Search Results (502)

High-purity quartz is an important raw material for strategic emerging industries, including photovoltaics and semiconductors. To improve the deep removal of impurities from granitic-pegmatite quartz and clarify the effects of calcination–water quenching, a quartz concentrate from the East Qinling Mountains was selected as the feed material. Calcination–water quenching, HF–HCl–HNO₃ mixed-acid leaching, and chlorination roasting were systematically investigated. The results showed that calcination temperature markedly affected quartz-sand whiteness and the occurrence of residue-like surface attachments. Treatment at 900 °C substantially reduced these attachments and enhanced subsequent acid-leaching efficiency. At final HF, HCl, and HNO₃ concentrations of 1, 2, and 1 mol/L, respectively, Al, Ca, Fe, K, Na, and other impurities were effectively removed, reducing the total concentration of 15 impurity elements to 19.43 μg/g. The inclusion area fraction decreased from 0.97% to 0.38%. Subsequent chlorination roasting at 900 °C further reduced the total impurity concentration to 17.26 μg/g, increased the nominal SiO₂ purity to 99.9982%, and decreased the inclusion area fraction to 0.31%. These results demonstrate the potential of East Qinling granitic-pegmatite quartz as a feedstock for photovoltaic-grade high-purity quartz sand. Full article

Carbonaceous gold ores are difficult to process due to the preg-robbing effect of carbonaceous matter and the encapsulation of gold within gangue minerals. In this study, fluidized bed oxidation roasting in a controlled O₂/CO₂ atmosphere (O₂:CO₂ ratio of 1:4 and a total flow rate of 2 L/min) was proposed as a pretreatment to enhance gold leaching from a refractory carbonaceous gold ore. The effects of roasting temperature on phase transformation, carbon removal, sulfur fixation, microstructure, porosity, gold dissociation, and leaching efficiency were systematically investigated through XRD, SEM, BET, and chemical phase analysis. The results demonstrated that roasting at 650 °C achieved efficient carbon removal (94.04%) and sulfur fixation (73.60% as anhydrite), while simultaneously inducing the thermal decomposition of carbonates and silicates, which generated a highly porous structure with an enlarged average pore diameter of 27.1 nm. These synergistic transformations liberated gold from its encapsulating matrix, increasing the proportion of exposed gold from 28.85% to 84.10% and yielding a maximum gold leaching efficiency of 80.26%. However, excessive temperature (700 °C) led to sintering and pore collapse, reducing the leaching efficiency to 73.87%. This study demonstrates that fluidized bed roasting in a controlled O₂/CO₂ atmosphere is a promising pretreatment strategy for refractory carbonaceous gold ores, though further optimization of roasting parameters is needed to improve gold recovery. Full article

This study investigated the effects of roasting temperature (130 °C, 150 °C, 180 °C) and grinding fineness (10, 50, and 100 mesh) on the nutritional quality and physicochemical properties of high-resistant starch rice flour (Youtangdao 3). The results revealed that the process of whole-grain moist roasting, followed by milling and sieving, markedly enhanced the resistant starch (RS) content while concurrently reducing the fraction of rapidly digestible starch (RDS). Specifically, roasting at 130 °C with coarse grinding (R130-10) yielded the highest absolute RS content (27.45 g/100 g). However, for fine-particle fractions essential for food texture, roasting at 150 °C (R150-100) proved optimal by achieving the highest RS proportion within the starch matrix (89.36% by Englyst method). Structural analysis via X-ray diffraction (XRD) and scanning electron microscopy (SEM) revealed that roasting facilitated the reorganization of starch chains. This molecular rearrangement led to a pronounced increase in crystallinity and induced distinct morphological alterations within the granules. Furthermore, Rapid Visco Analyzer (RVA) profiling indicated a substantial decline in peak viscosity for all roasted samples, indicating a significant loss of pasting ability and an increase in structural rigidity. In conclusion, the combination of moderate roasting temperature and precise particle size control effectively optimizes the nutritional value of high-RS rice flour. These insights provide a theoretical basis for developing high-RS rice flour ingredients. Full article

