Na 2 SO 4 solutions that did not contain organic substances. However, processing of waste solutions proceeds under a voltage higher by 0.2–0.4 V and therefore involves higher power consumption. Moreover, some of the organic substances are transferred from waste solutions to the products. [ABSTRACT FROM AUTHOR]

Red mud represents an environmental and economic liability for the alumina industry in the form of wasted raw material. Although some leaching studies have been performed, there are deficiencies in the current literature regarding the amounts of metals extracted relative to each other, and minimal information regarding silicon contamination of extracts. There is also limited knowledge of extraction efficiencies of different acids (particularly in the case of phosphoric acid) under the same experimental conditions. This study focused on the leaching behaviour of the four most extractable elements present within red mud (iron, titanium, aluminium and silicon). By varying the experimental conditions, acid concentration, and type of acid, a comprehensive dataset of leaching trends was obtained. This allowed for direct comparison of leaching efficiency for the four elements under the same conditions, which was difficult previously due to the variation of experimental conditions and red mud composition between studies. The patterns in recoveries were explained in terms of the reactivities of the mineral phases within red mud and the interaction between the different acids and the reaction surfaces. Out of the four acids studied (nitric, hydrochloric, sulfuric, and phosphoric) phosphoric and hydrochloric acids produced some of the best recoveries for iron (76–78%) and titanium (23–24%), and phosphoric acid also produced the highest recoveries for silicon (49%) and aluminium (50%). The differences observed between the acid types and reaction conditions revealed potential for development of element selective extraction methods. Additionally, explaining leaching behaviour in terms of the mineral phases present allowed easier prediction of expected leaching trends for these four elements, which made this study applicable to red muds with a wide variety of compositions. [ABSTRACT FROM AUTHOR]

Large amounts of food are wasted, and valuable contents are not utilized completely. Processing such wastes into biomass of defined composition is possible using insects. However, automation and decentralization of insect-based processes are necessary for certain applications. This study presents a modular design for rearing larvae of the black soldier fly, Hermetia illucens. A life cycle and economic assessment are carried out to check whether the process may be viable. A sales price of 3.55 € per kg of the product would make it profitable within five years. Production of 1 kg of dried larvae would be associated with 2.77 kg CO 2 eq emitted, 55.24 MJ of non-renewable energy use, and occupation of 0.68 m2 of organic arable land. Per kg protein, the insect biomass appears more sustainable than database benchmarks. These results indicate that even small-scale insect production processes have sustainability benefits when using food waste. • Container system could produce 37 kg dried larvae from 719 kg of food waste daily. • 3.64 kg CO 2 eq per kg protein produced, when considering avoided waste treatment. • largest share of impacts from drying (0.89 mPt) and climate control (0.73 mPt). • Not competitive as feed, food markets enable payback period of ≤5 years. [ABSTRACT FROM AUTHOR]

The influence of technogenic waste (burned and unburned mullite wool) on the properties of cement concrete as well as the influence of unburned mullite wool on the properties of ceramics are analysed in the paper. For the purpose of research, the part of sand in a cement concrete (2%, 4%, 6%, 8%, 10%) was replaced by a mullite wool waste. When 10% of the burned mullite wool waste was used the compressive strength of concrete increased by 7.7% after 7 days, and by 3.2% after 28 days. When 8% of the unburned mullite wool waste was used the compressive strength of concrete decreased by 3.4% after 7 days, and by 12.2% after 28 days. The ceramic samples were made from 4 different formation mixtures, in which the amount of unburned mullite wool waste was 0%, 5%, 10% and 15% (the amounts of quartz sand were replaced with waste). The samples were burned at the temperatures of 1050 °C and 1080 °C, keeping them at these temperatures for 4 h. The experimental results showed that the application of mullite wool waste in the manufacture of ceramic products is beneficial because of its positive impact on ceramic properties and the possibility to avoid overloading landfill sites. At the optimum burning temperature of 1080 °C, the significantly higher frost resistance, compressive strength and lower water absorption of ceramics is obtained. [ABSTRACT FROM AUTHOR]

Failure to accurately predict acid rock drainage (ARD) leads to long-term impacts on ecosystems and human health, in addition to substantial financial consequences and reputational damage to operators. Currently, a range of chemical static and kinetic tests are used to evaluate the acid producing nature of materials, from which risk assessments are prepared and waste classification schemes designed. However, these well-established tests and practices have inherent limitations, for example: (i) best-practice sampling is not pursued; (ii) risk assessments rely on limited static and kinetic test data, thus compromising the accuracy of resulting ARD block models; (iii) static tests are completed off-site and do not reflect actual field measurements; (iv) kinetic test data do not become available until later stages of mine development; (v) waste classification schemes generally categorise materials as only three types (i.e., PAF, NAF and UC) with other drainage forms (e.g., neutral metalliferous or saline) not considered; and (vi) conventional testing fails to consider that reactivity of waste is controlled by parameters other than chemistry (e.g., microbiology, type and occurrence of minerals, texture and hardness). Thus, accurate prediction is challenging because of the multifaceted processes leading to ARD. Hence, risk assessments need to consider mineralogical, textural and geometallurgical rock properties in addition to predictive geochemical test data. Instead, a new architecture of integrative, staged ARD testing should be pursued. Better ARD prediction must start with improving the definition of geoenvironmental models and waste units. Then, a range of low-cost and rapid tests for the screening of samples should be conducted on site prior to the performance of established tests and advanced analyses using state-of-the-art laboratories. Such an approach to ARD prediction would support more accurate and cost-effective waste management during operation, and ultimately less costly mine closure outcomes. [ABSTRACT FROM AUTHOR]

