Search Results (182)

Flotation was investigated to treat incineration fly ash with diesel, kerosene, TX-100, or SDS as a collector and methyl isobutyl carbinol (MIBC) or 2-Octyl alcohol as a frother. Fly ash was separated into light and residual materials. Comparison of yield, carbon and sulfur removal showed that kerosene and MIBC showed the best performance. The results revealed that flotation was a method that could simultaneously achieve the removal of organics and S-containing compounds. Specifically, approximately 7.63–9.45% of the total mass was collected as light material, which was enriched with organic carbon. Contents of organic carbon reached 14.35 wt%–14.56 wt% in the light materials from those of 2.74 wt%–3.52 wt% in the original fly ash. Elemental analysis further proved that sulfur was also accumulated in light material. Approximately 78.84–81.69% of the organic carbon and 80.47–82.66% of the sulfur were removed. Decarbonization was primarily achieved through the flotation of organic materials, while desulfurization resulted from both flotation and the dissolution of soluble salts. Furthermore, the contents of the chloride and heavy metals in the residual fly ash also decreased. Particle size analysis showed that flotation was effective in the removal of smaller particles, and those particles were also rich in heavy metals. Overall, by selecting the right collector and frother, flotation was also able to reduce the leaching toxicity of heavy metals. The residual fly ash was safe for further disposal. Organic carbon, sulfur and heavy metals were accumulated in the light materials, which accounted for less than 10% of the original mass. The portion of fly ash needing further treatment was therefore greatly reduced. Full article

Heavier element analogues of a ketone, a C=O double-bond compound, have been fascinating compounds from the viewpoint of main-group element chemistry because of their unique structural features and reactivity as compared with those of a ketone, which plays an important role in organic chemistry. We will report here the synthesis of diorgano-stannanethione and stannaneselone featuring tin–chalcogen double bonds, which are the heavy-element analogues of a ketone. The newly obtained stannaneselone has been structurally characterized by spectroscopic analyses and single-crystal X-ray diffraction (SC-XRD) analysis, showing the short Sn–Se bond length featuring π-bond character. The obtained bis(ferrocenyl)stannanechalcogenones were found to undergo [2+4]cycloaddition reactions with 2,3-dimethyl-1,3-butadiene, affording the corresponding six-membered ring compound. Notably, thermolysis of the [2+4]cycloadduct of the stannaneselone regenerated the stannaneselone via the retro[2+4]cycloaddition, whereas the sulfur analogue was thermally very stable. Full article

Electrolytic manganese residue (EMR), an acidic by-product from manganese production, presents dual challenges of environmental pollution and resource waste. This study developed a silicon–manganese organic compound fertilizer (SMOCF) via the aerobic fermentation of EMR supplemented with bagasse, molasses, and activated sludge. The physicochemical analysis revealed that the EMR’s composition was dominated by silicon (7.1% active Si), calcium, sulfur, and trace elements. Critical parameters during composting—including water-soluble Mn (1.48%), organic matter (8.05%), pH (7.4), moisture (20.28%), and germination index (GI = 87.78%)—met organic fertilizer standards, with the GI exceeding the phytotoxicity threshold (80%). The final SMOCF exhibited favorable agronomic properties: neutral pH, earthy texture, and essential macronutrients (1.36% K, 1.11% N, 0.48% P). Heavy metals (As, Cd, Cr, Pb) in the SMOCF predominantly existed in stable residual forms, with total concentrations complying with China’s organic fertilizer regulations (GB/T 32951-2016). The ecological risk assessment confirmed a minimal mobilization potential (risk assessment code < 5%), ensuring environmental safety. This work demonstrates a circular economy strategy to repurpose hazardous EMRs into agriculturally viable fertilizers, achieving simultaneous pollution mitigation and resource recovery. The optimized SMOCF meets quality benchmarks for organic fertilizers while addressing heavy metal concerns, providing a scalable solution for industrial EMR valorization. Further studies should validate the field performance and long-term ecological impacts to facilitate practical implementation. Full article

