High Copper Concentrations Research Articles

Heavy metal immobilisation with microbial-induced carbonate precipitation: a review

Microbial-induced carbonate precipitation (MICP) is a promising bioremediation technology for heavy metal immobilisation. This review explores the applications and efficacy of MICP in environmental challenges. It provides a comprehensive overview of the mechanism, primarily through ureolysis, detailing the process from urea hydrolysis to heavy metal precipitation as carbonate minerals. Alternative pathways like photosynthesis and nitrate reduction are also discussed, highlighting the broad applicability of MICP. The review covers the historical evolution and advancements of MICP as a sustainable solution for heavy metal contamination. Recent studies demonstrate the efficiency of MICP in achieving high removal rates in diverse environments. The sustainable operation, precise targeting of heavy metal species, and versatility of MICP are examined. Challenges such as high copper concentrations, acidic conditions, and cost considerations are addressed. The article provides future directions and solutions to these challenges, including leveraging machine learning for optimal performance and enhancing cost considerations through detailed analyses. This review improves understanding of MICP’s potential, provides a valuable resource for researchers in environmental engineering and the built environment, and encourages innovative approaches within these fields.

Copper biomarkers and their relationship with parameters of insulin resistance in obese women.

Some studies have demonstrated the involvement of high concentrations of copper in the manifestation of insulin resistance in individuals with obesity. The objective of this study was to evaluate the copper nutritional status and its relationship with parameters of glycemic control in women with obesity. An observational case-control clinical study involving 203 women aged between 20 and 50years, divided into two groups: obese (n = 84) and eutrophic (n = 119). Body weight, height and waist, hip and neck circumferences, dietary copper intake, copper biomarkers, determine ceruloplasmin activity and glycemic control parameters were measured. It was observed that women with obesity had higher copper concentrations in plasma and lower concentrations in erythrocytes when compared to the control group. Analysis of glycemic control parameters revealed a statistically significant difference in fasting blood glucose (p < 0.05) between groups. The study identified a significant positive correlation between plasma copper and fasting insulin values and the Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) index (p < 0.05). The results of this study demonstrate that obese women have high copper concentrations in plasma and lower concentrations in erythrocytes. Furthermore, the significant positive correlation between plasma copper and fasting insulin and HOMA-IR index suggests the influence of this mineral on glycemic control parameters in obese women.

Optimization of Copper-Ammonia-Sulfate Electrolyte for Maximizing Cu(I):Cu(II) Ratio Using pH and Copper Solubility

An investigation has been carried out to understand the solution chemistry of the Cu-NH−-SO4−2 system, focusing on the effect of pH on the solubility of copper in the solution and maximizing the Cu(I):Cu(II) ratio. A Pourbaix diagram for the Cu-N-S system has also been created using the HSC Chemistry software for a wide range of Cu-NH3 species, unlike most other studies that focused only on Cu(NH3)42+ and Cu(NH3)52+ (Cu(II)) as the dominant species. The Pourbaix diagram demonstrated that the Cu(I) exists as Cu(NH3)2+, while the Cu(II) species are present in the system as Cu(NH3)42+ and Cu(NH3)52+, depending upon the Eh and pH of the solution. Copper precipitation was observed in the electrolyte at pH values less than 8.0, and the precipitation behavior increased as the pH became acidic. The highest Cu(I):Cu(II) ratio was observed at higher pH values of 10.05 due to the higher solubility of copper at higher alkaline pH. The maximum Cu(II) concentration can be achieved at 4.0 M NH4OH and 0.76 M (NH4)2SO4. In the case of low pH, the highest Cu(I):Cu(II) ratio obtained was 0.91 against the 4.0 M and 0.25 M concentrations of NH4OH and (NH4)2SO4, respectively. Meanwhile, at high pH, the maximum Cu(I):Cu(II) ratio was 15.11 against the 0.25 M (NH4)2SO4 and 4.0 M NH4OH. Furthermore, the low pH experiments showed the equilibrium constant (K) K &lt; 1, and the high pH experiments demonstrated K &gt; 1, which justified the lower and higher copper concentrations in the solution, respectively.

The balance between alleviating copper damage and maintaining root function during root pruning with excessive copper.

