Metal Loading Research Articles

Distribution, toxicity load and risk assessment of heavy metals in the groundwater of Dhemaji, Assam, India

Metal contamination in drinking water has drawn attention since it gravely jeopardizes human health. This study was conducted in pre- and post-monsoon season in 2021 at Dhemaji, Assam, India. It characterized metal pollutants in groundwater, their distribution, possible sources, and evaluated the potential toxicity and associated health risk assessment. The seasonal mean concentration of Fe in both seasons is observed highest followed by Mn, Zn, Cu, As, and Ni. Furthermore, the metal concentrations during pre-monsoon are comparatively higher. The geogenic processes and agricultural practices are the major sources of groundwater metal contamination as evident from the statistical analysis. The different pollution indices viz. Heavy-metal Pollution Index (HPI), Heavy-metal Evaluation Index (HEI) and Degree of Contamination (Cd) suggested that groundwater is not suitable for drinking uses. The Heavy Metal Toxicity Load (HMTL) suggesting As, Co, Mn and Hg should be removed from the groundwater to ensure safety. Water pollution indices (WPI) suggest that Fe, Mn, As and Ni are the main pollution-causing metals in the study area which may be restored under the BIS and WHO limit by diluting the water. The human health risk has been calculated by carcinogenic and non-carcinogenic risk assessment. The non-carcinogenic risk for adults and children is within the threshold limit. The carcinogenic risk shows that continuous exposure of As and Ni may give rise to cancer among adults and children in the region. Therefore, comprehensive groundwater quality monitoring with well-planned treatment should be needed to provide safe and clean drinking water in the studied area.

Multimetal exposure: Challenges in diagnostics, prevention, and treatment.

Extensive use of heavy metals has posed a serious concern for ecosystem and human too. Heavy metals are toxic in nature and their accumulation in human body causes serious disorders such as neurological disease, cardiac disease, gastrointestinal problems, skin disorders, reproductive disease, lungs diseases, and so on. Furthermore, heavy metals not only affect the human health but also have a negative impact on the economy. In the current review, we have elaborated the impact of heavy metal exposure on human health and socioeconomics. We have discussed the molecular mechanism involved in the heavy metal-induced human disorders such as oxidative stress, neuroinflammation, and protein misfolding. Finally, we discussed the preventive measure and treatment strategy that could counter the negative effects of heavy metal intoxications. In conclusion, there is a substantial correlation between heavy metals and the onset and advancement of several health issues. Chelation treatment could be a useful tactic to lessen the toxic metal load and the difficulties that come with it.

Phytochemical Profiling, Evaluation of Heavy Metal Load, Antioxidant and Antibacterial Activity of Various Medicinal Plants

In Ethiopia, medicinal herbs have played a prominent role in relieving pain and curing various diseases for humans and animals for many years. However, consumers don't know what kinds of phytochemicals are in the plants or the amount of metal they contain. Thus, in this study, polyphenol content, flavonoid content, antioxidant capacities, antibacterial activity and the level of metals in Asparagus africanus root, Ferula communis, Stephania abyssinia, Brucea antidysenterica and Vernonia amygdalina, were analyzed. Identifying the phytochemicals, antioxidant and antibacterial activities, and levels of metals in medicinal plants ensures their safety and efficacy and provides a deeper understanding of the healing properties of plants in areas where modern medicines are not easily accessible. The antioxidant activity was determined by 2,2-diphenyl- 1-picrylhydrazyl (DPPH) radical assay, and the antibacterial activity was evaluated by disc diffusion method. Among the studied plant extracts, Vernonia amygdalina displayed the maximum phenolic content (810 mg GAE/100 g), flavonoid content (515.78 mg QE/100 g), and DPPH radical scavenging activity (14.42 mg AAE/g), whereas the least level of total phenolic (160.82 mg GAE/100 g), total flavonoid (30.65 mg QE/100 g), and DPPH radical scavenging (1.14 mg AAE/g) were recorded in Asparagus africanus. The highest inhibition zone was recorded, with an inhibitory zone of 11 mm for S. aurous and 11 mm for E. coli. The least zone of inhibition was obtained in gram-negative bacteria (K. pneumonia) with a diameter less than 8 mm. Asparagus africanus contained the highest levels of Mn and Fe, while Cu and Zn were found to be the highest in Stephania abyssinia. Cr was only detected in Ferula communis, and Cd was found to be below the detection limit. Due to their better antioxidant and antibacterial properties, the extracts of these plants might be used as a natural starting material in treating cancer and to prepare anti-cancer drugs.

