Search Results (15)

This paper endeavors to explore the impact of secondary aluminum dross (SAD) on the characteristics of sulfoaluminate cement mortar. Measurements were taken for the mortar’s slump flow, plastic viscosity, initial setting time, and drying shrinkage rate (DR). Additionally, the flexural, compressive, and bonding strengths were evaluated. The leached concentrations of chromium (Cr) and zinc (Zn) in the specimens were determined. Furthermore, the carbonation depth (Dc) and chloride ion migration coefficient (CMC) were calculated. Lastly, scanning electron microscope energy spectrum analysis (SEM-EDS) and X-ray diffraction (XRD) spectrum analysis were conducted to analyze the mortar’s performance. The findings revealed that the slump flow and plastic viscosity of fresh mortar exhibited negative and positive quadratic relationships, respectively, with the mass ratio of SAD. Specifically, SAD could reduce the slump flow by 1.57% to 2.72% and augment the plastic viscosity by 5.21% to 36.89%. The placement time contributed to a decrease in the slump flow of fresh mortar by up to 20.4% and an increase in plastic viscosity by up to 11.2%. The initial setting time, mechanical strength, and DR of the mortar demonstrated quadratic variations with the mass ratio of SAD. At a 15% SAD mass ratio, the mortar exhibited the highest initial setting time, mechanical strength, and DR. The inclusion of SAD could elevate the initial setting time, flexural strength, compressive strength, bonding strength, and DR of the mortar by 14.33% to 65.07%, −14.75% to 22.58%, −8.94% to 9.96%, −13.33% to 66.67%, and −13.33% to 26.67%, respectively. Full article

Surface quality control of hot-dip galvanized sheets is a critical research topic in the metallurgical industry. Zinc dross, the most common surface defect in the hot-dip galvanizing process, significantly affects the sheet’s service performance. In this manuscript, a novel magnetic flux leakage (MFL) detection method was proposed to detect zinc dross defects on the surface of hot-dip galvanized steel sheets. Instead of using exciting coils in traditional methods, a tiny permanent magnet with a millimeter magnitude was employed to reduce the size and weight of the equipment. Additionally, a high-precision tunnel magnetoresistance (TMR) sensor with a sensitivity of 300 mV/V/Oe was selected to achieve higher detection accuracy. The experimental setup was established, and the x-axis direction (sample movement direction) was determined as the best measurement axis by vector analysis through experiments and numerical simulation. The detection results indicate that this novel MFL detection method could detect industrial zinc dross with an equivalent size of 400 μm, with high signal repeatability and signal-to-noise ratio. In the range of 0–1200 mm/s, the detection speed has almost no effect on the measurement signal, which indicates that this novel method has higher adaptability to various conditions. The multi-path scanning method with a single probe was used to simulate the array measurement to detect a rectangular area of 30 × 60 mm. Ten zinc dross defects were detected across eight measurement paths with 4 mm intervals, and the positions of these zinc dross defects were successfully reconstructed. The research results indicate that this novel MFL detection method is simple and feasible. Furthermore, the implementation of array measurements provides valuable guidance for subsequent in-depth research and potential industrial applications in the future. Full article

The removal of zinc dross, which continuously generates and partially floats on a molten zinc surface, has been a persistent challenge during hot-dip galvanizing. Herein, a three-dimensional mathematical model coupled with the electromagnetic field, flow field and air-knife jet flow was established to investigate the flow and zinc dross removal in a zinc pot. Two types of traveling magnetic field combined modes (Mode 1 and Mode 2) were compared. The surface dross removal efficiency was introduced to evaluate the ability of the zinc flow field to compel the movement of zinc dross. The research findings indicate that, in comparison to the influence of strip steel line speed, both the electromagnetic field and air-knife jet have a more pronounced effect on altering the flow characteristics of a molten zinc at surface. The dross removal efficiency for Mode 1 is much far superior to that of Mode 2. With an increase in the driving current, the dross removal efficiency increases while the excessive driving current cannot promote the dross removal efficiency significantly. Full article

