High Metal Content Research Articles

N-Heterocyclic Carbene Deposition on a Copper Powder Surface Using Mechanochemistry.

Metal powders are crucial precursors for manufacturing surfaces through thermal spraying, cold spraying, and 3D printing methods. However, surface oxidation of these precursors poses a challenge to the coherence of the metallic materials during manufacturing processes. Herein, we introduce a method for surface modification of copper powder with N-heterocyclic carbenes (NHCs) using mechanochemistry to mitigate surface oxidation. A resonant acoustic mixer was used to deposit five different carbenes on copper powders using benzimidazolium hydrogen carbonate precursors and a trace amount of solvent. Significant oxide reduction was observed by X-ray photoelectron spectroscopy (XPS), and the immobilization of NHCs on the powder was confirmed by mass spectrometry and XPS. The consistent morphology of the modified copper powder minimizes any potential impact on subsequent manufacturing processes. Moreover, a life cycle assessment indicates the potential environmental hotspots, leading to recommendations to develop lower-footprint processes. Overall, the mechanochemical method to produce NHC-modified metal powders with a higher metallic content provides great prospects for powder precursors to produce coatings from thermal spray, cold spray, and additive manufacturing processes.

Prolonged Storage of Bound Organic Carbon in Wetland but Not Upland Soils: A 13C and 14C Perspective

AbstractProtection by metal (hydr) oxides is one of the key mechanisms for the long‐term stabilization of soil organic carbon (SOC). However, the source and turnover of (metal‐) bound organic carbon (OC) in soils are poorly constrained. Here we present the first large‐scale study on the 13C and 14C characteristics of bound OC in 15 wetland and upland soil profiles. We find that bound OC has similar δ13C as SOC, suggesting no preference for plant‐ or microbe‐derived carbon. However, bound OC Δ14C is more negative than SOC in wetland but not upland mineral soils, and decreases with increasing reactive minerals. Hence, in contrast to the conventional assumption, bound OC is better preserved relative to SOC in wetlands with high contents of reactive metals. Our finding highlights the dynamic exchange of bound OC with SOC in upland soils and calls for a better recognition of reactive metals in stabilizing OC in wetlands.

Study on the Adsorption Performance of Lead Ions in Water by Phosphate Base Polymer with Different Ratio

Red mud, a by-product of the aluminum industry, poses a threat to the environment with its high alkalinity and heavy metal content and may seep into the soil and groundwater, endangering ecology and health. Effective utilization of red mud can reduce pollution and achieve resource recycling. In this study, a metakaolin/red mud geopolymer was prepared by phosphoric acid excitation to investigate its adsorption capacity for lead ions. The ratio of metakaolin to red mud and the additions of phosphoric acid and water were optimized, and the optimal formulations were 3/7 mass ratio of metakaolin to red mud, 2.2 molar ratio of H3PO4/Al2O3, and 0.5 water-solid ratio, which demonstrated good stability and operability.

MACHINING OF PARTS AND REDUCING THE CONTENT OF COPPER CATIONS FROM AN AQUEOUS SOLUTION BY SORPTION ON A SOLID LAYER USING NATURAL AND MODIFIED CLINOPTILOLITE

Galvanic plating is one of the most widespread methods of surface treatment of metal parts. The process consists of immersion of modified parts in an electrolytic bath. These processes produce wastewater with a high metal content. One of the methods of reduction metal content in water is sorption on a solid layer. Natural zeolites in natural form, but also in modified form, can be used for these purposes. To be able to design organization of the cleaning process, it is necessary to know the kinetic course of sorption. The article contains the results of laboratory experiments aimed at determining the sorption parameters of the sorption of copper and nickel cations on natural zeolite - clinoptilolite, and on modified Fe-clinoptilolite.

