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According to the migration law of ore-forming elements in metal mines, copper ions migrate from ore body to soil and are absorbed by covered vegetation, resulting in increased heavy metal content in vegetation leaves, which causes spectral changes in vegetation leaves under stress. Hyperspectral remote sensing spectral characteristic analysis method was used to analyze the spectral characteristics of vegetation leaves under heavy metal stress and study the spectral changes under copper ion stress. The spectral resolution of hyperspectral remote sensing has the ability of fine detection of high-precision ground objects, and it is highly sensitive to the change of spectral characteristics of vegetation under heavy metal stress. The spectral characteristics of pomelo leaves in mining area and background area were quantitatively analyzed by using four indexes of spectral waveform characteristics, red edge position index, chlorophyll and water absorption characteristics, and vegetation index characteristics, and the spectral variation characteristics under copper ion stress were analyzed. The results show that there are significant differences in waveforms, red edge position, chlorophyll, water absorption and vegetation index of pomelo leaves under copper stress compared with the background area. [ABSTRACT FROM AUTHOR]

Leaching solutions of printed circuit boards (PCBs) contain noble and base metal ions. The precious metal ions present in the leaching solutions of PCBs could be separated by cementation with copper metal. After recovery of precious metal ions by cementation, the filtrate contains Cu(II) together with base metal ions like Al(III), Fe(III), Fe(II), Ni(II), Sn(II), and Zn(II). In this work, separation experiments were conducted to recover Cu(II) and Ni(II) from the filtrate. First, copper ions were completely separated from the filtrate by chemical reduction with hydrazine at the following conditions: a molar ratio of 8 for hydrazine to Cu(II), 20°C, 500 rpm, and 20 mins. By adding sodium oxalate to the solution after separation of Cu(II), most of the Ni(II) and 38% of the Zn(II) were co-precipitated at 20°C, 60 mins, 500 rpm, and a molar ratio of 20 for sodium oxalate to nickel. After dissolving the coprecipitates of Ni(II) and Zn(II) oxalates in a 0.5 M HCl solution, the Zn(II) was completely removed from the solution by a five-stage cross-current extraction with 2.5 M Cyanex 272. Nickel hydroxides were then recovered from the raffinate by precipitation with NaOH. The purity of the copper metal and nickel hydroxides was higher than 99%. A process was proposed to recover Au(III), Pd(II), Cu(II), and Ni(II) from the leaching solutions of PCBs. [ABSTRACT FROM AUTHOR]

Wastewater, discharged in copper (Cu) mining and smelting, usually contains a large amount of Cu2+. Immobilizing Cu2+ in aqueous solution and soils is deemed crucial in preventing its migration into surrounding environments. In recent years, the enzyme-induced carbonate precipitation (EICP) has been widely applied to Cu immobilization. However, the effect of Cu2+ toxicity denatures and even inactivates the urease. In the present work, the biopolymer-assisted EICP technology was proposed. The inherent mechanism affecting Cu immobilization was explored through a series of test tube experiments and soil column tests. Results indicated that 4 g/L chitosan may not correspond to a higher immobilization efficiency because it depends as well on surrounding pH conditions. The use of Ca2+ not only played a role in further protecting urease and regulating the environmental pH but also reduced the potential for Cu2+ to migrate into nearby environments when malachite and azurite minerals are wrapped by calcite minerals. The species of carbonate precipitation that are recognized in the numerical simulation and microscopic analysis supported the above claim. On the other hand, UC1 (urease and chitosan colloid) and UC2 (urea and calcium source) grouting reduced the effect of Cu2+ toxicity by transforming the exchangeable state-Cu into the carbonate combination state-Cu. The side effect, induced by 4 g/L chitosan, promoted the copper-ammonia complex formation in the shallow ground, while the acidic environments in the deep ground prevented Cu2+ from coordinating with soil minerals. These badly degraded the immobilization efficiency. The Raman spectroscopy and XRD test results tallied with the above results. The findings shed light on the potential of applying the biopolymer-assisted EICP technology to immobilizing Cu ions in water bodies and sites. [ABSTRACT FROM AUTHOR]

Corrosion failure is the bottleneck for restricting the application and development of copper-based metal materials. As a new technology of improving corrosion resistance, superhydrophobic surface provides an effective way to solve the problem of copper corrosion. In this work, the superhydrophobic copper surface was prepared by wire electrical discharge machining (WEDM) and surface modification with stearic acid. Subsequently, scanning electron microscope was used to observe the surface micro morphology, video optical contact angle meter was used to measure the wettability, and the corrosion behavior was further tested through the electrochemical workstation. Results showed that the micron strip nano stalactite graded composite structure on the copper surface had been successfully prepared, and the surface of the composite structure exihibited excellent superhydrophobic properties. In addition, compared with the substrate, the corrosion resistance of the prepared surface was increased by 99.35%. The corrosion prevention mechanism of the superhydrophobic surface was systematically studied and analyzed, and it was found that the formation of micro nano composite structure could effectively capture air to form a solid gas liquid interface on the surface of the sample, and the existence of the air layer further impeded the electron transfer and material transfer rate between the substrate and the electrolyte. Thereby, the electrochemical corrosion rate of the substrate was inhibited, and the corrosion resistance of the superhydrophobic copper sample was significantly improved. Overall, the method was simple, efficient and widely used, and the preparation process was environmentally friendly, which could be applied to large-scale production.

