Raw Material For Cement Production Research Articles

Generating sustainable cement material from seawater with low-cost ultrafiltration (UF) membrane electrolysis

Membrane electrolysis offers a promising avenue for in-situ generation of hydroxide ions (OH−), facilitating the recovery of magnesium (Mg2+) and calcium (Ca2+) ions from seawater as alkaline earth hydroxide precipitates. This process paves the way for an alternative greener method in the production of raw materials for cement manufacturing compared to limestone mining. Despite its potential, the application of conventional ion migration membranes, such as anion exchange membrane (AEM) and cation exchange membrane (CEM), is hampered by their high cost and low mechanical quality, posing significant barriers to industrial scalability. In this work, we introduce the utilization of commercially available high mechanical strength ultrafiltration (UF) membrane within a two-chamber electrochemical system, repurposing it as an ion migration membrane due to its distinct advantages in terms of simplicity and relative cost-efficiency than conventional AEM. This research demonstrates that the UF membrane exhibited a comparable performance to AEM in terms of OH− production. Both membranes achieved 97–99 % removal of Mg2+ and Ca2+ within 3 h at a current density of 8 mA/cm2 and maintained comparable migration rate of SO42− ion. Compared to AEM, a notable distinction of the UF membrane is its reduced migration rate of Cl− ions, resulting in lower membrane discoloration/oxidation. Furthermore, the investigation reveals that utilizing a Na2SO4 solution as an alternative anolyte, despite being slower for OH− production, offers economic advantages and facilitates higher selective recovery of Mg2+ over Ca2+. The end products of this process, MgO and CaO, are viable raw materials for cement production, underscoring a sustainable and low carbon approach compared to conventional limestone mining of cement production.

Geochemical Characterization of Sedimentary Materials (Limestone, Gypsum, Coal, and Iron Ore) along the Nile River Basin, South Wollo, Ethiopia

Sedimentary rocks are produced by the weathering of preexisting rocks and the subsequent transportation and deposition of the weathering products. Among the sedimentary rocks, especially limestone is a crucial raw material for cement production. The purpose of this study was to characterize the valuable industrial raw materials, limestone, gypsum, clay, coal, and iron ore, along with the Nile River basin. For sample collection, a random sampling method was applied. Different analytical methods were carried out for complete oxide analysis such as LiBO2 fusion, HF attack, and gravimetric, calorimetric, and atomic absorption spectroscopy (AAS). The percentages of oxides detected in this study are in the range of acceptable values (high content of CaO ranging from 47.3 to 50.4% and less content of SiO2 ranging from 8.72 to 11.24%) for good proposal as a potential raw material for cement production. The most dominant and wide-range coverage of limestone along with the Nile basin, particularly near Arsema Monastery, was found as matured limestone. The petrographic analysis of gypsum, sandstone, and clay samples indicated that all the samples taken from Wegidi revealed that the high percentage of gypsum ranges from 90 to 95%. Sandstone is dominantly preset in Kelala to Jamma road along with Beto River with high content of SiO2 ranging from 61 to 95%. The results of this study indicate that the treated coal samples are relative to high calorific value, fixed carbon, and low ash content. Coal and iron ore from Jamma revealed that high calorific value is 4929.24 and hematite content is 52.2, respectively. The result of this study revealed that a huge amount of limestone reservoir is detected in Borena Wereda, Amhara, Ethiopia.

Feasibility study on utilization of copper tailings as raw meal and addition for low carbon Portland cement production

Copper tailings (CT), the main tailings waste with high emissions and serious pollution, has been attempted to be used as raw materials for cement production. However, the amount of CT used in cement production has been remains low. In this study, 20.31 wt% CT as raw meal and 15 wt% CT as addition was used to prepare CT ordinary Portland cement (CTC15), and the corresponding indicators met P·O 42.5 grade. Saturated lime modulus, silicon modulus, aluminum modulus, holding time and sintering temperature were investigated to optimize CT clinker (CTC). The optimum amount of CT as addition was analyzed. Furthermore, CTC and CTC15 were evaluated in terms of economy and environment. Using only CTC to help the cement factory save natural resources by 234346 t·a−1. By producing CTC15, 293.00 MUSD·a−1 could be generated, reducing CO2 emissions by 44000 t·a−1. As a result, CT has feasibility and great potential in cement production.

