Alkali residue is a byproduct of the ammonia-soda process used to produce soda, characterized by high production volume, low utilization efficiency, high moisture content, high porosity, and fine particle size. The primary disposal methods for alkali residue include surface stacking (e.g., constructing tailing dams) and direct discharge into water bodies such as rivers or seas. The hazards associated with surface stacking include land resource occupation, reduced agricultural yield, groundwater and air contamination, soil pollution, adverse effects on vegetation growth, ecological imbalance, and the formation of saline-alkali land. Additionally, the discharge of alkali residue into rivers or seas can lead to water pollution, threatening the sustainability of aquatic ecosystems. Sedimentation may also occur, potentially blocking river channels, reducing flow cross-sections, and significantly impairing the river’s flood discharge capacity. These challenges have resulted in a large-scale accumulation of alkali residue, severely constraining the development of the soda industry. Therefore, there is an urgent need to accelerate its large-scale application. This study provides a comprehensive review of the latest research findings on the fundamental properties and engineering applications of alkali residue. The results indicate that similar to soil, alkali residue exhibits a three-phase system, where the solid phase, composed of various mineral components, forms a skeletal structure. In contrast, the liquid and gas phases fill the pores, creating a porous medium. The properties of alkali residue can be characterized using soil indicators. Its mineral composition includes CaCO3, CaSO4, CaCl2, and NaCl, where CaCO3 and CaSO4 are insoluble salts, while CaCl2 and NaCl readily dissolve in water. The CaCO3 content ranges from 32.52% to 64.00%, while the chemical composition is dominated by CaO, accounting for 32.25% to 74.20%. Alkali residue solutions are slightly alkaline, with pH values typically ranging from 8 to 12. As a general industrial solid waste, alkali residue contains heavy metals such as copper, zinc, cadmium, lead, total chromium, and chromium, all of which meet environmental standards. Alkali residue has been explored for various engineering applications, including the remediation of bioleached heavy metal-laden sediment, sludge, clay, expansive soil, contaminated soil, shield tunneling slag, weathered mudstone, and coal gangue, as well as for backfill materials and the preparation of alkali residue-based soil and composite cementitious materials. However, current application methods suffer from low alkali residue utilization efficiency, limited application scenarios, challenges in Cl- solidification, potential steel reinforcement corrosion, and risks of secondary pollution. To address these challenges, the author systematically investigates the fundamental properties of alkali residue from Lianyungang and proposes a method for producing alkali residue-based lightweight soil (A-LS) by combining alkali residue, cement, and granulated blast furnace slag (GGBS). A-LS was utilized as a roadbed filler in the Lianyungang—Suqian expressway, demonstrating compressive strength, California bearing ratio (CBR), rebound modulus, and deflection that met design and specification requirements. The material exhibited strong road performance, high resistance to wet-dry cycling, freeze-thaw cycling, and sulfate corrosion, with a durability coefficient ranging from 0.71 to 1.51. Furthermore, A-LS offers several advantages, including high strength, low density, a simple production process, high efficiency, and low cost. With a 28-day compressive strength ranging from 0.96 to 4.27 MPa, A-LS is suitable as a subgrade filling material. The alkali residue content in A-LS ranges from 87.01 to 164.35 kg·m−3, facilitating large-scale disposal and high-value utilization of alkali residue.
The geometric configuration and microstructure are crucial for the mechanical properties of the lattice structure formed by laser powder bed fusion (LPBF). In this study, a type of Ti–6Al–4V lattice structure with hexagonal-body-centered (HBC) structure was fabricated by LPBF and post β-annealing treatment. The microstructure, mechanical properties, energy absorption properties and deformation behavior of the Ti–6Al–4V HBC lattice structure was investigated by electron backscatter diffraction (EBSD), quasi-static compression tests and digital image correlation (DIC) techniques. The results showed that the β-annealing sample completely transformed from the αʹ martensitic microstructure to a completely stable α + β lamellar microstructure, which slightly reduced the ultimate compressive strength of the HBC lattice structure and increased the strain at the end of yielding. The β-annealed sample showed better plasticity and work-hardening rate during the loading process, which increased its absorption capacity by 74.7% compared to the un-annealed sample. Finally, the quantitative analysis of fracture morphology indicated that the HBC lattice structure subjected to β-annealing undergoes ductile-brittle fracture, significantly improving its deformation stability.
This study investigated the effects of aging processes on the microstructure, mechanical properties, and wear properties of Cu-Cr-Zr alloys prepared by vacuum melting. The experimental results show that the particles in the alloy are arranged along the rolling direction after rolling. After aging treatment at 450 °C for 6 h, the particles in the alloy are well-distributed without obvious agglomeration, and the alloy exhibits excellent comprehensive properties: the hardness is increased by about 35%, the electrical conductivity is improved by approximately 1.68 times, and the strength is enhanced by 14.46% compared with the unaged rolled samples. It is also found that the wear properties of the samples under different aging processes are related to the material hardness; as the material hardness increases, the wear mechanism transforms from material transfer to abrasive wear.