The development of environmentally acceptable benign techniques using purely natural methods is a cost-effective procedure with long-term benefits in all areas. With this consideration, myco synthesized silver nano particles (AgNPs) were studied and it acted as an impending corrosion inhibitor in the environment. Initially, AgNPs were evaluated by physical and surface characterizations and this evidence demonstrated that RYREʼs water-soluble molecules played an essential role in the synthesis of AgNPs in nano spherical size. The myco synthesized of AgNPs has showed an antibacterial activity against corrosive bacteria in cooling water system (CWS). Hence, the AgNPs were used in biocorrosion studies as an anticorrosive agent along with AgNO3 and RYRE was also checked. For this experiment, the copper (Cu) metal (CW024) which is commonly used was selected, the result of corrosion rate was decreased, and inhibition efficiency (82%) was higher in the presence of AgNPs in system IV. Even though, AgNO3 and RYRE had contributed significant inhibition efficiency on Cu at 47% and 61%, respectively. According to XRD, the reaction of AgNPs on Cu metal resulted in the formation of a protective coating of Fe2O3 against corrosion. EIS data also indicated that it could reduce the corrosion on the Cu metal surface. All of these findings point out the possibility that the myco-synthesized AgNPs were an effective copper metal corrosion inhibitor. As a result, we encourage the development of myco-synthesized AgNPs, which could be useful in the industrial settings. [ABSTRACT FROM AUTHOR]

Microbial induced carbonate precipitation (MICP) has recently applied to immobilize heavy metals toward preventing their threats to public health and sustainable development of surrounding environments. However, for copper metallurgy activities higher copper ion concentrations cause the ureolytic bacteria to lose their activity, leading to some difficulty in forming carbonate precipitation for copper immobilization (referred to also as "biomineralization"). A series test tube experiments were conducted in the present work to investigate the effects of bacterial inoculation and pH conditions on the copper immobilization efficiency. The numerical simulations mainly aimed to compare with the experimental results to verify its applicability. The copper immobilization efficiency was attained through azurite precipitation under pH in a 4-6 range, while due to Cu2+ migration and diffusion, it reduced to zero under pH below 4. In case pH fell within a 7-9 range, the immobilization efficiency was attained via malachite precipitation. The copper-ammonia complexes formation reduced the immobilization efficiency to zero. The reductions were attributed either to the low degree of urea hydrolysis or to inappropriate pH conditions. The findings shed light on the necessity of securing the urease activity and modifying pH conditions using the two-step biomineralization approach while applying the MICP technology to remedy copper-rich water bodies. [ABSTRACT FROM AUTHOR]

Biomineralization as an alternative to traditional remediation measures has been widely applied to remediate copper (Cu)-contaminated sites due to its environmental-friendly nature. Immobilizing Cu is, however, a challenging task as it inevitably causes inactivation of ureolytic bacteria. In the present work, a series of test tube experiments were conducted to derive the relationships of Cu immobilization efficiency versus pH conditions. The Cu speciation transformation that is invisible in the test tube experiments was investigated via numerical simulations. Apart from that, the one-dimensional soil column tests, accompanied by the X-ray diffraction (XRD) and Raman spectroscopy analysis, mainly aimed not only to investigate the variations of Cu immobilization efficiency with the depth but to reveal the underlying mechanisms affecting the Cu immobilization efficiency. The results of the test tube experiments highlight the necessity of narrowing pH ranges to as close as 7 by introducing an appropriate bacterial inoculation proportion. The coordination adsorption of Cu, while performing the one-dimensional soil column tests, is encouraged by alkaline environments, which differs from the test tube experiments where Cu2+ is capsulized by carbonate precipitates to prevent their migration. The findings highlight the potential of applying the microbial-induced carbonate precipitation (MICP) technology to Cu-rich water bodies and Cu-contaminated sites remediation. [Display omitted] • The relationships of copper immobilization efficiency vs. carbonate species are derived. • The test tube experiments highlight the necessity of narrowing pH to as close as 7. • Cu is coordinately adsorbed with minerals in the one-dimensional column tests. • The reduction in immobilization efficiency appears when under pH < 4 or pH > 9. [ABSTRACT FROM AUTHOR]

A novel setup for the in situ observation of electrochemical reactions in liquids through atmospheric scanning electron microscopy (SEM) is presented. The proposed liquid-phase electrochemical SEM system consists of a working electrode (WE) on an electrochemical chip and other two electrodes inserted into a liquid electrolyte; electrochemical reactions occurring at the WE are controlled precisely with an external potentiostat/galvanostat connected to the three electrodes. Copper deposition from a CuSO4 aqueous solution was conducted onto the WE, and simultaneous acquisition of nanoscale images and reliable electrochemical data was achieved with the proposed setup., (© The Author(s) 2022. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)