Waste Slag Research Articles

Appraisal of Heavy Metal Risk Hazards of Eisenia fetida-Mediated Steel Slag Vermicompost on Oryza sativa L.: Insights from Agro-Scale Inspection and Machine Learning Analytics

The steel industry drives world economic growth, yet it generates heavy metal-rich steel slag, which jeopardizes the environment. The utilization of vermi-technology is essential for the sustainable transformation of toxic steel waste slag (SW) into organic amendments, although field-scale use of vermiprocessed SW remains unexplored. To bridge the gap, this study evaluated the efficacy of vermiprocessed SW as an organic supplement for rice field cultivation, focusing on heavy metal (HM) bioavailability, human health risk, and yield in comparison to raw slag and NPK fertilizer. The results indicated a considerable decrease in the bioavailable fraction of heavy metals in T4 (1:1 SW vermicompost 50% + 50% fertilizer). In treatments, T9 (100% SW) and T10 (50% SW + 50% fertilizer) (FIAM) free ion activity modeling confirmed grain absorption of HMs, and the FIAM HQ values indicated the health risk for the direct application of steel slag waste on the field. The risk factor evaluation of HMs’ presence in treatments T9 and T10 established the possible cancer risk for living beings. Similarly, machine learning models like SOBOL sensitivity analysis and artificial neural networks revealed potential threats associated with HMs on different treatments, respectively. The correlation coefficient revealed the negative effects of bioavailable HMs on various soil microbial and enzymatic properties. Moreover, the abundant yield of rice was attributed to the combination treatment (1:1 50% + NPK 50%), which paved the way for an alternative agronomic approach based on the utilization of vermicomposted steel waste slag.

An infrared radiation-responsive high-entropy CoCaMgMnAlFe-LDHs for controllable hydrogen generation via NaBH4 hydrolysis: Utilization of steel slag and lithium-ion battery liquid waste

Green processing of steel slag and lithium-ion battery liquid waste poses a global environmental challenge. This study utilizes waste acid (containing Co2+, H+ and NO3–) and alkali solutions (containing Li+, Na+, OH– and CO32–) from lithium-ion battery manufacturing to recover metal cations from steel slag (containing Ca2+, Mg2+, Al3+, Fe3+, and Mn2+), preparing high-entropy CoCaMgMnAlFe-LDHs catalysts for controllable hydrogen generation via NaBH4 hydrolysis. The ultimate residue, without any residual hazardous metal cations, enabling safe reintroduction into the natural environment. The presence of Co2+ endows the CoCaMgMnAlFe-LDHs catalyst with rapid photo-thermal conversion capability, enabling it to rapidly heat up under infrared radiation and efficiently catalyze the reaction of NaBH4 hydrolysis. The hydrogen generation rate reaches 1.12 mol·h−1·g−1·W−1 driven by 1050 nm infrared radiation. This study provides a novel approach to the environmentally friendly treatment and high-value utilization of steel slag and lithium-ion battery liquid waste.

Analysis on the Influence law and Mechanism of the Strength of Reclaimed Aggregate-Industrial Waste Slag Solidified Silt

To optimize the usage of construction waste resources, industrial waste slag and silt, this paper used Portland cement, mineral waste residue and phosphogypsum composite to make cementing material (CMPS) with construction waste reclaimed aggregate to solidify silt. The laboratory solidification test and microscopic analysis were conducted to assess the mechanical characteristics of solidified sludge. In order to clarify the mineral composition, microscopic morphology and pore characteristics of the regenerated aggregate and CMPS solidified silt (SS), XRD, SEM and nitrogen adsorption pore analyzer were employed for further explore the regenerated aggregate and CMPS solidified silt effectively, and further reveal the internal mechanism of the regenerated aggregate and CMPS solidified silt effectively. The findings indicated that the strength of Portland cementmineral waste residue phosphogypsum terpolymer system curing agent increased by 107.34% than that of single Port-land cement SS at 56 d, and the strength of CMPS solidified silt increased by 25.68% under the action of reclaimed aggregate framework. The maintenance period and water composition of the silt have high correlation with the strength. Therefore, influence law of above two influencing factors on its mechanical properties were further explored and the strength prediction were made. The microscopic test results showed that, drawing from the hydration of Portland cement and pozzolans reaction of mineral waste residue, the solidified system has pre-pared CaSiO3 hydrate gel and ettringite crystals with gelatinous properties, which help to fill the pores and form a denser structure.

