Search Results (307)

This study evaluates an integrated approach for recovering lead and silver from lead cake through chlorination roasting followed by acid leaching. The lead cake originates from sulfuric acid leaching of zinc ferrite residues obtained during the hydrometallurgical processing of zinc calcine. The effects of roasting temperature, lead cake-to-NaCl mass ratio, and roasting duration on metal recovery were systematically examined to determine optimal process conditions. Based on the experimental results, roasting at 550 °C for 1.5 h with a lead cake-to-NaCl mass ratio of 1:3, followed by leaching in 1 M HCl, was selected as a representative and sufficiently effective condition for the combined process. Under these conditions, nearly complete dissolution of Pb and Ag was achieved, reducing their contents in the final solid residue to 0.90% and 0.0027%, respectively. Compared to direct chloride leaching, the combined process provided higher extraction efficiencies (Pb 98.67%, Ag 98.09%) and a lower final residue mass (34% vs. 45%). The roasting step enables the solid-state conversion of PbSO₄ into highly soluble chloride phases (PbCl₂ and Pb(OH)Cl), while ZnFe₂O₄, Fe₂O₃ and SiO₂ remain stable and form the inert matrix of the residue. Acid leaching at a lower solid-to-liquid ratio (1:10) ensures near-complete dissolution of Pb and Ag, whereas aqueous leaching at a high ratio (1:100) results in incomplete Pb removal. The compliance leaching test (EN 12457-2) confirmed that the residue produced after the optimized two-step treatment meets the EU criteria for inert waste. Overall, the proposed combined process enhances Pb and Ag recovery, minimizes environmental risk, and offers a technically robust and sustainable route for treating lead-containing industrial residues. Full article

The increasing demand for lithium and the limited availability of high-grade resources have accelerated interest in lithium-bearing clays as a promising alternative, despite their relatively lower lithium content. Lithium extraction from such clay minerals typically requires thermal treatment or acid leaching to disrupt the clay crystal lattice and enhance lithium solubility. The enrichment tailings from the Kırka Boron Processing Plant in Türkiye consist predominantly of dolomite-rich clay minerals and contain approximately 900–1200 ppm Li. Considering the substantial quantities of these tailings currently stored on-site, recovering lithium and converting these materials into a valuable resource would be of significant economic importance. However, due to their mineralogical composition, conventional acid leaching of these tailings demands relatively high sulfuric acid consumption (1.5–2.0 M H₂SO₄). This leads to excessively low solution pH and the generation of highly acidic waste streams, while also promoting the co-dissolution of iron (Fe) and aluminum (Al) ions at pH levels below 2, which negatively affects lithium recovery and downstream processing. In this study, mechanical activation was applied to the tailings prior to acid leaching. As a result, the acid requirement to achieve lithium extraction efficiencies of 90% and above was successfully reduced from 1.5 M to 1.0 M H₂SO₄. Moreover, solution pH was maintained near neutral (~7), and the undesirable dissolution of Fe and Al ions was effectively suppressed and kept under control. Full article

This study deals with the successful exploitation of easily available and renewable potato peel waste (PPW) as an excellent feedstock in the production of PHA using Ralstonia eutropha. The process entailed the extraction of bioactive components from PPW by use of solvent-based procedures and screening of their antioxidant and antidiabetic activity. The extracted PPW biomass was subject to acid hydrolysis using different concentrations of sulfuric acid for hydrolysis and solubilization of sugar components. The obtained liquid (acid) hydrolysates were initially assessed to biosynthesize PHA. Activated charcoal-based detoxification of acid hydrolysates was observed to be more efficient in promoting bacterial growth and accumulation of PHA. Acid-pretreated PPW biomass was further enzymatically hydrolysed to accomplish full saccharification and used to produce PHA. The effects of provision of nutrients and employing stress state conditions were assessed to improve bacterial growth and PHA accumulation. In both hydrolysates under optimal conditions, R. eutropha demonstrated the highest biomass productivity of 7.41 g/L and 7.75 g/L, PHA accumulation of 66% and 67% and PHA yield of 4.85 g/L and 5.19 g/L, respectively. XRD, FT-IR, TGA and DSC analysis of produced PHA were studied. The results showed that the produced PHA displayed similar physicochemical and thermal properties to commercially available PHB. Overall, this work illustrates the possibilities of abundantly available PPW, which can be transformed into bioactive compounds and high-value bioplastics via a coupled bioprocess. This approach can develop process economics and sustainability within a cyclic biorefinery system and serve further industry applications. Full article