Evaluation of Heavy Metal Contamination and Associated Human Health Risk in Soils around a Battery Industrial Zone in Henan Province, Central China

This research investigated the contamination characteristics, sources, and health risks of five metals in soils from two villages named DK and SXC, downstream from a battery industry hub in Xinxiang city, Henan Province, China. The average concentrations of Cd, Pb, Ni, Cu, and Zn in DK were 5.93, 41.31, 71.40, 62.20, and 115.83 mg/kg, respectively, and in SXC were 2.04, 30.41, 41.22, 36.18, and 96.04 mg/kg, respectively. The single factor pollution index (Pi) revealed a consistent descending order of Cd > Cu > Zn > Ni > Pb in DK and SXC. The geo-accumulation index (Igeo) indicated that the Cd pollution in DK was extreme, and in SXC was at a heavy to extreme level. The potential ecological risk index (PERI) indicated that Cd presented a significantly high ecological risk while it was low for other metals. Principal component analysis classified them into the anthropogenic origin of Cd and common mixed origin of others. The elevated levels and pollution load of heavy metals with closer proximity to the battery factory imply that the factory is a probable source of contamination. Overall, the health risks posed by heavy metals were more pronounced for local children compared to adults, with Cd being the primary contributor to both pollution and health risks. This investigation provides a crucial basis for the heavy metal pollution management and related risk prevention in areas affected by electronic waste irrigation.

Metal mobilization from thawing permafrost to aquatic ecosystems is driving rusting of Arctic streams

Climate change in the Arctic is altering watershed hydrologic processes and biogeochemistry. Here, we present an emergent threat to Arctic watersheds based on observations from 75 streams in Alaska’s Brooks Range that recently turned orange, reflecting increased loading of iron and toxic metals. Using remote sensing, we constrain the timing of stream discoloration to the last 10 years, a period of rapid warming and snowfall, suggesting impairment is likely due to permafrost thaw. Thawing permafrost can foster chemical weathering of minerals, microbial reduction of soil iron, and groundwater transport of metals to streams. Compared to clear reference streams, orange streams have lower pH, higher turbidity, and higher sulfate, iron, and trace metal concentrations, supporting sulfide mineral weathering as a primary mobilization process. Stream discoloration was associated with dramatic declines in macroinvertebrate diversity and fish abundance. These findings have considerable implications for drinking water supplies and subsistence fisheries in rural Alaska.

IrO2 Oxygen Evolution Catalysts Prepared by an Optimized Photodeposition Process on TiO2 Substrates.

Preparing high-performance oxygen evolution reaction (OER) catalysts with low precious metal loadings for water electrolysis applications (e.g., for green hydrogen production) is challenging and requires electrically conductive, high-surface-area, and stable support materials. Combining the properties of stable TiO2 with those of active iridium oxide, we synthesized highly active electrodes for OER in acidic media. TiO2 powders (both commercially available Degussa P-25® and hydrothermally prepared in the laboratory from TiOSO4, either as received/prepared or following ammonolysis to be converted to titania black), were decorated with IrO2 by UV photodeposition from Ir(III) aqueous solutions of varied methanol scavenger concentrations. TEM, EDS, FESEM, XPS, and XRD measurements demonstrate that the optimized version of the photodeposition preparation method (i.e., with no added methanol) leads to direct deposition of well-dispersed IrO2 nanoparticles. The electroactive surface area and electrocatalytic performance towards OER of these catalysts have been evaluated by cyclic voltammetry (CV), Linear Sweep Voltammetry (LSV), and Electrochemical Impedance Spectroscopy (EIS) in 0.1 M HClO4 solutions. All TiO2-based catalysts exhibited better mass-specific (as well as intrinsic) OER activity than commercial unsupported IrO2, with the best of them (IrO2 on Degussa P-25® ΤiO2 and laboratory-made TiO2 black) showing 100 mAmgIr-1 at an overpotential of η = 243 mV. Chronoamperometry (CA) experiments also proved good medium-term stability of the optimum IrO2/TiO2 electrodes during OER.