Intensified Bioaugmentation as a Strategy to Enhance Bioleaching of Mine Tailings with High Metal Content

Intensified Bioaugmentation as a Strategy to Enhance Bioleaching of Mine Tailings with High Metal Content

Effects of the reopening of the Grand-Bassam inlet on the seasonal dynamics of some trace metals in the superficial sediments from the area II of the Ébrié system

The objective of this work was to assess the impacts of the permanent reopening of the Grand-Bassam inlet on the seasonal dynamics of thirteen trace metals in the superficial sediments of the area II from the Ébrié system. In its implementation, the sediment samples were collected over a year (from May 2023 to April 2024). The concentrations of these trace metals were obtained by inductively coupled plasma mass spectrometry (ICP MS) according to ISO 17294-2 after dissolution according to NF X31-147. The results showed a significant input of these metals by meteorological inputs during the rainy, cold, and flood seasons, except for Cr, whose presence in these substrates was mainly related to the strong marine intrusion during the hot season. The modification of the geochemical and physical characteristics due to the reopening of this pass significantly influenced the presence of these trace metals in these substrates during the study period. A reduction in the use of inputs containing high concentrations of trace metals and the efficient treatment of anthropogenic discharges with high metal content in the watershed of this ecosystem should be considered to support the depollution initiated with the reopening of this inlet.

Health Risk Assessment of Heavy Metals in Soil-crop System in Different Ecological Regions of Ningxia

Heavy metals are characterized by toxicity，non-biodegradability，and accumulation in the food chain；hence，o the distribution of heavy metals in farmland soils and crop food safety have attracted much attention. A total of 1 274 soil samples and crop samples were collected from farmland in Ningxia from 2017 to 2021 and bioconcentration coefficients were used based on the analysis of the elemental contents of Zn，Cr，Ni，Cu，Pb，As，Cd，and Hg. The ecological risk index and correlation analysis were used to characterize the heavy metal content and health risk assessment of the soil-crop system in Ningxia. The results showed that the soils in the study area were alkaline and the mechanical composition was dominated by pulverized and sandy grains，with a relatively small content of clay grains. The heavy metal contents in the soils were in the following order：Zn>Cr>Ni>Cu>Pb>As>Cd> Hg. Except for that of Cu and Ni，the contents of other heavy metals in the soils of the northern region were higher than those of the central and southern regions. The ecological risk index of soil heavy metals was Hg>Cd>As>Cu>Pb>Ni>Cr>Zn and the proportion of points with low and medium ecological risk index levels was high（98.58%），indicating that the soil environment was generally good. The average content of the eight heavy metals in crops did not exceed the limit value，and the average health risk index value was <1. However， the health risk index（HRI）of As in individual crops existed at points >1 in all three sub-regions and individual points with high values of HRI（HRI>1）for Cu and Ni were observed in crops in the northern region and for Pb in the north and south of the country，which require further attention. From the bioconcentration factor，crops showed no accumulation effect （BCF<1）for heavy metals such as As，Cd，Cr，Cu，Ni，Pb，and Zn and although the average uptake of Hg by crops did not show accumulation，a total of 31 crops in the three ecological zones showed some accumulation（BCF>1），which also requires further monitoring. Analysis using the Mantel's test showed that except for As and Ni in crops，which had a weak correlation with Cu content in the soil（0.05>Mantel's P>0.01），the other heavy metals in crops did not have a significant correlation with the corresponding soil heavy metals （Mantel's P≥0.05），indicating that the heavy metal contents in crops were less affected by soil heavy metals. RDA analysis showed that the sand content had a strong positive correlation with the transfer coefficients of heavy metals such as Hg，Ni，Pb，and Cd，while the powder content showed a strong negative correlation；however，the transfer coefficients of Cu，Zn，As，and Cr were not much affected by the mechanical composition of soils，and the correlation between the soil organic matter content and the transfer coefficients of heavy metals was also small. In summary，the quality of the soil environment and crops in the study area is generally good；however，attention must still be paid to the areas with high heavy metal content or exceeding the standard value to strictly control the input of pollutants，and at the same time，establishing long-term monitoring of the quality status of soil and agricultural products in the crop production area is a necessary control initiative.

The disparities in health risks of multiple pollutants through soil and dietary exposure in a rural-urban area based on accessibility method.