This study investigates the impact of volcanic ash from Cotopaxi Volcano on the nutritional quality and biological traits of potato tubers (Solanum tuberosum L.) cultivated in the Cotopaxi region. Methods: Samples collected from exposed and unexposed areas were used to characterize the volcanic ash influence on the metabolic aspects of the potato crop. The colorimetric method; DPPH, ABTS, and FRAP assays; and ICP-OES were used to better understand potatoes’ reaction to the stress. Results: Antioxidant activity was significantly higher (4.80 ± 2.38 µmol Trolox g⁻¹ DW-DPPH assay; 11.05 ± 2.57 µmol Trolox g⁻¹ DW-ABTS assay; and 11.96 ± 4.57 µmol Fe²⁺ g⁻¹ DW-FRAP assay) in ash-exposed samples, suggesting enhanced stress responses. The bioactive compounds studied followed a comparable trend, with high content in the exposed tubers. Also, significant changes in elemental composition were registered: Potassium levels decreased in unexposed samples, while magnesium and iron levels increased. Metallic elements (zinc; lithium; boron; manganese; barium; lead; nickel; chromium; indium) were in concentrations <0.01 mg/kg. Conclusion: These findings demonstrate that volcanic ash alters the metabolic and antioxidant profiles of potato tubers, enhancing nutraceutical properties while posing food safety risks due to heavy metals. This dual impact highlights the challenges and opportunities for agriculture in volcanic regions like Cotopaxi. Full article

Among heavy metals, cadmium (Cd) is shown to have adverse consequences for plants. Due to its harmful nature and ability to move through the soil–plant system, it is a very worrying element for soil experts and plant physiologists. In this work, we designed a pot experiment to study the influence of three soil concentrations of cadmium (0, 15, and 30 mg/kg) to explore its physiological impacts, and its portioning in the whole plant of three hulless barley varieties. Our findings demonstrated marked Cd accumulation in roots, leaves, and stems under severe Cd stress (30 mg/kg). Cd stress was also shown to reduce photosynthetic activity, chlorophyll fluorescence (Fv/Fm), and transpiration rates (E). The application of Cd in the soil increased the activities of catalase (CAT), ascorbate peroxidase (APX), and guaiacol peroxidase (POD) enzymes, as well as the levels of oxidative stress markers such as malondialdehyde (MDA), hydrogen peroxide (H₂O₂), and proline. These results reflect the negative effects of cadmium on morpho-physiological traits in barley genotypes. However, the principal component analysis indicated a significant correlation between oxidative stress indicators and enzymatic activities, along with different levels of Cd tolerance between Tombari, Assiya, and Giza 130 genotypes. When exposed to Cd, these varieties shifted a significant amount of energy from growth to produce antioxidant compounds and osmolytes. Despite this, these defenses did not effectively shield the plant from the detrimental effects of oxidative stress induced by Cd accumulation at vegetative stages. Consequently, we highly recommend testing these varieties under Cd-contaminated soil to investigate the rate of cadmium accumulation in the seeds, the harvested part used in human nutrition. Full article

Barium slag, classified as HW47 hazardous waste, is produced in large quantities and has a high accumulation with heavy metal Ba ions that are significantly above the standard levels, posing a serious threat to the ecological environment and the growth of flora and fauna. Before barium slag can be stored, it must undergo harmless treatment, which is costly, and with the current large volume of accumulated barium slag, storage facilities are strained. There is an urgent need for new technologies to extract barium elements from barium slag while achieving reduction in volume. This study first treats the barium slag to reduce its oxidation state and then utilizes the density differences to separate barium-rich compounds through shaking table concentration. Macro and microanalytical methods such as XRD (X-ray diffraction), XRF (X-ray fluorescence), and SEM&EDS (Scanning Electron Microscopy & Energy-dispersive X-ray Spectroscopy) were employed. The results show that barium in the slag is evenly distributed, and after sufficient crushing, it can be separated by gravity concentration. The barium content can be enriched from 20% to over 80%. This research provides theoretical support for the separation of barium compounds from barium slag. Full article

Rhizobial bacteria perform a number of extremely important functions in the soil environment. In addition to fixing molecular nitrogen and transforming it into a form available to plants, they participate in the circulation of elements and the decomposition of complex compounds present in the soil, sometimes toxic to other organisms. This review article describes the molecular mechanisms occurring in the most diverse group of rhizobia, the genus Bradyrhizobium, allowing these bacteria to adapt to selected substances found in the soil. Firstly, the adaptation of bradyrhizobia to low and high concentrations of elements such as iron, phosphorus, sulfur, calcium and manganese was shown. Secondly, the processes activated in their cells in the presence of heavy metals such as lead, mercury and arsenic, as well as radionuclides, were described. Additionally, due to the potential use of Bradyrhziobium as biofertilizers, their response to pesticides commonly used in agriculture, such as glyphosate, sulfentrazone, chlorophenoxy herbicides, flumioxazine, imidazolinone, atrazine, and insecticides and fungicides, was also discussed. The paper shows the great genetic diversity of bradyrhizobia in terms of adapting to variable environmental conditions present in the soil. Full article

