Scrap Research Articles

Multi-Objective Optimization of the Recovery of Base and Precious Metals from Waste Printed Circuit Boards by Two-Stage Hydrometallurgical Process Using Taguchi-Based Grey Relationship Analysis

This study focused on determining the optimum conditions for the maximum recovery of base and precious metals from printed circuit boards of end-of-life desktop computer motherboards using Taguchi-based grey relation analysis. In the first stage of the two-stage study, optimum conditions were investigated for the dissolution of base metals (copper and zinc) in waste printed circuit boards under high-pressure leaching. The dissolution of base metals was performed based on the L25 orthogonal array designed by Taguchi method. In the second step, designed according to Taguchi L9 orthogonal array to recover gold and silver from the solid remaining from the pressure-leaching process. Optimum combinations of parameters in both stages were determined using the multi-criteria optimization technique grey relationship analysis. In the experiments carried out in the determined optimum combinations, 99.62% of copper, 98.76% of zinc, 99.15 of silver and 85.82% of gold in waste printed circuit boards were recovered.Graphical

Calculation of production balances and costs in ladle furnace refining process with addition of scrap steel

As increasing the scrap steel ratio has become an important approach for energy conservation and emission reduction in the steel industry, the technology of multi-point scrap addition has emerged. Ladle furnace (LF) refining is a feasible step for scrap steel utilisation, which is often overlooked and relied solely on empirical adjustment, resulting in difficulty of precise control. It is necessary to conduct in-depth research on this process using scientific methods and explore the impact of scrap steel addition on other materials. A comprehensive calculation model was established by scientifically investigating material and thermal balances in the LF process in this article, and the impact of initial steel and scrap compositions, temperature, mass and price of scrap on production costs were analysed and compared based on the model. The results showed that as the carbon and silicon content in the initial steel increase by every 0.01% could on average reduce the production cost per ton of steel by 4.013 CNY and 0.8473 CNY, respectively, and increases by 0.123 CNY as the sulphur content increase every 0.001%. The impact of scrap composition on costs is similar to that of the initial molten steel. Increasing the carbon and sulphur content in scrap by every 0.01% will on average increase costs by 0.0765 CNY and 0.01 CNY, respectively. When the price difference between scrap and the crude steel price is within 450–500 CNY/t, increasing scrap addition will create more profit. The relative reduction in smelting time is 7.97 s as the scrap temperature increases every 50°C. The present study holds academic and industrial significance in improving LF efficiency and promoting the LF process towards a more sustainable direction.

An experimental investigation of Marble Powder as a Partial Replacement of cement and Waste Metal Scrap as Reinforcing Material on the Mechanical Characteristics of Concrete

An experimental investigation of Marble Powder as a Partial Replacement of cement and Waste Metal Scrap as Reinforcing Material on the Mechanical Characteristics of Concrete

Research on the influence of image motion blur on the effectiveness of machine vision-based metal scraps separation system

Research on the influence of image motion blur on the effectiveness of machine vision-based metal scraps separation system

Investigation of sustainable pervious concrete pavement performance using waste travertine aggregate and powder

Travertine cutting generates rubble and waste powder, prompting the need for effective waste utilization. This study aims to develop travertine permeable concrete (TPC) using travertine aggregate and waste powder. An orthogonal test method assessed TPC variations in travertine powder replacement rates, aggregate grading, and void content for porosity, permeability, mechanical strength, and heavy metal adsorption ability. The void content greatly influences the amount of cementitious material and is crucial for TPC performance. To guarantee compliance with the engineering performance for fully pervious pavement, the recommended void content of TPC should not exceed 20 % to have satisfactory compressive strength and permeability. Cement replacement with 5–10 % travertine powder can satisfy engineering requirements, heavy metal adsorption, waste utilization, and CO2 emission reduction. TPC demonstrates much lower removal rates under the rapid method than the immersion method for Cd2+, Cu2+ and Pb2+, mainly due to the difference in contact time. After 25 cycles, the optimized TPC shows less mass and strength loss, demonstrating excellent freeze-thaw resistance. Furthermore, a novel lab-scale rainfall simulation system for travertine permeable concrete pavement (TPCP) was built to assess the water infiltration of TPCP. TPCP can effectively reduce runoff, reaching over 96 % within 1 h for various inflow intensities. After half an hour, the removal rates of Cd2+ and Cu2+ by TPCP were only 41.5 and 79.1 %, respectively, but TPCP achieves exceptional Pb2+ adsorption with a removal rate of over 97 % under the ternary competitive mechanism.