The reserves of non-refractory gold ores are continuously declining, while refractory gold ore deposits remain abundant. Therefore, developing more efficient technologies to utilize these ores is crucial for gold-related industries. Oxidation roasting is commonly used to eliminate the adverse effects of sulfur- and arsenic-bearing minerals, but its underlying mechanisms are still not fully understood. To address this gap, the present study investigated the effect of oxidation roasting on gold leaching rate. A combination of roasting–leaching experiments, X-ray diffraction (XRD), pore structure analysis, and scanning electron microscopy (SEM) was employed to examine the evolution of surface pore structures and their impact on leaching performance. The gold leaching rate of the raw material was only 10.13%, due to the encapsulation of gold particles within pyrite. Under optimal roasting conditions—600 °C for 2 h—the gold leaching rate reached a peak value of 88.06%. At this temperature, the dense surface of pyrite decomposed, forming a highly porous structure that allowed the JinChan lixiviant to fully contact the gold particles. However, increasing the roasting temperature or extending the roasting time promoted the formation of CaSO₄ and Mg₂SiO₄. These newly formed phases may have contributed to pore blockage on the hematite surface, which could explain the more compact structure and the subsequent decline in gold extraction. Based on these observations, a possible mechanism is proposed linking pore structure evolution and phase transformation during roasting to the leaching performance. Full article

To explore coffee’s effect on sweet rice wine quality, this study developed a novel fermented beverage using round glutinous rice and coffee powder as raw materials. The fermentation process was optimized using an orthogonal array design combined with fuzzy comprehensive evaluation. Flavor, physicochemical properties, and antioxidant activities were systematically evaluated via electronic tongue (E-tongue), gas chromatography–mass spectrometry (GC-MS), and gas chromatography–ion mobility spectrometry (GC-IMS). The optimal fermentation parameters were 0.6% fermentation starter (Jiuqu), 10% coffee powder, a fermentation time of 56 h, and a temperature of 28 °C. Adding coffee powder significantly increased total flavonoid content. Compared to the control group, the scavenging activities against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS⁺), as well as hydroxyl radicals, increased by 18.36%, 7.40%, and 10.96%, respectively, compared to the control group. Flavor analysis identified 173 volatile organic compounds, demonstrating strong complementarity between GC-MS and GC-IMS. The addition of coffee powder preserved traditional sweet rice wine components while introducing roasted heterocyclic compounds, such as 2-methylpyrazine and 2-ethylfuran, thereby imparting nutty and roasted characteristics. E-tongue analysis revealed enhanced sensor responses for sweetness, bitterness, and saltiness, along with decreased umami. In conclusion, the addition of coffee powder is an effective strategy to enhance the in vitro antioxidant activity and enrich the flavor profile of sweet rice wine. This study provides a scientific basis for the application of coffee in traditional fermented foods. Full article

Vanadium slag is an important secondary vanadium resource. Although microwave-assisted calcification roasting improves the leachability of vanadium-bearing phases, further extraction can still be limited during acid leaching, making optimization of the leaching process essential for efficient vanadium recovery. Using this slag, leaching was evaluated at different temperatures, times, liquid-to-solid ratios (L/S), sulfuric acid concentrations, and agitation speeds. A Box–Behnken design (BBD) was used to optimize leaching parameters within the selected ranges. Residue phase composition and microstructure were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). Leaching efficiency increased with temperature, L/S, and acid concentration, but plateaued above 60 °C, 6 mL·g⁻¹, and 14 wt.%, respectively; increases beyond 50 min or 200 rpm gave marginal improvements. Analysis of variance (ANOVA) of the BBD model ranked the statistical effects of the four linear terms within the investigated BBD range as sulfuric acid concentration > L/S > leaching time > temperature. Within the selected BBD parameter ranges, optimization yielded 64.95 °C, 55.21 min, 6.56 mL·g⁻¹, and 15.17 wt.% sulfuric acid, with agitation fixed at 200 rpm. Validation gave an average leaching efficiency of 92.92%, with a relative error of 0.205% compared with the model prediction. After leaching, Mn₂V₂O₇ was undetected. The residue mainly contained irregular particles, 10–30 μm acicular or plate-like CaSO₄·2H₂O crystals, and minor residual vanadium-bearing CrVO₃ and CaVH₂Si₄O₁₂ phases. Surface CaSO₄·2H₂O deposition and refractory-phase encapsulation of vanadium-bearing constituents increased mass-transfer resistance and limited further leaching. This study clarified the relative effects of the investigated leaching conditions on vanadium leaching efficiency within the design range and the interactions among these conditions, and provided microstructural evidence related to the factors limiting further vanadium leaching, thereby providing theoretical guidance for the efficient extraction of vanadium from vanadium slag. Full article