Optimizing mix design methods for using slag, ceramic, and glass waste powders in eco-friendly geopolymer mortars

Optimizing mix design methods for using slag, ceramic, and glass waste powders in eco-friendly geopolymer mortars

Phosphorus removal from steelmaking slag by selective leaching in the steel pickling waste liquor

Steelmaking slag and steel pickling waste liquor (SPWL) are two kinds of by-products in steel plants. The existence of phosphorus (P) in steelmaking slag is the main factor affecting its reuse within the steelmaking process. To remove P from steelmaking slag with a low-cost method, selective leaching was proposed by using SPWL as a leaching agent. SPWL generally contains a small amount of Fe3+ ions, and thus the effect of Fe3+ content in SPWL on the dissolution behavior (especially P element) of steelmaking slag was investigated, as well as the pH value and steelmaking slag type. The dissolution ratios of P from various slags in the SPWL containing 500 ppm Fe3+ exceeded 95 % at pH 1.5 while those of Fe, Mn, and Al were very low, exhibiting satisfied selective leaching of P. Increasing pH value and Fe3+ content (in SPWL) resulted in a decreasing P dissolution ratio while exerting an insignificant effect on the dissolution of other elements. The FeHPO4+ was predicted as the predominant species during leaching and the transformation of FeHPO4+ to FePO4 could be present. When the SPWL containing 800 ppm Fe3+ was used, FePO4 was observed in the residues after leaching at pH 2.0, resulting in a worse removal of P from slag. However, the residues including massive valuable components had an extremely low P content after leaching in the SPWL containing 500 ppm Fe3+ at pH 1.5, which can be used as a flux in the metallurgical process. To ensure a high P removal rate from steelmaking slag and to prevent FePO4 precipitation during leaching, a relatively low pH and Fe3+ content in the SPWL are necessary.

Complex additive for improving the strength properties of heavy concrete based on industrial waste

The article presents the results of using a complex modified additive to improve concrete's physical and mechanical properties. The complex additive includes industrial production wastes: metallurgical slag and alcohol production wastes (post-alcohol bard). To stabilize the hydrogen index the alkali KON is included in the composition of the additive. A set of laboratory studies was carried out to measure the strength, absorption, and frost resistance of test specimens to assess the effect of the additive on the properties of concrete. A comparison of physical and mechanical properties was made for samples of different concentrations of slag. The ratio of slag components to cement was from 5 to 25% by the total mass of the binder, a multiple of 5%. The optimal composition of the mixture, with maximum strength values, corresponds to the percentage of slag 15%, post-alcohol bard 22.5 liters, and alkali 150 grams. In general, the results obtained from data points of the compared parameters showed consistent results with minimal variation in the data. The results obtained are of practical value related to the reduction of the cost of production of structural concrete with an increase in its strength indicators.

Study on Impact Resistance of Alkali-Activated Slag Cementitious Material with Steel Fiber

Alkali-activated slag cementitious materials (AASCMs) use alkaline activators to activate blast furnace slag and waste slag to replace traditional Portland cement, which can reduce CO2 emissions. An impact resistance test and scanning electron microscopy (SEM) microscopic performance analysis of alkali-activated slag cementitious material specimens with four different steel-fiber contents are performed. The effects of steel-fiber volume content and strain rate on the dynamic elastic modulus Ed, dynamic compressive strength σd, dynamic peak compressive strain εc, and energy absorption of the AASCM-SS are studied. The results indicate that the dynamic elastic modulus Ed, dynamic compressive strength σd, and energy absorption of the AASCM-SS increase with the increase of strain rate, and the dynamic peak compressive strain εc decreases with the increase of strain rate. The dynamic elastic modulus Ed, dynamic compressive strength σd, and dynamic peak compressive strain εc of the SS-AASCM increase first and then decrease with the increase of steel-fiber content. When the steel-fiber content is 0.5%, the σd and εc of the AASCM-SS are the highest, increased by 9.9% and 19.3%. The energy absorption of AASCM-SS increases with the increase of steel-fiber content. A dynamic constitutive model of the FR-AASCM considering the influence of damage, strain rate, and steel-fiber volume fraction is established. The proposed constitutive model is in acceptable agreement with the experimental AASCM-SS dynamic stress–strain curve, and the correlation coefficient is 0.91.