Coating high concentrations of copper (Cu) on the inner wall of containers can efficiently inhibit root entanglement of container-grown seedlings. However, how the protective and defensive responses of roots maintain root structure and function during Cu-root pruning is still unclear. Here, Duranta erecta seedlings were planted in the containers coated with 40 (T1), 80 (T2), 100 (T3), 120 (T4), 140 (T5), and 160 (T6) g L-1 Cu(OH)2 with containers without Cu(OH)2 as the control. Although T5 and T6 produced the best inhibitory effect on root entanglement, root anatomy structure was damaged. T1 and T2 not only failed to completely control root circling, but also led to decreased root activity and stunted growth. Cu(OH)2 treatments significantly increased lignin concentration of roots with the highest values at T3 and T4. Compared with T3, seedlings at T4 had higher height, biomass, and root activity and no significant root entanglement. Excessive Cu accumulation in Cu(OH)2 treatments changed the absorption of other mineral nutrients and their allocation in the roots, stems, and leaves. Overall, Ca was decreased while Mg, Mn, Fe, and K were increased, especially K and Mn at T4 which is related to defense capacity. The results indicate that there is a Cu threshold to balance root entanglement control, defense capacity, and nutrient uptake function under excessive Cu for container-grown D. erecta seedlings.

4-Diphenylaminobenzaldehyde-formulated isonicotinohydrazide for the rapid recognition of Cu2+ ions; Application of RGB tool, pharmaceutical samples, and DFT studies

High copper concentrations have been linked to several harmful illnesses in humans and negatively affect the kidneys and liver. The design and synthesis of simple and effective chemosensors for recognizing copper (Cu2+) ions are extremely significant. However, most of the colorimetric chemosensors have been developed using an intramolecular charge transfer binding mechanism based on donor-acceptor conjugation systems. This study aimed to fabricate a novel Schiff base colorimetric chemosensor, N'-(4-(diphenylamine) benzylidene) isonicotinohydrazide (DPBA-INH), with high sensitivity and selectivity towards copper ions in the semi-aqueous medium (DMSO: H2O, 7:3, v/v). The synthesized receptor DPBA-INH was distinguished using various spectroscopic methods, including NMR analysis, Fourier transform infrared spectroscopy, HRMS, and ultraviolet-visible (UV–vis) spectroscopy. When exposed to sunlight, the receptor DPBA-INH with Cu2+ ion complexation exhibited a color change from orange to pale yellow. A Job's plot and electrospray ionization mass spectra confirmed the presence of complexation at a stoichiometric binding proportion of the receptor to Cu2+ ions of 1:1. The receptor DPBA-INH interacts with Cu2+ ions in a 1:1 stoichiometric manner with a detection limit of 1.40 × 10−7 M. The experimental results were supported by a theoretical DFT study. Moreover, the receptor effectively measured Cu2+ ions in pharmaceutical samples and test strip analyses. Furthermore, the rapid colorimetric recognition of Cu2+ ions in a semi-aqueous medium was achieved using DPBA-INH, which was demonstrated to be an excellent receptor. Notably, DPBA-INH was employed to detect copper ions in real water samples.

Fundamentals of copper(II) adsorption on phyllosilicate minerals relevant to crud formation in solvent extraction from heap leach liquors

Because of the common presence of different silicate minerals, like kaolinite, montmorillonite and muscovite as gangue minerals in the beneficiation of copper oxide ores, the interaction between copper(II) ions in solution and each of these minerals is a field of strong interest, considering their implications on the aggregation of these minerals in the extreme pH conditions typical of hydrometallurgical unit operations for copper production. After copper adsorption isotherms determination at pH 2 and 4, specific adsorption data were fitted to both Langmuir and Freundlich models. It was found that adsorption is systematically larger at pH 4, and that montmorillonite is the mineral that displays a larger adsorption capacity, as in principle expected by its larger cation exchange capacity, CEC. A good fitting to the Langmuir model was obtained for the three samples, and montmorillonite also appears to conform to Freundlich isotherm predictions, as the tested concentrations of copper(II) do not allow to reach saturation. Furthermore, some desorption is measured for kaolinite and muscovite at the highest copper concentrations, probably because of significant interactions between the adsorbed ions. No such desorption was detected in montmorillonite samples. An XPS analysis of the surfaces of the three minerals suggests that copper adsorption in kaolinite is not associated to a cation exchange process but rather to electrostatic interactions between silica-like faces of the clay. In contrast, ionic exchange of structural calcium (for montmorillonite) or potassium (in the case of muscovite) seems to be the predominant mechanism of Cu(II) adsorption in the other two samples. Electrophoretic mobility determinations agree with this hypothesis: the mobility (always negative, with no traces of charge inversion) decreases in absolute value when kaolinite particles are in contact with solutions of increasing copper concentration at pH 2 or pH 4. On the other hand, the electrophoretic mobility values of muscovite and montmorillonite showed a weak pH and copper concentration dependence, a result that matches well with the ion exchange processes detected in the XPS measurements.

