The influence of chlorination additives on metal separation during the pyrometallurgical recovery of spent lithium-ion batteries.

The difficulty of separating Li during pyrometallurgical smelting of spent lithium-ion batteries (LIBs) has limited the development of pyrometallurgical processes. Chlorination enables the conversion of Li from spent LIBs to the gas phase during the smelting process. In this paper, the effects of four solid chlorinating agents (KCl, NaCl, CaCl2 and MgCl2) on Li volatilization and metal (Co, Cu, Ni and Fe) recovery were investigated. The four solid chlorinating agents were systematically compared in terms of the direct chlorination capacities, indirect chlorination capacities, alloy physical losses and chemical losses in the slag. CaCl2 was better suited for use as a solid chlorinating agent to promote Li volatilization due to its excellent results in these indexes. The temperature required for the release of HCl from MgCl2, facilitated by CO2 and SiO2, was lower than 500 °C. The prematurely released HCl failed to participate in the chlorination reaction. This resulted in approximately 12 % less Li volatilization when MgCl2 was used as a chlorinating agent compared to when CaCl2 was used. In addition, the use of KCl as a chlorinating agent decreased the chemical dissolution loss of alloys in the slag. The performance of NaCl was mediocre. Finally, based on evaluations of the four indexes, recommendations for the selection and optimization of solid chlorinating agents were provided.

Removal of the heavy metals from copper slag by using carbonless additives.

The smelting processes account for over 80 % of global copper production, generating various slags in large quantities. Most of these slags do not contain the required amounts of valuable metals to justify economic revalorization, yet the concentrations present may negatively affect the environment. In this study, heavy and potentially toxic metals were removed by keeping the liquefied slag at 1300 °C for four hours, while the metals gathering was enhanced by adding silicon-copper compounds. Crystallography, metallography, gravimetric, thermogravimetric, and differential thermal analysis were employed to characterize the slag. Electron probe microanalysis was utilized to examine the distribution of heavy and potentially toxic metals from the original copper slag to the remaining slag and mattes formed in the lower portion of the containing vessel. In all instances, concentrations of the arsenic and zinc were reduced below the detection limit. Moreover, the cumulative concentrations of six heavy metals were reduced from 2400 ppm in the initial slag to 41.7 ppm in the remaining slag when using 30 wt%Si70wt%Cu additive. All potentially valuable or toxic metals gathered in the mattes that had oxygen concentrations about 50 times lower than in the initial slag, at 0.82, 0.56, and 0.68 wt% after the mixing slag with 10 wt%Si90%Cu, 30 wt%Si70wt%Cu, and 50 wt%Si50wt%Cu additives, respectively. Investigated practices can mitigate the threat of heavy and potentially toxic metals associated with the disposal of copper slags while also enabling the recovery of valuable metals and rendering the remaining slag suitable for construction or mine backfill purposes.

An efficient molten steel slag gas quenching process: Integrating carbon solidification and waste heat recovery.

The iron and steel-making industries have garnered significant attention in research related to low-carbon transitions and the reuse of steel slag. This industry is known for its high carbon emissions and the substantial amount of steel slag it generates. To address these challenges, a waste heat recovery process route has been developed for molten steel slag, which integrates CO2 capture and fixation as well as efficient utilization of steel slag. This process involves the use of lime kiln flue gas from the steel plant as the gas quenching agent, thereby mitigating carbon emissions and facilitating carbonation conversion of steel slag while simultaneously recovering waste heat. The established carbonation model of steel slag reveals that the insufficient diffusion of CO2 gas molecules within the product layer is the underlying mechanism hindering the carbonation performance of steel slag. This finding forms the basis for enhancing the carbonation performance of steel slag. The results of Aspen Plus simulation indicate that 1 t of steel slag (with a carbonation conversion rate of 15.169 %) can fix 55.19 kg of CO2, process 6.08 kmol of flue gas (with a carbon capture rate of 92.733 %), and recover 2.04 GJ of heat, 0.43 GJ of exergy, and 0.68 MWh of operating cost. These findings contribute to the development of sustainable and efficient solutions for steel slag management, with potential applications in the steel production industry and other relevant fields.

Biohydrometallurgy for Rare Earth Elements Recovery from Industrial Wastes.