Synthesis and Characterization of an Alkali-Activated Binder from Blast Furnace Slag and Marble Waste.

This study reports an alkali-activated binder including blast furnace slag (BFS) together with marble waste (MW). Cement is an industrial product that emits a significant amount of CO2 during its production and incurs high energy costs. MW is generated during the extraction, cutting, and processing of marble in production facilities, where dust mixes with water to form a settling sludge. This sludge is an environmentally harmful waste that must be disposed of in accordance with legal regulations. In this study, a substantial amount of MW, a by-product with considerable environmental and economic impacts worldwide, was utilized in the production of a binder through the alkaline activation of BFS. In doing this, different experimental parameters were tested to obtain the best binder samples according to workability and mechanical properties. Then, some experiments such as drying shrinkage determination, strength testing, and microstructure analyses were fulfilled through samples with the best values. The findings supported the improvement of the rapid-setting property of BFS by means of the addition of MW. MW reduced the time-dependent drying shrinkage values of BFS by 55%, especially in slag alkaline activation systems with a low or moderate alkali activator content. The substitution of MW (≤50%) in BFS increased flexural and compressive strengths (4.5 and 61.7 MPa), while a reference sample contained BFS only. Although the use of MW did not create a new phase, it contributed to a C-S-H bonding structure during the alkali activation of BFS in a microstructure analysis.

Modelling the properties of aerated concrete on the basis of raw materials and ash-and-slag wastes using machine learning paradigm

The thermal power industry, as a major consumer of hard coal, significantly contributes to harmful emissions, affecting both air quality and soil health during the operation and transportation of ash and slag waste. This study presents the modeling of aerated concrete using local raw materials and ash-and-slag waste in seismic areas through machine learning techniques. A comprehensive literature review and comparative analysis of normative documentation underscore the relevance and feasibility of employing non-autoclaved aerated concrete blocks in such regions. Machine learning methods are particularly effective for disjointed datasets, with neural networks demonstrating superior performance in modeling complex relationships for predicting concrete strength and density. The results reveal that neural networks, especially those with Bayesian Regularisation, consistently outperformed decision trees, achieving higher regression values (Rstrength = 0.9587 and Rdensity = 0.91997) and lower error metrics (MSE, RMSE, RIE, MAE). This indicates their advanced capability to capture intricate non-linear patterns. The study concludes that artificial neural networks are a robust tool for predicting concrete properties, crucial for producing non-autoclaved curing wall blocks suitable for earthquake-resistant construction. Future research should focus on optimizing the balance between density and strength of blocks by enhancing the properties of aerated concrete and utilizing reliable models.

To the problem of processing of waste slag from copper smelting plants in Kazakhstan

Дана характеристика отвальным медным шлакам, рассчитан их рациональный состав. Для эффективной переработки подобных шлаков предложено применение процесса выщелачивания растворами серной кислоты, не требующего затрат тепловой энергии извне, вследствие экзотермичности протекающих реакций. Выполнен расчет термодинамических характеристик реакций, возможных при выщелачивании отвальных медных шлаков растворами серной кислоты. Проведен анализ фазового равновесия процесса выщелачивания шлака при различных расходах серной кислоты, оценено влияние температуры на изменение состава фаз, построены диаграммы фазового равновесия. Выполнены исследования по сернокислотному выщелачиванию отвальных медных шлаков при комнатной температуре и при 80 °С. Выявлены проблемы сгущения и фильтрования пульпы после выщелачивания, связанные с образованием кремниевой кислоты Үйінді мыс шлактарына сипаттама беріліп, олардың рационалды құрамы есептелді. Мұндай шлактарды тиімді өңдеу үшін жүретін реакциялардың экзотермиялық болуына байланысты жылу энергиясының сырттан шығынын қажет етпейтін күкірт қышқылының ерітінділерімен шаймалау процесін қолдану ұсынылады. Үйінді мыс шлактарын күкірт қышқылының ерітінділерімен шаймалау кезінде мүмкін болатын реакциялардың термодинамикалық көрсеткіштері есептелді. Күкірт қышқылының әр түрлі шығындарында шлакты шаймалау процесінің фазалық тепе-теңдігіне талдау жүргізіліп, температураның фазалар құрамының өзгеруіне әсері бағаланды, фазалық тепе-теңдік диаграммалары тұрғызылды. Үйінді мыс шлактарын бөлме және 80 °С температураларда күкірт қышқылымен шаймалау бойынша зерттеулер жүргізілді. Кремний қышқылының түзілуіне байланысты шаймалаудан кейін пульпаның қоюланып сүзуге кедергі жасайтыны анықталды The characteristic of dump copper slag is given, their rational composition is calculated. For the effective processing of such slags, it is proposed to use the leaching process with sulfuric acid solutions, which does not require the expenditure of heat energy from outside, due to the exothermicity of the ongoing reactions. Calculation of thermodynamic characteristics of reactions possible at leaching of waste copper slags with solutions of sulphuric acid is carried out. The phase equilibrium of the slag leaching process was analysed at different sulphuric acid flow rates and the influence of temperature on the change of phase composition was evaluated, phase equilibrium diagrams were constructed. Studies on sulfuric acid leaching of waste copper slag at room temperature and at 80 °C. Problems of pulp thickening and filtration after leaching associated with the formation of silicic acid have been identified

