Search Results (125)

The sustainable utilization of solid waste is crucial for environmental protection. This work investigates the fabrication of foamed ceramics from Cr slag and municipal solid waste incineration (MSWI) fly ash, focusing on the effects of three inhibitors—NH₂SO₃H, ZnO·TiO₂, and (NH₄)₂HPO₄—on material properties and Cr leaching behavior. Experimental analysis, chemical thermodynamic calculations, and material characterization were all employed. Results show that the prepared foamed ceramics meet the JG/T 511-2017 standard for building materials, exhibiting excellent physical properties but significant Cr leaching. Among the inhibitors, (NH₄)₂HPO₄ with a molar ratio of n(P)/n(Cr) = 1 shows the best performance, achieving a bulk density of 205 kg/m³, compressive strength of 0.850 MPa, Cr leaching concentration of 188 μg/L, and a 70.0% of Cr leaching inhibition rate. The improvement is attributed to the AlPO₄ formation that enhancing the strength, and Ca₂P₂O₇ that stabilizing Cr during sintering. This work provides a feasible method for the safe resource utilization of Cr-containing waste. Full article

Red mud from bauxite processing is among the large-tonnage technogenic waste that poses a significant ecological threat. At the same time, red mud serves as a raw material source for expanding the resource base for obtaining iron, rare metals, and rare earth elements. Numerous studies on their utilization have shown that only through comprehensive processing, combining pyrometallurgical and hydrometallurgical methods, is it possible to maximize the extraction of all the useful components. This work addresses the first stage of a comprehensive technology for processing red mud through reduction smelting, separating iron in the form of pig iron, and producing slag. Studies were conducted on the reductive smelting of red mud using waste slurry from alumina production as the calcium-containing material, taken in proportions calculated to obtain a fluid slag with a hydraulic modulus of 0.55–0.8. The permissible mixing range of red mud with waste slurry was determined to be in the ratio of 0.56–1.2. In cases where the charge was prepared in violation of the required hydraulic modulus value, pig iron was not obtained during smelting. When the hydraulic modulus requirement was met, the temperature of the reductive smelting process was 1350–1400 °C. The total amount of recovered iron obtained as pig iron and fine fractions amounted to 99.5% of the original content. The low iron content (0.23–0.31%) in the non-magnetic slag fraction allows for the production of high-quality titanium oxide and rare earth element concentrates in the subsequent stages of the comprehensive hydrometallurgical processing of red mud, involving acid leaching. Based on the results of a phase analysis of the slag, pig iron, and melt, the reactions of the reductive smelting process were established, and their thermodynamic likelihood was determined. In fluid slags, the content of the sodium aluminosilicate phase is twice as high as that in slag with a higher hydraulic modulus. The reductive smelting of 100% red mud with the addition of calcium oxide, calculated to achieve a hydraulic module of 0.55 at a temperature of 1350–1400 °C, produced pig iron and slag with high alkali and iron contents. Full article

In this work, a gradient leaching strategy for stepwise extraction of tungsten and cerium from a spent W-Ce/TiO₂ catalyst has been developed. Results of a thermodynamic analysis indicated that high-temperature alkaline leaching and low-temperature acid leaching were conducive to the extraction of W and Ce, respectively. The effects of leaching agent type, concentration, temperature, and liquid-to-solid ratio on the leaching rates of W and Ce were systematically investigated. Experimental results revealed that the leaching ratio of W reached 90.92% under optimized conditions of 3 mol/L NaOH, 100 °C, 1 h, and a liquid-to-solid ratio of 20:1 for the alkaline leaching in the first stage. The leaching ratio for Ce reached 91.96% under optimized conditions of 1 mol/L H₂SO₄, 50 °C, 2 h, and a liquid-to-solid ratio of 12:1 for acidic leach in the second stage. The leaching ratios of titanium and aluminum were limited to 1.76% and 4.42%, respectively, indicating that >90% of these elements were virtually undissolved during the two-stage leaching process. The final leaching residue after the two-stage leaching contained >91.88 wt% TiO₂. Consequently, this study not only demonstrated effective separation of W, Ce, and Ti, but also provided an innovative solution for the environmentally friendly treatment and resource utilization for spent W-Ce/TiO₂ catalysts. Full article