Biohydrometallurgy recovers metals through microbially mediated processes and has been traditionally applied for the extraction of base metals from low-grade sulfidic ores. New investigations explore its potential for other types of critical resources, such as rare earth elements. In recent times, the interest in rare earth elements (REEs) is growing due to of their applications in novel technologies and green economy. The use of biohydrometallurgy for extracting resources from waste streams is also gaining attention to support innovative mining and promote a circular economy. The increase in wastes containing REEs turns them into a valuable alternative source. Most REE ores and industrial residues do not contain sulfides, and bioleaching processes use autotrophic or heterotrophic microorganisms to generate acids that dissolve the metals. This review gathers information towards the recycling of REE-bearing wastes (fluorescent lamp powder, spent cracking catalysts, e-wastes, etc.) using a more sustainable and environmentally friendly technology that reduces the impact on the environment.

The furnace and the goat-A spatio-temporal model of the fuelwood requirement for iron metallurgy on Elba Island, 4th century BCE to 2nd century ce.

Scholars frequently cite fuel scarcity after deforestation as a reason for the abandonment of most of the Roman iron smelting sites on Elba Island (Tuscan Archipelago, Italy) in the 1st century bce. Whereas the archaeological record clearly indicates the decrease in smelting activities, evidence confirming the 'deforestation narrative' is ambiguous. Therefore, we employed a stochastic, spatio-temporal model of the wood required and consumed for iron smelting on Elba Island in order to assess the availability of fuelwood on the island. We used Monte Carlo simulations to cope with the limited knowledge available on the past conditions on Elba Island and the related uncertainties in the input parameters. The model includes both, wood required for the furnaces and to supply the workforce employed in smelting. Although subject to high uncertainties, the outcomes of our model clearly indicate that it is unlikely that all woodlands on the island were cleared in the 1st century bce. A lack of fuel seems only likely if a relatively ineffective production process is assumed. Therefore, we propose taking a closer look at other reasons for the abandonment of smelting sites, e.g. the occupation of new Roman provinces with important iron ore deposits; or a resource-saving strategy in Italia. Additionally, we propose to read the development of the 'deforestation narrative' originating from the 18th/19th century in its historical context.

Purification of the leaching solution of recycling zinc from the hazardous electric arc furnace dust through an as-bearing jarosite.

Leaching of the hazardous electric arc furnace (EAF) dust containing mainly zinc ferrite and zinc oxide, accompanied by minor concentrations of arsenic compounds, was investigated using sulfuric acid. In order to reach the maximum recovery of zinc, the leaching solution was adjusted to recover both iron and zinc at their maximum possible values. To obtain a high recovery value of zinc and iron, analyzed by AAS, the optimum leaching condition was found to be the temperature of 90 °C, the sulfuric acid concentration of 3 M, the particle size of 75 µm, the S/L ratio of 1:10 g/mL and the leaching time of 2 h. The percentages of the zinc and iron recovery under the optimum condition were ca. 98.6% and 99.1% respectively, which were verified by a confirmation test and were very close to the predicted values of 100% based on the optimized model, obtained through the software. From the thermodynamics' point of view, it has been found that Zn2+ is the predominant species (90%) under the leaching condition applied. Moreover, the predominant species of iron are FeSO4+, FeHSO42+, Fe(SO4)2- and Fe3+ in the magnitudes of 65.8%, 25.6%, 4.4% and 4.0%, respectively. According to the kinetic results, the controlling step in the leaching was the chemical reaction at the most of the operating temperatures and times. In order to purify the zinc solution for electrowinning, iron and arsenic were removed through the jarosite formation process as confirmed by the XRD results. The speciation of arsenic in the precipitated jarosite was explored by XPS. Finally, the low concentrations of arsenic (less than 0.1 ppm) and iron (less than 50 ppm) were determined by the ICP analysis.

Bioleaching: urban mining option to curb the menace of E-waste challenge.