Propriedades reológicas e hidratação de cimentos ternários contendo resíduos de mármore, porcelanato, bloco cerâmico e fosfogesso

Abstract No research demonstrates the effect of combined waste raw materials as an alternative to natural sources in Limestone Calcined Clay Cement (LC3). In this context, this study aimed to evaluate the influence of the composition of ternary cements (TCs) containing industrial waste on their rheological and hydration properties. As raw materials, Portland cement and clay brick (CBW), clay tile (CTW), marble (MW), and phosphogypsum (PG) wastes were used. The rheological behaviour of the pastes was analysed by the mini-slump evolution over time and rotational rheometry. Hydration was evaluated by isothermal calorimetry and XRD/Rietveld. An increase in the specific surface area enhances the yield stress and plastic viscosity of the paste. CBW and CTW have pozzolanic reactivity, presenting an increase in the content of non-crystalline phases, including calcium silicate hydrate (C-S-H). The TCs reached at least 70% of the compressive strength of theHigh Early Strength Portland cement paste.The results suggest that CBW, CTW, MW and PG can be used as an alternative to reduce the clinker factor and decrease the environmental and economic impacts associated with extracting natural raw materials for cement production.

Efisiensi Persediaan Kantong Semen Berbasis Metode MIN-MAX, EOQ, dan TWO-BIN di Packing Plant PT AKA

PT AKA is a multinational enterprise engaged in the cement industry. One of the supporting raw materials in cement production is cement bags. Demand for cement bags is directly proportional to the demand for cement. The production division has been experiencing the problem of inefficiency in determining the supply of cement bags. This study aims to evaluate the company's policy in controlling the supply of raw materials for cement bags by comparing the 3 Min-Max, EOQ, and Two-Bin methods. Quantitative data were used: demand for cement bags, storage, and ordering costs. Forecasting data calculations were performed using Minitab software. The results showed that the Min-Max method produced the optimal efficiency with a total inventory cost of Rp. 119,107,700 for 40 kg cement bags, and Rp. 35,528,720 for 50 kg cement bag.

Innovative recycling approaches to enable new material loops for AAC

AbstractThis paper shows different approaches to save mineral resources or energy for the production of autoclaved aerated concrete (AAC) using secondary materials. The goal is to implement new recycling routes in the building industry and to establish new material loops. It could be shown, that AAC can act as a sink for fine fractions from building rubble consisting of waste concrete and calcium silicate masonry units (CSU) by replacing the primary quartz sand. By choosing secondary raw materials like rice husk ash with a higher solubility than quartz, it is even possible to achieve AAC with the desired properties at lower autoclaving temperatures. After the end of life, AAC can be treated with the patented approach “ENSUBA,” a wet‐chemical washing procedure, which enables the complete removal of sulfate ions, which usually cause problems in the recycling of AAC. After this treatment waste AAC can easily be brought back to the material cycle and for example be used as a raw material for cement production. Most importantly, this ENSUBA approach can be combined sensibly with a carbon capture technique like the chilled ammonia process. This process captures CO2 from the cement production in an ammonia solution, leading to the precipitation of ammonium carbonate, which is needed for the ENSUBA process.

A novel and clean utilization of converter sludge by co-reduction roasting with high-phosphorus iron ore to produce powdery reduced iron

The efficient and harmless utilization of converter sludge (CS) still faces problems. In the traditional roasting process of high-phosphorus iron ore (HPIO), a large amount of sodium or calcium salt needs to be added to enhance iron recovery and dephosphorization, which leads to an increase in production costs. In this paper, the co-reduction roasting followed by magnetic separation process was designed to realize the full recycling and clean utilization of CS and upgrade HPIO. The results show that the hazardous CS can serve as an ideal admixture in this process which ameliorated the conversion of iron oxides to metallic iron and inhibited the reduction of phosphorus in iron oxides in HPIO. And the element of iron in CS was fully recycled as well. Under optimal conditions, the powdery reduced iron with 93.45% Fe and 0.09% P was produced, which can be a superior substitute for scrap steel in steelmaking, and the iron recovery reached 96.10%. The tailings were cleaned with a leaching toxicity significantly lower than the standard threshold, and the composition indicate that they were excellent raw material for cement production. This novel process realizes the comprehensive and green utilization of CS.