Spatiotemporal and multi-isotope assessment of metal sedimentation in the Great Lakes

This study investigates spatiotemporal dynamics in metal sedimentation in the North American Great Lakes and their underlying biogeochemical controls. Bulk geochemical and isotope analyses of n=72 surface and core sediment samples show that metal (Cu, Zn, Pb) concentrations and their isotopic compositions vary spatially across oligotrophic to mesotrophic settings, with intra-lake heterogeneity being similar or higher than inter-lake (basin-scale) variability. Concentrations of Cu, Zn, and Pb in sediments from Lake Huron and Lake Erie vary from 5 to 73 mg/kg, 18 to 580 mg/kg, and 5 to 168 mg/kg, respectively, but metal enrichment factors were small (<2) across the surface- and core sediments. The isotopic signatures of surface sediment Cu (δ65Cu between −1.19‰ and +0.96‰), Zn (δ66Zn between −0.09‰ and +0.41‰) and Pb (206/207Pb from 1.200 to 1.263) indicate predominantly lithogenic metal sourcing. In addition, temporal trends in sediment cores from Lake Huron and Lake Erie show uniform metal concentrations, minor enrichment, and Zn and Pb isotopic signatures suggestive of negligible in-lake biogeochemical fractionation. In contrast, Cu isotopic signatures and correlation to chlorophyll and macronutrient levels suggest more differentiation from source variability and/or redox-dependent fractionation, likely related to biological scavenging. Our results are used to derive baseline metal sedimentation fluxes and will help optimize water quality management and strategies for reducing metal loads and enrichment in the Great Lakes and beyond.

Improvement of hydrogen production via aqueous phase reforming of glycerol with Ni-Co catalysts synthesized through controlled urea matrix combustion

The effect of synthesis variable control during the combustion of urea in solution to obtain a Ni-Co/γ-Al2O3 catalyst with a low metallic loads for producting hydrogen by reforming glycerol was studied. Catalysts with the same urea/metal molar ratio but synthesized by controlled or uncontrolled urea matrix combustion were compared. It has been observed that adopting a urea/metal molar ratio between 2 and 6 and a heating rate of 10 °C∙min−1 results in a catalyst with an active surface and high Ni-Co interaction. This leads to significant improvements in H2 yield (from 34 to 50%), glycerol conversion (from 35 to 50%), and H2 selectivity (from 96 to 99%), while maintaining stability during 420 min of reaction. The repeatability of controlled synthesis has shown differences in results of less than 2%. Controlled synthesis is an attractive approach for scaling up the process for treating glycerinous waters, effluents in biodiesel plants.

Spatial and temporal distribution of nitrogen, phosphorus, and heavy metals loads in Guanshan River Basin based on SWAT modeling

ABSTRACT This study takes Guanshan River Basin, a typical inflow river of the Danjiangkou Reservoir, as the research area, and the nonpoint source (NPS) pollution characteristics of nitrogen and phosphorus from 2013 to 2018 were evaluated by establishing a Soil and Water Assessment Tool (SWAT) model. The pollution characteristics of heavy metals were also evaluated by combining the SWAT and simple output coefficient method. The results show that the pollutant load in Guanshan River Basin contributes significantly to the Danjiangkou Reservoir. Temporally, pollutant loads were primarily concentrated in the flood season, which had a significant positive correlation with precipitation, water yield, and sediments in the abundant period. Among them, sediments were the most important driving factor, followed by water yield. Spatially, pollutant loads were mainly concentrated downstream of the basin, where cultivated land is widespread. In this regard, it is suggested that the input of chemical fertilizers, pesticides, and livestock manure in cultivated land should be controlled and soil erosion downstream of the basin should be prevented to mitigate nitrogen, phosphorus, and heavy metal pollution. This research offers a basis for the formulation and implementation of watershed management for the Danjiangkou Reservoir.

