High Cu2 Research Articles

Characteristics and Mechanism of Ammonia Nitrogen Removal by Heterotrophic Nitrification Bacterium Klebsiella pneumoniae LCU1 and Its Application in Wastewater Treatment

In this study, a novel strain exhibiting heterotrophic nitrification was screened; subsequently, the strain was identified as Klebsiella pneumoniae LCU1 using 16S rRNA gene sequencing. The aim of the study was to investigate the effects of external factors on the NH4+-N removal efficiency of strain LCU1 in order to elucidate the optimal conditions for NH4+-N removal by the strain and improve the removal efficiency. The findings indicated that the NH4+-N removal efficiency of the strain exceeded 80% under optimal conditions (sodium succinate carbon source, C/N ratio of 10, initial pH of 8.0, temperature of 30 °C, and speed of 180 rpm). The genome analysis of strain LCU1 showed that key genes involved in nitrogen metabolism, including narGHI, nirB, nxrAB, and nasAB, were successfully annotated; hao and amo were absent, but the nitrogen properties analysis determined that the strain had a heterotrophic nitrification ability. After 120 h, the NH4+-N removal efficiency of strain LCU1 was 34.5% at a high NH4+-N concentration of 2000 mg/L. More importantly, the NH4+-N removal efficiency of this strain was above 34.13% at higher Cu2+, Mn2+, and Zn2+ ion concentrations. Furthermore, strain LCU1 had the highest NH4+-N removal efficiency of 34.51% for unsterilised (LCU1-OC) aquaculture wastewater. This suggests that with intensive colonisation treatment, the strain has promising application potential in real wastewater treatment.

Self-Assembled Bolaamphiphile-Based Organic Nanotubes as Efficient Cu(II) Ion Adsorbents.

Self-assembled organic nanotubes (ONTs) have been actively examined for various applications such as chemical separations and catalysis owing to their well-defined tubular nanostructures with distinct chemical environments at the wall and internal/external surfaces. Adsorption of heavy metal ions onto ONTs plays an essential role in many of these applications but has rarely been assessed quantitatively. Herein, we investigated interactions between Cu2+ and single-/quadruple-wall bolaamphiphile-based ONTs having inner carboxyl groups with different inner diameters, COOH-ONT10nm and COOH-ONT20nm. We first examined the effects of Cu2+ on their nanotubular structures using SAXS, STEM, and AFM. COOH-ONT10nm was stable in aqueous Cu2+ solution in contrast to COOH-ONT20nm owing to the presence of polyglycine-II-type hydrogen bonding networks within its wall. Subsequently, we studied the Cu2+ adsorption behavior of COOH-ONT10nm by monitoring the concentration of unbound Cu2+ using linear sweep anodic stripping voltammetry. The Cu2+ adsorption was quick, attributable to efficient Cu2+ partitioning through the open ends of the ONT, followed by fast Cu2+ diffusion in the uniform, relatively large nanochannel. More importantly, the Cu2+ adsorption capacity and affinity of COOH-ONT10nm were measured under different pH conditions using the Langmuir adsorption model. The adsorption capacity was similar at the pH range examined, showing the participation of approximately 25% of the inner carboxyl groups in the adsorption. The adsorption affinity increased with pH, indicating the essential role of the deprotonated carboxyl groups in Cu2+ adsorption. Most interestingly, the Langmuir adsorption constant was significantly higher than those of previously reported synthetic adsorbents and planar monolayer based on carboxyl binding sites. The high Cu2+ affinity of the ONT was attributable to the highly dense binding sites on the well-defined nanoscale concave structure of the inner channel. These results provide a valuable guideline for designing self-assembled nanomaterials for efficient chemical separations, detection, and catalysis.

Antioxidant response fail to rescue growth of Hermetia illucens L. larvae induced by copper accumulated during long-term exposure

Antioxidant indices and hemocytes apoptosis in the 6th instar larvae of Hermetia illucens., and their correlation with larval growth were evaluated by exposing larvae to different concentrations of Cu2+ for 1, 3 and 5 generations. Cu2+ accumulated in larval hemolymph showed significant dose-dependent relationship with Cu2+ concentrations in diets within a generation. Larval growth was only promoted after low concentrations of Cu2+ exposure for 1 generation, while seriously affected after high concentrations of Cu2+ exposure. Though total antioxidant capacity activity in larval hemolymph in treatment groups was all higher than that in control, it was increased at lower levels of Cu2+, while decreased with increasing Cu2+ concentrations at higher levels of Cu2+ exposure. The catalase (CAT) activity and metallothioneins (MTs) levels were also characterized as improved at lower levels of Cu2+, and inhibited at higher levels of Cu2+ exposure. However, CAT activity and MTs levels at higher Cu2+ treatments were significantly lower than that in control. Apoptosis rate of hemocytes was increased with increasing Cu2+ concentrations. Annexin V - fluorescein isothiocyanate (FITC)/ propidium iodide (PI) staining was in accordance with the results exhibited in flow cytometer. Results from transmission electron microscope and comet assay further confirmed that membrane blebbing, nuclear condensation, and DNA fragmentation were gradually apparent with increasing Cu2+ concentration. All parameters in different generation had similar dose-dependent trends, but the effects were strongest in the fifth generation. This study indicated that at some extent growth of H. illucens were associated with antioxidant responses and apoptosis induced by Cu2+.

