Search Results (376)

Selective recovery of gold from cyanide leach liquors is hindered by the co-dissolution of iron minerals that generate ferrocyanide complexes which strongly compete with [Au(CN)₂]⁻ at ion-exchange sorbents. Here, we investigate mixed-bed interpolymer systems (IPS) composed of a strong-acid sulfonated polystyrene–divinylbenzene cation exchanger (TC007, Na⁺ form) and a strong-base quaternary ammonium anion exchanger (AV-17-8, Cl⁻ form) as a charge-selective platform for gold cyanide recovery. IPS compositions spanning cation-to-anion molar ratios from 6:0 to 0:6 were evaluated in batch contact with binary model solutions containing 30 mg L⁻¹ each of [Au(CN)₂]⁻ and [Fe(CN)₆]⁴⁻ at pH 10 and 25 °C. The optimal 1:5 IPS achieved an [Au(CN)₂]⁻ extraction degree of 79.88% and a selectivity coefficient β = D_Au/D_Fe = 4.95 at 48 h, whereas the pure AV-17-8 anion exchanger (0:6) reached only 37.55% Au extraction at 48 h, following an atypical delayed-uptake kinetic profile rather than the rapid, near-quantitative capture expected of an unmodified strong-base resin. Sorption kinetics were best described by a pseudo-second-order model (R² = 0.9992), confirming ion exchange at quaternary ammonium sites as the dominant rate-controlling step, with a ~30-fold increase in k₂ for [Au(CN)₂]⁻ in the 1:5 IPS relative to AV-17-8 alone. FTIR spectroscopy and TGA-DSC revealed the incorporation of metal cyanide complexes into the IPS matrix, with diagnostic C≡N stretching bands at 2108.7 and 2034.1 cm⁻¹ and an additional thermal event at 200–280 °C. These findings establish compositionally tunable IPS based on commercially available resins as a charge-selective sorbent platform demonstrating a capacity to regenerate under single-cycle elution conditions for gold cyanide recovery from ferrocyanide-containing process streams while highlighting the need for further evaluation under industrial Fe:Au ratios. Full article

Calcium-rich industrial wastes may serve as low-cost sorbents for near-source CO₂ capture, but their practical potential depends on the reactive calcium species and cyclic stability. This study compares steel slag (SS), air pollution control residue (APCr), and cement kiln dust (CKD) under controlled thermogravimetric analysis (TGA) conditions for direct gas–solid carbonation and calcination looping. X-ray diffraction identified Ca(OH)₂ in SS, CaClOH in APCr, and calcite-derived CaO in the calcined CKD as the principal reactive calcium species, corresponding to theoretical CO₂ sequestration capacities of 117.0, 58.2, and 365.2 g CO₂ kg⁻¹ waste, respectively, based on the reference intensity ratio method. After the isothermal carbonation for 1 h, experimental carbon sequestration capacities or CO₂ uptakes were 84, 39, and 201 g CO₂ kg⁻¹ waste, equivalent to conversion rates of 71.8, 67.0, and 55.0%. The CO₂ uptake curves showed that the carbonation kinetics of these wastes obeys a two-stage regime featuring an initial rapid carbonation stage followed by a slower one restricted by the product-layer diffusion of CO₂. Among the investigated industrial wastes, CKD exhibited the highest cyclic uptake of CO₂ and the lowest observed cyclic deactivation, whereas the lower cyclic performance of SS and APCr was largely limited by the calcium encapsulation and chloride-induced high-temperature sintering, respectively. This study provides an alternative solution for the valorization of industrial solid waste according to the “waste-for-waste” concept. Full article

Steam gasification of woody waste represents a sustainable pathway for addressing environmental issues with energy recovery. However, challenges such as low hydrogen content and high tar yield severely limit the gasification efficiency and hinder its large-scale application. In this study, a composite Ni/CaO catalyst was developed to enhance the yield of H₂-rich syngas in woody waste gasification, with Ni loading serving as the active site for catalytic cracking and CaO support as the CO₂ sorbent for sorption-enhancement. Ni nanoparticles ranging from 18 to 28 nm in diameter are uniformly distributed on the CaO support. At 700 °C, Ni/CaO with 10 wt.% Ni loading enables the 455.4 mL/g H₂ yield with an H₂/CO ratio of 1.93, representing increases of 137% and 230%, respectively, compared to non-catalytic conditions. Meanwhile, the tar yield was 12.1 wt.% with an aromatics selectivity of 37%, corresponding to reductions of 50.2% and 54%, respectively. Characterizations confirmed that Ni particles were uniformly distributed on the support in the form of metallic Ni. The Ni active sites promote syngas production by facilitating the cleavage of C-C and C-H bonds in volatiles, while the CaO support enhances H₂ generation by shifting the water–gas shift reaction equilibrium forward. This study provides a promising strategy for enhancing hydrogen-rich syngas production from woody waste gasification. Full article