The antibacterial activity of the copper for Staphylococcus aureus 124 and Pseudomonas aeruginosa 18 depends on its state: metalized, chelated and ionic.

The hypothesis that the antibacterial effect of copper depends on its state was tested. It was studied the antibacterial effect of copper applied to the fabric, copper in chelated and free (ionic) forms on the growth intensity of Staphylococcus aureus 124 and Pseudomonas aeruginosa 18 in the in vitro system after a single or “primary” contact. Classical microbiology methods were used. Copper was applied to the fabric by magnetron and arc planar discharge systems, and the culture of microalgae Dunaliella viridis, resistant to the action of high concentrations of copper, was used to obtain copper in chelated form. It was shown that a thin layer of copper (3 μm) applied to the fabric showed pronounced antibacterial activity against Staphylococcus (85% compared to the antibiotic meropenem) and less pronounced activity against Pseudomonas, which is resistant to meropenem. Copper in ionic form inhibited the growth of Staphylococcus aureus 124 as well as the antibiotic, and also effectively inhibited the growth of Pseudomonas aeruginosa 18 i.e., copper ions did not have species specificity like the antibiotic. Components of Dunaliella viridis microalgae cells had weakly expressed antibacterial effect to these types of bacteria, and supplementary addition of copper sulfate to the biomass of microalgae led to an increase of their antibacterial activity and this is more pronounced for microalgae culture in which the ratio «chelated/ionic» forms of copper is shifted to the ionic form. It was shown that the antibacterial activity of microalgae biomass after the first introduction into the tested bacterial cultures depends on the amount of free or “weakly bound” with cell components copper ions. It is suggested that the antibacterial effect of fabric with a thin layer of copper may be determined by two mechanisms: the action of copper ions and mechano-bactericidal effects, while chelated forms of copper may have a prolonged effect on bacterial cultures.

The experience of iron determination in technogenic materials with a high copper content by the redox titration method: case study of the waelz slag

Redox titration is one of the most common classical methods widely used in practice for the determination of total iron. A well-known procedure ISO 2597-1 (GOST 32517) includes the decomposition of a sample with dissolution, the reduction of Fe3+ to Fe2+ using a SnCl2 solution and its titration with a K2Cr2O7 solution in the presence of sodium or barium diphenylaminosulfonate as an indicator. We propose to use potassium tetrahydroborate KBH4 as a reducing agent for Fe3+ to Fe2+ instead of SnCl2 to modify a titrimetric method of total iron determination. The features of the well-known and considered methods are studied when using sintering for sample decomposition during the analysis of a large number of samples. Application of the developed method for the analysis of standard samples and technogenic materials with a high copper content, namely, Waelz slag showed a satisfactory accuracy and reproducibility of the obtained values of the total iron content. The results obtained indicate the possibility of the application of this method to the iron determination in the samples with a high copper content without an additional step of the iron separation from copper. A high productivity of the analysis (apart from the absence of the separation stage) is achieved due to the simplicity of the reduction process occurred at room temperature, no need for the control of the added amount of the reducing agent, and the possibility of holding the solutions for a long time before the titration. These advantages along with the no need for using toxic mercury compounds during the analysis make the method attractive for the analysis of a large number of samples.