Due to their large variety of applications, their low supply and high demand, the rare earth elements (REEs) are presently viewed as being among the most critical chemical elements. Because of this, their potential recovery from end-of-life waste products has been extensively discussed both in society and in the scientific literature. This concept of recovering elements contained in end-of-life products, known as urban mining, is regarded as an important step in achieving a sustainable, circular society. This review article discusses the perspectives of reclaiming the REEs from various waste streams using hydrometallurgical methods. Three main streams are discussed in detail (phosphor-containing products, NiMH batteries and permanent magnets), touching on the state-of-the-art of material pre-treatment, leaching and separation of REEs and refining. Comparisons with the extraction of REEs from ores are drawn, bringing forth both the advantages and some of the disadvantages of urban mining. [ABSTRACT FROM AUTHOR]

Bauxite residue (or red mud) is a waste generated during the Bayer process of alumina production. Its storage is a spatial and environmental concern. Currently, there are no bulk applications of bauxite residue except for minor use in cements and ceramics. Nonetheless, some types of bauxite residues are rich in rare-earth elements (REEs), and the extraction of scandium in particular is of special interest. Leaching experiments on Greek bauxite residue were performed with different acids at different concentrations, liquid-to-solid ratios, leaching times and temperatures. Extraction of the REEs was high for leaching in HCl solutions compared to other acids, but the dissolution of iron was high as well (∼60%). The maximum extraction of the REEs was around 80%. Sodium and calcium were completely dissolved during leaching. Dissolution of aluminum, silicon and titanium was between 30% and 50%. The leaching data show a very close association of scandium with the iron oxide phases. [ABSTRACT FROM AUTHOR]

Waste electrical and electronic equipment (WEEE) is currently one of the fastest growing waste streams in the world. Typical for WEEE is the high content of valuable and precious metals, as well as harmful contaminants like halogens, flame retardant chemicals and plastics. Currently, WEEE treatment and metal recovery methods are imperfect, polluting and energy intensive. In this paper, novel treatment possibilities are outlined for printed circuit boards (PCB) utilizing both the flotation separation technique and acid bioleaching. Flotation, conducted after crushing and sieving of PCB, produced two fractions: metal-rich concentrate, which is more suitable for pyrometallurgical treatment than untreated PCB, and metal-poor froth suitable for acid bioleaching. It was seen that especially low pH (1.6), high initial Fe 2+ concentration (7.8 g/l) and low PCB froth concentration in the bioleaching solution (50 g/l) were beneficial for the rapid and selective dissolution of copper. With these parameters, 99% of copper was solubilized from PCB froth in bioreactor treatment, with Cu (6.8 g/l) and Fe (7.0 g/l) being the only major metallic elements in bioleaching solution. [ABSTRACT FROM AUTHOR]

Flotation tailings dump material of the former lead–zinc mine near Freiberg (Germany) consists of fine grained quartz, feldspar, mica as well as the sulphide minerals pyrite, galena and sphalerite not recovered by flotation. Sphalerite contains, aside from iron, copper and cadmium, significant amounts of indium (up to 0.38% (w/w)) leading to indium contents up to 70 mg/kg in the mine tailings. Preliminary thermodynamic assessment showed a comparatively small Eh–pH-range where bioleaching is possible and indium is not hydrolytically precipitated. Shake flask bioleaching of original polymetallic sphalerite ore from the Freiberg mining district (400 mg/kg indium) showed maximum zinc and indium recovery rates of almost 100% or 80%, respectively. First bioleaching tests on tailings material achieved zinc and indium yields of up to 80%. A stepwise precipitation process is being developed for indium recovery from the PLS (pregnant leaching solution) consisting of combined iron/indium precipitation and subsequent processing of the indium pre-precipitate. [ABSTRACT FROM AUTHOR]

Abstract: Industrial symbiosis (IS) is a subdiscipline of Industrial Ecology that aims to bring together companies from different sectors to share resources, namely energy, materials, and water. The main goal of IS is to improve resource (materials, waste, energy) efficiency and lead to mutual environmental, financial and social benefits to participants. In this paper we present a semantic approach for IS input/output matching. This approach is based on knowledge modelling and ontologies. Ontologies are used to model all resources – waste, water, energy – along with details about their composition, characteristics (chemical and physical) and tacit knowledge about their flow. The input/output matching algorithm presented enables the valorisation of resources through industrial symbiosis networks. [Copyright &y& Elsevier]

In the process of industrial corporation activities a lot of waste, which pollutes the atmosphere, is generated, for example ash and slag. In Tomsk region, by estimates, ash stores occupy about 600 hectares, which contain about 25 million tons by weight. In Russian thermal power-stations ash disposal areas there are about 1.3 billion tons of ash, and only 10% of it is used. That is why this problem is topical enough. In this paper the scheme of producing ash ceramic bricks and complex ash and slag waste processing is shown. Besides, profitability of the project is presented. [ABSTRACT FROM AUTHOR]