The beneficiation of ferruginous manganese ores is limited by the intimate intergrowth of manganese-, iron-, and silicate-bearing phases. This study evaluated coal-based magnetizing roasting followed by dry magnetic separation in an externally heated chamber furnace with a charge capacity of up to 100 kg. A 0–5 mm ore fraction with an initial Mn/Fe ratio of 2.9 was roasted with Shubarkol coal. The best separation was obtained at an actual ore–coal bed temperature of 550–600 °C and an ore-to-coal mass ratio of 1:0.4. Relative to the magnetic-separation feed, 80.0–83.4% of Fe was recovered in the magnetic fraction, while 69.9–72.6% of Mn remained in the non-magnetic product. Its Fe content decreased to 3.2–3.5%, increasing the Mn/Fe ratio to 7.30–7.84. X-ray diffraction showed preferential concentration of magnetite and jacobsite in the magnetic fraction, whereas hausmannite and braunite were concentrated mainly in the non-magnetic fraction together with the gangue phases. Multipoint measurements also demonstrated a substantial difference between the combustion-zone and actual bed temperatures. The results demonstrate that controlled low-temperature roasting can generate sufficient magnetic contrast for selective iron removal from ferruginous manganese ore. Full article

Continuous carbon anode roasting in industrial parks requires a stable high-temperature heat supply and remains highly dependent on grid electricity and natural gas. However, existing energy-system studies rarely coordinate hydrogen production and storage, volumetric hydrogen blending, and temperature-graded waste-heat recovery under continuous production constraints. To address this gap, this study proposes an electricity–heat–gas–hydrogen integrated energy system for carbon anode industrial parks and develops a 24 h multi-objective scheduling model. The model coordinates heat demands at different temperature levels with hourly electricity and hydrogen flows, using surplus photovoltaic power to produce hydrogen for later high-load periods. The selected scheme achieves a daily volumetric hydrogen-blending ratio of 10.79%, with an operating cost of 82,985.75 CNY and carbon emissions of 54,371.53 kg. Relative to an otherwise equivalent non-hydrogen configuration, hydrogen coupling provides additional reductions of 7.2% in operating cost and 2.3% in carbon emissions. Compared with a basic conventional configuration, operating cost and carbon emissions decrease by 27.9% and 26.0%, respectively. Cascade recovery also increases the daily waste-heat utilization rate by approximately 30 percentage points. These results show that the proposed scheduling framework can coordinate hydrogen utilization and graded waste-heat recovery while maintaining continuous carbon anode production. Full article

Prunus tangutica is an underused wild nut of the Chinese highlands. Its kernels are rich in polyphenols and flavonoids but also contain amygdalin, so debittering must precede roasting, and how the two steps act together is not known. This study determined the effects of debittering and of roasting temperature and time on the bioactive components, antioxidant capacity and volatile profile of P. tangutica kernels from Diebu, Gansu Province, roasted at 100–180 °C for 10–30 min. Debittering markedly reduced polyphenols (from 0.21–0.36 to 0.09–0.27 mg GAE/g) and flavonoids (from 0.57–1.87 to 0.10–0.63 mg RE/g). Both declined as temperature and time increased, whereas antioxidant capacity rose under intense roasting. FRAP peaked at 180 °C/20 min in non-debittered samples and DPPH radical-scavenging activity at 180 °C/30 min in debittered samples, suggesting that Maillard reaction products may partially offset the loss of native antioxidants. Roasting strongly promoted pyrazine formation (2,5-dimethylpyrazine rose from 28.77 to 3909.28 µg/kg) but also increased benzaldehyde and benzyl cyanide, the thermal degradation products of amygdalin, at 180 °C/30 min. Of the conditions tested, 160 °C/30 min was the most suitable for debittered kernels, and 120 °C/30 min was the most suitable for non-debittered kernels; no condition is proposed for the direct consumption of non-debittered kernels, because residual cyanogenic compounds were not quantified. Full article