Revealing the Impact of Composition on Oil Monitoring Performance of Ni-Ti-Cu Coated Optical Fiber

Shape Memory Alloy-coated optical fiber provides an economical, Smart, and real-time monitoring technological solution for Industry 4.0. In this work, the compositional influence of Ni-Ti-Cu coating on optical signal actuation has been studied. Morphological studies showed improvement in the grain size, surface roughness, and a better shape memory effect. Thermal characteristics revealed an increase in the phase transformation temperature of NiTiCu with higher copper content. Experimental analysis of optical fiber sensors in Mineral Oil resulted in a gradual shift in the actuation temperature range. A sensitivity of ∼52 mV/°C was recorded in the actuation window, showcasing the improved response time for copper-rich composition. A comparison of coated-uncoated optical fiber performance in oil has also been presented, and delamination studies were conducted by continuously exposing the samples to hot oil. The work can be referred for requirement-based composition selection for real-time and smart monitoring capability in the Oil industries.

Effect of Cu content on the microstructure and properties of sintered Fe-0.8C-xCu antifriction materials

Abstract Ferrous antifriction materials (FAMs) play a crucial role in powder metallurgy. Previous studies have primarily focused on exploring the antifriction properties of Fe-C-Cu materials with low copper content (0–5 wt%), while there have been fewer studies on high copper content FAMs. In this study, to investigate the effect of Cu content on the microstructure and properties of sintered FAMs, Fe-0.8C-xCu (x = 5–25 wt%) materials were prepared by powder metallurgy method. The density, microstructure, mechanical performance, friction and wear properties of the samples were analyzed. The results demonstrated a significant change in the relative density, hardness, friction and wear properties of sintered Fe-0.8C-xCu samples with increasing Cu content. Particularly, the Fe-0.8C-15Cu samples exhibited outstanding properties, with a relative density of 77.8%, a hardness of 43 HRB, crushing strength of 380 MPa, an average friction coefficient of 0.21, and a wear rate of 1.36 × 10−8 mm3 N·mm−1. The primary wear mechanisms of the Fe-0.8C-xCu specimens include abrasive wear, adhesion wear, chafing fatigue, pitting, and oxidation. This study aims to provide an experimental and theoretical basis for the development of ferrous antifriction materials suitable for heavy-load conditions.

Effect of Citric Acid Hard Anodizing on the Mechanical Properties and Corrosion Resistance of Different Aluminum Alloys.

Hard anodizing is used to improve the anodic films' mechanical qualities and aluminum alloys' corrosion resistance. Applications for anodic oxide coatings on aluminum alloys include the space environment. In this work, the aluminum alloys 2024-T3 (Al-Cu), 6061-T6 (Al-Mg-Si), and 7075-T6 (Al-Zn) were prepared by hard anodizing electrochemical treatment using citric and sulfur acid baths at different concentrations. The aim of the work is to observe the effect of citric acid on the microstructure of the substrate, the mechanical properties, the corrosion resistance, and the morphology of the hard anodic layers. Hard anodizing was performed on three different aluminum alloys using three citric-sulfuric acid mixtures for 60 min and using current densities of 3.0 and 4.5 A/dm2. Vickers microhardness (HV) measurements and scanning electron microscopy (SEM) were utilized to determine the mechanical characteristics and microstructure of the hard anodizing material, and electrochemical techniques to understand the corrosion kinetics. The result indicates that the aluminum alloy 6061-T6 (Al-Mg-Si) has the maximum hard-coat thickness and hardness. The oxidation of Zn and Mg during the anodizing process found in the 7075-T6 (Al-Zn) alloy promotes oxide formation. Because of the high copper concentration, the oxide layer that forms on the 2024-T6 (Al-Cu) Al alloy has the lowest thickness, hardness, and corrosion resistance. Citric and sulfuric acid solutions can be used to provide hard anodizing in a variety of aluminum alloys that have corrosion resistance and mechanical qualities on par with or better than traditional sulfuric acid anodizing.

Functional genomics and taxonomic insights into heavymetaltolerant novel bacterium Brevibacterium metallidurans sp. nov. NCCP-602T isolated from tannery effluent in Pakistan.

