Industrial Waste Research Articles

Quantitative study on fatigue characteristics of warm mix recycled asphalt

The warm mix recycling technology of asphalt pavement can improve the utilization rate of solid waste in highway construction industry on a large scale, and reduce the emission of harmful gases ( NOX, CO2, benzopyrene, etc.) in the process of road construction. It is one of the effective ways to realize carbon neutrality in highway construction industry. The main purpose of this study is to systematically analyze the fatigue characteristics of warm mix recycled asphalt (WMRA) from the perspective of quantitative research, and to provide scientific basis for the popularization and application of this technology. Therefore, this study mainly evaluated the anti-fatigue characteristics of WMRA under different conditions based on the linear amplitude sweeping test ( LAS test). Based on the calculation and analysis of the commonly used fatigue judgment indexes ( stress-strain curve, phase angle-strain curve, S×N curve ( S is the ratio of the instantaneous modulus to the initial modulus of the material, which is often replaced by the virtual modulus in the LAS test, and N is the number of cyclic loadings.), virtual strain storage energy-strain curve), the peak strain of virtual strain storage energy is recommended as the fatigue judgment standard from the perspective of reliability and accuracy, and the peak strain of damage factor is proposed as one of the new fatigue judgment standards. In this paper, the nucleation of microcracks and the coalescence of microcracks are distinguished in the process of fatigue damage evolution, and the peak strain of virtual strain energy storage and the peak strain of damage factor are used as the judging indexes respectively. Finally, based on the theory of continuum damage mechanics, the loss modulus of WMRA is selected as the representative value of material properties to calculate the virtual modulus and damage factor, and the fatigue damage evolution model of WMRA based on the viscoelastic continuum damage model ( VECD model) was constructed. Based on this model, the anti-fatigue characteristics of WMRA with the reclaimed asphalt pavement ( RAP) content were analyzed.

Sustainability assessment and mechanical characteristics of high strength concrete blended with marble dust powder and wheat straw ash as cementitious materials by using RSM modelling

Research into environmentally favorable alternatives to conventional concrete, such as reengineering techniques and the recycling of industrial and agricultural waste, has increased dramatically over the past decade. This research intended to examine the potential benefits of utilizing wheat straw ash (WSA) and marble dust powder (MDP) as supplementary cementitious materials (SCM) in high-strength concrete (HSC). The intention is to decrease carbon dioxide emissions and the amount of Portland cement (PC) required. Concrete formulations containing 0%, 15%, 20%, 30%, and 40% by weight of MDP and WSA as SCM, respectively, were evaluated by using response surface methodology (RSM) modelling for multi-objective optimization. This research assessed the environmental ramifications of employing WSA and MDP as SCM in HSC. Specifically, it examined the impacts on embodied carbon and eco-strength efficiency. Cubical specimens underwent a series of tests to attain the desirable compressive strength of approximately 60 MPa after a period of 28 days. The workability of green concrete decreased as the proportion of WSA and MDP used as SCM increased, according to the study. The optimum compressive strength, flexural strength, splitting tensile strength, and modulus of elasticity of HSC was recorded by 68 MPa, 5.98 MPa, 4.25 MPa, and 40 GPa, at 15% of SCM (composed of 10% WSA and 5% MDP) at 28 days respectively. Using ANOVA, response prediction models were validated and developed with a confidence level of 95%. In summary, the increased application of 20% WSA and 20% MDP as SCM in concrete leads to a 31.64% reduction in the carbon footprint of the material.