Resource Recovery from Waste Electronics has emerged as one of the most imperative processes due to its pressing challenges all over the world. The Printed Circuit Board (PCB) is one of the typical E-waste components that comprise large varieties of metals and nonmetals. Urban Mining of these metals has received major attention all over the world. The existing treatment procedures used extensively for the resource extraction are hydrometallurgy and pyro-metallurgy and crude recycling practices in the informal sector. However, these methods are prone to cause secondary pollutants with certain drawbacks. Also, the existing informal recycling procedures resulted in insignificant occupational health hazards and severe environmental threats. The application of biotechnology is extensively exploited for metal extraction and emerged as one of the sustainable and eco-friendly tools. However, a limited field-scale study is prevailing in the realm of resource recovery from E-waste using bioleaching method. Hence, the application of bioleaching requires more attention and technical know-how in developing countries to curtail crude practices. The application of bioleaching in E-waste, including its available methods, kinetics mechanism associated opportunities, and barriers, have been discussed in this paper. A glance of E-waste management in India and the menace of 95% crude E-waste recycling are also elaborated. The incentives toward profit, socio-economic, and environmentally sustainable approaches have been delineated based on critical analysis of the available literature.

Steel slag amendment impacts on soil microbial communities and activities of rice (Oryza sativa L.).

With the increase in iron/steel production, the higher volume of by-products (slag) generated necessitates its efficient recycling. Because the Linz-Donawitz (LD) slag is rich in silicon (Si) and other fertilizer components, we aim to evaluate the impact of the LD slag amendment on soil quality (by measuring soil physicochemical and biological properties), plant nutrient uptake, and strengthens correlations between nutrient uptake and soil bacterial communities. We used 16 S rRNA illumine sequencing to study soil bacterial community and APIZYM assay to study soil enzymes involved in C, N, and P cycling. The LD slag was applied at 2 Mg ha-1 to Japonica and Indica rice cultivated under flooded conditions. The LD slag amendment significantly improved soil pH, plant photosynthesis, soil nutrient availability, and the crop yield, irrespective of cultivars. It significantly increased N, P, and Si uptake of rice straw. The slag amendment enhanced soil microbial biomass, soil enzyme activities and enriched certain bacterial taxa featuring copiotrophic lifestyles and having the potential role for ecosystem services provided to the benefit of the plant. The study evidenced that the short-term LD slag amendment in rice cropping systems is useful to improve soil physicochemical and biological status, and the crop yield.

Workplace environment of earth-moving machine operators in terms of anthropometric data development in the Slovak republic.

BACKGROUND: Population data are gathered using the sampling unit at the appropriate time and due to various reasons (e.g. nutrition survey of the population, style of living, etc.), they can be changed due to trends for longer periods of time. OBJECTIVE: The aim of the paper is to analyse selected anthropometric parameters relevant to the design of the earth-moving machine operator workplace environment and to compare the gathered data to the standard ISO 3411. METHODS: The set of five dimensions and factors of the Slovak adult male population was analysed over the course of the years 2002-2018. RESULTS: A significant increase in the parameter -body weight was observed. In total, mentioned dimension of male population increased by 0.4 kg (0.5%) during the time of analysis. Following the dot plot and linear regression equation the fact that the trend in growth is becoming a global phenomenon in Slovakia can be stated. CONCLUSIONS: In the future, it will be necessary to focus on updating the standards defining the workplace size in this industry sector as well as in others.

A direct metal laser sintering (DMLS) root analogue implant placed in the anterior maxilla. Case report.

BACKGROUND: Modern cone beam computed tomography (CBCT) acquisition and three-dimensional (3D) image processing, combined with direct metal laser sintering (DMLS), allows custom-made, root-analogue implants (RAIs). PURPOSE: To demonstrate how DMLS permits customized titanium RAI production, with immediate insertion and restoration in a fresh extraction socket of the anterior maxilla. MATERIALS AND METHODS: A titanium RAI perfect copy of the radicular unit needed for replacement was created by customized DMLS, and inserted into a fresh extraction socket of the esthetic area of the anterior maxilla. RESULTS: Follow-up after 1 year: the DMLS RAI implant showed a satisfactory functional and esthetic integration, with no bone resorption or soft tissue recessions. CONCLUSIONS: The production of customized DMLS RAIs opens new interesting perspectives for immediate implantation. KEY WORDS: Direct metal laser sintering, Root analogue implant.

Selective Recovery of Zinc from Metallurgical Waste Materials from Processing Zinc and Lead Ores.