Effect of the combination of polyvinyl chloride (PVC) and steel slag waste on the durability and mechanical properties of composite mortars

Effect of the combination of polyvinyl chloride (PVC) and steel slag waste on the durability and mechanical properties of composite mortars

Use of Waste Slag and Rubber Particles to Make Mortar for Filling the Joints of Snow-Melting Concrete Pavement

Use of Waste Slag and Rubber Particles to Make Mortar for Filling the Joints of Snow-Melting Concrete Pavement

Transforming industrial byproduct to eco-friendly functional material: Ground-granulated blast furnace slag reinforced paper for renewable energy storage

This study pioneered an eco-friendly approach for reutilizing Ground-granulated blast furnace slag (GGBFS) in paper production. This investigation is the first study focusing on the usage of paper production that presents both a new usage area of GGBFS and also a new sight. So, it can contribute to save the trees. Also, GGBFS gains economical value in paper production. 15–25 % integrated slag led to markedly enhanced brightness, density and smoothness accompanied by only minor mechanical strength decreases versus pure pulp. Significantly, the electrical analysis revealed a higher conductivity at higher frequency region reaching almost S value near to 1 which might be a good choice for electromagnetic shielding, thus; higher conductivity with increasing slag contents from pure paper's 10−11 S/cm up to 10−6 S/cm for 25 % addition which confirms the modified paper's usefulness as conductive slag agent. Although the higher addition of GGBFS has led to rising in relaxation time basically from 1.77e−4 to 2.95e−3 and based on Debye relaxation, the rising time in relaxation which was observed after the addition of GGBFS reveals better polarizability values 0.29–0.35 compared to control sample 0.26 by which both longer relaxation time and higher polarizability contribute to the ability of energy storage of modified papers. The conductive characteristics and improved qualities demonstrate these recyclable slag-modified papers present unique opportunities for emerging flexible, eco-friendly electronics, capacitors, electromagnetic shielding, and renewable energy storage applications. Overall, novel integration and characterization of slag waste for enhanced sustainable paper products pioneers an unexplored territory.

Ultrasonic Non-Destructive Testing of Accelerated Carbonation Cured-Eco-Bricks

This study aimed to investigate the behavior of accelerated carbonation-cured laboratory specimens using the ultrasonic non-destructive testing (UNDT) method and compare the results with the destructive testing (DT) method. The materials used in the study included a blend of lime kiln dust and ground granulated blast furnace slag (LKD-GBFS) wastes, natural fine aggregate (sand), and alternative fine aggregates from waste tires. The chemical analysis of the LKD and GBFS samples highlighted them as suitable alternatives to OPC, hence their utilization in the study. A 60:40 (LKD-GBFS) blending ratio and a 1:2 mix design (one part LKD-GBFS blend and two part sand) was considered. The natural fine aggregate was partially replaced with fine waste tire rubber crumbs (TRCs) in stepped increments of 0, 5, and 10% by the volume of the sand. The samples produced were cured using three curing regimens: humid curing (HC), accelerated carbonation curing (ACC) with no water curing (NWC) afterwards, and water curing after carbonation (WC). From the results, an exponential model was developed, which showed a direct correlation between the UNDT and DT results. The developed model is a useful tool that can predict the CS of carbonated samples when cast samples are unavailable. Lastly, a total CO2 uptake of 15,912 g (15.9 kg) was recorded, which underscores ACC as a promising curing technique that can be utilized in the construction industry. This technique will bring about savings in terms of the time required to produce masonry units while promoting a change in the basic assumptions of a safer and cleaner environment.