Interpretation of Chemical Analyses and Cement Modules in Flysch by (Geo)Statistical Methods, Example from the Southern Croatia

This study included the testing of normal (Gaussian) distribution of input data and, consequently, spatially interpolating maps of chemical components and cement modules in the flysch. This deposit contains the raw material for cement production. The researched area is located in southern Croatia, near Split, as part of the exploited field “St. Juraj–St. Kajo”. There are six lithological units: (1) alternation of marls and sandstones with inclusions of conglomerates, (2) marl, (3) calcsiltite, (4) calcarenite, (5) marl with nummulites, (6) debrites, and (7) clayey marl. All of them are deposited in the (a) northern and (b) southern beds. Only debrites are divided into the (a) western and (b) eastern layers. Those lithological units were divided technologically based on their cement modules (lime saturation factor (LSF), silicate module (SM), and aluminate module (AM)). The average thicknesses were analysed, followed by normality tests (Kolmogorov–Smirnov (K–S) and Shapiro–Wilk (S–W)) of the chemical analyses: CaO, SiO2, Al2O3, Fe2O3, MgO, SO3, Na2O, K2O, CaCO3 (%) and three cement modules (LSF, SM, AM), available in the six lithological units. The normality tests were applied based on a number of input data. The further interpolation was performed using two methods, kriging and inverse distance weighting, mapping CaO (%), SiO2 (%), and LSF (−) in three different lithological units. The interpolation methods were selected based on two criteria: (a) normality test pass or fail and (b) the amount of data. In total, 144 tests were calculated, including sets from 7 to 36 points. The results show the current situation in the quarry, after decades of production, making reliable the future predictions of cement raw material exploitation.

Natural fiber-reinforced light-weight cement blocks prepared from waste for sustainable development

Low density of the light-weight cement blocks offers an advantage in terms of dead load reduction, which is advantageous in structural design-reduction of size and numbers of load-carrying structural components is possible. Production of cement blocks, however, generally requires Ordinary Portland Cement (OPC) which creates harmful environmental impacts. Utilization of waste as alternative raw materials for cement production is a route to alleviate the problem. This research aims at synthesizing eco-friendly cement-like material for production of light-weight cement blocks. The cement-like material were prepared from eggshells, cockleshells, and rice husk ash (RHA). With high content of calcium oxide and silica, eggshells and cockleshells are potential sources of calcium, whereas RHA is a good source of silicon. Additionally, a fuel-efficient solution combustion technique was employed in synthesis of the cement-like material. Phase identification analysis of the synthesized powder indicated that tri-calcium silicate (C3S), di-calcium silicate (C2S), tri-calcium aluminate (C3A),and tetra-calcium alumino ferrite (C4AF), which are main constituents of OPC, were obtained. To fabricate eco-friendly light-weight cement blocks, the synthesized cement-like material were mixed with cement, water, and additional RHA and cast into blocks. The optimal compressive strength and density of the cement blocks were in comparable range with the standard light-weight concrete defined by Thai Industrial Standards Institute (TISI) and American Concrete Institute (ACI 213,2001). With jute fiber reinforcement, enhanced compressive strength of 20% was achieved, while elimination of spalling after compression test was clearly evident, implying a more ductile failure.

Utilization of Coal Combustion Waste (Fly Ash) For Geopolymer Concrete as Green Concrete

The use of Portland Cement as a paste in conventional concrete is still often the primary/favourite choice in civil engineering construction. In time, cement production will cause harm to the environment, especially in the production process, and the availability of natural raw materials in cement production will dwindle. Therefore, it is necessary to find an innovative alternative to replace cement utilization. From the test matrix that has been carried out, it can be concluded that the waste from burning coal (fly ash), can be used as a substitute for Portland cement, and also at the composition of 16 moles – the ratio of sodium silicate to sodium hydroxide of 1.5 has a strong quality much better compression than the composition when using a 100% Portland cement mixtureFrom the test matrix that has been carried out, it can be concluded that the waste from burning coal (fly ash), can be used as a substitute for Portland cement, and also at the composition of 16 moles – the ratio of sodium silicate to sodium hydroxide of 1.5 has a strong quality. much better compression than the composition when using a 100% Portland cement mixture.

Thermogravimetric study of textile lime sludge and cement raw meal for co-processing as alternative raw material for cement production using response surface methodology and neural networks