A method for processing of metallurgical waste materials (chemically defined as sulfur-bearing zinc-ferric materials) produced by plants processing zinc ores and their concentrates is proposed. The method proposed is a combination of pyro- and hydrometallurgical treatments of the waste material. The crucial steps in the developed method include: roasting the material at 450 °C to generate sulfur dioxide (SO2), absorption of SO2 in an aqueous system to form sulfuric acid (IV), carbothermic decomposition of zinc ferrite compounds, and leaching of zinc from the roasted material using sulfuric (IV) acid. The method allows one to extract up to 40% of zinc from the waste material and, consequently, to generate a fraction of material with substantially higher content of iron oxides. The proposed method takes advantage of the presence of sulfur in the processed material which upon roasting is converted to sulfuric acid (IV)-a leaching agent for selective extraction of zinc. The properly adjusted pH of the aqueous medium in which the leaching process is carried out is the key factor determining the quantitative and selective separation of zinc. If the amount of sulfur in the processed material is insufficient, it may be supplemented by adding sulfuric acid (VI) to adjust the pH. The method proposed was tested at a laboratory scale and quarter industrial scale using the real samples taken from stockpiles in the vicinity of the plant processing zinc and lead ores in Poland. It may also work for any zinc-ferric materials from various sources.

Recovery opportunities of valuable and critical elements from WEEE treatment residues by hydrometallurgical processes.

Due to the increasing demand of metals by industry and the limited availability of natural resources, the secondary supply of these elements from discarded products, such as waste electrical and electronic equipment (WEEE), is an important strategy for pursuing a sustainable development. Nevertheless, the complex and heterogeneous composition of this waste stream stands as one of the main drawbacks in the definition of innovative recovery processes. This study investigated the recovery potential of a multi-step leaching process to extract the strategic metals, namely precious metals and rare earth elements (REEs), from the dust produced during the industrial shredding treatment of WEEE. Using a first double-oxidative step with sulfuric acid, most rare earth elements contained in the dust were dissolved at high percentages. Moreover, around 50% of gold was extracted in a second leaching step using 0.25 M thiourea, in a solid to liquid ratio of 0.2 g/70 mL, at 600 rpm. In this regard, the optimum operating conditions were studied by a 23 full factorial design. Experimental results address the definition of a novel approach, pursuing the recovery of resources of great industrial interest from the residues originating from WEEE mechanical treatments typically performed at large scale. As this dust fraction is not sent for recovery but currently disposed, the proposed recycling strategy promotes the diversion of waste from landfill while reducing the need for virgin materials via lower-impact metallurgical processes.

On-line prediction of ferrous ion concentration in goethite process based on self-adjusting structure RBF neural network.

Outlet ferrous ion concentration is an essential indicator to manipulate the goethite process in the zinc hydrometallurgy plant. However, it cannot be measured on-line, which leads to the delay of this feedback information. In this study, a self-adjusting structure radial basis function neural network (SAS-RBFNN) is developed to predict the outlet ferrous ion concentration on-line. First, a supervised cluster algorithm is proposed to initialize the RBFNN. Then, the network structure is adjusted by the developed self-adjusting structure mechanism. This mechanism can merge or divide the hidden neurons according to the distance of the clusters to achieve the adaptability of the RBFNN. Finally, the connection weights are determined by the gradient-based algorithm. The convergence of the SAS-RBFNN is analyzed by the Lyapunov criterion. A simulation for a benchmark problem shows the effectiveness of the proposed network. The SAS-RBFNN is then applied to predict the outlet ferrous ion concentration in the goethite process. The results demonstrate that this network can provide a more accurate prediction than the mathematical model, even under the fluctuating production condition.

Mechanism underlying the bioleaching process of LiCoO2 by sulfur-oxidizing and iron-oxidizing bacteria.