The growing volume of crustacean shell waste generated during seafood processing poses a serious environmental problem. However, this type of biowaste remains underutilized, despite being a promising renewable raw material for the production of functional carbon materials. This study aims to investigate how synthesis parameters influence the formation of a hierarchical porous structure in shrimp shell-based carbon materials and to optimize these parameters to improve CO₂ adsorption efficiency. Under optimal carbonization conditions (holding time: 2 h; temperature: 650 °C) and activation conditions (holding time: 2 h; temperature: 750 °C) with activator-to-carbon weight ratios (A/C) of 1/1, 2/1 and 4/1, the resulting porous carbon samples exhibited relatively high S_BET values (1175, 2708 and 3052 m²/g, respectively) and V_T (0.70, 1.55 and 2.60 cm³/g, respectively), as well as different pore size distributions. Notably, the resulting carbon materials demonstrated exceptional CO₂ adsorption performance at 298 K, reaching a maximum adsorption capacity of 40.03 mmol/g at 40 bar for sample SS_652_41752, 15.12 mmol/g at 15 bar for SS_652_21752, and 3.41 mmol/g at 1 bar for SS_652_11752. These values rank among the highest ever reported for biomass-derived porous carbon materials. The adsorption behavior of the most efficient sorbent, SS_652_41752, was further analyzed using Langmuir and Freundlich isotherm models over the temperature range of 298–318 K and at pressures up to 40 bar, and the isosteric heats of adsorption were calculated to elucidate adsorbent–adsorbate interactions. It was found that the differential molar isosteric heat of CO₂ adsorption decreased from approximately 20 to approximately 17 kJ/mol with increasing adsorption uptake, confirming the physisorption nature of the process. These results demonstrate that crustacean shell waste is a promising feedstock for producing carbon materials with tailored properties and significant potential for CO₂ adsorption applications. Full article

Multimetallic layered double hydroxides (LDHs) are promising oxyanion sorbents, but their practical use requires evaluation of sorption efficiency and chemical stability. This study examined how introducing Cu²⁺ and Zn²⁺ into the LDH structure affects As(V) sorption, comparing binary Mg₃Al₁ and four-component Mg₂Cu_0.5Zn_0.5Al₁ in carbonate and chloride forms. The materials were synthesised by the co-precipitation method and characterised using XRD, FTIR, SEM, BET, and XPS, while their layer metal composition was determined by ICP-OES. The sorption studies were supplemented by chemical stability analysis (pH 4–11) and As(V) desorption experiments. Equilibrium data were evaluated using the Redlich–Peterson isotherm model. The four-component LDH showed higher As(V) sorption capacity than the conventional MgAl system, with the best performance observed for chloride forms: 37.5 mg/g for MgCuZnAl-LDH and 22.5 mg/g for MgAl-LDH. The sorption kinetics are well described by the pseudo-second-order and Elovich models, indicating a significant contribution from chemisorption. The results suggest that As(V) removal involves the combined action of anion exchange, electrostatic interactions and inner-sphere complex formation, controlled by the composition of the LDH layer and the type of interlayer anion. The introduction of Cu²⁺ and Zn²⁺ promoted additional active sites and stronger As(V) surface interactions. The results indicate that MgCuZnAl-LDH, particularly in the chloride form, exhibits promising As(V) sorption performance under model conditions involving a single solute. Full article

Chili products are vulnerable to the addition of unauthorized substances, including Sudan dyes, Rhodamine B, Basic Orange 2, poppy-derived materials and improperly used processing chemicals. Their analysis is complicated by the high contents of lipids, carotenoids, capsaicinoids and other co-extracted matrix components in chili powder, chili oil, chili sauce and composite seasonings. This review critically evaluates conventional and emerging sample-preparation strategies, including solid-phase extraction; the quick, easy, cheap, effective, rugged and safe (QuEChERS) procedure; deep eutectic solvent (DES)-assisted extraction; enhanced matrix removal for lipids (EMR-Lipid); and molecularly imprinted sorbents. Laboratory methods based on high-performance liquid chromatography (HPLC), liquid chromatography–tandem mass spectrometry (LC–MS/MS) and gas chromatography–mass spectrometry (GC–MS) are compared with enzyme-linked immunosorbent assay (ELISA), surface-enhanced Raman spectroscopy (SERS), electrochemical sensors, miniature mass spectrometry and artificial intelligence-assisted hyperspectral imaging (AI–HSI). The comparison considers representative limits of detection and quantification, recovery, precision, sample-preparation burden, cost, portability, validation status and regulatory role. LC–MS/MS remains the preferred confirmatory platform for targeted multi-residue analysis, whereas rapid and portable methods are more appropriate for screening and sample triage. A three-tier workflow linking rapid screening, laboratory confirmation, and emerging-risk identification and traceability is proposed. Future priorities include standardized chili reference materials, open AI training and validation datasets, greener DES-based extraction and interlaboratory validation of field-deployable methods. Full article