Renewable ammonium chloride-induced calcium leaching of gold and copper tailings and selective preparation of vaterite CaCO3 by CO2 mineralization

This study introduced a high-value green processing solution for copper tailings to prepare high-purity vaterite from gold-copper tailings. The active reaction components were determined through Gibbs free energy calculations. The study discusses the impact of different experimental parameters on the leaching rate of Ca2+ and the degree of mineralization in gold-copper tailings, and then considers the influence of different dispersants on improving the stability of vaterite. The results show that the optimal leaching efficiency of Ca2+ in the NH4Cl solution is 75%, and the optimal mineralization efficiency is 87%. Under appropriate mineralization conditions, vaterite CaCO3 with d50 < 12 μm, a purity of 98%, and a whiteness of 98.7% can be prepared. The precipitated vaterite is affected by the pH swing method connected with the neutralization reaction. The presence of excess NH3 and supersaturated CO2 are necessary for the formation of vaterite-type CaCO3. Morphological analysis results show that dispersants such as polyacrylamide and sodium tripolyphosphate can improve the dispersibility of vaterite, preventing agglomeration and enabling its stable existence in aqueous solutions. Nanoparticle aggregation and crystal growth are two possible mechanisms for the formation of vaterite. The leaching-mineralization cycle technology using NH4Cl as the leaching solution meets the requirements for CO2 removal and alkaline industrial waste residue treatment, while avoiding the significant consumption of chemical reagents in traditional mineralization. This method provides a pathway for producing vaterite using copper tailings and has a broad market prospect.

Effect of ratio of desulfurization gypsum to carbide slag on low-carbon phase change composites for energy storage

To recycle industrial wastes sufficiently, this work innovatively proposed a mixture of desulfurization gypsum and carbide slag as skeleton material to fabricate phase-change composites with NaNO3 as phase change material in a mass ratio of 5 to 5. Four phase-change composites were fabricated with different ratio of desulfurization gypsum to carbide slag by the cold compression-hot sintering method, and then key thermal and mechanical properties, microscopic morphology and chemical compatibility between components were investigated in detail. Results show that the mixture of desulfurization gypsum and carbide slag as skeleton material is feasible and reliable and an optimal mass ratio of desulfurization gypsum to carbide slag was obtained to be 3.5 to 1.5; the phase-change composite with the optimal mass ratio possesses good mechanical strength of up to 134.116 MPa and an energy storage capacity of 483.151 J/g in the range of 100 to 400 °C, as well as excellent thermal stability and chemical compatibility between components, inside which the NaNO3 is well encapsulated. Moreover, the phase-change composites fabricated in this work have far low energy consumption and carbon dioxide emission.

Đánh giá mức độ phát thải của các chất polyclodibenzo-p-dioxin và polyclodibenzofuran phát sinh không chủ định từ lò đốt rác chất thải sinh hoạt và rác thải công nghiệp ở Việt Nam

Polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) are the most toxic substances among the group of unintentional persistent organic pollutants (U - POP) generated from many sources, in which domestic and industrial waste incinerators are the highest emission risk. Assessment of pollution potential and dioxin/furan emissions from incinerators in developing countries, including Vietnam, is still limited; especially in-depth studies on the content and characteristics of PCDD/PCDF emitted into the atmosphere. Therefore, the research team evaluated the emission potential and characteristics of 07 PCDD and 10 PCDF, those are considered to be the most toxic isomers and congeners, from stack gas samples collected from incinerators at 33 facilities in 11 provinces in Vietnam. The total concentration of PCDD/PCDF in the industrial incinerators’ emission ranged from 37.3 to 3348.6 pg TEQs/m3 and domestic waste incinerators had lower total concentrations and fluctuated within about 37.3-1323.8 pg TEQs/m3. The characteristic of incinerator emissions is that the proportion of 2,3,7,8- TCDD accounts for 2.9 to 9.04%. The highest contributing concentrations were congeners 1,2,3,7,8-PeCDD, with its contributing percentage from 22.95-32.42%. The second largest contributor is congeners 2,3,4,7,8- PeCDF, accounting for 20.94- 21.50% of the total toxic congeners of PCDD/PCDF in both types of incinerators. However, in terms of toxic equivalency (TEQ), the concentration of industrial waste incinerators is much higher than that of domestic waste incinerators. The results of stack gas samples showed that the PCDD/PCDF content for domestic waste incinerators has 5/17 establishments that exceeded the permissible standard threshold: 0.6 ng/Nm3, according to QCVN 61-MT:2016/BTNMT. Industrial waste incinerators have 5/16 establishments that exceeded the permissible standard threshold: 0.6ng/Nm3 for furnaces with a capacity of 300kg/hour according to QCVN 30:2012/BTNMT.