This study presents an innovative approach to processing refractory zinc-bearing clinker using microwave thermal treatment followed by acid leaching. Microwave irradiation induces phase transformations, converting sphalerite (ZnS) to zincite (ZnO), and generates microcracks that enhance clinker porosity and reactivity. These changes significantly improve zinc dissolution during sulfuric acid leaching. Key parameters—acid concentration, temperature, solid-to-liquid ratio, and leaching time—were optimized, achieving a zinc extraction of 92.5% under optimal conditions (40 g/L H₂SO₄, solid-to-liquid ratio 1:4, 600 °C, 5–7 min) compared to 39.1% without pre-treatment. Thermodynamic analysis confirms the higher reactivity of ZnO, driven by favorable Gibbs free energy and exothermic reaction characteristics. These findings demonstrate the potential of microwave processing to intensify hydrometallurgical processes, offering energy efficiency and environmental benefits for industrial zinc recovery. Full article

Leaching from cement can lead to a loss in performance and durability and can also have an environmental impact. Therefore, it is an important aspect to consider when new cements are being developed and where concrete is to be placed that could lead to the contamination of groundwater. Calibrated thermodynamic models can provide very useful predictions in a matter of seconds for any cement-based material. However, such models need to include accurate representations of the solid-solution nature of the C-S-H gels that are included for the incongruent dissolution of calcium and silica. This study presents the calibration of a thermodynamic model employing the pH-REdox-Equilibrium geochemical software 3.8.7, written in C (PHREEQC 3.8.7), to model the change in the pH and the leaching of calcium (Ca) and silica (Si) from cement against the Ca/Si ratio and over time. The predicted concentrations of Ca and Si and the pH in the leachate were calculated using three solid-solution C-S-H gel models that were taken from the cemdata18 database, namely, CSHQ, CSH3T, and tobermorite–jennite, which have not been analysed before and show good agreement. The calibrated model was used to predict leaching from a CEM II/A-L cement and a blended CEM I + fly-ash with a cement replacement level of 35%. The effect of a sulphate environment (Na₂SO₄) was also analysed. Full article

Copper shaft furnace (CSF) dust containing valuable metals with a composition of 44.02% Zn and 14.57% Pb, in the form of oxides (PbO and ZnO), was used for leaching in 1 mol/L sodium hydroxide lixiviant at a temperature of 80 °C. The leaching efficiency for lead removal was 98%. The leaching of CSF dust in sodium hydroxide was thermodynamically studied using Pourbaix diagrams for the Pb/Zn/-Na–H₂O system at temperatures of 25 °C and 80 °C. A suitable precipitating agent was 0.5 mol/L sulfuric acid at pH 3. The formation of lead sulfate as the final product was confirmed by SEM, EDX, and XRD analysis. Although increasing the temperature reduced the aging time required for the precipitation, it did not affect the amount of lead precipitated. The solution, after lead precipitation and containing zinc (Zn²⁺), was further treated with ammonium carbonate for zinc precipitation. Various analytical methods, including SEM, EDX, XRD, XRF, and AAS, were used to analyze the input samples and the final products obtained after alkali leaching of CSF dust and lead and zinc precipitation. Full article

Referencing ion exchange applied in the extraction of ion-adsorption minerals, a mathematical model based on thermodynamic equilibrium has been researched and established to reveal and represent the chemical reaction between minerals and the leaching solution. Meanwhile, a Python-based numerical solver has been developed and programmed to solve the equations of the established model in order to achieve computational efficiency and obtain an accurate solution. Based on the simulation and computation with the established mathematical model, the effects of leaching solution concentration and mineral grade distribution on the extraction of ion-adsorption minerals can be evaluated, validating the set value of 20 g/L for the initial leaching solution concentration and the extraction rate of above 90% for the cut-off grade. Furthermore, the established mathematical model can be integrated into the simulation system for the overall multi-field extraction of ion-adsorption minerals, illustrating the relationship between extracted metal ion concentration in the aqueous phase over time and providing theoretical support for the engineering project. Full article

The lithium market has been expanding due to the high demand for lithium-ion batteries, which are essential for electric and hybrid vehicles as well as portable devices. This has driven the search for new lithium ore deposits and the development of more efficient extraction and processing technologies. The main methods used for lithium extraction from hard rock ores include the acid process, the alkaline process, and chlorination roasting. This study investigated a chlorination process applied to α-spodumene extracted in Brazil for lithium chloride (LiCl) production. The ore underwent thermal treatment in the presence of calcium chloride (CaCl₂) and magnesium chloride (MgCl₂), followed by water leaching at 90 °C. The thermodynamics of the α-Li₂O·Al₂O₃·SiO₂ system, combined with calcium and magnesium chlorides, was analyzed using HSC 5.1 software. The main objective of this study was to produce lithium chloride from alpha spodumene and avoid decrepitation of the ore to the beta phase before mixing with the reagents, making the process faster and less expensive compared to traditional extraction methods. Pyrometallurgical tests were conducted in a muffle furnace, varying the molar ratio between chlorides (MgCl₂:CaCl₂) at 1:0, 0:1, 1:1, 2:1, and 1:2 and the mass ratio of spodumene to chlorides at 1:4, 1:6, and 1:8. The best lithium extraction result was approximately 95%, the conditions for obtaining the result were a spodumene:chloride ratio of 1:6 and a molar ratio between chlorides of 2:1. The results provide a better understanding of the chlorination roasting process and demonstrate the potential of the chlorination technique as a viable alternative to conventional lithium extraction methods. Full article