담합 사례 연구 : 철스크랩 구매가격 담합 사건에서 개별 기업의 담합 실행 여부에 대한 실증적 검증

담합 사례 연구 : 철스크랩 구매가격 담합 사건에서 개별 기업의 담합 실행 여부에 대한 실증적 검증

Utilization of industrial waste metal alloy powder as fuel

Metal powders including aluminum, iron and metal alloys have been considered as a fuel for energy generation without releasing carbon dioxide and being recyclable. While additive manufacturing processes desire feedstock microparticles with a specific size range, a significant amount of metallic powders is left in its waste stream. In this work to investigate the potential applications of these alloy powders, they are mixed with solid metal oxide particles for combustion tests in ambient and low-pressure environments. The thermochemical properties and exothermic characteristics are measured on the mixtures of micro-sized AlSi10Mg particles with a median diameter of 13 µm and CuO nanoparticles of 500 nm. Experimental results indicate, compared to Al micron particles with a similar average diameter, the reaction between AlSi10Mg powder and oxygen shows a comparable onset temperature (around 1000⁰C), a similar activation energy (316.9 kJ/mol), but a much higher energy release (11.5 kJ/g vs. 4.2 kJ/g). When mixed with CuO nanoparticles, AlSi10Mg/CuO and Al/CuO mixtures exhibit a similar reaction kinetics which is characterized by the diffusion of gaseous oxygen produced from the thermal decomposition of CuO. In the ambient combustion tests, the AlSi10Mg/CuO powder shows a 20 % shorter ignition delay, 3 times faster burning rate, and up to 2 times higher impulse than these of the Al/CuO powder. When a low air pressure (about 100 Pa) is applied, the AlSi10Mg/CuO powder is successfully ignited and combusted, while the micron-Al/CuO powder cannot be ignited. We conclude the micro-sized Al-Si-Mg alloy particles recycled from the advanced manufacturing processes can be a good candidate for metal fuel.

Synergetic integration of machining metal scrap for enhanced evaporation in solar stills: A sustainable novel solution for potable water production

The global water crisis necessitates innovative solutions for sustainable potable water production. Solar stills represent a promising technology for harnessing solar energy to meet this demand. However, solar stills often face limitations regarding yield and cost-effectiveness. This research addresses the pressing need to augment the performance of solar stills by introducing amendments such as utilizing black-coated metal scrap as a photothermal absorber in the absorber basin. These modifications aim to boost the absorption of solar radiation, thereby increasing potable water yield and improving the system’s economic viability. The study explores the utilization of black-coated metal scrap as a photothermal absorber to modify the absorber basin. Experimental results demonstrate a significant improvement in potable water yield, with a 129.85 % increase on day 1 and 127.21 % on day 2, reaching 3080 mL/m2 and 3090 mL/m2, respectively. Compared to conventional solar stills, the newly developed double slope solar still with an absorber basin featuring metal scrap exhibits a remarkable economic advantage, with a payback period (PBP) of 5.4 months, as opposed to 9.45 months for the traditional system. Additionally, the cost per liter (CPL) of potable water generated by the innovative system is 75.53 % lower than that of the conventional solar still system.

Electric recycling of Portland cement at scale

Cement production causes 7.5% of global anthropogenic CO2 emissions, arising from limestone decarbonation and fossil-fuel combustion1–3. Current decarbonation strategies include substituting Portland clinker with supplementary materials, but these mainly arise in emitting processes, developing alternative binders but none yet promises scale, or adopting carbon capture and storage that still releases some emissions4–8. However, used cement is potentially an abundant, decarbonated feedstock. Here we show that recovered cement paste can be reclinkered if used as a partial substitute for the lime–dolomite flux used in steel recycling nowadays. The resulting slag can meet existing specifications for Portland clinker and can be blended effectively with calcined clay and limestone. The process is sensitive to the silica content of the recovered cement paste, and silica and alumina that may come from the scrap, but this can be adjusted easily. We show that the proposed process may be economically competitive, and if powered by emissions-free electricity, can lead to zero emissions cement while also reducing the emissions of steel recycling by reducing lime flux requirements. The global supply of scrap steel for recycling may treble by 2050, and it is likely that more slag can be made per unit of steel recycled. With material efficiency in construction9,10, future global cement requirements could be met by this route.