Ecofriendly Utilization of Distillery Spentwash for Enhancing Growth and Yield of Pearl Millet

The Post Biomethanated Distillery Spentwash (PBDSW) is effective organic liquid manure derived from sugar industry waste materials. Spentwash contain high amount of nutrients like Nitrogen, Phosphorus, Potassium, Calcium and Sulfur. In addition, it contains sufficient amount of micronutrients such as Iron, Zinc, Copper, Manganese, Boron and Molybdenum. The spentwash application on land is beneficial to control the water pollution and agricultural production. The experiment was performed with different doses of Post Biomethanated Distillery Spentwash (PBDSW) as a source of nutrients in various proportions with inorganic fertilizer using pearl millet as the test crop. The results of the experiment showed that the application of PBDSW at the rate of 100 KL ha-1 in combination with NPK recorded higher ear head, grain and stover yield as compared to other substitution level, split application and control.

Adsorption of Heavy Metal from Wastewater by Bioabsorbent Modified Azolla microphylla and Lemna minor

Environmental toxicity from rapid industrialization raises concerns about water pollution caused by industrial waste and urban sewage. Aquatic macrophytes, such as the Azolla species, have shown promise in absorbing heavy metals and nutrients from water. This study introduces a novel approach by evaluating Azolla Microphylla and lemna minor as an economical adsorbent for copper removal from rivers. Moreover, this study stands out by conducting thorough characterization analyses. The adsorbent material underwent XRD, SEM, BET, and FTIR analyses after being crushed and sieved to 1-2 mm. Copper was extracted from river water using UV-Vis detection at 285 nm. Optimal conditions for adsorption were determined at pH 4, 30 minutes of contact time, and 0.4 g of adsorbent. Copper concentrations in the Sungai Petani, Sungai Selangor, and Sungai Langat ranged from 2 mgL-1 to 5 mgL-1. Azolla proves effective as a copper adsorbent due to its simplicity in sample preparation, time-saving benefits, cost-effectiveness compared to conventional systems, and high copper recovery rate. By successfully removing copper, a prevalent heavy metal contaminant in industrial waste and urban sewage, this research contributes to achieving Sustainable Development Goal 6 for clean and safe water supplies.

Soil Stabilization Using Rice Husk Ash and Sugarcane Bagasse Ash

Abstract: Soil stabilization has become a major issue in construction engineering and the researches regarding the effectiveness of using industrial wastes are rapidly increasing. The present experimental work briefly describes the suitability of the locally available Rice Husk Ash (RHA) and Sugarcane Bagasse Ash (SCBA) to be used in the local construction industry in a way to minimize the amount of waste to be disposed to the environment causing environmental pollution. The common soil stabilization techniques are becoming costly day by day due to the rise of cost of the stabilizing agents like, cement, lime, etc. The cost of stabilization may be minimized by replacing a good proportion of stabilizing agent using RHA. It will minimize the environmental hazards also. Addition of rice husk ash and cement decreases the maximum dry density and increases the optimum moisture content.