A possible thermodynamic study of processing Cu (Ag, Au) and Fe sulfide concentrate as a by-product after the processing of tetrahedrite concentrate, applying pyrometallurgical and hydrometallurgical methods, was studied. The sample of sulfide concentrate, 34.7 wt. % Cu, 21.4% Fe, 12 g/t Au, and 7.317 g/t Ag was contained. Analytical technique AAS was used to analyze the sample before conducting a thermodynamic study of the leaching of sulfide concentrate by applying Pourbaix Eh–pH diagrams. The outcome of this thermodynamic research will provide essential data to support recent hydrometallurgical technologies. If its correctness can be verified experimentally, this result will be promoted to developing a new alternative copper-production technology. The minor components Sb, As, Hg, and Bi are also present in the concentrate in the form of sulfides Sb₂S₃, As₂S₃, Bi₂S₃, and HgS. This theoretical proposed hydrometallurgical technology shows that it is possible to obtain Fe in the form of Fe(OH)₃, and after its thermal decomposition, it can be prepared as Fe₂O₃ as a marketable product. In any case, the most economically advantageous would be complete hydrometallurgical processing, i.e., also Cu(Ag,Au)Fe sulfide concentrate, with the possibility of valorizing Cu, Ag, and Au in metallic form. Full article

To achieve the resource utilization of iron ore tailings (IOTs), two different IOTs were investigated as sustainable adsorbents for ciprofloxacin (CIP) removal from aqueous systems. Through systematic batch experiments, key adsorption parameters including initial pH, adsorbent dosage, contact time, ionic strength, and temperature were comprehensively evaluated. The results showed that CIP adsorption by IOTs remained relatively stable across a broad initial pH range (2–10), with maximum adsorption capacities of 5-IOT and 14-IOT observed at the initial pH values of 10.1 and 9.16, respectively. Competitive ion experiments revealed a gradual decrease in CIP adsorption capacity with increasing ionic strength (Na⁺, Mg²⁺, and Ca²⁺). Thermodynamic analyses indicated an inverse relationship between adsorption capacity and temperature, yielding maximum adsorption capacities (Q_max) of 16.64 mg/g (5-IOT) and 13.68 mg/g (14-IOT) at 288.15 K. Mechanistic investigations combining material characterization and adsorption modeling identified ion exchange as the predominant interaction mechanism. Notably, trace elements (Cd, Co, Cr, Cu, Fe, Ni, Pb, and Zn) were released during leaching tests, with concentrations consistently below environmental safety thresholds. A back-propagation artificial neural network (BP-ANN) with optimized architecture (8-11-1 topology) demonstrated high predictive accuracy (MSE = 0.0031, R² = 0.9907) for adsorption behavior. These findings suggested IOTs as cost-effective, environmentally compatible adsorbents for CIP remediation, offering the dual advantages of pharmaceutical pollutant removal and industrial waste valorization. Full article

Acid leaching is an effective method for dephosphorization; however, it is time-consuming and requires a high amount of acid consumption, resulting in increased production costs and environmental risks. This work aims to remove silicon, aluminum, and phosphorus from high-phosphorus oolitic magnetite concentrate through high-pressure alkaline leaching and ultrasonic acid leaching. Compared with traditional acid leaching processes, the sulfuric acid dosage can be significantly reduced from 200 kg/t to 100 kg/t, and the pickling time is shortened from 60 min to 10 min. Thermodynamic and kinetic studies have demonstrated that acid leaching facilitates apatite dissolution at low temperatures, whereas the dephosphorization reaction is controlled mainly by diffusion. The application of ultrasonic waves leads to finer particle sizes and greatly increased specific surface areas, thereby accelerating the diffusion rate of the leaching agent. Furthermore, microscopic analysis revealed that under the influence of ultrasonic waves, numerous micro-fragments and pores form on particle surfaces due to cavitation effects and mechanical forces generated by ultrasonic waves. These factors promote both the reaction rates and diffusion processes of the leaching agent while enhancing the overall leaching efficiency. Full article