The strain designated NCCP-602T was isolated from tannery effluent, and displayed aerobic, gram-positive, rod-shaped cells that were characterized by oxidase negative, catalase positive, and non-motile features. The most favourable growth conditions were observed at a temperature of 30°C, pH 7.0, and NaCl concentration of 1% (w/v). It tolerated heavy metals at high concentrations of chromium (3600 ppm), copper (3300 ppm), cadmium (3000 ppm), arsenic (1200 ppm) and lead (1500 ppm). The results of phylogenetic analysis, derived from sequences of the 16S rRNA gene, indicated the position of strain NCCP-602T within genus Brevibacterium and showed that it was closely related to Brevibacterium ammoniilyticum JCM 17537T. Strain NCCP-602T formed a robust branch that was clearly separate from closely related taxa. A comparison of 16S rRNA gene sequence similarity and dDDH values between the closely related type strains and strain NCCP-602T provided additional evidence supporting the classification of strain NCCP-602T as a distinct novel genospecies. The polar lipid profile included diphosphatidylglycerol, glycolipid, phospholipids and amino lipids. MK-7 and MK-8 were found as the respiratory quinones, while anteiso-C15:0, iso-C15:0, iso-C16:0, iso-C17:0, and anteiso-C17:0 were identified as the predominant cellular fatty acids (> 10%). Considering the convergence of phylogenetic, phenotypic, chemotaxonomic, and genotypic traits, it is suggested that strain NCCP-602T be classified as a distinct species Brevibacterium metallidurans sp. nov. within genus Brevibacterium with type strain NCCP-602T (JCM 18882T = CGMCC1.62055T).

Migration of copper(II) ions in humic systems—effect of incorporated calcium(II), magnesium(II), and iron(III) ions

The mobility of heavy metals in natural soil systems can be affected by the properties and compositions of those systems: the content and quality of organic matter as well as the character of inorganic constituents. In this work, the diffusion of copper(II) ions in humic hydrogels with incorporated calcium(II), magnesium(II), and iron(III) ions was investigated. The methods of instantaneous planar source and of constant source were used. Experimental data yielded the time development of the concentration in hydrogels and the values of effective diffusion coefficients. The coefficients include both the influence of the hydrogel structure and the interaction of diffusing particles with the hydrogel. Our results showed that the presence of natural metal ions such as calcium, magnesium, or iron can strongly affect the diffusivity of copper in humic systems. They indicate that the mobility of copper ions depends on their concentration. The mobility can be supported by higher contents of copper in the system. While the incorporation of Ca and Mg resulted in the decrease in the diffusivity of copper ions, the incorporation of Fe(III) into humic hydrogel resulted in an increase in the diffusivity of Cu(II) in the hydrogel in comparison with pure humic hydrogel.

Superior performance of hierarchical 3D microflower CuS grown on carbon cloth as binder free electrode for supercapacitor applications

Copper sulfide (CuS) was grown on the carbon cloth (CC) utilizing the traditional hydrothermal method. The role of different reaction time of 5 h, 10 h, and 15 h (C15) were investigated with fixed reaction time of 150 °C. XRD confirmed the growth of pure CuS on CC. Macroscopic changes in morphology were observed with increasing the reaction time and C15 showed ∼3.08 μm diameter of CuS microflowers with ∼ 34.68 nm thickness of nanosheets embedded in the microflowers. C15 showed a lowest bandgap of 1.8 eV with high copper content of 34 % and the copper content increases fast electron movement and maintains structural stability. The supercapacitor behavior was investigated in 1 M Mg(NO3)2 aqueous electrolyte and C15 demonstrated the highest specific capacitance of 83.70 F/g at 5 mV/s. An aqueous symmetric electrode made with C15 displays 149 F/g specific capacitance and 87.2 % retention at 1 A/g for 1000 cycles.