Rapid urbanization has resulted in disparities in environmental conditions for different communities in suburban area. This study presents a comprehensive investigation into the occurrence of pollutants in the soil and dietary food, and associated health risks in an urban-rural transitional area. The levels of potential toxic pollutants, notably metals, organophosphate esters (OPEs), and agrochemicals in surface soil and dietary food were evaluated. Higher levels of metals and OPEs were found in soils of industrial area, and agricultural soils had an elevated level of agrochemicals. The highest health risk was found for Chromium (Cr) which exceeded 1, indicating a high probability of adverse non-cancer effect to local residents. The levels of contaminants in food showed higher variability in community market and farmers' market than in supermarket, while higher levels of OPEs were found in food from supermarkets. The accessibility to fresh food mainly determined the differences in health risks of different communities. For dietary exposure, residents of industrial areas have higher levels of risk than other neighborhoods, mainly due to the possibility of exposure of foodstuffs with higher metal contents. In terms of market type, community markets mainly contributed to the comprehensive health risk through dietary exposure, especially for industrial and agricultural communities. The findings of this study provided further understanding of the spatial distribution of various contaminants as well as their health risks for different communities, which could guide the monitoring and management of potential toxic pollutants to safeguard public health in rural-urban transitional regions.

Застосування фторидних вогнетривів для отримання функціо-наль¬них сплавів, що містять хімічно активні компоненти Ti, Zr, Hf, Nb, V

Refractory crucibles, cups and other products made of material based on alkaline earth metals fluorides, which are used for casting, isothermal melting, high-temperature homogenization of chemically aggressive alloys containing a large amount of Ti, Zr, Hf, V, Nb, have been developed and manufactured. However, due to the large difference in coefficients of thermal linear expansion (KTLE) of fluorides and metals, mechanical compression of the crystallizing alloy in the crucible occurs.Such a difference in KTLE leads to cracking and destruction of crucibles. Crucibles that can be disassembled into several parts have been developed. This makes it possible to use such crucibles a large number of times for high-temperature homogenization and melting of chemically active alloys containing Ti, Zr, V, Nb.The developed refractory and special cups made from it also provide new opportunities for scientific research: studying the capillary characteristics (surface tension) of metal melts with a high content of reactive metals, which was previously practically impossible, as well as determining thermodynamic properties (enthalpy of mixing and formation of alloys, activity of components) for these alloys. Keywords: functional metal materials, refractory materials, fluorides of alkaline earth metals, collapsible crucibles, chemically aggressive metals.

The effect of adding sewage sludge compost and sheep manure on the accumulation of some heavy metals in the soil in Syria

This research aimed to study the effect of composting sewage sludge sheep manure on the accumulation of heavy metals in the soil. It was conducted in 2020 at the Center for Agricultural Scientific Research in the Dowier region of Homs Governorate. Compost made from sewage sludge sheep manure was added to the soil at a rate of (20-40) t/ha to determine the effect of the different quantities added on the chemical properties of the soil and the heavy metals accumulation in the soil (Cr, Pb, Cd). The addition of compost (sewage sludge, sheep manure) resulted in an apparent decrease in soil PH The value of the electrical conductivity of soil increased with the addition of compost. Sheep manure excelled on the compost of Sewage sludge in its effect on the ratio of organic matter; the effect was consistent with the increase in the addition rate. Compost addition was a cause of the high soil content of heavy metals (Cr, Pb), but it remained below the limits allowed in the soil according to Syrian standards. The addition of compost did not affect the soil content of (Cd).

Molecular disruptions in microalgae caused by Acidithiobacillus ferrooxidans: Photosynthesis, oxidative stress, and energy metabolism in acid mine drainage.