This research investigated the volatilization and enrichment of metallic and non-metallic elements in municipal solid waste incineration fly ash during thermal treatment. The high-temperature treatment resulted in both the volatilization and stabilization of heavy metals in fly ash. The split of volatilization and stabilization depended highly on the original speciation. The results showed that loosely bound heavy metals were the main contributors to the leaching toxicity of the raw fly ash. These metals were also easily volatilized. The volatilization of heavy metals was accompanied by de-chlorination, indicating that the loss of heavy metals may be related to the evaporation of chloride compounds. On the other hand, heavy metals that were strongly bound with the fly ash were less volatile. For the six heavy metals investigated, 42% and 58% of Cd and Pb were volatilized at 800 °C. By comparison, the volatilizations of Cu, Zn, Cr, and Ni amounted to 18–31% at the same temperature. The remaining heavy metals became more stable. Stabilization could be attributed to reactions between decomposition products; thus, new and more complicated structures, such as Ca₃Mg(SiO₄)₂, Ca₂Al₂SiO_7, and CuSiO_3, were formed. Heavy metals were incorporated into the structures and stabilized. Moreover, analyses of other elements showed that thermal treatment resulted in the enrichment of elements, including Mn, Mg, Si, and Al. This is conducive to reusing fly ash. Full article

This study focused on the nature of rare earth metal complex compounds that can form during the carbonate–alkaline processing of industrial waste materials, such as phosphogypsum and red mud, at 70–100 °C and 1–10 atm. Experimental findings revealed that the dissolution of synthetic carbonates of rare earth elements (REEs) in a concentrated carbonate-ion medium (3 mol/L) leads to the formation of ion-associates of varying strengths. Light (lanthanum, praseodymium, and neodymium) and medium (samarium) REE groups exhibited a tendency to form loose ion-associates, whereas heavy REEs (terbium, dysprosium, holmium, erbium, thulium, lutetium, and yttrium) formed close ion-associates. To confirm the existence of these ion-associates, the specific conductivity of solutions was measured after dissolving thulium (III) and samarium (III) carbonates at phase ratios ranging from 1:2000 g/mL to 1:40 g/mL in a potassium carbonate medium. The decay of ion-associates, leading to the precipitation of rare earth metal (III) carbonates, was tested in an ammonium carbonate medium. Thermal decomposition of ammonium carbonate at 70–75 °C during 1–4 h was accompanied by full rare earth carbonates’ sedimentation and its in-the-way separation into groups because of the varied strength of ion-associates. The results of this study provide a basis for developing processes to separate rare earth metals into groups during their carbonate–alkaline extraction into solution. Full article

This study explores the chemical composition of different macrophyte species and infers their potential in extracting nutrients and some heavy metals from water as well as the use of macrophytes’ biomass as natural fertilizers. It used a dataset obtained from a previous study composed of 445 samples of chemical concentrations in the dried biomass of 16 macrophyte species collected from the Santana Reservoir in Rio de Janeiro, Brazil. Correlation tests, analysis of variance, and factor analysis of mixed data were performed to infer correspondences between the macrophyte species. The results showed that the macrophyte species can be grouped into three different clusters with significantly different profiles of chemical element concentrations (N, P, K⁺, Ca²⁺, Mg²⁺, S, B, Cu²⁺, Fe²⁺, Mn²⁺, Zn²⁺, Cr³⁺, Cd²⁺, Ni²⁺, Pb²⁺) in their biomass (factorial map from PCA). Most marginal macrophytes have a lower concentration of chemical elements (ANOVA p-value < 0.05). Submerged and floating macrophyte species presented a higher concentration of metallic and non-metallic chemical elements in their biomass (ANOVA p-value < 0.05), revealing their potential in phytoremediation and the removal of toxic compounds (such as heavy metal molecules) from water. A cluster of macrophyte species also exhibited high concentrations of macronutrients and micronutrients (ANOVA p-value < 0.05), indicating their potential for use as soil fertilizers. These results reveal that the plant’s location in the reservoir (marginal, floating, or submerged) is a relevant feature associated with macrophytes’ ability to remove chemical components from the water. The obtained results can contribute to planning the management of macrophyte species in large water reservoirs. Full article