Understanding indoor and outdoor airborne organic mixtures, including semi-volatile organic compounds (sVOCs), remains challenging as quantitative monitoring is often costly and difficult to scale across buildings and individuals. Here we present a low-cost, miniaturised passive sampler-based methodology for static and wearable deployment to generate time-integrated chemical fingerprints and source prioritisation. New sampler devices containing replicate 9 mm sorbent discs (Tenax^® TA and/or polydimethylsiloxane) were deployed for 28 days in indoor (kitchen, bedroom) and outdoor (roadside) environments and worn by five participants; extracts were analysed by liquid extraction and gas chromatography–mass spectrometry (GC-MS) using conservative, transparent criteria for tentative compound identification. Across the household deployments, 52 compounds met inclusion criteria and distinct room-specific and outdoor chemical signatures were observed. Wearable deployments also produced differentiable chemical profiles, with greater similarity among co-inhabitants, but still could differentiate co-habitant activities based on exposure. These results demonstrate the feasibility of using miniature passive samplers to obtain reproducible, information-rich profiles that can help discriminate environments and exposure scenarios. Full article

This study investigated carbonaceous materials prepared from Paulownia tomentosa leaves by hydrothermal carbonization, slow pyrolysis, and HCl post-treatment for the adsorption of metribuzin and tebuconazole from water. Hydrochars were prepared at 180–220 °C, pyrochars at 400–600 °C, and the pyrochar produced at 600 °C was further treated with HCl. The materials were characterized by yield, ash content, active and exchangeable pH, oxidizable organic carbon content, FTIR, SEM, and CO₂-derived surface and pore properties. Increasing processing temperature reduced the yield in both conversion routes. Hydrochars retained more oxygen-containing and oxidizable organic structures, whereas pyrochars showed stronger carbonization, higher ash content, and higher CO₂-derived surface area. HCl treatment decreased the ash residue, thereby resulting in improved CO₂-accessible surface and pore properties and more fragmented morphology. Metribuzin adsorption was better described by the pseudo-second-order kinetic model across all sorbents, with the highest fitted equilibrium adsorbed amount observed following HCl treatment. Tebuconazole showed higher initial uptake toward most untreated materials, but its kinetic profiles were non-monotonic, with a decrease in the adsorbed amount at longer contact times. Consequently, the conventional PFO and PSO models did not adequately describe its complete kinetic behavior. Nonlinear isotherm modeling showed predominantly Freundlich-type fitting for metribuzin, suggesting heterogeneous adsorption sites, whereas tebuconazole was formally better described by Langmuir-type fitting, although with poorer fit quality for several materials. The results show that Paulownia tomentosa leaves are a suitable precursor for carbonaceous sorbents and that HCl-treated pyrochar is the most promising material for metribuzin adsorption. Full article

Carbon dioxide (CO₂) capture through adsorption using porous materials has emerged as a promising strategy for mitigating industrial greenhouse gas emissions. However, selecting an optimal adsorbent material under varying operating conditions remains a complex and time-consuming process when relying solely on experimental studies. In this project, a machine-learning-based framework is developed to predict CO₂ adsorption capacity and identify the most suitable adsorbent material using process and material parameters. A comprehensive dataset was constructed comprising multiple classes of adsorbent materials including activated carbon, zeolites, metal–organic frameworks (MOFs), porous organic polymers (POPs), alumina/silica, and amine-functionalized sorbents. The dataset includes key parameters such as temperature, pressure, CO₂ mole fraction, humidity, BET surface area, micropore characteristics, amine loading, heat of adsorption, particle density, pellet diameter, and bed void fraction. Two machine learning models based on the XGBoost algorithm were implemented. An XGBoost Regressor was used to predict the experimental CO₂ adsorption capacity, while an XGBoost Classifier was trained to identify the type of adsorbent used based on the input parameters. The models were trained and validated using a train–test split approach to ensure reliable performance evaluation. The results demonstrate that gradient boosting models can accurately capture complex nonlinear relationships between adsorption conditions, material properties, and adsorption performance. The developed framework provides a fast and efficient predictive tool that can assist researchers and engineers in screening adsorbent materials and optimizing CO₂ capture systems for industrial applications. Using this model, one can predict the adsorption capacity of any adsorbent used in the training dataset and predict its type with 95% accuracy. Full article