Effects of the Type and Loading of Rare-Earth Metals (Pr, Yb, Ho) on the para-Selectivity of HTsVM Zeolite in Toluene Ethylation

Effects of the Type and Loading of Rare-Earth Metals (Pr, Yb, Ho) on the para-Selectivity of HTsVM Zeolite in Toluene Ethylation

Experimental study of low-temperature combustion performance in hydrogen/air mixtures over Pt–Cu/HZSM-5/cordierite bimetallic catalysts

Catalytic combustion provides a feasible technology to effectively avoid NOx formation due to the high temperature in the process of hydrogen combustion. Recently, the development of efficient and affordable catalysts has attracted extensive attention as the cost of noble metals remained high. In this study, a list of cordierite monolithic catalysts with low noble metal loading are prepared by introducing the appropriate amount of transition metals (Mn, Cu, Fe, Co, and Ce), and their catalytic performance are further investigated. On this basis, the study on catalytic stability and kinetic is carried out, and the synergistic interaction between the bimetals is revealed with comprehensive characterization methods. The results show that Cu could promote the reaction rate of the Pt-based catalyst which show the best catalytic performance with the Cu loading of 1 g/L. The ignition temperature T10 is 58.5 °C, and the burnout temperature T100 is 100 °C, with activation energy as low as 44.00 kJ/mol. The enhancement of the catalytic performance is attributed to the interaction between the bimetallic elements. On the one hand, the valence state of Cu and Pt is changed, and on the other hand the dispersion of Pt get improved, which contributed to the catalytic reaction rate.

Spray‐dried Ni‐Co bimetallic catalysts for dry reforming of methane

Dry reforming of methane (DRM) is an attractive reaction for synthesis gas production, since it converts two green‐ house gases into valuable chemical feedstock. Silica sup‐ ported bimetallic catalysts with constant metal loading but varying Ni/Co ratios (xNi = 1, 0.8, 0.6, 0.5, 0.4, 0.2, 0) were produced via spray‐drying for the application in DRM, aim‐ ing at the identification of compositions with superior activ‐ ity. In this study, building block particles refer to an inert framework, supporting the catalyst. The elemental distri‐ bution of Si, Ni, and Co within such building block parti‐ cles was evaluated using scanning transmission electron mi‐ croscopy. Additionally, X‐ray diffraction and temperature‐ programmed reduction experiments confirmed that Ni and Co initially exist in an oxidic state within the SiO2 frame‐ work after production and later transform into an alloyed metallic state upon reduction with hydrogen, as confirmed by X‐ray photoelectron spectroscopy. A systematic compar‐ ison of the activity over a temperature range (323‐1150 K) was performed using temperature scanning measurements. The highest intrinsic activity was found with the bimetallic Ni40Co60 particles.

Pseudo-total metal loads in dusts and soils of the steel city and coal capital of India: source apportionment and assessment of human health and ecological risks

Pseudo-total metal loads in dusts and soils of the steel city and coal capital of India: source apportionment and assessment of human health and ecological risks

Advanced polymer electrolyte membrane water electrolysis for power to gas applications

Abstract Water electrolysis fed by renewable energy is the foremost technology to generate green hydrogen. Relevant challenges regard decrease of precious metal loadings and performance enhancement while maintaining cutting edge efficiency. Next generation electrolysers must provide dynamic behaviour to improve grid-balancing services and thus integrate with the grid the intermittent renewable energy sources. The HPEM2GAS project developed a low-cost optimised PEM electrolyser for grid management through both stack and balance of plant innovations.