In the present study, the recycling process of bottom zinc dross was performed by evaporation and subsequent condensation at 800 °C for 30 min with an observed argon flow rate of 100–400 mL/min to ensure an inert atmosphere, to observe the evaporation rate and final form of the product. Under the set conditions of over 98% zinc purity, products in the form of nanofibres (thickness 500 nm), powder (size of spherical particles 2–5 μm), dendrites, and metallic forms were obtained. The employed mathematical modelling (via Ansys 2023R1 software) predicted the behaviour of the argon flow current in the quartz tube, as well as the temperature gradient in the quartz tube and in the close vicinity of the zinc sample. Via Inventor 2014 software, the rate of zinc sample heating was calculated. All the simulations were compared with the physical measurements and correlation was proven. Full article

During hot-dip galvanization, wastes such as bottom dross, zinc ash, spent pre-treatment solutions, and galvanizing flue dust (GFD) are generated. In scientific publications, research devoted to GFD waste recycling is absent, and companies generating this waste require a solution to this complex problem. GFD is often landfilled in hazardous waste landfills. However, it is possible to process this waste hydrometallurgically, where GFD is first leached, the solution is refined, and finally, zinc metal is obtained by electrowinning. During specific environmentally friendly leaching, not all solid GFD is dissolved, and the aim of this study is to process the remaining solid GFD residue. The analysis shows that the GFD residue material mainly contains zinc (42.46%) in the form of oxides, but there is also a small amount of polluting elements such as Al, Fe, and Pb. This study examines the leaching of the samples in HCl and H₂SO₄ under different conditions with the aim of obtaining a solution with a high concentration and high leaching efficiency of zinc. The L/S ratio of 3, 4 M H₂SO_4, and ambient temperature proved to be optimal for the leaching of the GFD residue, where 96.24% of zinc was leached out, which represents a zinc concentration of 136.532 g/L. Full article

This study presents a theoretical and practical evaluation of zinc evaporation from bottom zinc dross (hard zinc) as a secondary zinc source (zinc content approximately 94–97%), which originates in the batch hot-dip galvanizing process. The thermodynamics of the zinc evaporation process were studied under the normal pressure (100 kPa) in the inert atmosphere, using argon with flow rate 90 mL/min. Samples were subjected to the evaporation process for 5, 10 and 20 min under the temperature of 700 °C and 800 °C, respectively. For the theoretical thermodynamic study, HSC Chemistry 6.1 software was used and final products, as well as residuals after the evaporation process, were analyzed by SEM (Scanning Electron Microscopy) and EDX (Energy Dispersive X-ray). Calculated and experimental argon consumption in the process of zinc evaporation has been compared. A high purity zinc with efficiency over 99% was reached. Due to a dynamic regime, argon consumption at the temperature of 700 °C and 800 °C were 7 times and 3 times, respectively, less than calculated. Full article

The forming of zinc dross floating on the surface of molten zinc in zinc pot is inevitable during hot-dip galvanizing production. The cleaning of zinc dross has always been a challenge and a difficult problem to solve. Based on the electromagnetic field theory and its application, a new electromagnetic dross removal technology was proposed, and the zinc dross driven by flowing molten zinc was possible to remove in an electromagnetic field circumstance. Through the coupling simulation of electromagnetic field and flow field, the electromagnetic force acting on molten zinc and the flow situation of molten zinc were simulated. The results showed that electromagnetic field can effectively act on the top surface of molten zinc and affect the flow of molten zinc. Different load conditions of electromagnetic field and the distance between the bottom surface of the iron core and the top surface of molten zinc related to zinc dross removal effect were discussed. Finally, the optimal application parameters of the electromagnetic dross removal technology were put forward. Full article