Thorium (Th) is increasingly considered a promising fertile material for sustainable nuclear energy—which is not fissile itself, but convertible to fissile ²³³U—particularly as a by-product of rare earth element (REE) processing. This study develops a parametric techno-economic assessment (TEA) framework synthesizing published data from China, Russia, the USA, India, and Europe to establish the methodological foundation for evaluating thorium recovery economics from monazite ores and REE tailings under Central Asian conditions. Monazite typically contains 4–12% ThO₂, while tailings contain 0.1–3%, making secondary resources attractive for future recovery strategies. Particular attention is given to integration with uranium tailings and the application of advanced materials such as nanocomposite sorbents and carbon-based electrodes. Reported production costs of ThO₂ range from 50 to 500 USD/kg depending on process scale, feedstock quality, and co-production of REEs. The reviewed studies consistently show that coupling thorium recovery with REE processing improves economic feasibility. Modern approaches, including hybrid technologies and electrosorption systems, may reduce operational costs and improve process efficiency. Despite challenges related to capital investment, market uncertainty, and radioactive waste management, thorium continues to attract growing interest as a potential component of future nuclear fuel cycles and advanced reactor systems, including small modular reactors. To the best of the authors’ knowledge, this is the first parametric TEA framework structured around Central Asian conditions, combining literature-derived regional data, scenario-based process economics, and Monte Carlo sensitivity analysis within a single discounted cash flow structure. Full article

Amid growing pressure to reduce carbon emissions, carbon capture, utilization, and storage (CCUS) has become an important pathway toward deep decarbonization. However, the conventional separated “capture–release–conversion” process suffers from high energy consumption and system complexity, which severely limits its large-scale application. Integrated CO₂ Capture and Utilization (ICCU), which enables the capture, activation, and conversion of CO₂ within a single system, has attracted widespread attention because it can effectively reduce intermediate energy-intensive steps and improve carbon utilization efficiency. This review systematically summarizes recent progress in ICCU technology, with particular emphasis on reaction mechanisms and interfacial coupling characteristics. The performance features of solvent-based chemical absorption and solid-sorbent adsorption, two widely studied capture routes, are summarized, and typical integrated conversion pathways, including reverse water–gas shift, methanation, and dry reforming of methane, are discussed. On this basis, the roles of non-conventional energy-assisted strategies, such as photocatalysis, electrocatalysis, non-thermal plasma, and microwave irradiation, in expanding ICCU systems are further examined, together with their system-level coupling potential in carbon-intensive industries such as steel, cement, and power generation. Finally, the key scientific issues and engineering challenges currently facing ICCU are analyzed from the perspectives of fundamental mechanisms, material design, and system engineering, and future development directions are proposed. This review highlights that elucidating multiscale synergistic mechanisms, developing high-performance dual-function materials, and optimizing system integration are crucial to promoting the industrial application of ICCU technology. Full article

Contamination of water bodies by emulsified gasoline hydrocarbons, particularly BTEX compounds (benzene, toluene, ethylbenzene, and xylenes), represents a critical environmental challenge due to their toxicity and resistance to conventional treatment methods. In this study, carbonized biosorbents derived from rice husk (CRH) and walnut shell (CWS) were developed for efficient removal of emulsified gasoline from water. The materials were prepared via carbonization under CO₂ atmosphere (300–800 °C), enabling simultaneous carbonization and activation. Structural and surface properties were characterized using Brunauer–Emmett–Teller (BET) analysis, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray fluorescence spectroscopy (XRF). The results demonstrated a strong dependence of adsorption performance on carbonization temperature, with maximum removal efficiencies of 90.2% (CRH-600) and 96.5% (CWS-700). The superior performance of CWS-700 was associated with its highly developed hierarchical pore structure (up to 670 m² g⁻¹), increased carbon content, and enhanced hydrophobicity. Kinetic studies revealed pseudo-second-order behavior, with equilibrium achieved within 25–30 min at near-neutral pH. Gas chromatographic analysis confirmed the complete removal of BTEX and light hydrocarbons (C1–C9) using CWS-700, highlighting its high selectivity toward aromatic compounds. The adsorption mechanism was attributed to the synergistic effect of micropore filling, hydrophobic interactions, and π-π interactions with aromatic hydrocarbons. The obtained results demonstrate that biomass-derived carbon materials, particularly walnut shell-based sorbents, are promising low-cost candidates for the treatment of complex water systems contaminated with emulsified petroleum hydrocarbons. Full article