A Descriptive Study on Performance Evaluation of Sewage Treatment System

Abstract: As The rapid expansion of modern housing and industrialization around the cities has polluted environment. This trend was observed in many developed countries in the beginning of nineteenth century which resulted in the contamination of air, water, soil etc. with pollutants. If the pollutants are released in the environment and left untreated they would cause serious diseases in both humans and animals. Large scale pollution of water bodies around the globe became a major problem due to release of industrial and domestic waste directly in water streams. To prevent the leaching of pollutants in the ground water scientist developed various methods of wastewater treatment based on the hazardous chemicals and microorganisms, which were present in the untreated water. Modern sewage treatment plants were installed in big cities to treat the water released from households. Most STPs were designed based on the stringent criteria to check the pollutants levels in the treated water so that when it is released or recycled it is safe to the environment. Modern day STP plants have a high cost of operation due to huge power consumption. In order to reduce the pollutant levels in the wastewater this study was conducted using a Eco Bio Block (EBB) techniques with aeration and without aeration. A comparison of EBB was also carried out with MBBR technique. Our results show that when EBB technique was applied with aeration it is effective in reducing pollutant levels in the wastewater akin to MBBR. In addition, we tested the EBB without aeration and found that the treated waste water has relatively low levels of BOD, COD and turbidity, suggesting that the treated water can be utilized for landscaping and horticulture activities. Overall, the outcomes from this study are encouraging to adopt EBB in smaller towns and in small housing societies to treat the wastewater prior to release. The paper focuses on reviewing the various sewage treatment methods and their results.

Evaluating the effectiveness of heavy metals removal from mine wastewater using agricultural waste materials

Polluted water bodies pose a danger to both aquatic and terrestrial lives, and recent development in the mining centre has escalated this pollution through the disposal of its industrial wastes. The objective was to investigate the potential of four different agricultural waste materials in eliminating the heavy metals from mine wastewater. The results show that the best performance in terms of adsorption capacity and removal efficiency was observed with coconut husk-activated carbon. The Arsenic (As) concentration decreased from 3.185 mg/kg to 1.570 mg/kg, and the Mercury (Hg) content decreased from 0.0307 mg/kg to 0.0064 mg/kg. The corresponding removal efficiencies were 51% for Arsenic and 79% for Mercury after 120 minutes of contact time at a speed of 250 rpm. The results suggest that coconut husk-activated carbon exhibited superior adsorption capacity and removal efficiency compared to the other agricultural waste materials (maize cob, rice husk, and sawdust). This indicates that the natural properties of coconut husk are more effective in removing heavy metals from mine wastewater.

Investigating the grinding characteristics of vanadium-titanium iron ore tailings for sustainable utilization in cementitious material preparation

The study of the cementitious material activity of industrial solid wastes is a key issue in the comprehensive utilization of its green building materials. In this study, mechanical activation was used to prepare cementitious materials from vanadium-titanium iron ore tailings (VTIOT) as the main raw materials, and the effects of grinding time, the key parameter, on the grinding characteristics of VTIOT, the mechanical properties of the VTIOT cementitious material, and the hydration mechanism were investigated by means of surface area analysis, particle size analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), alkali leaching, mechanical testing, hydration heat analysis, and thermogravimetric analysis (TGA). The results show that: the grinding time and specific surface area of VTIOT exhibit a linear correlation. Prolonging the grinding time, the fractal dimension of the particles gradually increases. The activity of Si4+ and Al3+ elements increases rapidly, reaching a Si4+ and Al3+ content of 96 mg·L−1 at 90 min of grinding. With a VTIOT mixing amount of 30 %, a mortar paste ratio of 1:3, and a water cement ratio of 0.5, the 50 min ground VTIOT mortar demonstrates 7 d and 28 d compressive strengths of 29 MPa and 38.7 MPa, corresponding to the highest values of the activity index, measured at 71.4 % and 75.2 %, respectively. Under standard curing conditions, the hydration products of cementitious materials at 7 d are ettringite (AFt), calcium silicate hydrate (C-S-H), alumina, ferric oxide, monsulfate (AFm), calcium hydroxide (Ca(OH)2), and calcium silica (CS). In the hydration process of 7 d, the exothermic peak and exothermic amount of the 50 min VTIOT cementitious materials are greater than those observed for other grinding times, but lower than those of pure reference cement.