In this paper, research on the effects of agitation rate for desilvering tin silver alloy residue by using pyrometallurgy was carried out. SnAg alloy residue with 92 wt.% tin and 3.56 wt.% silver was used in this study, and 99.999 wt.% zinc was added as metal solvent. Residues were melted to a temperature of 400 °C for enriching tin silver alloy. The obtained tin silver alloy was melted in a temperature range of 450 °C to 500 °C by adding zinc to evaluate zinc dissolution. The obtained tin silver zinc was agitated at different agitation rates for 20 min at a temperature of 480 °C, then cooled down while stirring to an eutectic point of tin zinc alloy (198.9 °C) to remove silver zinc dross. X-ray Fluorescent-1800 (XRF-1800) and Field Emission Scanning Electron Microscopy Energy Dispersive Spectroscopy (FE-SEM-EDS) analyses were performed in this research. Different factors including holding time, zinc dissolution, agitation time and agitation rate were evaluated. The results revealed that an agitation rate of 600 RPM, 25% Zn and 60 min at a temperature of 198.9 °C were efficient. Zinc silver was removed as dross every 20 min to get 92% silver separation efficiency, and the use of supergravity centrifuge is highly recommended to get best separation efficiency. Full article

Dross from hot-dip galvanizing is an important source of pure zinc ingots and zinc oxide for use as mineral additives in animal and poultry feed. Thermodynamic calculations have shown the possibility of solving the issue of dross processing by roasting using CaCl₂ and NH₄Cl. The influence of the consumption of chlorinating reagents, the roasting temperature on the degree of sublimation of Pb, Fe, Ni, Cu and Cd has been investigated. It has been shown that the best results are achieved when roasting the dross with the simultaneous use of CaCl₂ and NH₄Cl in amounts of 6 and 15% by weight of the feed material. The optimal roasting parameters were established: T = 1000 °C, duration—60 min, air flow—0.1 L/min. Recovered pure zinc oxide composition (%) was: 0.05 Pb, 0.15 Fe, 0.06 Ni, 0.003 Cu and 0.001 Cd. The degree of sublimation of copper, nickel and iron chlorides was ~75%, with lead and cadmium at 90–98% of their initial amount in the dross. Full article

In this study, we report the synthesis of ZnO nanoparticles from Zn dross via hydrometallurgical method by using acetic acid as a leaching agent. D205 dye molecules were then adsorbed onto Zn dross originated ZnO nanoparticle film. The optical absorption confirms the photosensitization of the synthesized ZnO nanoparticles with dye. The photoluminescence spectra reveal the excitonic- and defect-related emission of ZnO nanoparticles. Compared to ZnO nanoparticles only, the longer emission lifetime of ZnO nanoparticles with adsorbed dye indicates the transfer of photoexcited electrons from dye to the ZnO nanoparticles. Furthermore, photodetection characterization of ZnO film show the enhanced current density with the presence of dye under simulated solar illumination, while that measured at dark is similar in both films with and without dye. This result confirms the potentiality of Zn dross to be recycled into valuable ZnO nanoparticles particularly for the applications in the visible light region, especially for sensing. Full article

Cementation of germanium from sulphate solution obtained after the leaching of GeIn dross using zinc dust was investigated. The composition of the examined solution was 5.15 Ge, 1.52 In, and 5.81 g/dm³ Zn. In order to resemble the solution before detinning, Sn concentration between 2–10 g/dm³ was also investigated. It was found that >99% of germanium may be precipitated from the solution. In order to achieve high selectivity, a detinned solution should be used because the precipitation yields of germanium and tin from the solution containing Sn were similar. For cementation with Zn powder at 75 °C for 2 h with a final pH of 2.0, over 99% of the germanium was removed from the solution, while the indium precipitation yield was 12%. The obtained cementate contained 50% Ge, mainly in elementary form. Full article