Microalgae are recognized for their potential in the bioremediation of acid mine drainage (AMD), despite the challenges posed by AMD's low pH, high heavy metal content, and oligotrophic conditions. However, the impact of AMD chemoautotrophic microorganisms on microalgal growth and remediation efforts within AMD has been largely overlooked. This study aims to elucidate the effects the chemoautotrophic microorganism, Acidithiobacillus ferrooxidans, on the growth activity and metabolism of acid-tolerant microalgae, and to explore the molecular mechanisms of microalgal response. Our findings reveal that the presence of A. ferrooxidans inhibits the growth and alkaline production of Parachlorella sp. MP1, resulting in a 90.86 % reduction in biomass. Physiological, biochemical, and transcriptomic studies, indicate that oxidative stress, photosynthesis, and energy metabolism are the metabolic processes most affected by A. ferrooxidans. Specifically, A. ferrooxidans introduces an increased production of reactive oxygen species (ROS) in Parachlorella sp. MP1, leading to an upregulation of genes and enzymes associated with peroxisome activity and intensifying oxidative stress within the cells. Downregulation of photosynthesis-related genes disrupts the electron transport chain, inhibiting photosynthesis. Furthermore, alterations in the gene expression of pyruvate and acetyl-CoA metabolic pathways result in energetic pathway disruption. These insights contribute to a better understanding of how A. ferrooxidans influence the growth metabolism of acid-tolerant microalgae in AMD environments and inform the optimization of microalgal application strategies in AMD bioremediation engineering.

Five years of monitoring the swampy forest system: a pilot project for acid mine drainage treatment to achieve threshold value

Abstract This research evaluated the effectiveness of the swampy forest system, a unique and cost-effective approach developed based on a conventional method for acid mine drainage treatment at the Jorong coal mine in South Kalimantan, Indonesia. The conventional method uses lime for acid neutralization and is often considered expensive. Acid mine drainage, with its high acidity and heavy metal contents, must be mitigated to achieve threshold values before being released into public waters. This research aimed to determine whether the swampy forest system pilot project, implemented in 2019, had sustainable and proper operations. As mandated by applicable regulations, quarterly observations of seven threshold parameters before and after acid mine drainage were conducted between 2019 and 2024. The observations revealed that the swampy forest system could change the parameter values to achieve the threshold value within five years of operations, demonstrating its exceptional long-term sustainability. Conclusively, this system is viable for natural application at a low cost at the closure stage of the abandoned mine.

Towards sustainability: A novel process for recycling vanadium and molybdenum from waste hydrogenation catalysts

Waste hydrogenation catalysts are usually listed as hazardous wastes due to their high heavy metal contents. These heavy metals such as molybdenum, vanadium, nickel, and cobalt will affect environment, human health, and wildlife. Moreover, the waste hydrogenation catalysts represent a valuable secondary resource, containing a significant quantity of valuable metals, recycling them will bring economic benefits, alleviate the need for mining investment, and reduce the environmental impact of mining. However, the current process presents many environmental and economic challenges, including sulfur dioxide pollution, more reagent consumption, and complicated operation. As a result, a new method is necessary to alleviate these drawbacks. In this work, a novel calcification roasting-acid leaching method was proposed to recycle the waste catalyst. The calcification roasting process was studied focally and systematically, including thermodynamics, reaction mechanisms, and phase transformation. The behaviors of Mo, V, Ni, and Al in the leaching process were studied, and influence factors, including roasting temperature, calcium additives feeding, acid concentration, leaching temperature, leaching time, liquid-solid ratio, and particle size were explored. Under the optimal conditions, the leaching efficiency for Mo and V reached 98.02 % and 97.28 % respectively. In contrast, there is no Ni and Al in the post-leaching solution, demonstrating excellent leaching ability for Mo and V, and robust leaching selectivity. Moreover, this novel method shows environmentally friendly properties, as it reduces SO2 generation. From the perspectives of resources, environment, and economy, this novel approach shows a competitive advantage and bright prospect.

Waste-Derived carbon porous materials for enhanced performance in adsorption chillers: A Step toward a circular economy

In this study, a comprehensive examination of commercial activated carbons and novel porous carbon materials derived from waste was conducted to evaluate their potential as bed materials in adsorption chillers driven by waste heat. The research uniquely focuses on synthesizing and analyzing sorbents from two distinct waste sources: lignin and excavated waste, aiming to expand the sustainable application of waste-derived materials. A thorough characterisation of the sorption properties was performed using mercury intrusion porosimetry, low-temperature gas adsorption, and dynamic vapour sorption measurements with methanol. These techniques provided detailed insights into the microporous structure and surface areas of the materials, ranging from 500 to 2000 m2/g for the activated carbons. Notably, the lignin-derived magnetic biochar demonstrated an exceptionally well-developed surface area and superior sorption properties at operational conditions of 30 °C, reaching relative adsorption of 59.89 % at P/Po of 100 %—up to 70 % higher than that of commercially available activated carbons. This material’s performance highlights its potential as a high-efficiency adsorbent in adsorption chillers, surpassing many commercially available options. However, the char obtained from excavated waste exhibited limitations due to high ash and heavy metal content (786 mg/kg Pb and 127 mg/kg Zn), suggesting challenges for its use in activated carbon synthesis. This study bridges a critical knowledge gap by exploring innovative pathways for utilizing waste-derived porous carbon materials in adsorption cooling, thus contributing to the development of sustainable, waste-based solutions for heat-driven cooling applications.