In the textile industry-water treatment process, lime sludge is generated and usually piled up in nearby barren lands to avoid transportation costs. However, the textile sludge could have disposal value as an alternative raw material in cement kilns. Advanced analytical techniques were employed to investigate the raw material property of textile sludge for cement production. Fourier Transform Infrared(FTIR) Spectroscopy Analysis and Thermo-gravimetric hyphenated FTIR analysis revealed that textile sludge was predominantly inorganic and gas emissions mainly were CO 2 . Sludge was fused at calcination temperatures, and the phase transition was compared to the Hot Meal (HM) formed from the raw meal. Inductively coupled plasma optical emission spectrometry(ICP-OES) revealed that textile sludge is rich in metal oxides such as 45% CaO, 11% SiO 2 , 0.44% Al 2 O 3 , 8.57% Fe 2 O 3 , 7.85% MgO, respectively, which are essential raw materials for the cement manufacturing process. The thermal degradation kinetics were computed under non-isothermal conditions (30–900 °C) at 10, 15, 20°C/min. Response surface regression techniques identified the effect of heating rate and temperature on mass loss. Regression Coefficient of the predictive models were above 0.90. The prediction accuracy increased by Artificial neural network using MSE as performance function and TRANSIG as transfer function. • The activation energy of textile sludge is 160 kJ/mol and raw meal 230 kj/mol. • In RSM, TGA mass loss had quadratic relationship for textile sludge & raw meal. • Multilayer ANN model for a better fit using TRANSIG & MSEREG. • TGA-FTIR studies to study the gases that evolved during combustion.

Tirilolo village community vulnerability and perceptions of the cement industry planning in Baucau District, Timor Leste

The cement industry investment in Baucau Regency is agreed to be the key to economic growth, creating new jobs, and reducing poverty. To support this investment in the cement industry sector, the government of Timor Leste issued Government Resolution no. 14/2016 regarding the Special Investment Agreement submitted by the Company TL Cement, Lda. Baucau Regency area has a good stretch of karst for the supply of the main raw material for cement production, thus chosen as an investment location. Tirilolo village as well as the surrounding community, where they plan to establish a limestone factory and mine is planned – will receive both benefits and risks from the investment planning. This study uses a mixed-method with a survey approach, interviews, and questionnaires, with socio-economic risk assessment at the local level in the cement industry investment plan sector. This study uses secondary data analysis and field observations. The data obtained will be analyzed descriptively and using a scoring technique on each indicator. Some of the research results obtained indicate a basic vulnerability, that the population density in Tirilolo Village is 52 people/ha, with female household heads 5%, people with disabilities 7%, vulnerable age population 26%. In the education sector, 68.75% of the population did not go to school, while only 17% graduated from elementary school, 5.2% graduated from junior high school, and 8.3% graduated from high school. The average community income is less than $100 per month. The results of structured interviews and focus group discussions show that even though factories and mines carry risks, people look forward to jobs that will emerge to make changes in their lives.

Characterization and comparison of the cement produced using clam wreckage and limestone: Cement clinker, freeze–thaw resistance, and hydration products

Limestone accounts for more than 85 wt% raw materials for cement production. Clam wreckage, a calcareous residual, brings serious harm to the environment, such as attracting mosquitoes and releasing unpleasant odors after decay. This work produced a cement (lime coefficient: 0.97, silica coefficient: 2.04, and alumina coefficient: 1.37) using the clam wreckage as an alternative to limestone and done a comparison with the cement produced with limestone in the calcined temperature of production, mineral phases, freeze–thaw resistance, and hydration products and their formation amount and microstructures. Results show that clam wreckage contains more calcite than limestone so that the addition of clam wreckage to cement production is lower than that of limestone at the same clinker coefficient. The optimum calcined temperature for the production of cement using clam wreckage is 1350 °C, leading to a reduction of 100 °C comparing to the cement using limestone. The mineral phases of the two cements are the same, but the clam wreckage promotes the formation of C3A, and C4AF as well as the conversion of C2S into C3S, at 1350 °C. The hydration products are all the virgulate 3CaO·Al2O3·3CaSO4·32H2O, petal-like sheet Ca(OH)2, and close-grained and glazed C-S-H; but their formation amount in cement produced with 78.98 wt% clam wreckage are higher than that with 85.81 wt% limestone, leading to the cement with clam wreckage shows better freeze–thaw resistance at the same curing ages compared to that with limestone. This work is helpful to the upcycling of clam wreckage and provides an alternative to limestone in cement production.