There is an increasing interest in biodegradable metal implants made from magnesium (Mg), iron (Fe), zinc (Zn) and their alloys because they are well tolerated in vivo and have mechanical properties that approach those of non-degradable metals. In particular, Zn and its alloys show the potential to be the next generation of biodegradable materials for medical implants. However, Zn has not been as well-studied as Mg, especially for stent applications. Manufacturing stents by laser cutting has become an industry standard. Nevertheless, the use of this approach with Zn faces some challenges, such as generating thermal stress, dross sticking on the device, surface oxidation, and the need for expensive thin-walled Zn tubing and post-treatment. All of these challenges motivated us to employ photo-chemical etching for fabricating different designs of Zn (99.95% pure) stents. The stents were constructed with different strut patterns, made by photo-chemical etching, and mechanically tested to evaluate radial forces. Stents with rhombus design patterns showed a promising 0.167N/mm radial force, which was comparable to Mg-based stents. In vitro studies were conducted with uncoated Zn stents as control and Parylene C-coated Zn stents to determine corrosion rates. The Parylene C coating reduced the corrosion rate by 50% compared to uncoated stents. In vivo studies were carried out by implanting photo-chemically etched, uncoated Zn stent segments subcutaneously in a C57BL/6 mice model. Histological analyses provided favorable data about the surrounding tissue status, as well as nerve and blood vessel responses near the implant, providing insights into the in vivo degradation of the metal struts. All of these experiments confirmed that Zn has the potential for use in biodegradable stent applications. Full article

The precipitation of tannin complex of germanium from sulfuric solutions obtained after dross leaching was investigated. The tested solutions contained mainly zinc, germanium, indium, and tin. The influence of temperature, time, amount of added tannic acid and its purity was determined. The application of pure tannic acid allowed the precipitation of >99% of germanium and decreased its concentration in a solution <0.015 g/dm³. It required ca. 11–13 g of pure tannic acid per each 1 g of dissolved germanium. The preferred process conditions for Ge precipitation using powder tannic acid were 90 °C, 90 min, whereas for 20% aq. solution—5 min. It was found that 40% to 50% of tin coprecipitated at these conditions. Therefore, a detinning operation using hydrogen peroxide was proposed. It allowed the removal of >99% Sn and reduced its concentration in the solution below 0.025 g/dm³. Full article

Leaching of the dross containing 28.7% Sn, 18.0 Pb, 10.6% Cu, 8.9% Ge, 8.1% Zn, and 2.7% In in sulphuric and oxalic acid solution was investigated. The dross was obtained from thermal oxidation of by-product alloy generated during a New Jersey (NJ) zinc rectification process. The influence of different process conditions (temperature, time, acid concentration, and solid to liquid ratio) on leaching yield of the main components was determined. Additionally, the impact of oxidant (hydrogen peroxide, sodium hypochlorite, manganese (IV) oxide) addition on leachabilities was investigated. Germanium leaching yields exceeding 80% were observed for both sulphuric and oxalic acid solutions. Indium leachability in H₂C₂O_4(aq) was found at the level of 20%, while in H₂SO_4(aq), it strongly depends on process temperature, and reached 80% at 80 °C. Full article

A primary lead smelter operated in Santo Amaro City in Brazil from 1960 to 1993, leaving approximately 500,000 tons of industrial dross containing 2–3% of lead and other toxic elements that contaminated the industry grounds and the urban environment. This study aimed to present the local residents’ perception towards soil contamination by the smelter. In a cross-sectional study, 208 residents from randomly selected households were interviewed about dross hazards and proposals for its management. A city map depicts the distribution and concentration of lead, cadmium, arsenic, zinc, nickel, and antimony, measured in the soil of the 39 households with visible smelter dross. Only one site complies with the soil quality reference values; 27 (69.2%) call for preventive measures, and 11 (28.2%) require intervention. The smelter dross continues widely spread over the city. Thirty (76.9%) out of the 39 residents were able to recognize the smelter dross on household surroundings. However, this ability was not associated with the concentrations of toxic elements in the soil of their residences and surroundings. The smelter and the local Prefecture were most frequently held liable for taking soil cleanup actions. The most frequently (38.0%) cited solution for managing the dross found in the households was “to provide the residents with information about health risks related to the dross”. Full article