This paper examined the effect of marble powder (MP) on air-cured cement-based materials when subjected to sulfuric acid (H₂SO₄) attack. Four MP replacement levels were tested: 0%, 5%, 10%, and 15% by weight of cement. The prepared samples were cured for 90 days prior to being exposed to H₂SO₄. Macroscopic tests for apparent density and compressive strength along with microstructural characterization using X-ray diffraction (XRD) and scanning electron microscopy (SEM) were performed to determine the effect of MP on the properties of the materials. The Rietveld method was used to analyze the amounts of different crystalline phases and amorphous calcium silicate hydrate (C-S-H). The obtained results indicate that 5% MP in air-cured cement -based materials exhibited the best behavior with acceptable resistance to acid attacks. This level of MP replacement was found to optimize the filler effect, improve the hydration process, and enhance the matrix density, which in turn reduces the permeability of the material and increases acid resistance. This is attributed to the balanced contribution of MP to phase formation, particularly calcite, which helps to counteract acid-induced dissolution, while also preserving the stability of C-S-H phases. This study provides a new perspective of the role of MP in influencing phase content (crystalline and amorphous phases) and their possible impacts on macroscopic properties such as apparent density and compressive strength. MP behaved as a filler, to improve hydration and resistance to acid attacks. Additionally, using MP as a replacement for ordinary Portland cement (OPC) offers a sustainable alternative by reducing waste and promoting the recycling of marble industry by-products, thereby contributing to environmental sustainability. It is recommended that, 5% MP is the optimal replacement content to enhance durability and mechanical properties in air-cured cement-based materials in aggressive environments, as it is both practical and achievable for infrastructure to be subjected to the aggressive environment. Full article

Lignin obtained in acidic conditions is a waste product in various technological processes like sulfite pulping, organosolv pulping, or bioethanol production. Knowing the structure of the lignin enables its use in high-value-added applications. In this paper, the lignin structure isolated from Pinus sylvestris L. and Populus deltoides × maximowiczii wood in acidic conditions was investigated. Two methods of lignin isolation (Klason method and a method using a sulfuric and phosphoric acid mixture) were compared. Additionally, lignin acetylation was performed. The lignin samples were analyzed using different instrumental techniques, such as size exclusion chromatography (SEC), attenuated total reflection–Fourier transform infrared spectroscopy (ATR-FTIR), and scanning electron microscopy (SEM). Based on the studies carried out, it was found out that the lignin isolated from pine and poplar wood in acidic conditions had a highly condensed structure. This was evidenced by the high-weight average molar mass of lignin (up to 118,700 g/mol) and the precipitates, aggregates, and agglomerates on its surface. Moreover, the characteristic signals of condensed lignin in ATR-FTIR analysis (band with wavenumber of 767 cm⁻¹) and their decrease/disappearance (band that usually occurs with a wavenumber of about 814 cm⁻¹) were observed. Lignin acetylation and analysis in the 0.5% LiCl/DMAc system have proven particularly effective in the case of the condensed poplar lignin. The beneficial effect of lignin acetylation was confirmed by SEM analysis. The high-molecular-weight condensed lignin, despite some of its problematic properties connected mainly with solubility, is a valuable substance that can be used for different applications (carbon fibers or as an additive for thermoplastic blends), which was confirmed by the studies in this paper and the findings of other scientists. Full article