Tungsten (W), a rare metal, is categorized as a Critical and Strategic Raw Material (CRM) by the European Union (EU), with the highest economic importance of all selected CRMs since 2014. Tungsten and its derivatives are extracted from their commercial raw materials, mainly wolframite [(Fe,Mn)WO₄] and scheelite (CaWO₄) ores. Subsequently to mining and mineral processing, the W ore is submitted to thermal treatment and hydrometallurgy under aggressive conditions (high pressure and temperature), which are usually applied for the extraction of tungsten compounds. This paper aims to investigate a thermal route for scheelite processing using various selected chemical agents, resulting in a W-bearing material that is capable of being leached under softer conditions. In this context, a thermodynamic study of the interaction between FeWO₄, MnWO₄ and CaWO₄ and various chemical reagents is described. The thermochemical calculations and data modeling show that, among other considerations, the reaction of CaWO₄ with magnesium chloride (MgCl₂) can lead to the formation of magnesium tungsten oxide (MgWO₄), which appears to be more easily leachable than CaWO₄. Experimental tests of the reaction of scheelite with MgCl₂ appear to validate the thermodynamic predictions with satisfactory process kinetics at temperatures from 725 to 775 °C. Full article

It is essential to recycle zinc leaching residue (ZLR) generated by the conventional zinc hydrometallurgy process, as it is a hazardous and potentially valuable industrial waste. A combined calcification roasting–acid leaching process was developed to selectively separate and recover zinc from ZLR. This work investigates the effectiveness of using calcium oxide as an additive to transform zinc ferrite during the roasting process. The feasibility of the reaction was investigated based on thermodynamic calculations and compositional analysis. The transformation ratio of zinc ferrite reached 95.27% after roasting at 900 °C for 2 h with a Ca/Fe molar ratio of 3. During the calcification roasting process, the zinc ferrite was effectively converted into zinc oxide and calcium ferrite. The selective leaching of zinc was achieved at an L/S of 15, 25 g/L H₂SO₄, 60 °C, and 90 min. The extraction ratios of Zn and Fe were 86.26% and 0.06%, respectively. After the leachate was evaporated and purified, metallic zinc with a purity of 99.53% was obtained by constant current electrolysis for 60 min with a current efficiency of 86.7%. The proposed process provides a viable alternative method for recycling zinc resources from ZLR by an environmentally friendly method. Full article

Waste-to-energy (WtE) is a key part of modern waste management. In the European Union, approximately 500 WtE plants process more than 100 million tons of waste yearly, while globally, more than 2700 plants handle over 500 million tons. Roughly 20% of the waste processed is bottom ash (BA). However, this ash can contain heavy metals in concentrations that may render it hazardous. This paper presents a study focusing on stabilizing municipal solid waste incineration BA using simple and industrially viable treatments. The Slovenian WtE plant operator wishes to install the stabilization process; thus, the samples obtained from the plant were treated (1) with a CO₂ gas flow, (2) with water spraying, and (3) with a combination of water spraying and a CO₂ gas flow under laboratory conditions. Thermodynamic calculations were applied to define potential reactions during the treatment processes in the temperature range from 0 to 100 °C and to define the equilibrium composition of the treated ash with additions of CO₂ and water. The standard leaching test EN 12457-4 of treated ash shows a reduction of over 40% in barium concentration and over 30% in lead concentration in leachates. Full article

Owing to the intensive development of electrical and electronic equipment, there is an increasing demand for precious metals, which are often used for its production. Due to their scarce supply, it is important to recover them from secondary sources. A promising way to recover precious metals are impregnated resins. In this research, Amberlite XAD-16 was impregnated with TBP at the weight ratios of 1:2 and 1:3 using the ‘warm impregnation’ method. Studies were carried out on the sorption of Au(III), Pd(II), Pt(IV), and Rh(III) ions from the model chloride solutions as well as the real solution formed after leaching the smart card chips. Only Au(III) ions were efficiently sorbed on the prepared impregnated sorbents. The best results were obtained at 6 M HCl and the sorbent mass: 0.1 g/25 mL. The maximum sorption capacity for the impregnated sorbents was: 147.91 mg/g (ratio 1:2) and 149.66 mg/g (ratio 1:3). Recovery of Au(III) ions from the real leaching solution was: 97.36% and 97.77%, respectively. The Langmuir isotherm was the best-fit model for the experimental results. Thermodynamic studies proved that the investigated sorption process is spontaneous and exothermic. The desorption process can be easily carried out with 1 M HCl/1 M TU. Full article