[Display omitted] Large amounts of food are wasted and valuable contents are not utilized completely. Methods to process such wastes into biomass of defined composition automatically and in decentralized locations are lacking. Thus, this study presents a modular design for residue utilization and continuous production of the heterotrophic alga Galdieria sulphuraria. A life cycle and economic assessment are carried out on the hypothetical design to define whether the proposed system can be ecologically and economically viable. Producing one kg of dried biomass would cost 4.38 € and be associated with 3.8 kg CO 2 eq emitted, 69.9 MJ of non-renewable energy use, and 0.09 m2 of land occupation. Sustainability is comparable to conventional protein sources, with further improvement foreseen through avoidance of drying. These results demonstrate how circular bioeconomy potentials of residues could be realized using heterotrophic G. sulphuraria. It highlights key issues of developing an environmentally and economically sustainable concept. [ABSTRACT FROM AUTHOR]

Cu–NH 3 bearing effluents arise from electroplating and metal extraction industries, requiring innovative and sustainable Cu recovery technologies to reduce their adverse environmental impact. CO 3 2− and Zn are often co-occurring, and thus, selective Cu recovery from these complex liquid streams is required for economic viability. This study assessed 23 sustainable biosorbents classified as tannin-rich, lignin-rich, chitosan/chitin, dead biomass, macroalgae or biochar for their Cu adsorption capacity and selectivity in a complex NH 3 -bearing bioleachate. Under a preliminary screen with 12 mM Cu in 1 M ammoniacal solution, most biosorbents showed optimal Cu adsorption at pH 11, with pinecone remarkably showing high removal efficiencies (up to 68%) at all tested pH values. Further refinements on select biosorbents with pH, contact time, and presence of NH 3 , Zn and CO 3 2− showed again that pinecone has a high maximum adsorption capacity (1.07 mmol g−1), worked over pH 5–12 and was Cu-selective with 3.97 selectivity quotient (K Cu/Zn). Importantly, pinecone performance was maintained in a real Cu/NH 3 /Zn/CO 3 2− bioleachate, with 69.4% Cu removal efficiency. Unlike synthetic adsorbents, pinecones require no pre-treatment, which together with its abundance, selectivity, and efficiency without the need for prior NH 3 removal, makes it a competitive and sustainable Cu biosorbent for complex Cu–NH 3 bearing streams. Overall, this study demonstrated the potential of integrating bioleaching and biosorption as a clean Cu recovery technology utilizing only sustainable resources (i.e., bio-lixiviant and biosorbents). This presents a closed-loop approach to Cu extraction and recovery from wastes, thus effectively addressing elemental sustainability. • A top-down approach optimized Cu biosorption from a real Cu–NH 3 leachate. • Pinecone (PC) has a high Cu q max of 1.1 mmol g−1 despite 2 M NH 3 and 5 mM Zn present. • PC works over wide pH range (5−12) relevant for treating (NH 4) 2 CO 3 rich effluents. • PC has a selectivity quotient (K Cu/Zn) of 3.97 making it selective for Cu over Zn. • The presence of Zn can improve the q max of PC for Cu from NH 3 -rich streams. [ABSTRACT FROM AUTHOR]

Highlights: [•] We investigate delivered waste material and RDF-incinerator feedstock. [•] We elaborate sampling plan in accordance to the relevant guidelines and standards. [•] Results of manual sorting and chemical analyses (e.g. feedstock 48×) are presented. [•] Production of high quality RDF requires a multiple-stage waste treatment process. [•] Type of waste input is more important than fuel recovery process itself. [ABSTRACT FROM AUTHOR]

Abstract: Bioleaching is a potential route for the valorisation of low value natural and waste alkaline materials. It may serve as a pre-treatment stage to mineral carbonation and sorbent synthesis processes by increasing the surface area and altering the mineralogy of the solid material and by generating an alkaline rich (Ca and Mg) aqueous stream. It may also aid the extraction of high value metals from these materials (e.g. Ni), transforming them into valuable ore reserves. The bioleaching potential of several bacteria (Bacillus circulans, Bacillus licheniformis, Bacillus mucilaginosus, Sporosarcina ureae) and fungi (Aspergillus niger, Humicola grisea, Penicillium chrysogenum) towards the alteration of chemical, mineralogical and morphological properties of pure alkaline materials (wollastonite and olivine) and alkaline waste residues (AOD and BOF steel slags, and MSWI boiler fly ash) at natural pH (neutral to basic) was assessed. Bioleaching was conducted using one-step and two-step methodologies. Increased solubilisation of alkaline earth metals and nickel were verified. Alteration in basicity was accompanied by alteration of mineralogy. AOD slag experienced solubilisation–precipitation mechanism, as evidenced by the decline of primary phases (such as dicalcium-silicate, bredigite and periclase) and the augmentation of secondary phases (e.g. merwinite and calcite). Nickel-bearing minerals of olivine (clinochlore, lizardite, nimite and willemseite) significantly diminished in quantity after bioleaching. Altered mineralogy resulted in morphological changes of the solid materials and, in particular, in increased specific surface areas. The bioleaching effect can be attributed to the production of organic acids (principally gluconic acid) and exopolysaccharides (EPSs) by the microorganisms. The similarities between fungal and bacterial mediated bioleaching suggest that biogenic substances contribute mostly to its effects, as opposed to bioaccumulation or other direct action of living cells. [Copyright &y& Elsevier]