The study focused on leaching complex copper–cobalt oxide ore from Zebesha Mine in Zambia. The chemical analysis indicated the presence of cobalt, copper, nickel, manganese and iron as base metals. Copper is predominantly found in malachite and a small portion in heterogenite mineral along with cobalt, iron, manganese and nickel. The leaching process involved using solutions containing iron: ferrous sulphate, FeSO4·7H2O; ferrous ammonium sulphate, (NH4)2Fe(SO4)2·6H2O; and ferric sulphate, Fe2(SO4)3. The effects of temperature and salt concentrations were studied alongside metal content determination through titration-atomic absorption spectroscopy techniques. It was observed that the preferential dissolution of copper occurred with Fe2 (SO4)3 while temperatures above 70°C leaching with FeSO4·7H2O resulted in the recovery of over 80% of manganese and cobalt. This study suggests that ferrous containing lixiviants can effectively promote the manganese and cobalt dissolution but are not efficient for extracting copper. Furthermore, using Fe2(SO4)3 may allow for selective leaching of copper.
Ekaterina I. Karchina, Mariya V. Ivanova, Аlla T. Volokhina
et al.
The lack of a unified approach to the assessment of professional risks in fuel and energy companies (FEC) in the national regulatory environment and a high degree of subjectivity of the results of hazard identification and risk assessment makes mathematically sound recruitment of an expert group urgent and necessary. The article presents the results of a comprehensive study on hazard identification and risk assessment at 6,105 workplaces in 24 branches of a FEC company based on the application of the expert assessment method and a scientifically sound qualitative and quantitative selection of experts. The priority vectors of factors are determined, global priorities are calculated, the size of the expert group (15 persons) is determined and mathematically substantiated for carrying out hazard identification and risk assessment at workplaces with sufficient reliability of results. For the first time, a set of factors characterizing the FEC companies that influence the determination of professional competence of experts is proposed. The formed expert group presented more precise, objective and consistent results of risk assessment. Standards for free distribution of personal protective equipment (PPE) and wash-off agents to 7,234 company employees for implementation and trial use were developed. A fragment of the results obtained for a driller's workplace is presented. This approach allows a significant increase in objectivity and efficiency of the professional risk management system and provision of the PPE to employees in the concept of a risk-oriented approach helping to prevent industrial injuries
and improve the level of occupational safety culture in fuel and energy companies taking into account global practice.
As a source of corrosion inhibitors, 2.5% Mo powder was mixed with Type 304L stainless steel powder and spark-plasma sintered to a fabricate Mo-encapsulated Type 304L stainless steel. The Mo particles formed a core/shell structure. The localized corrosion resistance of the fabricated Mo-encapsulated Type 304L stainless steel was compared with those of spark-plasma-sintered Type 304L and Type 316L stainless steels. Potentiodynamic polarization in 0.1 M NaCl suggested that the Mo cores could release molybdate, which acts as an inhibitor. However, the shells did not dissolve, preventing the Mo-enriched particles from acting as pit initiation sites. Similarly, the surface of the Mo core dissolved during dip-and-dry cycles using 0.1 M NaCl, but the shell was less prone to dissolution. Although the fabricated Mo-encapsulated stainless steel did not contain Mo as a solid solution, its rust resistance was equivalent to that of spark-plasma-sintered Type 316L stainless steel. In potentiodynamic polarization, the initiation potential for localized corrosion of the Mo-encapsulated Type 304L stainless steel was remarkably higher than those of the sintered Type 304L and Type 316L stainless steels. The corrosion inhibition mechanism of the Mo-encapsulated Type 304L stainless steel was discussed from three viewpoints: (1) passive film modification on the steel matrix, (2) cathodic protection of the steel matrix by the Mo core dissolution, and (3) corrosion inhibition by molybdate dissolved from the Mo-enriched particles, and the last one appeared to be the most likely.
Discrete Element Method (DEM) was used to analyze palletization process of MgO-fluxed pellets in cylinder pelletizer. The effects of the charge ratio and rotational speed of the cylinder pelletizer on the behavior of MgO-fluxed pellets were investigated by using the simulation. The simulation results show that under the condition of a certain gradient angle of the cylinder pelletizer (The gradient angle is 3°), the suitable parameters of the cylinder pelletizer are that the charge ratio is 3 % and the rotational speed N/ critical rotational speed N<sub>C</sub> is 0,3.
Aiming at the problems of high labor intensity, low degree of automation and low positioning accuracy of single way in the construction process of existing coal mine anchor digging machine, a long-distance positioning system suitable for anchor digging machine is developed by using sensor measurement, machine vision, inertial navigation and other technologies. The system consists of anchor digger, inertial positioning subsystem, visual positioning subsystem, total station positioning subsystem and parameter monitoring subsystem. Anchor digger main machine adopts MB670-1 anchor digger; the inertial navigation and positioning subsystem is composed of built-in optical fiber inertial navigation and explosion-proof computer. The visual positioning subsystem includes infrared explosion-proof target, laser pointing device, front explosion-proof industrial camera and explosion-proof computer. The positioning subsystem of total station consists of 360° prism, three laser pointing instrument and rearview prism. Parameter monitoring subsystem includes parameter display, parameter setting and parameter solution module. The system was successfully developed and tested in Dahaize Coal Mine of China National Coal Group. The experiment shows that the long-distance high-precision positioning system of the all-in-one anchor digger has the advantages of flexible operation and highpositioning accuracy, and can realize the positioning and parameter monitoring of the all-in-one anchor digger.