Colloidal magnetic gels for the decontamination of limited access metallic surfaces

Handling nuclear metallic waste is a crucial issue for the nuclear industry, notably by using adapted decontamination processes. Colloidal gels can be applied by spraying for nuclear decontamination of large and plane metallic surfaces, such as walls or floors. However, this implementation mode limits their use for the decontamination of inaccessible or complex geometries surfaces. For that purpose, decontamination magnetic gels have been formulated by incorporating magnetite particles in a pre-synthesized colloidal gel able to decontaminate stainless steel. Such gels can thus be attracted by a magnet, allowing remote application to surfaces with limited access. The presence of magnetite particles does not influence the inherent decontamination properties of the gel, but plays a significant role on the spreading properties by increasing the gel viscosity. Then, a linear relationship between the gel thickness and the decontamination possibilities has been highlighted. Furthermore, as the magnetite particles dissolve in the gel with time, spreading properties, and consequently the decontamination properties, are modified. Finally, a formulation compromise has to be found for a long-term storage of the gels, while maintaining their efficiency.

Scrap Steel Recycling: A Carbon Emission Reduction Index for China

Accurately assessing carbon emissions from recycling scrap steel is essential for reducing emissions in the steel industry, especially in China, the world’s largest crude steel producer. In this study, a carbon emission reduction index was introduced to evaluate the effectiveness of recycling scrap steel in reducing emissions. The index considers the three processes used in scrap steel recycling: blast furnace ironmaking, converter steelmaking, and electric arc furnace steelmaking. This study developed an evaluation model using fuzzy analytic hierarchy process and iterative cluster analysis to determine the reduction of carbon emission. From a life cycle perspective, this study identified primary factors contributing to emissions, including fuel, raw materials, electric energy, and auxiliary materials. Then, the carbon emission reduction index for scrap recycling was developed by examining the production of one ton of steel and each additional ton of scrap steel, which can provide valuable insights into the environmental impact of scrap recycling. Finally, the study forecasts the future Carbon Emission Reduction Index for steel scrap recycling. The study indicates an increase in the carbon emission reduction index for scrap recycling prior to 2017, followed by a decrease about 11.8% from 2017 to 2018 and increases from 2018 to 2021. Finally, it dropped by 8.7% per cent in 2022. Similarly, the carbon emission reduction index for electric furnace steelmaking increased prior to 2019, then subsequently decreased. It is changing by ten per cent a year. Additionally, the scrap recycling index experienced a significant decrease of 90% in 2015, followed by a gradual increase until 2017 and then a consistent decrease every year thereafter. The index suddenly rose in 2021 and then decreased change for policy reasons. The forecast results suggest a gradual increase in the carbon emission reduction index per ton of steel scrap in the future. In conclusion, the practicable modeling methodology has the ability to assist government organizations and private enterprises in devising efficient green and low-carbon development tactics.

Evaluating the Effects of Metallic Waste on the Structural and Gamma-Ray Shielding Properties of Epoxy Composites.

The objective of the research is to develop novel materials that are both inexpensive and have a low density, while also being able to endure the transportation of γ-photons with low-to-medium energy levels. The outcome consisted of four epoxy resins that were strengthened with different quantities of heavy metallic waste. The density of the formed composites improved from 1.134 ± 0.022 g/cm3 to 1.560 ± 0.0312 g/cm3 when the waste content was raised from 0 to 40 weight percent. The theoretical investigation was determined using Monte Carlo (MCNP) simulation software, and the results of linear attenuation coefficient were justified experimentally in a low and medium energy range of 15-662 keV. The mass attenuation coefficient results in a low gamma energy range (15-122 keV) varied in between 3.175 and 0.159 cm2/g (for E-MW0 composite) and in between 8.212 and 0.164 cm2/g (for E-MW40 composite). The decrease in mass attenuation coefficient was detected in a medium gamma photon energy range (122-662 keV) with 0.123-0.082 cm2/g (for E-MW0 composite) and 0.121-0.080 cm2/g (for E-MW40 composite). The density of the enhanced composites influenced these parameters. As the metallic waste composition increased, the fabricated composites' half-value thickness decreased. At 15 keV, the half-value thickness decreased from 0.19 to 0.05 cm. At 59 keV, it fell from 2.70 to 1.41 cm. At 122 keV, it fell from 3.90 to 2.72 cm. At 662 keV, it fell from 7.45 to 5.56 cm. This decrease occurred as the heavy metal waste concentration increased from 0 to 40 wt.%. The study indicates that as metallic waste concentrations rise, there is a rise in the effective atomic number and a decline in the buildup factors.