Abstract: The main waste product generated by bauxite flotation in China is aluminosilicate tailings. The dark color caused by high iron content limits the application of bauxite tailings in polymers. We developed a new method for whitening bauxite tailings by adding phosphoric acid. The whiteness of bauxite tailings was considerably improved from 19% to 73% with the addition of 17g of 85% phosphoric acid and calcination at temperature 550°C. XRD, EDS and FTIR analyses showed that the particles of the whitened bauxite tailings are coated with a mixture of phosphates and polyphosphates. The amount of the both increased with increasing phosphorus content. N2 adsorption analysis indicated that the surface area of the whitened bauxite tailings gradually decreased, whereas pore size expanded with increasing phosphorus content. [Copyright &y& Elsevier]

Abstract: Aluminium salt slag (also known as aluminium salt cake), which is produced by the secondary aluminium industry, is formed during aluminium scrap/dross melting and contains 15–30% aluminium oxide, 30–55% sodium chloride, 15–30% potassium chloride, 5–7% metallic aluminium and impurities (carbides, nitrides, sulphides and phosphides). Depending on the raw mix the amount of salt slag produced per tonne of secondary aluminium ranges from 200 to 500kg. As salt slag has been classified as toxic and hazardous waste, it should be managed in compliance with the current legislation. Its landfill disposal is forbidden in most of the European countries and it should be recycled and processed in a proper way by taking the environmental impact into consideration. This paper presents a review of the aluminium salt slag chemical and mineralogical characteristics, as well as various processes for metal recovery, recycling of sodium and potassium chlorides content back to the smelting process and preparation of value added products from the final non metallic residue. [Copyright &y& Elsevier]

Abstract: Mechanical Biological Treatment inert reject (MBTr) is mostly composed by recyclable glass. Yet, it is usually sent to landfills because, due to the small particle size and high level of particle surface organic contamination, the processes commonly used in glass recycling, like optical sorting, are inefficient in the separation of glass from contaminants. This paper presents the results of a study undertook to characterize MBTr, aiming at the subsequent separation of recyclable glass from contaminants. A representative sample of the reject from a MBT plant was collected. The particle size analysis was carried out and the composition of the different size fractions was determined. It was found that the MBTr sample was composed by almost 80% of recyclable glass. The product is quite fine. About 80% in weight of the product has a particle size lower than 10mm. However, the size fraction below 2mm is insignificant since it represents less than 3% in weight and contains less than 1% of the recyclable glass in MBTr. Using methods of image analysis, the shape of each individual particle, separated by material class and by size fraction, was evaluated. It was observed that the average shape of the particles of “stone”, the main contaminant, is significantly different from the shape of other materials, including recyclable glass. Gravity concentration methods may take advantage of the shape of the particles and are thus potentially adequate to recover recyclable glass from MBT. [Copyright &y& Elsevier]

Abstract: If formulated optimally, geopolymer cement made from fly ash, metallurgical slags and natural pozzolans could reduce by 80% the CO2 emissions associated with the manufacturing of cement. However, almost all standards and design codes governing the use of cementitious binders and concrete in construction are based on the use of Portland cement. The 100+ year track record of in-service application of Portland cement is inherently assumed to validate the protocols used for accelerated durability testing. Moreover, the entire supply chain associated with cementitious materials is based on the production of Portland cement. The geopolymerisation of aluminosilicates constitutes a radical change in construction materials chemistry and synthesis pathways compared with the calcium silicate hydrate chemistry which underpins Portland cement. Consequently, there are regulatory, supply chain, product confidence and technical barriers which must be overcome before geopolymer cement could be widely adopted. High profile demonstration projects in Australia have highlighted the complex regulatory, asset management, liability and industry stakeholder engagement process required to commercialise geopolymer cement. While the scale-up from the laboratory to the real-world is technically challenging, the core challenge is the scale-up of industry participation and acceptance of geopolymer cement. Demand pull by a carbon conscious market continues to be the key driver for the short term adoption of geopolymer cement. In the absence of an in-service track record comparable in scale and longevity to Portland cement, research is essential to validate durability testing methodology and improve geopolymer cement technology. Colloid and interface science, gel chemistry, phase formation, reaction kinetics, transport phenomena, comminution, particle packing and rheology, which are familiar concepts to minerals engineers, are also key building blocks in the development of geopolymer knowledge. Analysis of the nanostructure of geopolymer gels has enabled the tailored selection of geopolymer precursors and the design of alkali activator composition, aiding in establishing the relationship between geopolymer gel microstructure and durability. [Copyright &y& Elsevier]