Three-Dimensional Printing of Metallic Parts by Means of Fused Filament Fabrication (FFF)

Obtaining metallic parts via Additive Manufacturing can yield several advantages over using other traditional manufacturing methods such as machining. Material extrusion (MEX) can handle complex shapes with porous structures and, at the present time, much low-end and desktop equipment is available. In the present work, different industrial and medical applications of metallic Fused Filament Fabrication (FFF) parts are presented. First, an overview of the process, equipment, and of the metal-filled filaments currently available is provided. Then, the properties of parts and different applications are shown. For example, metal-filled filaments with a low metal content that can be used to obtain plastic parts with metallic appearance (with either steel, copper, or bronze), and filaments with a high metallic content allow obtaining metallic parts with high mechanical strength after a sintering operation. The present contribution aims to be an up-to-date panorama for current industrial and medical results and lessons learnt from the application of FFF to obtain metallic parts.

Research on heavy metal enrichment and transportation in tea plant-soil systems of different varieties.

This study aimed to investigate heavy metal enrichment in different tea plant varieties and their distribution within different plant parts and to clarify the behavioral characteristics of heavy metals in the tea tree-soil system and their influencing factors. In this study, soil samples were collected from the root zones of 13 tea tree varieties in Guizhou, which had been planted for 10years. The aim was to compare the physicochemical properties of tea plantation soils under soil-forming matrixes and consistent management. Additionally, the study investigated the enrichment and transportation patterns of Cd, Cr, Cu, Pb, Zn, and Ni in the tea tree-soil systems of different tea tree varieties. The results showed that the planting of tea trees decreased the soil pH by 0.5; soil nutrients decreased; soil Pb, Cr, Ni, Cu, and Zn contents in the root zone increased; and Cd content decreased. Heavy metals were mainly enriched in the roots, and Zn, Cu, Ni, and other elements related to the protein and enzyme synthesis of tea trees could be mostly transported to the stems and leaves. There were significant differences in the enrichment and transportation of heavy metals among the different tea tree varieties. Under consistent soil-forming parent material, soil pH, organic matter, nutrients, and other indices only had a significant effect on heavy metal enrichment in the tea tree roots. Therefore, in areas with high background soil heavy metal contents, the construction of tea plantations should be based on regional soil environmental conditions to choose tea tree varieties with low heavy metal enrichment capacities to avoid the risk of high background soil heavy metals on the safe production of tea for consumers.

Gallium Methylene Ga8(CH2)12 on Mesoporous Silica

Gallium methylene Ga8(CH2)12 was grafted onto large‐pore mesoporous silica SBA‐15500 and mesoporous silica MCM‐41500 with smaller mesopores, each thermally pretreated at 500 °C. For comparability reasons, trimethylgallium was employed as a grafting reagent. The hybrid materials Ga8(CH2)12@SBA‐15500, GaMe3@SBA‐15500, Ga8(CH2)12@MCM‐41500 and GaMe3@MCM‐41500 were characterized by ICP‐OES, N2 physisorption, elemental analysis, solid‐state 1H/13C/29Si NMR spectroscopy and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. To gain further insight into potential surface species, the molecular compound Ga8(CH2)12 was treated with excess (eight equivalents) of HOSi(OtBu)3, which gave the dimeric species [GaMe2{OSi(OtBu)3}]2, being isolable also from the reaction of GaMe3 with one equivalent of silanol. The hybrid materials revealed high metal contents and surface species with intact Ga–CH2–Ga linkages as proposed by NMR spectroscopy and their reactivity toward benzophenone.