High-temperature chlorination roasting is a critical technique for achieving ultra-high-purity quartz required in semiconductor, photovoltaic, and fiber-optic applications. However, the removal mechanisms of lattice-bound impurities remain poorly understood due to a lack of integrated thermodynamic and kinetic analysis. This study systematically investigates the removal behavior of seven key lattice impurities, namely Ti, Al, B, Fe, Li, Na, and K, during chlorination roasting using combined thermodynamic modeling and diffusion kinetics. Thermodynamic calculations reveal that carbonaceous reductants are indispensable for enabling spontaneous chlorination of substitutional impurities such as Ti, Al, and B, while alkali metals including Na, K, and Li can be effectively removed under HCl atmosphere at moderate temperatures. Kinetic analysis identifies solid-state diffusion through the SiO₂ lattice as the likely rate-determining step based on the modeling framework, with activation energies ranging from approximately 90 kJ/mol for Na⁺ to 400 kJ/mol for Ti⁴⁺. A significant diffusion crossover effect is observed, where high-activation-energy impurities exhibit exponential mobility gains above 1200 °C. An alkali-first, Al-follows coupled diffusion mechanism is elucidated for aluminum removal. Based on these findings, a temperature-staged, atmosphere-segmented roasting strategy is proposed. This work provides a quantitative mechanistic framework for deep impurity removal and offers practical guidance for overcoming the 4N8 purity bottleneck in high-purity quartz production. Full article

Taking pickling sludge generated from the steel rolling process at a Chinese steel mill as the subject of study, this research investigates a combined mineral processing and metallurgical process involving gasification-reduction roasting, magnetic separation, and waste acid recovery. The main elements in this pickling sludge are Fe and Cl, with contents of 46.50% and 12.70%, respectively. The primary component is chlorine-containing iron oxide, and a significant amount of amorphous material is also present. The study investigated the effects of various calcination temperatures, calcination times, reducing agent dosages, and material thicknesses on gasification-reduction performance indicators. The results indicate that using a reduction calcination–grinding–magnetic separation process, with coal as the reducing agent, a calcination temperature of 1100 °C, a reducing agent dosage of 15%, and a calcination time of 2 h, the chlorine volatilization rate exceeds 97%. Furthermore, when the roasted ore is ground to a particle size where 85% passes through a −0.076 mm screen and is recovered via magnetic separation, an iron concentrate with a grade of over 69.50% can be obtained. This iron concentrate meets the quality requirements for high-grade iron concentrates used in direct reduced iron (DRI) production. The small amount of tailings from the iron concentration process can be utilized in the production of bricks, cement, and other products, thereby achieving the efficient comprehensive utilization of acid washing sludge. Full article

Polycyclic aromatic hydrocarbons (PAHs) are hazardous contaminants formed during incomplete combustion and frequently detected in smoked, grilled, roasted, and fried meat products. Their formation is influenced by temperature, smoking duration, fuel type, fat content, and the distance from the heat source. Available studies indicate that traditionally smoked and charcoal-grilled products contain higher PAH concentrations than raw or less processed meat. Under Regulation (EU) 2023/915, the maximum permitted levels are 2 µg/kg for benzo[a]pyrene (BaP) and 12 µg/kg for the sum of four marker PAHs (PAH4) in standard smoked meat products, while derogation limits of 5 and 30 µg/kg, respectively, apply to certain traditionally smoked products. Chromatographic methods enable sensitive PAH determination, with limits of detection of 0.003–0.200 µg/kg reported for high-performance liquid chromatography with fluorescence detection (HPLC–FLD) of meat products. Literature data indicate that PAH formation can be reduced through indirect smoking, appropriate fuel selection, smoke purification, prevention of fat dripping, and antioxidant-rich marinades. Overall, effective PAH control requires optimized processing technologies, sensitive analytical monitoring, and compliance with regulatory standards while preserving product quality and traditional practices. Unlike reviews focusing on individual aspects, this review integrates current knowledge on PAH formation, occurrence, health risks, analytical determination, legislation, and mitigation within a single meat-focused framework. Full article