Abstract: The generation of waste electrical and electronic equipment (WEEE) is large and rapidly increasing, and even though WEEE is recycled today there are still valuable residues left after recycling, ending up in landfills. This paper shows how microwave pyrolysis can be a plausible way to recycle the residues. Six different fractions (from light dust to particles sized 7–12mm) of landfill waste were analysed and pyrolysed. The process was successful producing oil, gas and a solid residue, and the mass reduction was determined as a function of process time. Mass reduction seemed to be rather stable, independent of the temperature scatter during pyrolysis and a substantial reduction was observed for all of the materials. The major part of mass reduction was observed in the heating phase already above 100°C, and the heating rate was slower for the particulate materials. [Copyright &y& Elsevier]

Abstract: Even though innovative resource conservation and recycling initiatives in mineral processing projects satisfy the aims of corporate sustainability principles and polices, such initiatives are often bypassed in favour of tried and tested solutions which are perceived to have lower technical and financial risks. This is, in part, a result of project management systems lacking a suitable systematic and rigorous framework to allow sustainability aligned initiatives proper consideration, analysis and assessment. In an attempt to address this shortcoming, a collaborative research team has developed the Sustainable Operations framework, SUSOP®, a guiding framework for projects to make a proper contribution to sustainability without compromising on financial rigour. This paper argues the need for a framework to address sustainability objectives, presents the key elements of SUSOP®, highlights the learnings from industry case studies, and discusses why such a framework will have growing importance into the future. [Copyright &y& Elsevier]

Abstract: The granites of South-West England are a potential source of lithium which is generally found within the mica mineral, zinnwaldite. It is mainly found in the central and western end of the St. Austell granite. When kaolin extraction occurs in these areas a mica-rich waste product is produced which is currently disposed of in tailings storage facilities. In this study a tailings sample containing 0.84% Li2O was upgraded by a combination of froth flotation, using dodecylamine as the collector, and wet high intensity magnetic separation (WHIMS) to 2.07% Li2O. The concentrate was then roasted with various additives, including limestone, gypsum and sodium sulphate, over a range of temperatures. The resulting products were then pulverised before being leached with water at 85°C. Analysis of these products by XRD revealed that the water-soluble sulphates, KLiSO4 and Li2KNa(SO4)2, were produced under specific conditions. A maximum lithium extraction of approximately 84% was obtained using gypsum at 1050°C. Sodium sulphate produced a superior lithium extraction of up to 97% at 850°C. In all cases iron extraction was very low. Preliminary tests on the leach solution obtained by using sodium sulphate as an additive have shown that a Li2CO3 product with a purity of >90% could be produced by precipitation with sodium carbonate although more work is required to reach the industrial target of >99%. [Copyright &y& Elsevier]

Abstract: The acid rock drainage index (ARDI) was developed to predict acid formation based on intact rock texture. Five textural parameters which have direct control on acid formation are evaluated. The ARDI forms part of the geochemistry–mineralogy–texture (GMT) approach to undertaking acid rock drainage (ARD) predictive tests. This staged-approach involves parallel use of geochemical, mineralogical and textural analyses. Sample screening is performed at stage-one, and a general classification given. Stage-two involves the use of routine geochemical tests in order to cross-check stage-one results, and also to quantify the acid forming/neutralising potential. Stage-three uses advanced geochemical tests and microanalytical tools to cross-check any ambiguous results from the previous stages, and for detailed characterisation of acid forming sulphide phases. Samples were obtained from two mine sites in Queensland, Australia, from which seventeen mesotextural groups were identified (A–Q). The ARDI identified mesotextural groups J (quartz–pyrite) and H (quartz–arsenopyrite–pyrite) as extremely acid forming. Routinely used geochemical classifications also identified these as the most acid forming groups. Four mesotextural groups (K–O) were classified as having acid neutralising capacity after full GMT classification. The remainder of mesotextural groups were classified as not acid forming. Mesotextural groups G (quartz–galena–sphalerite), H and J only require kinetic testing to resolve the lag-time to, and longevity of acid formation, and to measure the concentration of potentially deleterious elements released. The ARDI was not able to confidently discern between samples with the capacity to neutralise acid, and those which are not acid forming. Therefore, further refinement of the ARDI is required. However, in its current form the ARDI is suitable for mineral deposits with low-carbonate contents. This paper demonstrates its use as part of stage-one of the GMT approach at both operational and abandoned mine sites to screen and classify acid forming potential. [Copyright &y& Elsevier]

Abstract: Solid waste from the copper smelting industry may be harmful if disposed of in the environment, but it may be a valuable resource if metals can be recovered. The purpose of this study was to evaluate the acid bioleaching of metals from a sample of final smelter slag and the recovery of metals from the leach liquors. Bioleaching was tested in a continuously stirred tank reactor (CSTR) at 20–25°C with 5% pulp density (particle size 75% <47μm). The yields of metal solubilization after 29days of contact were 41% Fe, 62% Cu, 35% Zn and 44% Ni. Metals were precipitated in a separate CSTR by titrating the leach liquors with sulfide-rich effluent from a sulfate-reducing fluidized-bed reactor (FBR) (25°C) to desired pH values. Over 98% of the Cu precipitated at pH⩾2.8 and over 99% of the Zn precipitated at pH⩾3.9. The precipitation of Ni and Fe required higher pH values and was less efficient than Cu and Zn recovery. In addition, bulk precipitation of metals was also tested by feeding the leach liquor directly to another sulfate-reducing FBR. In order to reduce its toxicity and maintain stable sulfate reduction performance in the FBR, the leach liquor had to be diluted ten-fold and the pH adjusted from 0.6 to approximately 4. [Copyright &y& Elsevier]