Effects of reducing copper and zinc supplementation on the performance and mineral status of fattening pigs

Pig manure with high copper (Cu) and zinc (Zn) concentration is applied to the soil, and these trace minerals can accumulate in the topsoil and decrease its fertility. Thus, adjusting concentrations of Cu and Zn in pig diets below current maximum allowance can prevent this risk. Reduction of dietary concentrations of Cu and Zn reduces their faecal excretion since only a small portion is retained in the pig’s body. The aim of this study was to evaluate the effects of reducing concentration of dietary Cu and Zn or withdrawing their supplementation on the performance and mineral status of fattening pigs. Four dietary treatments were compared: a basal diet (WS; withdraw supplementation), with no Cu or Zn supplementation (5 and 29 mg/kg of native Cu and Zn, respectively); intermediate concentration (OINT), supplemented with Cu and Zn oxides to obtain mean dietary concentration of 7.4 and 47.5 mg/kg of Cu and Zn, respectively; and two diets supplemented with oxides (OREG) or sulphates (SREG) at concentration similar to European Union limits (i.e. 25 and 120 mg/kg of total Cu and Zn, respectively), as commonly used on commercial farms. Ninety-six pigs (24.3 ± 3.3 kg BW) were each assigned to one of the four treatments and reared in individual pens for 14 weeks (up to 110.3 ± 8.9 kg BW). Animal performances were measured, and samples of plasma (on day 1 and day 41 of experimentation and at slaughter), bones and the liver (at slaughter) were collected from all pigs. Faecal samples were collected from all pigs every 3 weeks to determine the Cu and Zn excretion. Over the entire experiment, neither the concentration nor the source of Cu and Zn influenced feed intake, BW or the feed conversion ratio. Plasma Cu and Zn concentrations were not influenced by the treatment but increased as the age of the pigs increased. Liver Cu concentration increased (P < 0.05) as dietary concentrations increased (OREG> WS). Neither the concentration nor the source of Cu and Zn influenced bone Cu and Zn concentration or physical bone parameters. However, SREG had a higher maximum load until bone breaking (P < 0.05) than OREG. As expected, faecal excretion of Cu and Zn decreased (P < 0.01) as dietary concentration decreased. Dietary Cu and Zn can be reduced without decreasing the performance or mineral status of pigs, and these results should be validated on commercial farms that have more challenging health conditions.

Regulation and microbial response mechanism of nitric oxide to copper-containing swine wastewater treated by Pistia stratiotes

As a signaling molecule, Nitric oxide (NO) has been widely used in abiotic stress mitigation studies.Pistia stratiotes showed a good synergistic removal effect on heavy metals, nitrogen and phosphorus, but the high concentration of copper(Cu) in swine wastewater inhibited the comprehensive removal ability of Pistia stratiotes. At present, it is not clear how the addition of NO regulates the stress resistance mechanism of Pistia stratiotes to copper in swine wastewater, and the microbial response mechanism accompanying this process is not yet clear. Therefore, in the concentration range of 0.31∼4 mg·L−1Cu2+ and NO concentration of 0,0.05 and 0.1 mg L−1, the removal effect of Pistia stratiotes on copper from swine wastewater was studied. The results showed as follows: The treatment of non-available copper in groups M and H increased by 10.67% and 22.31%, respectively, compared with that in group L. The critical point of inhibiting effect of NO on growth rate was 2.03 mg·L−1Cu. By measuring three-dimensional fluorescence spectrum, combined with parallel factor analysis and principal component analysis, it was confirmed that exogenous addition of NO affected the humification degree of dissolved organic matter(DOM) and promoted the chelation of organic matter with copper. With the increase of Cu concentration, the Reyranella and Prosthecobacter with certain copper resistance gradually gained advantages. Redundancy analysis(RDA) showed that Emiticicia had a strong correlation with the removal rates of ammonia nitrogen, total phosphorus and copper in swine wastewater, while hgcI_clade had a strong correlation with the removal rates of total nitrogen. In conclusion, controlling the dosage of NO can effectively improve the tolerance and removal effect of Pistia stratiotes on copper in swine wastewater, which is of great significance for promoting the treatment and resource transformation of swine wastewater.

Strategic Development of Ni–Cu–Fe2O3 Composite Coatings to Strengthen Mild Steel Against Corrosion

Mild steel is extensively employed in various industries due to its affordability and versatility. However, its susceptibility to corrosion poses a significant challenge. This study explores the efficacy of protecting mild steel by applying coatings composed of highly noble copper and its alloys. In this direction, Ni–Cu alloy and Ni–Cu–Fe2O3 coating have been developed from a sulfate citrate bath on mild steel through the electrodeposition method. The alloy and composite coating deposition was done at different current densities 1 A dm−2, 2 A dm−2, 3 A dm−2, and 4 A dm−2. The copper content of the coating has increased with an increase in current density in both alloy and composite coatings. The deposit with a high Copper content showed lower crystallite size with a lower corrosion rate value at a current density of 3 A dm−2. The trace addition of Fe2O3 into the Ni–Cu alloy matrix has improved the overall corrosion resistance of the mild steel materials as compared to bare Ni–Cu alloy coating.