Surface modified FeCoZn-ZIF derived polyhedral electrocatalysts for ORR under alkaline and acidic conditions

Electrocatalysts for catalyzing oxygen reduction reactions at variable pH conditions are essential for energy conversion and storage. Herein, Fe@FeCoZn–CN electrocatalysts were prepared with internal and external doping approach. The Fe@FeCoZn–CN electrocatalyst exhibits a desirable ORR performance in both acid and alkaline electrolytes. Specifically, the half-wave potential (E1/2) of Fe@FeCoZn–CN electrocatalyst is 0.890 V which far beyond Pt/C electrocatalyst (0.839 V) in alkaline electrolyte. In addition, Fe@FeCoZn–CN electrocatalyst also exhibits improved ORR activity (E1/2 = 0.801 V) compared to Pt/C (0.797 V) electrocatalysts in acidic electrolytes. What's exciting is that the rechargeable ZABs based on Fe@FeCoZn–CN electrocatalysts exhibit an impressive performance with a favorable open-circuit potential of 1.517 V and a promising specific capacity is 833.7 mA h gzn−1, good charge/discharge cycle stability. The remarkable ORR catalytic performance of Fe@FeCoZn–CN electrocatalysts can be traced to the internal doping of metals which prevent excessive metal aggregation and surface modified which can increase the metal loading to expose more active sites.

Heavy metals in afforested mangrove sediment from the world's largest delta: Distributional mapping, contamination status, risk assessment and source tracing

This study aims to assess seasonal and spatial variations, contamination status, ecological risks, and metal sources (Ni, Pb, Cr, Cu, Mn, and Zn) in human-afforested mangrove sediments in a deltaic region. Five sampling locations were sampled during dry and wet seasons. Heavy metal concentrations followed the order: Mn > Zn > Ni > Cr > Cu > Pb. Metal loads, except Cu and Pb, were higher during the dry season, aligning with national and international recommendations. Sediment quality guidelines, contamination factor, geoaccumulation index, enrichment factors, and pollution load index indicated uncontaminated sediment in both seasons. Potential ecological risk assessment showed low risk conditions in all sites. However, modified hazard quotient indicated moderate pollution risk from all metals except Pb. Analysis suggests anthropogenic sources, particularly evident near shipbreaking yards in Sitakunda. While initially uncontaminated, ongoing metal influx poses a potential risk to mangrove ecosystems.

Boosting photocatalytic water splitting of TiO2 using metal (Ru, Co, or Ni) co-catalysts for hydrogen generation

The photocatalytic activity of titanium dioxide (TiO2) nanoparticles toward hydrogen generation can be significantly improved via the loading of various metals e.g., Ru, Co, Ni as co-catalysts. The metal co-catalysts are loaded into TiO2 nanoparticles via different deposition methods; incipient wet impregnation (Imp), hydrothermal (HT), or photocatalytic deposition (PCD). Among all of the tested materials, 0.1 wt% Ru–TiO2 (Imp) provided the highest initial hydrogen catalytic rate of 23.9 mmol h−1 g−1, compared to 10.82 and 16.55 mmol h−1 g−1 for 0.3 wt% Ni–TiO2 (Imp) and 0.3 wt% Co–TiO2 (Imp), respectively. The loading procedures, co-catalyst metals type, and their loading play a significant role in elevating the photocatalytic activity of pristine TiO2 semiconductors toward hydrogen generation. Redox transition metals e.g., Co and Ni exhibit comparable photocatalytic performance to expensive elements such as Ru.

Valorization of agroindustrial orange peel waste during the optimization of activated carbon–multiwalled carbon nanotubes–zinc oxide composites used in the removal of methylene blue in wastewater