Sensory evaluation is the reference method for assessing specialty coffee quality; however, the descriptive narratives generated by certified Q Arabica Graders remain an underutilized source of information. This study developed an integrated analytical framework combining conventional sensory evaluation with natural language processing (NLP) to characterize the evolution of specialty coffee quality during accelerated storage under different packaging systems. Green and roasted coffee stored in eight packaging configurations were subjected to accelerated storage at 40, 50, and 60 °C, and sensory evaluations were performed according to the Specialty Coffee Association protocol. Textual sensory descriptions were analyzed using descriptor frequency analysis, term frequency–inverse document frequency (TF–IDF) weighting, co-occurrence networks, topic modeling, and topic prevalence analysis. The results demonstrated that the evaluated packaging–product configurations (PPCs), together with storage temperature, influenced the sensory stability of specialty coffee under accelerated storage conditions. Vacuum packaging and multilayer laminated bags more effectively preserved desirable sensory attributes and higher cup scores, whereas elevated temperatures and coffee grinding accelerated quality deterioration, leading to the progressive replacement of freshness-related descriptors by undesirable storage-related sensory characteristics. The combined application of multiple text-mining approaches consistently revealed systematic semantic changes in sensory perception that complemented conventional cup scores and provided a more comprehensive characterization of quality evolution during storage. These findings demonstrate that integrating conventional sensory evaluation with natural language processing transforms expert sensory narratives into reproducible quantitative information, providing a reproducible analytical framework for the objective characterization and comparison of sensory changes during accelerated storage of specialty coffee. Full article

The growing demand for natural food colorants has increased interest in sustainable alternatives derived from agro-industrial by-products. This study developed and characterized a food-grade natural brown colorant from date seed waste of Phoenix dactylifera L. (Khalas variety) by process optimization, mineral profiling, phenolic characterization and analysis of its storage stability. A food-grade aqueous extraction system was employed, and a Taguchi L9 orthogonal array was used to optimize the processing parameters affecting color development. Roasting temperature was identified as the most influential factor, contributing 85.75% of the variation in color intensity. Signal-to-noise ratio analysis determined the optimum processing conditions as 200 °C roasting temperature, 5 min roasting time, and 15 min extraction time, yielding an OD₄₂₀ value of 0.927. FTIR analysis confirmed the presence of hydroxyl, carbonyl, aromatic, and carbohydrate-associated functional groups related to thermally generated brown pigments. Further studies demonstrated that both temperature and opaqueness of the storage bottle significantly influence colorant stability. Refrigerated storage in amber containers provided superior retention of total phenolic and flavonoid contents, in addition to a superior antioxidant activity compared with room-temperature storage in clear containers. Mineral profiling revealed significantly high levels of potassium, calcium, phosphorus, and magnesium, with the mineral composition remaining largely stable during storage. HPLC analysis identified catechin and gallic acid as the major phenolic compounds, while ellagic acid was detected exclusively in the glycerol–water extract, indicating enhanced recovery of selected phenolics through solvent modification. Overall, the developed date seed colorant combines color-forming, antioxidant and nutritional properties, while providing a sustainable approach for the valorization of date-processing by-products. The findings highlight the potential application of date seed colorant as a clean-label alternative to synthetic brown colorants and support the development of sustainable food ingredients aligned with sustainable development goals. Full article

To elucidate the synergistic effects of storage temperature and packaging on N-nitrosodimethylamine (NDMA) and its precursors dimethylamine (DMA) and trimethylamine N-oxide (TMAO) in roasted Alaska pollock fillets, two storage experiments were conducted. In Experiment I, commercially packaged fillets were stored at −20, 4, 10, 20, and 30 °C for 310 d. A two-way factorial ANOVA revealed a significant temperature × time interaction (F(24, 70) = 39.386, p < 0.001, partial η² = 0.931). NDMA formation was delayed until day 172 at −20 °C; however, the 4, 10, and 20 °C groups exceeded the 4 μg/kg limit by day 263, with the 20 °C group peaking at day 263 (4.26 μg/kg) before declining to 3.73 μg/kg by day 310. In Experiment II, a three-way factorial ANOVA was applied to samples stored under oxygen-absorber or vacuum packaging at refrigerated (4 °C) or ambient (22 °C) temperature for 270 days. The temperature × packaging × time interaction was significant for NDMA, DMA, and TMAO (p < 0.001). The partial η² for NDMA (0.933) was markedly larger than for DMA (0.540) and TMAO (0.607), indicating stronger combined effects on NDMA. The main effect of temperature on DMA was dominant (partial η² = 0.994), whereas NDMA formation depended strongly on both temperature and packaging. During the 270-day storage, all refrigerated groups remained below the 4 μg/kg limit throughout; however, the ambient vacuum-packaged (BCZ) group transiently exceeded the limit (reaching 4.21 μg/kg on day 60) and subsequently fluctuated near the limit. These findings provide a scientific basis for designing safer storage and packaging strategies for such dried aquatic products. Full article