Analysis of the melting process of carbon-bearing pellets in iron bath, slag bath and graphite crucible

Background With the increase in the amount of scrap steel in society, the proportion of electric furnace steelmaking is increasing year by year, especially in China. Due to the high Zn content, the electric furnace arc dust (EAFD) needs to be recovered by non-blast furnace process. Due to EAFD containing a large amount of zinc ferrite, it needs to be recovered by fire process. It is a promising process to melt the EAFD pellets to get the discount and zinc-rich secondary ash. Methods To clarify the melting behavior of pellets in the metallurgical process, the slag phase diagram and the effect of temperature and FeO on slag viscosity were calculated using FactSage, and the melting process of electric furnace arc dust (EAFD) pellets in a graphite crucible, iron bath, and slag bath were experimentally investigated. Results The experimental results show that the viscosity of the slag system decreases with increasing temperature and FeO content, and the effect of FeO on viscosity is greater. The viscosity decreased from 0.305 to 0.276 Pa·s when the FeO content in the slag was increased from 0 wt. % to 2 wt.% at 1773 K. The melting process of the EAFD pellets in an iron bath and graphite crucible was consistent, and after the formation of liquid-phase slag in the pellets, the liquid-phase slag was diffused to melt the pellets. Conclusions The iron bath improved the heat transfer conditions of the pellets, reducing the smelting time from 600 to 360 s. The slag bath promoted the slagging reaction of the contact part to change the pellet melting process and increase the pellet melting speed, and the EAFD pellets melted within 240 s in a slag bath.

GARBAGE COLLECTOR USING ARDUINO

The amount of Solid waste that is being produced through our everyday activities is huge and is getting unmanageable day by day. This is mainly due to increasing population leading to haphazard dumping and increasing transportation costs with already few cost-effective methods to treat the solid waste. According to an estimate in 2016, 277 million tons of solid waste is produced by India every year. It is also projected to increase to 387 million tons by 2030 and 543 million tons by 2050. The very first method involved in the Solid Waste Management is sorting of waste which simplifies the further procedure as to what to do with the waste i.e., should it be treated thermally, biologically or dumped. Improper segregation of solid waste and segregation at secondary levels of waste management is only going to delay the waste management process and sometimes even lead to inappropriate dumping. This project suggests a way to deal with segregation process so as to make the whole solid waste management easier and more efficient. Automatic Waste Segregation system provides a practical segregation process of solid waste into metal waste, dry waste and wet waste at the primary level right where the waste is being generated. An Automatic Waste Segregator with simpler mechanism than that of previous models is designed and a detailed methodology of the working of the segregation process is provided. Selection of the required equipment has been mentioned. This project aims at segregating the waste produced at the primary level and reducing the burden at secondary levels and cost of transportation of the waste. The results obtained after testing the Automatic Waste Segregator with wastes proved to be functional and can be comfortably relied upon to segregate the wastes.