Benefiting from lower operational costs and energy requirements than do hydrometallurgical and pyrometallurgical processes in metal recovery, the bioleaching of LiCoO2 through the use of sulfur-oxidizing and iron-oxidizing bacteria has drawn increasing attention. However, the bioleaching mechanism of LiCoO2 has not been clearly elaborated. In the present study, the effects of the energy source of bacteria, such as Fe2+, pyrite and S0, and the products of bacterial oxidation, such as Fe3+ and sulfuric acid, on the chemical leaching of LiCoO2 were studied. The results indicated that lithium was dissolved by acid, and cobalt was released by the reduction of Fe2+ and acid dissolution. The recovery of Li+ and Co2+ could be significantly improved by pH adjustment. Finally, optimal recoveries of Li+ and Co2+ were observed in the pyrite group, reaching 91.4% and 94.2%, respectively. By using pyrite as the energy source, the role of bacteria in bioleaching of LiCoO2 was investigated. The results showed that bacteria could produce sulfuric acid by oxidizing pyrite to promote the mobilization of Li+ and Co2+. The recovery of lithium and cobalt could be increased to 100.0% and 99.3% by bacteria. Moreover, extracellular polymeric substances secreted by bacteria were found to be a factor for the improvement of Li+ and Co2+ recovery.

Emergy-based environmental accounting of one mining system.

Metal production from mineral resources is crucial for economic development. However, most mining activities usually target short-term financial benefits, rather than long-term consideration on ecological sustainability. To better understand the impact of metal production, systematic evaluation methods should be applied to complement current economic accounting tools. Under such a circumstance, this study proposes an emergy-based metal production evaluation framework, taking a life cycle perspective from the formation of mineral deposit to the final production of metal. Ecosystem service loss, CO2 emissions, and emissions' impact are quantified, evaluating the comprehensive performance of a lead and zinc production system in Yunnan Province of China. The results show that minerals contribute significantly to the formation of lead and zinc production; however, emergy received in terms of money substantially undervalues environmental work associated with production. Such a metal production system relies heavily on nonrenewable resources and put enormous pressures on local ecosystems. The beneficiation subsystem generates the highest negative impact per emergy output, followed by the smelting and refining subsystem and the underground mining subsystem. From climate change point of view, producing 1 ton of lead bullion leads to 1.79E+03 kg CO2eq. Electricity use contributes a dominated share to the total CO2 emission of all subsystems. In addition, lead recycling can greatly reduce the overall CO2 emission, indicating that it is necessary to build up a regional lead collection and recycling system. Finally, several policy suggestions are raised by considering the local realities, aiming to promote sustainable development of this industry.

Comparative study on Ti-Nb binary alloys fabricated through spark plasma sintering and conventional P/M routes for biomedical application.

The main purpose of this work is to obtain homogenous, single ß phase in binary Ti-xNb (x = 18.75, 25, and 31.25 at.%) alloys by simple mixing of pure elemental powders using different sintering techniques such as spark plasma sintering (pressure-assisted sintering) and conventional powder metallurgy (pressure-less sintering). Synthesis parameters such as sintering temperature and holding time etc. are optimized in both techniques in order to get homogenous microstructure. In spark plasma sintering (SPS), complete homogeneous ß phase is achieved in Ti25at.%Nb using 1300 °C sintering temperature with 60 min holding time under 50 MPa pressure. On the other hand, complete ß phase is obtained in Ti25at.%Nb through conventional powder metallurgy (P/M) route using sintering temperature of 1400 °C for 120 min holding time which are adopted from the dilatometry studies. Nano-indentation is carried out for mechanical properties such as Young's modulus and nano-hardness. Elastic properties of binary Ti-xNb compositions are fallen within the range of 80-90 GPa. Cytotoxicity as well as cell adhesion studies carried out using MG63, osteoblast-like cells showed excellent biocompatibility of thus developed Ti25at.%Nb surface irrespective of fabrication route.

Effect of sintering parameters on physical and mechanical properties of powder injection moulded stainless steel-hydroxyapatite composite.

The combination of metallic bio-inert material, stainless-steel 316L (SS316L) and a bio-active material, hydroxyapatite (HA) can produce a composite which has superior properties for orthopaedic applications. The main objective of this study is to investigate the effects of sintering temperature and holding time on the physical and mechanical properties of the sintered part. 50wt.% SS316L and 50wt.% HA were mixed with a binder system of palm stearin (PS) and polyethylene (PE) at 61 vol.% powder loading. Rheological properties show a pseudo-plastic behaviour of the feedstock, where viscosity decreases with increasing shear rate. The feedstock was injection moulded into a tensile bar shape while thermal debinding was carried out at 320°C and 500°C. The brown parts were sintered at 1000, 1100, 1200 and 1300°C, with three different sintering times of 1, 3 and 5 hours in the furnace. It was found that the highest sintered density measured was 95.61% of the theoretical density. In addition, the highest hardness and Young's modulus measured were 150.45 HV and 52.61 GPa respectively, which are higher than those of human bone. The lowest percentage of carbon content was 0.022wt.% given by the sample sintered at 1300°C for 1 hour. Therefore, SS316L/HA composite with good mechanical and physical properties was successfully produced through the PIM process.