Enhanced vanadium recovery from vanadium-bearing steel slag is essential in the sustainable use of metallurgical solid waste. This study uses microwave-assisted acid leaching on roasted clinker and systematically investigates it to enhance vanadium recovery; uses response surface methodology (RSM) to identify optimal parameters for leaching; and the influences of sulfuric acid concentration, leaching time, liquid-to-solid ratio (L/S ratio), and leaching temperature on vanadium dissolution are evaluated. The optimal leaching parameters are identified as an L/S ratio of 10:1, 41% sulfuric acid concentration, 65 min leaching time, and 92 °C leaching temperature, under which the highest vanadium extraction rate is 84.58%. Kinetic studies revealed that the leaching behavior during the initial 30 min followed a shrinking core model with fixed particle size. The vanadium microwave-assisted acid leaching process exhibited the observed activation energy (E_a) of 37.30 kJ·mol⁻¹, following a kinetic order of 1.5392 relative to sulfuric acid concentration, implying that ion transport across the solid phase formed during the reaction determined the step that limits the reaction rate. The semi-empirical kinetic equation established in this study accurately describes the leaching behavior under different conditions. This research establishes a theoretical framework and technical reference for boosting vanadium recovery from steel slag, which uses microwave-assisted leaching technology. Full article

The comprehensive utilization of hazardous waste may introduce heavy metals, organic pollutants, etc., into products, resulting in secondary pollution. The environmental risk assessment method for hazardous waste resource utilization products is an important technical means of environmental management. We have established a standardized method for hazard identification, exposure evaluation and risk characterization. This study selects waste sulfuric acid generated in the integrated circuit industry as the object and investigates the use of waste sulfuric acid to react with aluminum hydroxide to produce liquid aluminum sulfate flocculant, as well as the environmental risks brought to practitioners and the potential relevant population in the sewage treatment process. By analyzing sulfuric acid and aluminum hydroxide, toxic substances such as nitrate ions, fluorides, As, Pb, Cr, Hg, Cd, etc., were identified. Through exposure scenario analysis, the exposure levels of occupational and non-occupational populations were determined. Based on the dose–response relationship data in the IRIS database of the United States and the carcinogenic and non-carcinogenic data of skin contact routes, it was suggested that chromium and its compounds were the main contributors to carcinogenic risk, and cadmium, its compounds, and mercuric chloride were the contributors to the non-carcinogenic risk. The total carcinogenic risk to human health in occupational populations was 5.31 × 10⁻⁵, and the total non-carcinogenic risk was 8.80 × 10⁻¹. The total carcinogenic risk to human health in non-occupational populations was 1.73 × 10⁻¹⁵, and the total non-carcinogenic risk was 1.23 × 10⁻¹¹. Based on this research, it is clear that the production of liquid aluminum sulfate flocculants from waste sulfuric acid generated in the integrated circuit industry has a low impact on occupational and other populations during use, and the environmental risks generated by this product are acceptable even under the most dangerous conditions. Full article

Municipal solid waste incineration generates by-products like nitrogen oxides, sulfur dioxide, and hydrogen chloride, contributing to environmental issues such as acid rain, ozone depletion, and photochemical smog. While industrial sites use desulfurization and denitrification to reduce emissions, no studies have modeled the formation mechanisms and influencing factors of these pollutants from a pollution reduction perspective. This study first analyzes the municipal solid waste incineration process to identify the main factors affecting the concentration of pollutants related to desulfurization and denitrification. A coupled numerical simulation model for the whole life cycle desulfurization and denitrification process in real municipal solid waste incineration power plants is then constructed using a method that couples two software tools. Next, based on a double orthogonal experimental design, virtual simulation data are generated using the numerical simulation model. Finally, an improved interval type-II fuzzy broad learning algorithm is applied to construct a mechanism model for the whole process of desulfurization and denitrification-related pollutant concentration, using the obtained virtual simulated data. Using a Beijing incineration plant as a case study, the whole life cycle model is successfully established. The research provides data for optimizing pollutant reduction, examines influencing factors, and lays the groundwork for future intelligent control. Full article