Spatiotemporal distributions, sources, and health risks of heavy metals in an acid mine drainage (AMD)-contaminated karst river in southwest China

Acid mine drainage (AMD), characterized by its acidity and high content of heavy metals, is a significant global environmental problem that harms human health through its impact on rivers. Therefore, this study aims to identify heavy metals in both surface and underground AMD-polluted karst rivers, focusing on the Zhijin River area which is severely affected by AMD, and assess their health risks to residents. Through the collection of 30 surface water samples and 16 groundwater samples from both wet and dry seasons, the study examines the concentration, sources of pollution, and health implications of six heavy metals (Fe, Mn, Cr, Cd, As, and Hg). The results showed that Fe and Mn levels in surface water were highly polluted during both seasons, especially during the wet season, with Fe levels reaching 20.0 mg/L and Mn levels reaching 1.9 mg/L. Further correlation and principal component analyses revealed that mining activities are the primary contributors to the contamination in this region. Health risk assessments and Monte Carlo simulation, including both deterministic and probabilistic, showed that the noncarcinogenic health risk indices for surface water and groundwater were within acceptable limits for both seasons. However, groundwater poses a higher carcinogenic risk to children, with As levels during the wet season and Cr levels during the dry season warranting close monitoring. Factors such as body weight and intake rate played a crucial role in health risk evaluations. This study underscores the need for further attention to groundwater risk, temporal heterogeneity in the Zhijin River.

Scalable synthesis of Robust, high-loading nitrogen-infused intermetallic FePt@Pt (core@shell) catalyst for proton exchange membrane fuel cells

In this study, we propose PtFeIMN@Pt/C, featuring a Pt shell on a nitrogen-infused PtFe intermetallic core structure, and attempt large-scale synthesis of catalysts with high metal content (>50 wt%). Using the ultrasound-assisted polyol synthesis method, we synthesize core@shell structured PtFe@Pt/C catalysts with approximately 60 wt% metal content at a 10 g scale in a single step. Post-treatments, including annealing, acid treatment, and nitriding in high-pressure NH3 gas, follow to synthesize the target catalysts. Optimizing the annealing temperature reveals a trade-off relationship affecting catalyst activity and durability. The PtFeIMN@Pt/C_600 °C, synthesized under optimized conditions, exhibits superior electrochemical performance and durability compared to commercial Pt/C catalysts. The accelerated stability test (AST) further shows significantly enhanced durability when nitrogen is included in the core. In the single cell tests, PtFeIMN@Pt/C_600 °C demonstrates approximately four times higher mass activity than commercial Pt/C catalysts and a 29.9 mV voltage drop at 0.8 A cm−2 after AST, meeting the U.S. Department of Energy's targets.

Biofilm formation dynamics in long-distance water conveyance pipelines: Impacts of nutrient levels and metal stress

Biofilm formation in long-distance water conveyance pipelines poses significant risks to water quality, particularly under varying nutrient levels and heavy metal stress. However, the impacts of pipeline material on biofilm formation dynamics under different raw water conditions remain elusive. This study investigated the effects of nutrient availability and Fe-Mn stress on biofilm development, structural stability, bacterial community composition, and the occurrence of viable but non-culturable (VBNC) bacteria. Using reactors with different nutrient conditions, we observed that increased nutrient levels promote biofilm growth but lead to greater instability, heightening the risk of secondary contamination. Notably, nutrient escalation beyond a critical threshold had a diminishing impact on biofilm community composition. Additionally, Fe-Mn stress, while initially enhancing microbial adhesion and metabolic activity, ultimately inhibited biofilm formation over time and increases the prevalence of VBNC bacteria, particularly on stainless steel (SS) surfaces. Our findings also highlighted the importance of material selection for pipelines, with polyvinyl chloride (PVC) showing reduced biofilm formation compared to SS, making it a more suitable option for transporting raw water in environments with high metal content. Dispersal limitation determined the bacterial community assembly during the biofilm formation, accounting for 64.53–90.67 % of the variability in different scenarios. These insights offer valuable guidance for managing biofilm-related issues in water distribution systems, emphasizing the need for careful control of nutrient levels and material choice to ensure water safety over long distances.