Impact of pyrometallurgical slags on sunflower growth, metal accumulation and rhizosphere microbial communities.

Metallurgical exploitation originates metal-rich by-products termed slags, which are often disposed in the environment being a source of heavy metal pollution. Despite the environmental risk that this may pose for living organisms, little is known about the impact of slags on biotic components of the ecosystem like plants and rhizosphere microbial communities. In this study, metal-rich (Cu, Pb, Zn) granulated slags (GS) derived from Cu production process, were used for a leaching test in the presence of the soil pore solution, showing that soil solution enhanced the release of Cu from GS. A pot experiment was conducted using as growing substrate for sunflower (Helianthus annuus) a 50% w/w mix of an agricultural soil and GS. Bioavailability of metals in soil was, in increasing order: Pb < Zn < Cu. Sunflower was able to grow in the presence of GS and accumulated metals preferentially in above-ground tissues. Microbial diversity was assessed in rhizosphere and bulk soil using community level physiological profiling (CLPP) and 16S rRNA gene based denaturing gradient gel electrophoresis (DGGE) analyses, which demonstrated a shift in the diversity of microbial communities induced by GS. Overall, these results suggest that metallurgical wastes should not be considered inert when dumped in the soil. Implications from this study are expected to contribute to the development of sustainable practices for the management of pyrometallurgical slags, possibly involving a phytomanagement approach.

Isolation and identification of Penicillium chrysogenum strain Y5 and its copper extraction characterization from waste printed circuit boards.

Biohydrometallurgy is generally considered as a green technology for the recycling of industrial solid waste. In this study, an indigenous fungal strain named Y5 with the ability of high-yielding organic acids was isolated and applied in bioleaching of waste printed circuit boards (PCBs). The strain Y5 was identified as Penicillium chrysogenum by morphological and molecular identification. Meanwhile, we investigated that an optimal set of culturing conditions for the fungal growth and acids secretion was 15 g/L glucose with initial pH 5.0, temperature 25°C and shaking speed 120 rpm in shaken flasks culture. Moreover, three bioleaching processes such as one-step, two-step and spent medium processes were conducted to extract copper from waste PCBs. Spent medium bioleaching showed higher copper extraction percentage and it was 47% under 5%(w/v) pulp density. Transmission electron microscope (TEM) observation combining with energy dispersive analysis of X-rays (EDAX) showed that the leached metal ions did not obviously damage the hypha cells. All above results indicated that P.chrysogenum strain Y5 has the tolerance to metal ions, suggesting its potential in recycling of metals from waste PCBs in industry.

Engineering strategies for enhancing C. vulgaris ESP-31 lipid production using effluents of coke-making wastewater.

Microalgae cultivation using wastewater is an approach for simultaneous wastewater treatment and biofuels/chemicals productions. In this study, three microalgae species Chorella vulgaris ESP-31, Chorella sorokiniana CY-1 and Scenedesmus sp. were cultivated using coke-making wastewater generated from a steel-making company. Of these, C.vulgaris ESP-31 had the best tolerance towards wastewater, with maximal biomass concentration of 2.82 g/l and lipid productivity of 32.3 mg/l/d. The highest biomass concentration 3.98 g/l and lipid productivity of 47.1 mg/l/d was obtained in 20% wastewater. Immobilization approach was applied to boost biomass growth and lipid production. Both maximal biomass growth (5.17 g/l) and lipid productivity (68.4 mg/l/d) was significantly enhanced with activated charcoal addition. Semi-batch cultivation resulted in stable biomass production and lipid productivity of 5.18 g/l and 77.3 mg/l/d, respectively. This study has revealed that C. vulgaris ESP-31 is a potential candidate for growth in coke making wastewater and biofuel production.