Evaluation on Preparation and Performance of a Low-Carbon Alkali-Activated Recycled Concrete under Different Cementitious Material Systems.

A green, low-carbon concrete is a top way to recycle waste in construction. This study uses industrial solid waste slag powder (S95) and fly ash (FA) as binders to completely replace cement. This study used recycled coarse aggregate (RCA) instead of natural coarse aggregate (NCA). This is to prepare alkali-activated recycled concrete (AARC) with different cementitious material systems. Alkali-activated concrete (AAC) mixtures are modified for strength and performance based on the mechanical qualities and durability of AARC. Also, the time-varying effects of the environment on AARC properties are explored. The results show that with the performance enhancement of RCA, the mechanical performance of AARC is significantly improved. As RCA's quality improves, so does AARC's compressive strength. At a cementitious material content of 550 kg/m3, AARC's 28d compressive strengths using I-, II-, and III-class RCA were reduced by 2.2%, 12.7%, and 21.8%, respectively. I-class AARC has characteristics similar to natural aggregate concrete (NAC) in terms of shrinkage, resistance to chloride penetration, carbonization, and frost resistance. AARC is a new type of green building material that uses industrial solid waste to prepare alkali-activated cementitious materials. It can effectively reduce the amount of cement and alleviate energy consumption. This is conducive to the reuse of resources, environmental protection, and sustainable development.

Studies of the sintering method of ash and slag waste for the production of alumina from self-disintegrating sinters

The goal of this research is to select the optimal composition of the sintering charge of ash and slag waste for maximum extraction of alumina and obtaining self-disintegrating sinters of a given chemical composition. Experiments have shown that sintering of ash and slag waste using two-component charges makes it possible to extract alumina from sinters by no more than 60 %. The highest sintering rates were made using three-component charges. So, when sintering ash and slag waste from Almaty TPP-2 on a three-component charge of the composition CaO:SiO2 = 2; Na2O:(Al2O3+Fe2O3) = 1 at a duration of 60 min and a temperature of 1200 °C, alumina extraction was 83.68 %, under the same conditions, alumina extraction of 87.07 % was obtained during sintering of ash and slag waste from the Eurasian Energy Corporation, and alumina extraction was 90.2 % during sintering of ash and slag waste obtained after preliminary chemical activation.As a result of the conducted research on sintering of ash and slag waste in a three–component charge system, a self-disintegrating sinter of the following chemical composition was obtained, %: Na2O – 0.07; CaO – 26.88; SiO2 – 2.06; Fe2O3 – 5.01; Al2O3– 5.059.

Reclaiming Ti-bearing blast furnace slag into wide-temperature and sulfur-resistant catalyst to boost flue gas demercuration

Elimination of neurotoxic mercury from coal-fired flue gas is imperative to the global environment. This work reclaimed waste Ti-bearing blast furnace slags (TBFS) into perovskite-type catalyst for efficient flue gas demercuration (DeHg). Through mild impregnation with Mn and Ce, the TBFS-based catalyst exhibited desirable DeHg performance at wide-range temperatures (50 ∼ 300 °C), good tolerance to varied SO2 concentrations (400 ∼ 1200 ppm), and long-term DeHg stability (30 h, > 85 % DeHg efficiency) under typical coal-fired flue gas conditions, thereby outperforming existing Mn- and Ce-containing catalysts (perovskites, spinels, and other synthetic oxides). Mn-Ce interplay was well characterized to facilitate O2 dissociation and mitigate SO2 competition by modulating the redox activity of MnCe/TBFS catalyst. DFT calculations revealed in-depth that Hg0 oxidation over MnCe/TFBS was rate-determined by O2 dissociation and significantly promoted by the activated oxygens. Our attempt herein has exemplified a feasible strategy to deal with waste slag disposal and Hg emission synergistically.