Abstract: Sodium oxalate is an organic impurity produced during the Bayer refining of bauxite as a result of the degradation of humic materials associated with the ore. Physico-chemical oxalate destruction techniques, such as combustion, are often expensive and often pose greater environmental risk than the storage of solid oxalate waste. Biodegradation is a more economical and environmentally friendly way to degrade oxalate, but the microbial communities responsible for oxalate degradation have remained largely uncharacterised. In the present work, the microbial community of a full-scale bioreactor achieving complete degradation of oxalate was characterised using 16S rRNA gene clone libraries followed by phylogenetic analysis of the cloned near full-length 16S rRNA sequences. The community was dominated by species belonging to the α-, β- and γ-Proteobacteria groups. Novel oxalate-degrading bacteria belonging to the genus Halomonas and the β-Proteobacteria group were isolated from the microbial community and are currently being characterised. [Copyright &y& Elsevier]

Abstract: In this study, the beneficiation of two lignite tailings by Multi Gravity Separator (MGS) was investigated. The tailings samples from the Tunçbilek/Kütahya and Soma/Manisa regions have ash contents of 66.21% and 52.65%, respectively. Significant operational parameters of MGS such as solid ratio, drum speed, tilt angle, shaking amplitude, wash water rate, and feed rate were varied. Empirical equations for recovery and ash content were derived by a least squares method using Minitab 15. The equations, which are second-order response functions, were expressed as functions of the six operating parameters of MGS. The results showed that it is possible to produce a coal concentrate containing 22.83% ash with a recovery of 49.32% from Tunçbilek coal tailings, and a coal concentrate containing 22.89% ash with a recovery of 60.01% from Soma coal tailings. [Copyright &y& Elsevier]

Abstract: The Falcon concentrator is an enhanced-gravity separator used for the concentration of fine and ultra-fine minerals. This study was conducted to evaluate the effects of different process variables on the performance of the Falcon SB-40 concentrator for beneficiation of tailings to recover ultra-fine coal. Various operating and design conditions such as bowl speed (G force), water pressure, pulp solid ratio and pulp feed rate were investigated. A hydrocyclone was used for pre-enrichment with the Falcon concentrator. Operation parameters of the hydrocyclone, namely feed solids, inlet pressure, vortex finder and apex diameters were investigated. In order to produce fine coal concentrates, regression equations were derived by applying the least squares method using Minitab 15 software. Response functions were produced for the ash content and the recovery of the clean coal concentrates for the performance of the hydrocyclone and Falcon concentrator under different operating conditions. Predicted values were found with the experimental values giving R 2 values of between 0.73 and 0.58 for ash content and between 0.65 and 0.39 for recovery of the clean coal. It was shown that under optimized conditions the Falcon concentrator can produce a clean coal with an ash value of 36% from a feed coal of about 66% ash. [Copyright &y& Elsevier]

Abstract: A two-step process for boron recovery from borax sludge is proposed in the present work. The borax sludge was leached with sulphuric acid solution. Then, for the removal of alkaline species from the leachate, calcium and magnesium were precipitated by adjusting the pH of leachate using 1.5M NaOH and 1.5M HCl solutions. The effects of pH, temperature, concentration and time on the precipitation process were investigated. It was determined that the calcium and magnesium concentrations in the leachate were reduced from 121mg/L to 2.6mg/L and from 145mg/L to 4.0mg/L, respectively, at a pH value of 12, a temperature of 70°C, an initial boron concentration of 500mg/L and a precipitation time of 3h. Under these optimum conditions, it was observed that the boron concentration in the solution decreased very slightly. In this process, the alkaline species were successfully separated from the boron. Finally, borax pentahydrate (Na2B4O7·5H2O) was produced by the evaporation of the final solution obtained after precipitation process. [Copyright &y& Elsevier]

Abstract: Industrial mineral carbonation of alkaline wastes, an increasingly promising component of carbon capture and storage, may play an important role as a CO2 mitigation strategy in the context of climate change. Steelmaking slags are of particular interest owing to their high content of calcium. The cumulated ‘effective’ CO2-specific sequestration capacity (calculated on the basis of calcium and magnesium extracted to a 0.5M HNO3 solution) of three basic oxygen and one electric arc furnace slags generated at steel mills in South Africa was 253kt CO2 per annum, which was 25.2% lower than their cumulated ‘theoretical’ capacity (estimated on the basis of total calcium and magnesium content in slags). The mineralogical composition and solubility characteristics of slags conferred very distinct leaching behaviours to the slags, including differences in: (i) the amount of heat generated during their dissolution, (ii) their buffering capacity, (iii) the rate and extent of calcium and magnesium extraction from the slags, and (iv) the mineralogical composition of the non-dissolved residues. These findings suggest that separate leaching processes may need to be developed for slags with largely distinct mineralogical compositions and structural features. [Copyright &y& Elsevier]