The aim of our study was to compare the composition of polyphenolic compounds between the Croatian acacia (Robinia pseudoacacia L.) and chestnut (Castanea sativa Mill.) honey from several aspects: production season, hive position (on the edge and in the middle of a series of hives), part of the hive (small or normal extension), and honey extraction method (centrifuging or draining honey combs). Additionally, in acacia honey, we also monitored the influence of different storage temperatures (room temperature (RT) and 4 °C) on the content of phenolic compounds. To separate, identify and quantify individual flavonoids and phenolic acids from the honey, we used the HPLC method. The total polyphenols and antioxidant activity of the samples, their antimicrobial activity and their elemental content were also measured. The significant influence of the season, hive position, and extraction method on the total identified phenolic compounds, phenolic acids, flavonoids, total phenols and antioxidant activity was detected in almost all the acacia and chestnut honey samples. Chestnut honey from 2013 had more total phenolics (TPs) and antioxidant capacity (FRAP) than chestnut from 2014 and 2015. Honey collected from smaller extensions of hives had significantly higher TPs and FRAP compared to normal hive extensions. Centrifugation reduced the TPs and FRAP in most cases, but not always uniformly. Storage at RT led to the predominance of gallic, p-coumaric and benzoic acid in acacia honey, while storage at 4 °C maintained p-coumaric acid as the dominant phenolic acid. Flavonoids, particularly pinobanksin in acacia honey and hesperetin/pinobanksin in chestnut honey, were less affected by the storage conditions compared to phenolic acids. The non-centrifuged chestnut sample from 2015 showed the lowest MIC values against the most tested pathogenic bacteria. All the honey samples showed an extremely low concentration of heavy metals and relatively high concentrations of potassium and calcium. Full article

In order to study the geochemical characteristics of coal in the Ningwu Coalfield of Shanxi Province and the coal-forming environments reflected by it, a detailed geochemical study was carried out on the No. 5 coal of the Zhaokai Mine. The results show that the content of major-element oxides SiO₂ and Al₂O₃ is high. The trace elements Ni, Nb, Mo, Cd, Sn, Hf, Ta, W, Th, and U are slightly enriched, while the elements Li and Zr are enriched, indicating an overall LREY enrichment type in the samples. Elemental parameters suggest that the sedimentary environment in the study area is continental sedimentary, and the whole environment is reductive. The macerals in the coal samples are mainly vitrinite, with an average vitrinite reflectance (R_o) of 0.744%. The distribution range of n-alkanes in the coal samples is from n-C₁₄~n-C₃₂, with the main peak carbons being n-C₂₄ and n-C₂₅, showing the post-single-peak type distribution pattern. The average odd–even predominance index (OEP) is 0.40, the average of the light and heavy hydrocarbons ratio (${\displaystyle \sum {\mathrm{C}}_{21}^{-}}/{\displaystyle \sum {\mathrm{C}}_{22}^{+}}$) is 0.42, and the average of Pr/n-C₁₇ and Ph/n-C₁₈ are 1.08 and 0.23, respectively. The coal samples also contain various aromatic hydrocarbons, mainly from the naphthalene- and phenanthrene-series compounds. Biomarker parameters indicate that the parent material of the coal samples in the study area is mainly continental higher plants. The maturity is low, and the coal-forming environment is a reduction environment. This study of the No. 5 coal’s geochemical characteristics has laid a foundation for the efficient, green, and comprehensive exploitation of coal resources in this region, and has also provided an important basis for the sustainable development of coal resources. Full article