The rapid increase in atmospheric ${\mathrm{CO}}_2$ concentration has made carbon capture an essential strategy for mitigating climate change. This review systematically summarizes ${\mathrm{CO}}_2$ capture technologies following the complete process chain. First, three major routes based on combustion stages are introduced: pre-combustion (e.g., coal gasification, biomass co-firing), combustion-based (oxy-fuel combustion and chemical looping combustion), and post-combustion capture. For post-combustion capture, which is the most widely applicable to existing emission sources, three core separation methods are further elaborated: absorption (amine blends, ionic liquids, deep eutectic solvents), adsorption (zeolites, activated carbon, MOFs, COFs, solid amine sorbents), and membrane separation (polymeric, inorganic, and mixed matrix membranes). Key strategies for performance enhancement—such as functionalization, pore engineering, and composite systems—are highlighted. Despite significant advances, large-scale deployment remains challenged by high costs, high energy consumption, and inadequate material stability. Future research should prioritize low-cost, energy-efficient, and robust capture materials and processes to enable net-zero and negative carbon emissions. Full article

Solid amine adsorbents can capture CO₂ at indoor-relevant concentrations (~1000 ppm), but many high-capacity adsorbents rely on granular or powdery supports that are difficult to integrate directly into air purification systems. Here, we applied three amination strategies to commercial fibrous substrates: bridge-grafting on viscose (TEPA-AMVF), direct grafting on polyacrylonitrile (TEPA-PAN), and physical impregnation on pore-engineered activated carbon fibre felt (PEI-ACF). These adsorbents were systematically screened under simulated indoor conditions (1000 ppm CO₂, 27 °C, 50% RH). A significant capacity difference was observed: TEPA-AMVF (24.8 mg g⁻¹) < TEPA-PAN (35.8 mg g⁻¹) ≪ PEI-ACF (97.0 mg g⁻¹). The superior performance of PEI-ACF was attributed to KOH activation, which produced a mesopore-rich structure (average pore diameter 26.1 nm at an optimal KOH/carbon ratio of 1.25) and enabled high nominal amine utilisation (0.19 mmol CO₂ mmol N⁻¹). PEI-ACF maintained high breakthrough-derived CO₂ uptake across realistic indoor conditions (64.2–118.6 mg g⁻¹ over 0%–100% RH; 71.6–124.5 mg g⁻¹ over 400–5000 ppm CO₂), exhibited rapid kinetics (pseudo-first-order rate constant k = 1.77 h⁻¹; 81.7% of equilibrium uptake within 1 h), and showed stable but partial regeneration over four adsorption–desorption cycles at 60–70 °C under N₂. Compared with granular or resin-based amine sorbents, the self-supporting PEI-ACF felt is expected to offer practical advantages for filter-integrated CO₂ removal, including mechanical integrity under airflow, reduced risk of particle leakage, and compatibility with HVAC filter slots. Remaining challenges include direct pressure-drop validation, operation in O₂-containing indoor air, long-term cycling, and management of CO₂ released during regeneration. Full article

The combustion of candles is known to emit various air pollutants, including particulate matter (PM) and volatile organic compounds (VOCs), into the air. This study characterizes emissions of these pollutants from natural and synthetic candles in a standard, sealed, unventilated residential environment. In addition, computational fluid dynamics (CFD) modeling was used to study the potential effects of inlet air velocity on a paraffin candle flame. A laminar diffusion flame model simulated the distributions of temperature, CO₂, and H₂O. A Testo DiSC mini air sampler was used for ultrafine particles and Lung-Deposited Surface Area (LDSA) data collection, and a CEM DT-9881 sampler was used for recording larger particle number concentrations, temperature, and relative humidity. VOC sorbent tubes were used for the collection of individual and total VOCs. Study findings showed that natural candles produced significantly (p < 0.05) higher LDSA ranges (mean 195.2 µm²/cm³) and ultrafine particle concentrations (mean 8.4 × 10¹¹ No/m³), while paraffin wax synthetic candles exhibited higher 0.3–10 µm PM concentrations (mean 2.0 × 10⁷ No/m³). CFD modeling showed that increasing air velocity produced a shorter, more compact flame and reduced CO₂ and H₂O mass fractions due to enhanced mixing and aerodynamic dilution, highlighting the strong interaction between airflow, temperature, and product formation in laminar paraffin flames. Full article