Abstract: Acid mine drainage (AMD) is one of the most serious and pervasive challenges facing the minerals industry. Current philosophy in sulfide tailings management takes an end-of-pipe approach which is yet to be shown to be sufficient to prevent post-closure impacts from AMD and guarantee “walk-away” status. An improved, integrated approach to tailings management and AMD mitigation is proposed, whereby conventional tailings are separated with the use of flotation into a largely benign tailings stream and a sulfide-rich product. The key features of this conceptual approach are outlined and partly demonstrated for the case of porphyry-type copper sulfide tailings. The significance of this approach is that it provides a basis for the identification of opportunities for the development of new process designs incorporating waste management systems for mitigating AMD in a manner consistent with the principles of cleaner production and sustainable development. [Copyright &y& Elsevier]

Abstract: The characteristics of cemented products ranging in initial consistency from ‘paste-like’ to ‘flowable’, relevant to paste backfill and backfill with controlled low strength materials (CLSM), respectively, were compared for mixes incorporating waste from pilot scale bioleaching of European refractory gold, copper and copper/nickel sulphide flotation concentrates. Compositional and structural properties were linked to mechanical strength, hydraulic conductivity and hydrolytic stability (leachability) in fabricated laboratory specimens containing sand, pulverised fuel ash, waste and Portland cement in the proportions 70, 15, 10 and 5, respectively, together with variable quantities of water. In some experiments, sand was replaced by flotation tailings. The results showed that mixtures containing 10% of waste with 15.0–37.5% water by mass gave cemented materials with unconfined compressive strength (UCS) in the range 0.4–3.0MPa after 28 days of hardening, this range encompassing typical paste-fill and CLSM formulations. They also indicated formulations giving maximum UCS and retention of strength at higher water content in the presence of the (finer sized) waste. Hydraulic conductivity (10−7–10−9 m/s) was comparable to commercial CLSM. Chemical analysis indicated low levels of most toxic elements and correspondingly low diffusion leaching, thus reducing requirements for special lining or encapsulation procedures to avoid groundwater contamination. However, chromium leaching, for example, remained an issue, thus indicating a need for further development before regulatory acceptance and deployment in field applications can become feasible. The formulated materials are consistent in principle with a scheme of integrated waste management based on designed combinations of paste (for mine backfill), CLSM (for engineering foundation construction) and mineral bulk (for site landscape/soil restoration). In particular, they facilitate production of different materials for paste backfill and CLSM applications by judicious adjustment of water content. [Copyright &y& Elsevier]

Abstract: A study was conducted on leaching of fly ash mixed with NaOH solution and on mixing procedure for preparing geopolymer. Leaching of SiO2 and Al2O3 was investigated by mixing fly ash with NaOH solution for different time intervals and leachates were analyzed in terms of silica and alumina contents. To make geopolymer paste, separate mixing and normal mixing were used. For separate mixing, NaOH solution was mixed with fly ash for the first 10min; subsequently sodium silicate solution was added into the mixture. For normal mixing, fly ash, sodium hydroxide and sodium silicate solution were incorporated and mixed at the same time. Geopolymers were cured at 65°C for 48h. Microstructure of paste and compressive strength of mortar were investigated. Results revealed that solubility of fly ash depended on concentration of NaOH and duration of mixing with NaOH. For mixing procedure, separate mixing gave slightly better strength mortar than normal mixing. High strength geopolymer mortar up to 70.0MPa was obtained when the mixture was formulated with 10M NaOH and sodium silicate to NaOH ratio of 1.0, and the separate mixing sequence was used. [Copyright &y& Elsevier]

Abstract: Electric arc furnace (EAF) dust is produced when automobile scrap is remelted in an electric arc furnace and about 10–20 kilograms are generated per ton of steel. The major elements present in the dust are usually zinc, iron and calcium with smaller amounts of numerous other elements such as lead, copper and nickel. Typically, in the pyrometallurgical EAF dust treatment processes, the lead and zinc are separated as a crude zinc oxide while the iron is generally not worth recovering. Copper and nickel are usually not recovered as they report either to the oxide residue or to any metallic iron that is produced. In the present research, the recovery of the non-ferrous metals in a multiphase system consisting of gas, slag, matte, metal and solid carbon phases was investigated. The equilibrium compositions of the various phases, resulting from the smelting of the dust, were calculated using the SOLGASMIX module of Outokumpu HSC Chemistry. The effects of the following operating variables were investigated; carbon additions, sulphur additions, nitrogen and oxygen additions, temperature and dust composition. The thermodynamic modelling results show that the majority of the non-ferrous metals can be recovered, with the zinc and lead concentrating in the gas phase and the nickel and copper concentrating in the matte phase. [Copyright &y& Elsevier]