The speciation of heavy metals (Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb) in the bottom sediments of the Mozhaisk Reservoir and the Moskva River is described. They were characterized using the Tessier sequential selective extraction procedure trace element concentrations determined by inductively coupled plasma–mass spectrometry (ICP-MS). The bottom sediments of the Mozhaisk Reservoir are characterized by higher concentrations of the examined metals compared to the channel alluvium of the Moskva River. In this case, the most widespread metal compounds in the bottom sediments of the Mozhaisk Reservoir are firmly bound (stable form) to the mineral matrix. High concentrations of the firmly bound forms of metals (Co, Ni, Cu, Zn, Cd, Pb, and Fe) in the bottom sediments are due to an increased proportion of the silt fraction (0.1–0.01 mm) entering the reservoir due to abrasion of its shores. The only exceptions are Mn and Cd, which are present in labile compounds with carbonates and hydroxides of iron and manganese. In the bottom sediments of the Moskva River, strongly bound forms prevail for most metals—for Ni, Zn, and Cd, they are complex compounds with Fe and Mn hydroxides; for Co, Cu, Pb, and Fe, they are compounds with stable silicate minerals. The proportion of labile bioavailable forms of metals in the bottom sediments of the Moskva River is higher than in the reservoir due to anthropogenic input. Among the labile forms of the metal compounds, carbonates predominate. The proportion of elements in the most mobile exchange form and in compounds with organic matter is not large and does not exceed 14% for most elements. The only exceptions are Co and Cd, for which the concentration of the exchange form reaches 25%. Full article

The objective of this study is to examine the effectiveness of the electrocoagulation (EC) process in treating real produced water (PW). The impact of the EC process on water quality parameters (pH and conductivity, turbidity, and oil content) was studied using bench-scale 5 L PW for this process. The findings indicate that prolonged EC leads to the release of metal ions and secondary electrode reactions, which resultantly increase the pH of the outlet water. The EC process decreased in several water quality parameters, including Chemical Oxygen Demand (COD), Total Organic Carbon (TOC), and oil and grease (O&G). COD decreased by roughly 1300 mg/L, resulting in a 33% removal. In the same manner, TOC dropped from an initial value of 1300 mg/L to approximately 585 mg/L, exhibiting a maximum removal efficacy of nearly 60%. Oil and gas (O&G) decreased to a value below 10 mg/L, accompanied by a remarkable removal efficacy of up to 99.6%. The turbidity, which was initially recorded at an average of 160 NTU, was reduced to approximately 70 NTU, which is a 44% reduction. The application of centrifugation after EC treatment resulted in a turbidity reduction above 99%. EC treatment removed BTEX (benzene, toluene, ethyl benzene, and xylenes) from PW by more than 99%. The inorganic constituents, specifically heavy metals, exhibited minimal changes following the application of EC, emphasizing the necessity for additional treatment methods to effectively address their presence. In summary, EC demonstrates an acceptable level of efficacy in the removal of turbidity and pollutants from PW, with a special emphasis on organic compounds such as BTEX, but it does not address the elimination of inorganic compounds. Subsequent investigations should prioritize the optimization of EC parameters and the integration of supplementary interventions to effectively address the removal of inorganic elements and insoluble metals from treated PW. The study evaluates the pollutant removal efficiency using iron and aluminum electrodes and the effects of the applied current and electrolysis time on the EC process. Full article

Insectary plants, such as sweet alyssum, coriander, and white mustard, are well known for their traits that attract beneficial insects, allowing them to protect crops from pests. The aim of the study was to analyze the compounds that are important in the antioxidant response, such as malondialdehyde, ascorbic acid, proline, total phenolics, and total flavonoids, as well as the content of elements, including macroelements (K, Mg, Na, Ca, P, and S) and heavy metals (Cd, Cu, Zn, Pb, Ni, Mn, and Fe) in broad bean plants. These plants were grown in field conditions as the main protected plant alongside a mixture of three insectary plants at different proportions of the individual components. The soil was analyzed in terms of the above-mentioned elements, as well as in terms of its enzymatic activity (arylsulfatase, β-glucosidase, dehydrogenase, FDA (fluorescein diacetate), and acid phosphatase). The introduction of insectary plant mixtures did not cause major changes in the content of the elements in the soil. The changes in the content of elements in broad bean leaves depended on the type of element and the proportion of individual components in the companion plant mixture. However, a general trend of increasing macronutrient content was observed, influenced by the presence of companion plants. All types of companion plant mixtures used enhanced the activity of FDA, while the mixture with 50% sweet alyssum additionally caused an increase in arylsulfatase activity (more than 2 fold). The companion plants improved the physiological condition of the protected plant, which was reflected in the reduced content of proline and total flavonoids. Considering the response of the protected plant to the proposed intercropped plant mixtures and their effect on broad bean growth, it appears that the most suitable mixtures are those with an equal share of all three plant species or a mixture with a predominance of sweet alyssum. Full article