Development of Sustainable 3D Printable Ternary Composite

3D printing technology has the potential to reduce construction waste through its controlled manufacturing process and optimized material consumption, making it a promising sustainable construction approach with reduced environmental impact. However, current 3D printed structures often have a high carbon footprint due to the large amounts of fine-grained primary materials used in mortar composites. Most efforts to develop 3D printed structures are associated with concrete and Portland cement-based materials.This research presents an innovative approach for the reuse of gypsum to develop a material suitable for 3D printing, with the goal to industrialize the usage of waste gypsum in civil engineering. The objective of this study is to develop a sustainable gypsum-cement-pozzolanic (GCP) ternary binder composite, incorporating recycled industrial waste gypsum materials such as construction demolition waste gypsum (CDG), along with Portland cement and secondary pozzolanic materials. The GCP ternary composite combines the desired properties of gypsum, such as fast setting time, with those of Portland cement, which offers high final strength. The addition of a pozzolanic component is essential to ensure the chemical stability of this ternary system.As part of this study, ternary composites were designed and tested for their mechanical properties, durability, and suitability for 3D printing. Development and optimization of the ternary composite was carried out as a loop of procedures (Fig.1). Through these optimization procedures, a range of mixtures with necessary properties for 3D printing was found. To ensure sustainability and to assess the environmental impact of the mixtures, life cycle assessment (LCA) was performed.The LCA of GCP composites showed at least 1.5 times lower embodied energy and carbon dioxide emissions compared to Portland cement-based mortars. This is without considering avoided emissions from the end-of-life stage of gypsum waste, as well as higher technical properties that make GCP composites superior to regular cement composites. Considering these factors, GCP composites exhibit even lower emissions and are considered a viable alternative to Portland cement-based mortars.

Recycling Possibilities of Wood-Cement Particle Board Manufacturing Waste

Wood-cement particle boards are gaining popularity within construction materials as they combine natural fiber architectural value with Portland cement durability. The production of the material is associated with processing the produced fiberboards, which includes cutting, grinding, and polishing. The remaining wood-cement dust residues are classified as production waste, which is now deposited in the dump and gives extra expenditure for the enterprise. The utilization of wood-cement dust would also benefit the circular economy and reduce the environmental impact of the production process. Two scenarios are analyzed in this research, and the life cycle assessment (LCA) tool with SimaPro software is compared. The first scenario is associated with the partial replacement of Portland cement with wood-cement dust powder. The second scenario offers re-activation of the wood-cement dust at 450 °C to obtain binder properties. Both materials' mechanical strength is comparable, reaching 10 MPa after 28d curing. To maintain target strength, 70 % of Portland cement can be replaced. To produce 1 t of binder by heating at 450 °C, 1.2 t of wood-cement dust is needed as natural moisture evaporates, and wood dust particles go through pyrolysis, giving extra heat and CO2 emissions as well. LCA results indicate the 70% replacement of Portland cement reduces CO2 emissions from 597 kg of CO2/ton of CEM II/A-LL 42,5 to 179 kg of CO2/ton, while the second scenario is associated with high energy consumption during burning of the binder and increased CO2 value due to fossil fuel consumption and CO2 release from burning organic compounds in the material.

انی کی آلودگی اور ضیاع: اسباب، اثرات، اور حل کی تلاش سیرت طیبہ کی روشنی میں

Allah Almighty sent the Prophet (PBUH) with the Holy Quran, which guides us on how to solve problems at individual, social, national, and international levels. The Prophet (PBUH) is the epitome of guidance provided in the book of Allah. Therefore, the Ummah has preserved all aspects of the prophetic life in a collection called Fiqh al Sirah, so that we may overcome the hurdles and complications in our lives. Whenever ummah feels any hurdle in the way of social life, they seek guidance from the books written on the matter of Fiqh al Seerah. Water is a fundamental necessity of life that is bestowed upon us by Allah Almighty. The significance of water is not only emphasized in Islamic texts like the Quran, Hadith, and Fiqh but also in various scientific studies. However, in recent times, water pollution has become a major threat to human health and the environment. The contamination of natural water resources by various pollutants has led to severe consequences. To address this issue, it is crucial to understand the causes and impacts of water pollution. Some of the major causes of water pollution include industrial waste, domestic waste, and agricultural practices. To combat this issue, it is essential to adopt sustainable practices that reduce water pollution. This article aims to provide an in-depth analysis of the causes, impacts, and possible solutions to water pollution. The significance of this article is that it provides a comprehensive solution to the problem of water pollution, based on an in-depth analysis of the Islamic perspective extracted from Qyran, Seerah and Fiqh on environmental conservation.