The adsorptive removal of tetracycline (TC) in aqueous solution, a widely used antibiotic, was investigated using activated carbon derived from cotton textile waste. The valorization of textile waste provides a sustainable strategy that not only reduces the growing accumulation of discarded textiles but also supports a circular economy by transforming waste into efficient adsorbent materials for the removal pharmaceutical contaminants. This dual environmental and economic benefit underscores the novelty and significance of using cotton-based activated carbons in wastewater treatment. In this study, cotton textile waste was utilized as a raw material for the preparation of adsorbents via pyrolysis under nitrogen at 600 °C followed by chemical modification with H₂SO₄ solutions (1, 2, and 3 M). The sulfuric-acid modified-carbons (SMCs) were characterized by BET surface area analysis, FTIR spectroscopy and SEM imaging. Batch adsorption experiments were carried out to evaluate the effects of key operational parameters including contact time, initial TC concentration and solution pH. The results showed that the material treated with 2 M H₂SO₄ displayed the highest adsorption performance, with a specific surface area of 700 m²/g and a pore volume of 0.352 m³/g. The pH has a great influence on TC adsorption; the adsorbed amount increases with the initial TC concentration from 5 to 100 mg/L and the maximum adsorption capacity (74.02 mg/g) is obtained at pH = 3.8. The adsorption behavior was best described by Freundlich isotherm and pseudo-second-order kinetic models. This study demonstrates that low-cost and abundantly available material, such as cotton textile waste, can be effectively repurposed effective adsorbents for the removal of pharmaceutical pollutants from aqueous media. Full article

Fly ash from coal-fired power plants is a promising precursor for zeolite synthesis due to its aluminosilicate-rich composition. However, its direct utilization is often limited by impurities and a low silicon-to-aluminum ratio (SAR). This study demonstrates the conversion of Class C fly ash from the Soma thermal power plant (Turkey) into FAU- and CHA-type zeolites through optimized acid leaching and hydrothermal synthesis. Acid treatment increased the SAR from 1.33 to 2.85 and effectively reduced calcium-, sulfur-, and iron-bearing impurities. The SAR enhancement by acid leaching was found to be reproducible among Class C fly ashes, whereas Class F materials exhibited a limited response due to their acid-resistant framework. Subsequent optimization of alkaline fusion-assisted synthesis enabled selective crystallization of FAU and CHA, while GIS and MER appeared under prolonged crystallization or higher alkalinity. SEM revealed distinct morphologies, with MER forming rod-shaped clusters, and CHA exhibiting disc-like aggregates. Water sorption analysis showed superior uptake for metastable FAU (~23 wt%) and CHA (~18 wt%) compared to stable GIS and MER (~12–13 wt%). Overall, this study establishes a scalable and sustainable route for producing high-performance zeolites from industrial fly ash waste, offering significant potential for adsorption-based applications in dehumidification, heat pumps, and gas separation. Full article

This review examines the current status and future potential of plasma-induced acidification (PIA) as a sustainable method for managing nitrogen-rich organic waste streams such as livestock slurry and digestate. Conventional acidification using sulfuric or nitric acid reduces ammonia (NH₃) emissions but raises concerns related to safety, cost, and environmental impacts. Plasma-assisted systems offer an alternative by generating reactive nitrogen and oxygen species (RNS/ROS) in situ, lowering pH and stabilizing ammonia (NH₃), as ammonium (NH₄⁺), thereby enhancing fertiliser value and reducing emissions of NH₃, methane (CH₄), and odours. Key technologies such as dielectric barrier discharge (DBD), corona discharge, and gliding arc reactors show promise in laboratory-scale studies, but barriers like energy consumption, scalability, and N₂O trade-offs limit commercial adoption. The paper reviews the mechanisms behind PIA, compares it to conventional approaches, and assesses its agronomic and environmental benefits. Valorisation opportunities, including the recovery of nitrate-rich fractions and integration with biogas systems, align plasma treatment with circular economy goals. However, challenges remain, including reactor design, energy efficiency, and lack of recognition as a Best Available Technique (BAT). A roadmap is proposed for transitioning from lab to farm-scale application, involving cross-sector collaboration, lifecycle assessments, and policy support to accelerate adoption and realise environmental and economic gains. Full article