RESEARCH OF THE POSSIBILITY OF USING CHP ASH IN THE PRODUCTION OF FIRED ASH GRAVEL

The article presents a comparative analysis of the characteristics of the dump ash of the Kyzylorda CHP hydraulic removal. A huge amount of ash, slag waste is collected in the dumps of the CHP, their accumulation in the dumps leads to a violation of the ecology of the environment. The issue of ash, slag waste disposal is an urgent problem. The use of ash and slag not only solves the issue of availability of raw materials, but also allows to improve the quality of products while reducing their cost. One of the valuable components of ash and slag waste is hydraulic removal ash. Hydraulic removal ash as a raw material can be used for the manufacture of artificial concrete aggregates (ash, agglomerate gravel, etc.). Studies were conducted to study the physico-chemical composition, determine the specific effective activity of natural radionuclides, loss during calcination of two types of hydraulic removal ash samples from Kyzylorda CHP (black and gray), which differ in sampling sites from ash dump. When studying the properties of the ash, X-Ray phase analysis was carried out, with the help of which the phase composition of the ash was determined. Work was carried out on the X-Ray phase analysis of ash, determination of the specific effective activity of natural radionuclides, calcination losses, which showed the possibility of using ash for the production of building materials. The conducted studies have confirmed the expediency of using the ash of the Kyzylorda thermal power plant in the production of fired ash gravel.

Simultaneous preparation of high-purity Si and eutectic Si-Nd alloy utilizing Nd2O3-containing waste slag and diamond-wire sawing silicon waste

Nd2O3-containing waste slag (NCWS) and diamond-wire sawing silicon waste (DSSW) are important rare earth and Si secondary resources, respectively. Currently, NCWS and DSSW are recycled respectively by at least two different routes, which is not efficient and increases the burden on the environment. The present study proposed a novel technical route for preparing high-purity bulk Si and eutectic Si-Nd alloy simultaneously using NCWS and DSSW as raw materials, depending on the concept of using waste to treat waste. The new technical route has only two steps: initially, raw Si-Nd alloys were obtained by extracting Nd from NCWS utilizing DSSW as a low-cost reductant, and the impurity, oxygen, in the DSSW was effectively removed utilizing NCWS; the highest extraction rate of Nd from NCWS reached 68.3%, and the oxygen removal rate in DSSW was 99.89%; in the subsequent step, the obtained raw Si-Nd alloys were separated and purified to produce high-purity bulk Si (＞99.98%) and eutectic Si-Nd alloy (＞99%) through a physical and clean method-electromagnetic directional crystallization. This novel route is considered effective and environmentally-friendly for the sustainability of rare earth and Si resources, because no gas and liquid wastes discharged throughout the whole route, and two high value products can be prepared simultaneously using two wastes.

Migration mechanism of PTEs in polymetallic mines under pioneer phytoremediation: A Lanmuchang mercury-thallium mine perspective

The establishment of pioneer plants in waste slag sites not only modifies the nutrient content of the waste, but also plays a significant role in regulating the pH and potentially toxic elements (PTEs), thereby providing favorable conditions for the quick introduction of other plants. However, the mechanisms by which pioneer plants impact the migration and transformation of PTEs in polymetallic mines have rarely been studied. In this study, we investigated the effects of pioneer phytoremediation on the migration and transformation of PTEs, specifically thallium (Tl), mercury (Hg), arsenic (As), and antimony (Sb), in mercury-thallium mine waste. The results showed that pioneer phytoremediation increased esters and ethers containing C-O and P-O groups in dissolved organic matter, which subsequently formed soluble complexes with Hg, As, and Sb. Nevertheless, pioneer phytoremediation reduced the migration of Tl in the waste, this was mainly because pioneer phytoremediation reduced Fe3+ in silicate minerals and iron-containing minerals to more reactive Fe2+, thereby increasing the electronegativity (El) of the waste and enhancing its adsorption capacity for metal cations, such as Hg and Tl, thus maintaining electrical neutrality. However, the increased El of the waste was detrimental to the adsorption of negatively charged oxygen-containing anions, such as As and Sb. At the same time, the dissolution of Fe2+ resulted in the release and mobility of As and Sb that had been adsorbed onto iron oxides. The results offer significant theoretical support for guiding the ecological restoration of PTEs in polymetallic mines.