Speciation of toxic metals in metal finishing filter cake by X-ray absorption spectroscopy

The speciation of Cr, Zn, Cu and Pb in two metal finishing filter cakes (TX and ST) was investigated by X-ray absorption spectroscopy (XAS) complemented by X-ray fluorescence (XRF) and X-ray diffraction (XRD). XRF showed that concentrations of Cr, Zn, Cu and Pb were 1.4%, 0.19%, 0.20% and 0.01%, respectively, in TX, and 12.6%, 3.3%, 1.3% and 0.21% in ST. No crystalline phases were detected in TX by XRD whereas ST was dominated by calcite. Cr and Fe K edge XAS showed Cr to be trivalent and octahedrally coordinated, co-precipitated with Fe as CrxFe1-x-(oxy)hydroxides in both filter cakes. Zn, P and Ca K edge XAS showed that 2ZnCO3∙3Zn(OH)2 and Zn3(PO4)2 were the dominant zinc-containing phases, with combined tetrahedral and octahedral coordination; Zn phases were slightly more crystalline in TX than ST. Pb L3 edge X-ray absorption near edge spectroscopy (XANES) found that Pb was likely adsorbed on amorphous SiO2. Cu, Si and S K edge XAS showed that all Cu was divalent, and the dominant copper phases were found to be Cu2Cl(OH)3, Cu(OH)2 and CuSO4·5H2O for ST, whereas Cu appeared to adsorb to amorphous SiO2 for TX, which contained much less Pb. Cr is thus immobilized in the filter cakes in a phase with low solubility at environmentally feasible pH values, whereas Zn, Cu and Pb could be released when the pH decreases below 8 or above 11. These findings are significant for the development of waste management regulations and/or metal recovery methods (e.g., hydro/pyrometallurgy).

Evaluation of asphalt film thickness and heavy metal leaching of oxidizing slag used as an aggregate material in dense-graded asphalt concrete.

Electric-arc-furnace (EAF) steelmaking uses scrap iron and steel as raw materials. Scrap iron and steel originate from complex sources and may contain heavy metal components which can leach into the environment over time due to wear-and-tear. A by-product of the EAF steelmaking process is oxidizing slag, and approximately 1.2 million metric tons is produced every year in Taiwan alone. This study investigated substitution of natural aggregates with oxidizing slag in dense-graded asphalt concrete. We evaluated the water resistance and asphalt film thickness of the oxidizing slag substituted asphalt concrete and further explored the performance of oxidizing slag as paving material. We determined the dissolved and total amounts of heavy metals in the oxidizing slag, comparing these results with current regulatory controls to assess the environmental compatibility of the oxidizing slag. We found that due to the complicated sources of oxidizing slag, the basic properties should be analyzed on a batch-to-batch basis. Furthermore, we recommend trial mixing before upscaling the production of oxidizing slag substituted dense-graded asphalt concrete to confirm the mixing time required to achieve uniformity. The results also show that in comparison to natural aggregates used in asphalt concrete, oxidizing slag exhibits superior performance in terms of increased asphalt film thickness and improved water resistance. Furthermore, oxidizing slag as an aggregate material was associated with decreased heavy metal leaching and reduced environmental pollution. The results of the toxicity characteristic leaching procedure (TCLP) met regulatory requirements. However, the microwave-assisted aqua-regia digestion procedure showed heavy metal concentrations exceeding the monitoring standards for food crops. Considering environmental compatibility, it is recommended that controlling the total amount of heavy metals in oxidizing slag should be included in regulatory requirements. Furthermore, we should prohibit the use of materials such as oxidizing slag and other steel furnace slag in the roadways adjacent to edible crop farmlands.

Effect of activator type and Pozzocrete waste on the mechanical and microstructural properties of eco-friendly geopolymer incorporating electric arc furnace slag

ABSTRACT The precursor type and activator are two primary factors that significantly affect the properties of geopolymers. Most of the previous studies used byproduct materials such as fly ash (FA) and slag as geopolymer precursors, while too limited studies used electric arc furnace slag (EAFS) for this purpose. The EAFS is a type of steel slag, which can be produced when scrap steel is melted. The preliminary usage of EAFS as a precursor in the geopolymer system has not been sufficiently highlighted. To make this come true, the current procedure employed EAFS as a precursor material for the geopolymeric system. Due to superior properties, EAFS was partially replaced with 10–50 wt% pozzocrete (Pz). Two different types of alkaline activators, NaOH and Na2CO3, were used to activate EAFS slurries supported by Pz. The results indicated that the optimal ratio of Pz to be replaced by EAFS to achieve the target properties varies according to the type of activator. The inclusion of 10% Pz exhibited maximum compressive strength when Na2CO3 was used, whilst 50% Pz exhibited maximum compressive strength when NaOH was used. The coexistence between N-A-S-H from Pz and C-(A)-S-H gel from EAFS is the main reason for the enhanced strength.