Nguyen Hoang Lam, Nguyen Tam Nguyen Truong, Chau Thi Thanh Thuy
et al.
CuO thin films with broccoli-like structure were prepared using a facile hydrothermal method to construct photocathodes for water-splitting application. The morphological, structural, and optical properties of thin films were characterized and measured using several techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and ultraviolet-visible spectroscopy (UV-Vis). The thickness, structure, and morphology of CuO thin films can be controlled by varying the precursor concentration (C<sub>p</sub>) and reaction temperature (T<sub>r</sub>), which are also discussed. Moreover, the electrical properties of CuO thin films were also measured in the three-electrode system. The photocurrent density of photocathodes, when synthesized by a 0.5 M solution at 150 °C for 12 h, was 0.5 mA/cm<sup>2</sup> at −0.6 V vs. Ag/AgCl, which is 1.8 times higher than that of photocathodes synthesized in a 0.1 M solution at 100 °C with the same reaction time. In addition, increasing the reaction temperature and precursor concentration aided in the enhancement of the IPCE and APCE values, which peaked at a wavelength range of 330–400 nm.
Rolling contact fatigue (RCF) and wear are important problems for the wheel and rail. RCF and wear is caused by contact stress and the slip ratio between the wheel and the rail. The material properties of the wheel and rail are an important factor to prevent the degradation caused by RCF and wear. In this study, the mechanical properties and fatigue characteristics of the two types of wheel and rail were evaluated, and the effects on wear and contact fatigue were examined. We found that the crack growth rate and the hardness were important factors in the contact fatigue and the wear. The rail steel with a higher crack growth rate and hardness had a low resistance to contact fatigue with large size damage. The hardness ratio and the total hardness are important factors in evaluating the wear resistance. In addition, we found that the residual stress increased proportionally to the maximum shear stress.
Stress analysis and deformation prediction have always been the focuses of the field of mechanics. The accurate force prediction in plate deformation plays important role in the production, processing and performance analysis of materials. In this paper, we propose an ARIMA-FEM method, which can be used to solve some mechanical problems of 2D porous elastic plate. We have given a detailed theory and solving steps of ARIMA-FEM. In addition, three numerical examples are given to predict the stress–strain of thin porous elastic metal plates. This article uses CST, LST and Q4 elements to discrete the rectangular plates, square plates and circle plates with holes. As for variable force prediction, this paper compared with linear regression, nonlinear regression and neural network prediction, and the results show that the ARIMA method has a higher prediction accuracy. Furthermore, we calculate the numerical solution at four mesh scales, and the numerical convergence is consistent with the theoretical convergence, which also shows the effectiveness of our method. The image smoothing algorithm is applied to keep edge information with high resolution, which can more concisely describe the plate internal changes. Finally, the application scope of ARIMA-FEM, model expansion, superconvergence analysis and other issues have been given enlightening views in the discussion section. In fact, this algorithm combined statistics and mechanics. It also reflects the knowledge integration of interdisciplinary and uses it better to serve practical applications.
The atmospheric corrosion behavior and mechanism of the 7A85 aluminum alloy exposed to the Qingdao industrial-marine atmospheric environment for five years was investigated using the weight-loss method, mechanical property analysis, morphology observations, scanning Kelvin probe force microscopy, and corrosion product analysis. The results showed that the mechanical properties of the exposed 7A85 Al alloy deteriorated considerably, which was mainly induced by pitting corrosion and intergranular corrosion. Al2CuMg and Al7Cu2Fe intermetallic particles were the main precipitates in the 7A85 Al alloy, and the particles not only induced a defective film but also acted as cathode phases in the precipitate–matrix galvanic corrosion couple, which led to pitting corrosion initiation during atmospheric corrosion in Qingdao. Moreover, intergranular corrosion initiated and then propagated owing to micro-galvanic corrosion along the grain boundaries.
Smelter grade alumina (SGA) plays multiple roles in the Hall−Héroult process for primary aluminum production. Given its very porous nature, one major role of SGA is to adsorb toxic hydrogen fluoride (HF) in the dry scrubber. However, also because of its porous nature, SGA inevitably adsorbs ambient moisture. This paper discusses the influence of alumina properties, including pore size distribution and specific surface area, on the physical adsorption of water vapor on SGA, as well as the adsorption kinetics. The result shows that the adsorption enthalpy of moisture on SGA is in the range of 4−13 kJ/mol. The adsorption capacity increases significantly with the particle specific surface area and total pore volume. A higher adsorption temperature indicates a much faster adsorption rate but corresponds to a lower equilibrium adsorption capacity.