Abstract: Salt cakes, which are nominally waste products derived from aluminium dross melting furnaces, are complex mixtures of some 20 different compounds made up of many different elements. Normally they are regarded as waste products and they are disposed of in toxic waste dumps. However, it is shown here that some components are readily recoverable as high-grade products for recycling or sale and that the residues thus generated can be non-toxic. Recoverable components include metallic aluminium, salt (halite (NaCl) and sylvite (KCl)), alumina-containing compounds, and possibly hydrogen gas. Metallic aluminium is soft and malleable and is not reduced in size by crushing and grinding, whereas the other components in salt cake are soft and brittle or are readily dissolved in water. Hence the coarse metallic aluminium can be readily recovered by crushing and screening and the finer metallic aluminium can be recovered by fine grinding and screening, froth flotation, or possibly electrostatic separation. Aqueous acid or alkaline leaching has also been proposed to recover aluminium metal from salt cake. The halite and sylvite are easily extracted by leaching ground salt cake with cold water and filtering off the saline solution. This solution can be sent to solar evaporation ponds where the water is evaporated and the dry salt harvested for recycling to dross treatment furnaces or other markets. Some of the water-insoluble or oxide aluminium compounds present are soluble in Bayer-type leach solutions and could possibly be sent to a Bayer-type leach plant for production of high-grade alumina for aluminium production. Alternatively, because the oxide aluminium compounds are inert they could be sent to a non-toxic dump. The possibility of integrated flowsheets to recover more than one product in a single plant is also discussed. [Copyright &y& Elsevier]

Abstract: The main objective of this work was to investigate the recovery of silver from mining wastewaters using a hybrid cyanidation and high-pressure membrane process. The tested hybrid process in lab-scale experiments includes the concentration and recovery of silver by nanofiltration (NF) or reverse osmosis (RO) after the silver is taken into solution as AgCN employing re-cyanidation and subsequent sedimentation and/or pre-filtration of wastewaters. Synthetic water experiments were conducted in this work. In synthetic water experiments (in distilled and deionized water), the soluble AgCN complex was formed after cyanidation of low-soluble AgCl particles which were added to the leach tank. Two different NF membranes and one RO membrane were tested in a lab-scale flat-sheet configuration test unit. The results indicated that although a significant amount of silver was lost on the RO membrane due to irreversible sorption, RO membrane performed better than NF membranes based on higher silver rejections, thus higher mass recoveries. Therefore, RO membrane was found to be more effective in terms of precious metal recovery and production of high quality permeate that can be reused in the leaching process. The tested hybrid cyanidation (leaching) and high-pressure membrane process in this work may be an effective approach in recovering precious metals and producing reusable water from wastes or wastewaters of mining industry. [Copyright &y& Elsevier]

Abstract: The fine fraction of the argon oxygen decarburization with lance (AOD-L) sludge is a hazardous waste generated by the stainless steel industry which is normally disposed in landfills. Due to the relative high content of Fe, Cr and Ni as well as its low granulometry, a hydrometallurgical route based on sequential leaching steps is being investigated to treat it. In this paper, an attempt made to remove Fe from the sludge and concentrate Cr and Ni in the solid is highlighted. Leaching was carried out at atmospheric pressure using H2SO4 and HCl at varying temperature (25, 40, 55 and 70°C) and acid concentration (3, 6 and 12%, v/v). For both acids, leaching rate increased with temperature and acid concentration, and higher dissolutions of Fe and Ni were obtained in comparison with that of Cr. HCl was found more selective for Fe over Ni and Cr. The content of Fe was reduced nearly 50% (w/w) at 70°C and HCl 12% (v/v), while Cr remained mostly in the solid; however, around 40% (w/w) of Ni was dissolved and it may hinder such leaching step in the studied route. The study points out that total metal leaching of sludge under high temperature and pressure conditions must be considered. [Copyright &y& Elsevier]

Abstract: The paper is concerned with a simple hydrometallurgical method for selective recovery of copper and cobalt from industrial copper converter slag. The following consecutive stages are proposed: roasting of the slag in reduction conditions to produce Cu–Co–Fe–Pb alloy, electrolytic dissolution of the alloy in an ammonia–ammonium chloride solution, ammoniacal leaching of the slime, selective copper and cobalt electrowinning. Cu27–Co6–Fe64–Pb1.5 alloy was a five-phase system and did not dissolve uniformly during electrolysis. This resulted in the separation of the metals, wherein iron remained in the slime, while copper and cobalt were components of slime, electrolyte and cathodic deposit. A mechanism of the alloy dissolution was developed. A series of secondary processes took place in the system: precipitation of iron compounds, copper cementation with cobalt and iron; adsorption of copper and cobalt ions on the iron precipitates. Final products were metals of high purity (99.9% Cu, 92% Co). [Copyright &y& Elsevier]

Abstract: Municipal solid waste (MSW) molten fly ash is classified as a hazardous waste because it contains considerable amount of heavy metals, which pose environmental concern due to their leaching potential in landfill environment. This study proposes carrier-in-pulp (CIP) method as a new hydrometallurgical route to extract and recover Pb, Zn, Cu, and Cd from molten fly ash before landfilling. In this method, a carrier material, which recovers the extracted metals, is added simultaneously with fly ash to a leaching solution and is harvested from the pulp by physical separation method, such as magnetic separation or sieving. To demonstrate the effect of the CIP method, shaking flask experiments were conducted under various conditions using NaCl solution, iron powder as carrier, and molten fly ash. More than 99wt% Pb, Zn, and Cd, and 97wt% Cu were extracted from the ash. However, only Pb and Cu were recovered (96.3wt% Pb and 94.3wt% Cu) by the iron powder through cementation, leaving behind Zn and Cd ions in the solution phase. The leaching test conducted on the treated fly ash residue revealed that the CIP method suppressed the solubilization of Pb to a value below the landfill disposal guideline. [Copyright &y& Elsevier]