Metal Release from Manganese Nodules in Anoxic Seawater and Implications for Deep-Sea Mining Dewatering Operations.

The potential mining of deep-sea polymetallic nodules has been gaining increasing attention due to their enrichment in metals essential for a low-carbon future. To date, there have been few scientific studies concerning the geochemical consequences of dewatered mining waste discharge into the pelagic water column, which can inform best practices in future mining operations. Here, we report the results of laboratory incubation experiments that simulate mining discharge into anoxic waters such as those that overlie potential mining sites in the North Pacific Ocean. We find that manganese nodules are reductively dissolved, with an apparent activation energy of 42.8 kJ mol-1, leading to the release of associated metals in the order manganese > nickel > copper > cobalt > cadmium > lead. The composition of trace metals released during the incubation allows us to estimate a likely trace metal budget from the simulated dewatering waste plume. These estimates suggest that released cobalt and copper are the most enriched trace metals within the plume, up to ∼15 times more elevated than the background seawater. High copper concentrations can be toxic to marine organisms. Future work on metal toxicity to mesopelagic communities could help us better understand the ecological effects of these fluxes of trace metals.

Temperature-copper content induced wear mechanism transition in Cu/Ni60A composites

Coppery blast furnace tuyere is easily damaged in high temperature wear environment. Preparing a Ni60A coating by plasma cladding is an effective method to improve its wear resistance and service life. Controlling the appropriate dilution rate is the key to obtain high-quality coatings. The existing research has no clear conclusion on the range of dilution rate of coating for coppery tuyere. In this paper, a series of Cu/Ni60A composites with different copper content (10 wt%, 20 wt%, 40 wt% and 60 wt%) were prepared to mimic Ni60A coatings exhibiting distinct dilution rate. Under the coupling change of temperature and copper content, the wear mechanism of Cu/Ni60A composites showed a complex transition law. Copper content, surface oxide layer (NiO or CuO) and high-temperature softening temperature were the decisive factors of wear transition. The applicable temperatures of Cu/Ni60A composites with low copper content (10 %, 20 %), middle copper content (40 %) and high copper content (60 %) were about 600 °C, 400 °C and 300 °C, respectively. Combined with the heat transfer analysis results, the suitable dilution rates for the coating applied to the inner wall (＜10 %) and front end (10 %-20 %) of tuyere was revealed.

Determination of potentially toxic heavy metals in selected wood treatment sites in Uasin Gishu County and their associated health concerns

One of the monumental environmental and public health concerns of our time lies in the use of toxic preservatives in wood treatment plants. In this investigation, we report the results of potentially toxic heavy metals from wood treatment plants in Uasin Gishu County. A 20 g ground and sieved soil sample from each sampling site Cheplaskei (CK), Outspan (OS) and Sukunanga (SK) was weighed and treated with 0.5 M nitric acid for 2 h. The sample was then analyzed for potentially toxic metals using inductively coupled plasma atomic emission spectroscopy (ICP-AES). The statistical treatment of the data was done using Principal component analysis (PCA) and Pearson’s correlation. The highest concentration of copper was observed at SK, which contributed approximately 37% of all the potentially toxic heavy metal content analyzed, whereas the concentration of lead was found to be about 33% of the total heavy metal content analyzed at the same sampling site. Furthermore, the most abundant metal in the sampled sites is manganese, which was found to be 390.0 ± 8.63, 279.0 ± 8.05and 44.5 ± 2.95 ppm in OS, CK, and SK, respectively. PCA showed that the heavy metals in the sample sites originated from two independent sources—natural and anthropogenic. Evidently from the concentration profile data, all the potentially toxic heavy metals had concentrations above the World Health Organization (WHO) acceptable limits, although, based on the contamination factors determined, the wood treatment sites are less polluted; however, there is need for regular monitoring to ensure adherence to proper public and environmental health practices.