Analysis of Steel Slag Sand – An Eco Friendly Fine Aggregate for Construction

Industrial waste slag is a major issue concerning the environmentalists today. The steel making industry produces a large amount of byproduct which is termed as Slag. Slag is produced during the steel-making operations that utilize Electric Arc Furnaces (EAF) and operate by smelting iron ore in the Basic Oxygen Furnace (BOF). Steel slag finds numerous uses in the construction industry e.g in the applications involving hot mixture asphalt, in Stone Matrix Asphalt (SMA), berms and embankments constructions, main ingredient in manufacturing of Portland cement, as fine and coarse aggregates, to name a few. But steel slag has a negative impact on the environment when disposed of. In that case a wide variety of use of steel slag becomes relevant. Steel Slag is a perfect candidate to replace the coarse and fine aggregates in the traditional concrete used in the construction industry. Most of the volume of concrete is aggregate. Steel Slag can be used as replacement to these aggregates in a more prominent way. In this research study, we will be making steel slag as substitution for raw fine aggregate. Fine aggregate would be replaced by these wastes in different proportions (20%, 40%, &amp; 60 %) by weight of fine aggregate. The aim of this study is to investigate the compressive strength, split tensile strength and Material properties of concrete with partial replacement for fine aggregate. We will be performing pull off test on the applications of this modified concrete and checking the results for strength and durability.

Optimal Ratio of Steel and Polyester Fibers on the Mechanical Behavior of Alkali-Activated Concrete Produced by Industrial Waste Minerals

Optimal Ratio of Steel and Polyester Fibers on the Mechanical Behavior of Alkali-Activated Concrete Produced by Industrial Waste Minerals

Uncovering the potential of industrial waste: turning discarded resources into sustainable advanced materials

To identify solutions for utilizing industrial wastes (slag, sludge, fly ash, and bottom ash) in the development of pro-environmental systems, this paper reviews existing literature and explores material characterization methods. A review analysis was conducted to uncover their potential, and it was found that many utilizations can be made to recycle them into sustainable materials. Structure characterization, optical-dielectric function, and morphology analysis were analyzed to confirm the recent review. Structural properties are represented by crystallite size and crystallinity, where nickel slag shows the smallest distribution (55 ± 10) nm with the highest crystallinity (25.42%), indicating its association with uniformity of response to external disturbances and micro-structural stability. From the analysis of optical and dielectric functions via Kramers Kronig relation, the widening of ∆(LO−TO) was shown by fly ash and slag indicating stable bonding suitable as x-ray shielding and sensor, while high electron loss functions were shown by sludge and bottom ash indicating high potential electronic transition performance. Based on their chemical and physical properties, these industrial wastes are not limited as construction materials and can even be upgraded to more advanced development materials.

Marine microalgae Schizochytrium demonstrates strong production of essential fatty acids in various cultivation conditions, advancing dietary self-sufficiency

IntroductionPolyunsaturated fatty acids (PUFAs) are essential nutrients that humans obtain from their diet, primarily through fish oil consumption. However, fish oil production is no longer sustainable. An alternative approach is to produce PUFAs through marine microalgae. Despite the potential of algae strains to accumulate high concentrations of PUFAs, including essential fatty acids (EFAs), many aspects of PUFA production by microalgae remain unexplored and their current production outputs are frequently suboptimal.MethodsIn this study, we optimized biomass and selected ω-3 PUFAs production in two strains of algae, Schizochytrium marinum AN-4 and Schizochytrium limacinum CO3H. We examined a broad range of cultivation conditions, including pH, temperature, stirring intensity, nutrient concentrations, and their combinations.ResultsWe found that both strains grew well at low pH levels (4.5), which could reduce bacterial contamination and facilitate the use of industrial waste products as substrate supplements. Intensive stirring was necessary for rapid biomass accumulation but caused cell disruption during lipid accumulation. Docosahexaenoic acid (DHA) yield was independent of cultivation temperature within a range of 28–34°C. We also achieved high cell densities (up to 9 g/L) and stable DHA production (average around 0.1 g/L/d) under diverse conditions and nutrient concentrations, with minimal nutrients required for stable production including standard sea salt, glucose or glycerol, and yeast extract.DiscussionOur findings demonstrate the potential of Schizochytrium strains to boost industrial-scale PUFA production and make it more economically viable. Additionally, these results may pave the way for smaller-scale production of essential fatty acids in a domestic setting. The development of a new minimal culturing medium with reduced ionic strength and antibacterial pH could further enhance the feasibility of this approach.