TO THE QUESTION OF THE GENESIS OF THE LIMESTONE OF THE GUIDIRIM AND SEVERIN DEPOSITS

Problem Statement and Purpose. In Transnistria, the deposits of Sarmatian-age limestone are explored and exploited. These minerals are used as raw materials for cement production, as well as for the production of buta and rubble. The issues of genesis and facial transitions of these deposits remain under-studied. Data & Methods. The purpose of this work is to determine the genetic affiliation of the limestone deposits of the Gidirim and Severin deposits on the basis of facial and chemical analysis. The materials of the research are the limestones of two deposits of Transnistria. The object is the limestone of the Sarmatian age of the deposits of Transnistria. The subject of the study is the lithological and paleontological characteristic, the chemical composition of these limestones. Research methods: topical; biofacial, computer processing with GIS – programs; Laboratory quality diagnostics, chemical and physical-chemical methods of quantifying the main components of carbonate rocks. Results. The geological conditions of the Severin and Gidirim deposits were studied, and the place of productive layers of deposits in the stratigraphic scheme of Transnistria was determined on the basis of the lithological and paleontological characteristics of the rocks. Limestones mined at the Gidirim field belong to the May Day retinue, and the limestone of Severinovsky belongs to the Bessarabian reefs. Chemical analysis of limestone samples extracted from the deposits was carried out and differences in the chemical composition of the limestone of these deposits were determined. The limestone deposits in the content of calcium carbonate are clean. The concentration of silicon dioxide in the samples of the Severin field is higher than in the samples of the Giderim field, the content of one-and-a-half oxides, on the contrary, in Severinovka – 0.68%, in samples of the Giderim field – 1.04%. Analysis of the lithological composition and fauna of limestones has made it possible to distinguish within the Middle-Sarmatian basin of sedimentopulation: (a) accumulation of biogenic-chemogenic limestone of the near shelf, b) biogenic precipitation of the transition zone (reefs), c) silicate-terrigenous formations of the far shelf. The variety of phased conditions in the basin is associated with the position of the coastline and the inflection of the bottom on the boundary of the near and far shelf. The limestone of the studied deposits was formed in two different facial environments: the chemogenic-carbonate and the transient, which is associated with the formation of a strip of Bessarabian reefs. The study of paleontological residues, lithology and chemical composition of rhypogenic limestone showed the autonomy of this environment, as it has features of sedimentogenesis and near and far shelf.

Production System in a Collaborative Supply Chain Considering Deterioration

This research presents a mathematical model for a collaborative planning of the supply chain involving four echelons (supplier, production plants, distribution, retails, or clients). The model seeks to maximize profit (utility) when all members of the chain share information related to demand. It is developed for the aggregate consolidation of different raw materials in cement production. The novelty of the model is the consideration of products that deteriorate in the process and thus it has effect on the production times in the plant and lead time. In this supply chain, quality and compliant products and the return of deteriorated products are two flows. The considerations are lead time, inventories with shortages and excesses, production times in normal and extra days, and subcontracting, among others. A mixed integer linear programming with demand scenario analysis is used to optimize and analyze the uncertainty that is consistent with the performance of the construction sector. The model is formed considering two suppliers, two production plants, two distributors, two retailers and two end customers. Four manufacturing inputs (raw materials) are considered for the manufacture of two types of products. A case study of the cement production supply chain of Cartagena (Colombia) is illustrated. The shared benefit is generated around 5 billion pesos (COP) for all members of the chain in a period of 6 months.

Formation of Friedel’s salt in simulated municipal solid waste incineration bottom ash

To recycle incineration bottom ash as a raw material in cement production, it is important to reduce the chlorides in the ash. Due to Friedel’s salt, washing only is insufficient to remove the chlorides. However, limited research has examined the mechanism of Friedel’s salt formation in ash. In particular, the effect of heating in an incinerator has not been reported. In this study, we investigated the formation of Friedel’s salt using reagents. Friedel’s salt was sufficiently formed upon heating at 1350 °C for 24 h and curing for 30 days. Higher temperatures than actual incineration conditions were required to produce pure Friedel’s salt, but a small amount of chlorine was also fixed in samples closer to actual incineration conditions. XRD and TG/DTA showed that the fixed chlorine most likely contained Friedel’s salt analogues. Washing experiments conducted to understand the leachability of chlorides from samples showed that 20–69% of the fixed chlorine did not dissolve during washing. The leaching behavior of the coexisting materials suggested that some of the fixed chlorine was present not in the form of Ca4Al2O6Cl2·10H2O but in chlorides or mixtures of chlorides with Ca and Cl bound at ratios of 1:1–2, which are more easily dissolved.

Hydration and Strength Development of Cementitious Materials Prepared with Phosphorous-Bearing Clinkers.