Activated carbons (AC) produced from agroindustrial orange peel (OP) wastes and/or commercial multi–walled carbon nanotubes (MWCNTs) were modified with ZnO nanoparticles in different amounts (15 and 30 wt–%) for the removal of methylene blue in aqueous solutions. The MWCNTs functionalization was carried out by typical procedure in acid medium using a ratio of 3:1 (HNO3/H2SO4). A batch adsorption analysis was carried out evaluating different parameters: MB concentration from 40 to 100 mg L–1; pH values between 4 and 10 and adsorption time that varied from 1 to 48 h. The modified materials were characterized through the techniques XRD, FTIR, BET, TGA, SEM and UV–vis. The results showed an adequate dispersion of ZnO NPs on the carbon surfaces with a typical flower–like morphology this type of shape developed micropores that facilitate adsorption phenomena. Under the evaluation conditions, 20 mg of carbon–based materials can remove up to 89.5 ± 4.47 % of MB (80 ppm) after 24 h of exposure at a regulated pH of 8. The equilibrium adsorption data were better fitted by a Langmuir isotherm (R2 = 0.9999) than the Freundlich model (R2 = 0.9366); showing in the best case a maximum adsorption capacity of 1250 mg g−1 for both materials with 30 wt–% of ZnO NPs (AC–MWCTs or MWCNTs). Experimental data also suggest that the most likely mechanism is chemisorption followed by physical adsorption. Then, the compounds with 30 wt–% metal loading (ZnO NPs), AC–MWCNTs–ZnO or MWCNTs–ZnO, displayed the most interesting properties for MB dye removal. AC–ZnO compounds can also remove about 88.75 ± 4.43 % of MB, demonstrating that it can also be a facile and low–cost method to improve the surface area in carbonaceous structures by promoting a strong interaction with the ZnO NPs, which in turn helps to remove contaminants in water efficiently.

Unveiling the effects of nickel loading on methane dry reforming: Perspectives from ni/fibrous Zeolite-Y catalysts

The development of new technologies that employ greenhouse gases, such as CO2 and CH4, is becoming more important in the fight against global warming. Catalytic methane dry reforming (MDR) is one straightforward way to reduce CO2 and CH4. In this study, the influence of nickel (Ni) loading on the catalytic performance of fibrous zeolite-Y catalysts (Ni/FHY) for MDR was explored. The study involved the synthesis and testing of Ni/FHY with varying Ni loadings (1 wt% to 10 wt%). The results demonstrate that the metal loading significantly affects the catalysts' performance through metal-support interaction. The catalytic activity showed that the performance of FHY increased with optimum metal loading of 5 wt% where the CO2 conversion increased to 90.3% from 82.2%, and CH4 conversion to 94.2% from 79.6%. The findings suggest that the 5 wt% optimal Ni loading showed the critical role of the metal-support interaction in shaping catalytic properties. Hence, this work provides insights into catalyst optimization for sustainable industrial processes, highlights the importance of the synergistic metal-support interaction, and provides insights into the relationship between Ni content and catalytic behavior. Thus, it offers a basis for optimizing catalysts in MDR and contributes to the advancement of sustainable industrial processes.

TiO2 nanotubes modification by photodeposition with noble metals: Characterization, optimization, photocatalytic activity, and by-products analysis

Self-organized TiO2 nanotubes (TNTs) with 4 µm length were obtained by anodization method and calcined to obtain anatase crystallite phase. The photocatalysts were further decorated with Au, Ag, Pt or Pd nanoparticles (NPs), varying the metal loads (0.50, 0.75, 1, 2 and 5 mol%) by photodeposition. The material characterization confirmed the presence of nanoparticles in the TNTs surface, signs of the localized surface plasmon resonance (LSPR) effect for some samples and a bandgap energy of 3.1–3.2 eV. Photoluminescence measurements also confirmed that most of the samples with metallic nanoparticles had the recombination of photogenerated carriers lowered due to the trapping effect of the deposited metal NPs. The photoactivity was evaluated by phenol degradation using UV-Vis or visible radiation. Under UV-Vis, the best samples (2 and 5 mol% of Au-TNTs and 0.75, 1, and 2 mol% of Pd-TNTs) led to 97% phenol removal in 60 min while pristine TNTs reached 92% removal. Under visible radiation, the pristine and the Au-TNTs led to about 3% removal, with the best sample being 2 mol% Pd-TNTs with 14% removal in 60 min. Similar results were obtained for 1 and 5 mol% Pd-TNTs (12% and 13% of phenol removal, respectively). The by-products analysis suggest different degradation mechanisms and it is observed different kinetic rates for different metal types, metal loads or types of radiation.