NEW TECHNOLOGIES FOR PROCESSING TAILINGS OF A COPPER PROCESSING PLANT FOR THE EXTRACTION OF PLATINOIDS

The most important task of the mining and metallurgical industry in the world is the development of technology for the processing of industrial waste from metallurgical industries. In the world, balance ores of precious metals are practically available. This issue develops the processing of man-made waste, refractory ores, off-balance and low-grade dumps. The article considers studies of the material and rational compositions of the tailings of a copper concentrating plant in the conditions of JSC Almalyk MMC, determines the optimal method for tailings enrichment with an increase in the content of precious metals in the concentrate, and enhances an unconventional new scheme for processing platinum group concentrates with the extraction of platinum, palladium, silver and high recovery gold. Based on the learned subjects and analysis of studies results, the authors concluded that the centrifugal concentration of platinoids from the composition of the tailings was achieved due to accurate determinations of the particle size in the tailings with the selection of intense gravity modes. Combined hydrometallurgical methods for purifying platinoids and gold from impurities using combinations of chemical solvents have been developed. As a result, the developed technologies have achieved the possibility of complex extraction of platinum group metals from the tailings of concentrating plants of copper production with high degrees, through extraction of all precious metals.

Effect of high temperature on mechanical properties of lithium slag concrete

As the main gel material of concrete, cement is used in an astonishing amount every year in the construction industry. However, a large amount of CO2 is emitted into the atmosphere while producing cement. Therefore, it is the general trend to look for substitutes for cement and develop new green concrete. Lithium slag (LS) is the industrial waste discharged from lithium salt plants. Through testing, it is found that the chemical composition of LS has a high degree of coincidence with ordinary Portland cement (OPC) Therefore, LS can be incorporated into concrete as supplementary cementations material (SCM) to prepare lithium slag concrete (LSC). The pollution of the natural environment caused by a large number of piled-up and landfilled LS is immeasurable. Consuming and using LS in large quantities and with high efficiency not only eliminates the pollution of lithium slag to the natural environment, but also helps to reduce the amount of cement used in green concrete and truly reuse waste resources. In order to study the mechanical properties of post-heated LSC, the test were carried out for LSC specimens after high-temperature. The main influence factors were considered, including the temperatures of 20℃, 100 ℃, 300 ℃, 500 ℃ and 700 ℃, the contents of lithium slag in LSC of 0%, 10%, 20% and 30%, cooling method of LSC after exposure high temperature. The results showed that the mechanical properties of LS concrete specimens were slightly improved at 100 ℃, and when the temperature was 300 ℃ or higher, the damage to the specimens was huge and irreversible. An appropriate amount of LS (20% lithium slag content) could improve the strength of LSC. This paper also studied the relationship between lithium slag content and strengths of LS concrete. The research results show that adding an appropriate amount of LS to concrete improves the mechanical properties of concrete. When the LS replacement rate is 20%, the mass loss rate of LSC after different high temperature treatments was the minimum. The cubic compressive strength, axial compressive strength, and flexural strength of specimens with 20% LS substitution can be increased by 8.16%, 8.33%, and 13.46% after high temperature. The cubic compressive strength, axial compressive strength, and flexural strength of specimens with 20% LS substitution can be increased by 8.16%, 8.33%, and 13.46% after high temperature.