Bioplastics are plastics derived from natural resources like corn starch, biomass, sugarcane bagasse, and food waste. Unlike fossil-fuel-based plastics, they are entirely or partially bio-degradable. Cellulose- and starch-based bioplastics are already used for applications like packaging, cutlery, bowls, straws, and shopping bags. With the aim of developing eco-friendly biofilms for various applications, cellulose nanocrystals (CNCs) were obtained by sulfuric acid hydrolysis of waste cellulose and functionalized by transesterification with exhausted oils. The resulting transesterified nanocellulose (TCNC) was used as a reinforced material of PLA at different concentrations to develop biofilms using the solvent casting method. The biofilms composed of PLA and TCNC were assessed through Fourier-transform infrared spectroscopy (FTIR), mechanical properties, moisture barrier property (water vapor permeability rate—WVTR), and measurements of the water contact angle (WCA). A scanning electron microscopy (SEM) analysis confirmed the high compatibility of the PLA blended with TCNC at 1% and 3%. The inclusion of transesterified cellulose nanocrystals (TCNCs) to PLA increased the hydrophobicity, the film tensile strength, and the water vapor barrier properties of the final composite films. Full article

Serpentinite rocks and their processing waste represent a valuable source of magnesium and silicon; however, their complex composition complicates the efficient recovery of individual components. This study investigates the combined acid–alkali processing of serpentinite waste from the Zhitikara deposit (Kazakhstan). In the acid leaching stage, sulfuric acid enables magnesium extraction, while subsequent treatment with sodium hydroxide (NaOH) facilitates the selective recovery of silica gel formed during acid attack. At the final neutralization step, amorphous silica is precipitated with a yield exceeding 60% of its initial content. The obtained silica was characterized using FTIR spectroscopy, X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), inductively coupled plasma mass spectrometry (ICP-MS, Thermo iCAP-Q), and nitrogen adsorption measurements via the BET method. It was established that the synthesized silica gel, according to the IUPAC classification, belongs to mesoporous materials, possesses a well-developed specific surface area (400 m²·g⁻¹), and is suitable for adsorption and catalytic applications. Full article

Thiochromen-4-ones are known to possess useful optical properties and rich bioactivities, including antioxidant, antimicrobial, and anticancer properties. They are known to inhibit tumor cell growth, induce apoptosis, and have antiplatelet aggregation effects. Thiochromen-4-ones are also used as synthons and precursors in organic synthesis for bioactive agents. Although many synthetic approaches to oxygen-containing counterparts, chromones, have been reported, research on the synthesis of thiochromen-4-ones is scarce. The synthesis of thiochromen-4-ones can be challenging due to the inherent nature of sulfur, including its multiple oxidation states and tendency to form diverse bonding patterns. Here, we report the one-pot synthesis of thiochromen-4-ones, where two transformations of the starting material, 3-(arylthio)propanoic acid, are performed within a single reaction vessel, eliminating the need for an intermediate purification step. This one-pot reaction worked well with a variety of substrates with both electron-withdrawing and donating groups on the aromatic ring of 3-(arylthio)propanoic acids to give thiochromen-4-ones with good yields (up to 81%). This approach offers advantages like time and cost savings, increased efficiency, and reduced waste. This synthetic approach will allow access to a broader scope of thiochromen-4-ones due to the readily available thiophenols. Full article

This study was conducted to improve the heat performance of bitumen. The effect of eggshells on the performance of bitumen was investigated. Eggshell waste was ground and mixed with bitumen at 1%, 2%, and 3% by weight. Sulfuric acid was used as a catalyst for maximum interaction of eggshells with bitumen. The high heat performance and rutting resistance of modified bitumen formed at 160 °C were determined by the Dynamic Shear Rheometer (DSR) test. In addition, the low heat performance of modified bitumen was determined with the Bending Beam Rheometer (BBR) test. It was determined that the high heat performance of modified bitumen increased by 16.22% and the low heat performance (creep values) by 11.43% compared to pure bitumen. In addition, it was determined that the rutting resistance values of modified bitumen increased compared to pure bitumen. Full article