To rationally use low-grade phosphorous limestone as the raw materials for cement production, the influence of phosphorous introduced by fluorapatite during the clinker calcination process on the mechanical properties of cementitious materials is investigated. Hydration kinetics, phase evolutions, and microstructure of cement pastes have been studied by using calorimetry, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results indicate that the mechanical properties of cementitious materials can be slightly improved due to the mineralization effect of the small amount of phosphorous in the clinker and significantly decreased with an increase of phosphorous. High content of phosphorous will reduce the content of C3S and make the formation of α′-C2S-xC3P(x: 0–0.05), whose hydration reactivity is rather lower, such that on the one hand less-hydrated products, such as calcium silicate hydrate (C-S-H) gel, can be obtained, and on the other hand, the hydration reaction will be slowed by severely prolonging the induction period. Interestingly, small particles can be observed on the surface of hydration products, but no new phase can be detected by XRD. When the content of P2O5 is 2.0%, the cement can meet the requirements of P·II 42.5 cement in China. Hopefully, this can provide significant guidance for the use of cement prepared by fluorapatite as raw material.

Physical and Chemical Fundamentals and Technical Solutions for Recovery of Non-ferrous and Rare Metals from Industrial Wastes


 
 
 The increasing demand for zinc and a range of zinc-related metals (for example: lead; indium; tin; cadmium; and copper) in the Russian Federation cannot be satisfied by the existing production plants due to the lack of raw materials. At the same time, ferrous and non-ferrous metallurgy and the chemical industry have accumulated hundreds of millions of tons of zinc wastes (falling into the hazard categories 2 to 4), the processing of which could not only make up the raw material base, but also improve the environmental situation. In the world, over 85% of ferrous dust is recycled using the Waelz process. The Waeltz process is used for distilling separation of elements under reducing conditions. In this study, a block diagram for production of the following elements from industrial wastes is proposed: zinc, cadmium and indium in form of massive metals; zinc and indium in the form of fine powders; and clinker as a raw material for cement production. The technical and scientific details of this new process have been patented in the Russian Federation and abroad. For the first time, the following operations have been implemented with the use of large-sized Waelz kilns: vapour-oxidized Waeltz treatment of polymetallic wastes; recycling of heat from gases and solid products with generation of process fumes; and implementation of alternative flux (dolomite) and alternative fuel (petroleum coke).
 Keywords: Waelz process, industrial wastes, heat recycling, vapour-oxidized Waelz processing
 
 

Enhanced elution of chloride ions from incinerator bottom ash

Recycling of the incinerator bottom ash, which is discharged from solid waste treatment plants, is important since the landfilling capacity is limited, and if it is left untreated, it would generate a great environmental burden. Besides, the incinerator bottom ash has a similar chemical composition to that of cement and therefore it can be used as a substitute raw material in cement manufacturing. This recycling method would, in turn, reduce the consumption of natural resources, such as limestone and clay. Generally speaking, a high concentration of chloride leads to severe corrosion of steel, which can damage the reinforced concrete structure. The removal of chloride ions from the ash should, therefore, be carried out in advance to use it as a raw material for cement production. Thus, this study aims to find an effective method for eluting chloride ion from the incinerator bottom ash for recycling. One of the main findings of this work was that the residual chloride concentration in the incinerator bottom ash was reduced to 1.70 g/kg, eluting 87.78% of initial Cl concentration, when the ash was washed with an acetic acid solution (concentration: 1.5 mol/L) saturated with CO2 micro-bubbles.

Efficiency of Chemical and Biological Leaching of Copper Slag for the Recovery of Metals and Valorisation of the Leach Residue as Raw Material in Cement Production

Copper slags produced in vast quantities in smelting operations could be considered as secondary material sources instead of stockpiling them in landfills. This study investigates the recovery of valuable metals from copper slag and the valorisation of the leach residue as construction material in line with the principles of a circular economy. By taking into account that the environmental characterization of the as-received copper slag did not allow its disposal in landfills without prior treatment, chemical and biological leaching were tested for the recovery of metals. Pre-treatment with acids, namely HNO3 and H2SO4, resulted in the extraction of several target metals and the production of an almost inert waste. Despite the clearly better oxidative conditions prevailing in the bioleaching reactors, chemical leaching resulted in the higher dissolution of Cu (71% vs. 51%), Co (70% vs. 36%), and Zn (65% vs. 44%). The acid consumption was much lower during the bioleaching experiments compared to the chemical leaching. The bioleach residue was suitable for its use as supplementary cementitious material, showing a better performance than the reference sample without causing any detrimental effects to the calcium aluminate cement (CAC) quality. The complete valorisation of copper slags is expected to improve the economics of the process, by avoiding landfill costs and producing saleable products with high added value.