Matrix effect correction in active neutron interrogation for residual fissile mass assessment in radioactive waste drums

Metallic waste in the form of shells and nozzles remains following the reprocessing of spent fuel at La Hague plant (France). Before the final disposal, drums containing the waste are transported to the compaction facility where its volume is reduced by a factor of 5. With the objective of controlling the criticality/safety levels, an active neutron interrogation system at the entrance of the facility is used to assess the residual fissile mass remaining in the waste, which relies on prompt fission neutron detection (known as the differential die-away technique, DDA). The measured signal is proportionally linked to the fissile mass by a calibration coefficient. However, two effects can produce an inaccurate prediction. The number of induced fissions for the same fissile mass varies according to the waste matrix composition, particularly the neutron slow-down and absorption ratio. Secondly, the presence of fissile clusters can impact the neutron interrogation due to an increase in self-shielding effect. This work presents a matrix effect correction method based on the use of internal flux monitors (sensitive to the neutron absorption ratio) and the transmission signal (sensitive to the slow-down ratio). It relies on a numerical model of the whole measurement cell developed with the Monte-Carlo N-Particle transport (MCNP) code. The calibration coefficient of 72 different matrices, representative of the waste produced at La Hague, were simulated and a statistical model using a multilinear regression was then established. This simulated-based approach provides a more robust and comprehensive estimation of the residual fissile mass without impacting accuracy thanks to the flux monitors and the transmission signals.

Exploring the Aesthetic and Functional Aspects of Recycled Furniture in Promoting Sustainable Development: An Applied Approach for Interior Design Students

This study aimed to explore the sustainable aesthetic and functional dimensions of environmental waste in the context of interior design applications by students. Employing both descriptive and applied methodologies, a series of artistic works derived from environmental waste, specifically metal and wood, were conceptualized and executed by art education students. These works, totaling 11 artistic models in interior design, underwent chemical treatment as part of the process. An evaluation card, assessed by arbitrators, was utilized to gauge the standards of aesthetic and functional sustainability inherent in the artworks. Technical data were collected and subsequently analyzed using SPSS software, which facilitated the calculation of arithmetic averages, standard deviations, and t-tests to ascertain the extent to which sustainability standards were met within the aesthetic and functional dimensions of the works. The study findings indicated that the average response scores for the aesthetic and functional dimensions, pertaining to the achievement of sustainability for wood and metal waste, were notably high. This underscores the potential of producing artful works suitable for interior design applications within the spaces of the College of Education. With an average score of 3.984, students exhibited positive engagement with the aesthetic and functional aspects of their artistic products, indicative of their considerable ethical significance. This augurs well for the feasibility of attaining sustainability through the recycling of wood and metal waste. Furthermore, this research underscores the necessity of integrating aesthetic, environmental, and social values in achieving sustainable aesthetic and functional environmental values within the interior design curriculum. This integration demands a comprehensive understanding of user expectations, technological advancements, and the cultural background, customs, and traditions of both users and society at large.

Multi-class waste segregation using computer vision and robotic arm

Waste segregation is an essential aspect of a smoothly functioning waste management system. Usually, various recyclable waste types are disposed of together at the source, and this brings in the necessity to segregate them into their categories. Dry waste needs to be separated into its own categories to ensure that the proper procedures are implemented to treat and process it, which leads to an overall increased recycling rate and reduced landfill impact. Paper, plastics, metals, and glass are just a few examples of the many dry waste materials that can be recycled or recovered to create new goods or energy. Over the past years, much research has been conducted to devise effective and productive ways to achieve proper segregation for the waste that is being produced at an ever-increasing rate. This article introduces a multi-class garbage segregation system employing the YOLOv5 object detection model. Our final prototype demonstrates the capability of classifying dry waste categories and segregating them into their respective bins using a 3D-printed robotic arm. Within our controlled test environment, the system correctly segregated waste classes, mainly paper, plastic, metal, and glass, eight out of 10 times successfully. By integrating the principles of artificial intelligence and robotics, our approach simplifies and optimizes the traditional waste segregation process.