Electrochemical activation of MnS as an efficient conversion-type Cu2+ storage electrode

Electrochemical activation can turn inactive materials into active materials in situ for energy storage facilely, controllably and efficiently, which makes metal sulfides feasible for Cu2+ storage based on electrochemical activated into CuS. Among common heavy metal sulfides, MnS has the highest solubility product and high Cu2+ adsorption and exchange rate in the copper removal by vulcanization in nickel electrolytic anodic solution. Here, MnS is electrochemical activated in situ in aqueous Cu-ion battery, and the effects of crystal structure and particle size on the electrochemical activation of MnS were revealed. The results show that both α, γ-MnS can be electrochemical activated, and activation cycling number is related to the particle size of MnS. When the MnS particle size is ball-milled small enough (1–2 μm), MnS will be completely transformed into CuS during the first discharge process, and then CuS↔Cu2S will participate in the reversible conversion reaction for copper storage. When the MnS particle size is larger (> 10 μm), the α-MnS electrode capacity gradually increases and becomes stable after 30 cycles, and the capacity remains at 458.6 mAh g–1 after 300 cycles.

Dual electric field and defect engineering induced multi-channel electron transfer for boosting photocatalytic hydrogen production on Cu2+-doped ZnMoO4/ZnIn2S4 heterojunction

Serious recombination of photogenerated carriers is the bottleneck problem of achieving high-performance photocatalytic reaction. A high efficient Cu2+-doped ZnMoO4/ZnIn2S4 (CZMOZIS) heterojunction was synthesized by hydrothermal method. The CZMOZIS heterostructure achieved hydrogen production of 11637.5 µmol g−1 within 5 h, which was 9.7 times higher than that of pure ZnIn2S4. Comprehensive characterization and theoretical calculation demonstrated that the CZMOZIS composites exhibited broad light absorption, an increased specific surface area and an optimized Gibbs free energy. The presence of oxygen vacancies in CZMOZIS composites was confirmed by X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy, revealing the formation of defect levels below the conduction band (CB) of ZnMoO4. Kelvin probe force microscopy (KPFM) and Zeta potential demonstrated that the intrinsic electric field (IEF) of the CZMOZIS heterojunction was enhanced, which may be attributed to the generation of polarization electric field (PEF). The double electric field provided a robust driving force for the photogenerated carrier migration and separation. The electrons in the CB and defect levels of Cu2+-ZnMoO4 could be coupled with the holes of ZnIn2S4, thereby forming a multi-channel electron transfer. This work provides a theoretical support for promoting charge transfer to improve photocatalytic performance by dual electric field and defect engineering.

Acute copper stress showed toxic effects on the physiological metabolism of Ulva lactuca, a common green macroalgae

The pollution by heavy metals in coastal waters has gradually intensified due to industrial development. In this study, physiological responses of Ulva lactuca, one of the most common green seaweeds with important ecological and economic value in the global intertidal zone, to acute copper stress were investigated. Results showed that an increase in copper ions concentration significantly inhibited photosynthetic activity and inorganic nitrogen utilization by U. lactuca but, increased its respiration. Copper stress limited the activity and gene expression of enzymes related to carbon and nitrogen assimilation of U. lactuca. Under moderate copper stress, U. lactuca had higher soluble carbohydrate and soluble protein contents, whereas under high copper stress, these components decreased sharply. Copper stress increased malonaldehyde content, and relative electrical conductivity in U. lactuca, but changes in antioxidant enzyme activities were not significant and even slightly decreased. Moreover, the contents of 8-hydroxy-deoxyguanosine and polyADP ribose polymerase in U. lactuca increased by high Cu2+ concentration culture, indicating that oxidative damage caused by high Cu2+ level involved its DNA damage and interfered with DNA repair in the alga. Copper stress seemed to be more damaging to the carbon assimilation process of U. lactuca, resulting in weakened resistance to copper stress and lower growth rate. This reflected the threat of coastal high copper stress to intertidal biodiversity. This provided ecological reference for the assessment of offshore heavy metal pollution represented by copper.

Exploring the Physicochemical Characteristics of Marine Protein Hydrolysates and the Impact of In Vitro Gastrointestinal Digestion on Their Bioactivity.

Fish protein hydrolysates (FPHs) were obtained from different fish sources using a combination of microbial enzymes. The industrially produced FPHs from blue whiting (Micromesistius poutassou) and sprat (Sprattus sprattus) were compared to freeze-dried FPHs generated in-house from hake (Merluccius merluccius) and mackerel (Scomber scombrus) in terms of their physicochemical composition and functionality. Significant differences (p < 0.05) were observed in the protein, moisture, and ash contents of the FPHs, with the majority having high levels of protein (73.24-89.31%). Fractions that were more extensively hydrolysed exhibited a high solubility index (74.05-98.99%) at different pHs. Blue whiting protein hydrolysate-B (BWPH-B) had the highest foaming capacity at pH 4 (146.98 ± 4.28%) and foam stability over 5 min (90-100%) at pH 4, 6, and 8. The emulsifying capacity ranged from 61.11-108.90 m2/g, while emulsion stability was 37.82-76.99% at 0.5% (w/v) concentration. In terms of peptide bioactivity, sprat protein hydrolysate (SPH) had the strongest overall reducing power. The highest Cu2+ chelating activity was exhibited by hake protein hydrolysate (HPH) and mackerel protein hydrolysate (MPH), with IC50 values of 0.66 and 0.78 mg protein/mL, respectively, while blue whiting protein hydrolysate-A (BWPH-A) had the highest activity against Fe2+ (IC50 = 1.89 mg protein/mL). SPH scavenged DPPH and ABTS radicals best with IC50 values of 0.73 and 2.76 mg protein/mL, respectively. All FPHs displayed noteworthy scavenging activity against hydroxyl radicals, with IC50 values ranging from 0.48-3.46 mg protein/mL. SPH and MPH showed the highest scavenging potential against superoxide radicals with IC50 values of 1.75 and 2.53 mg protein/mL and against hydrogen peroxide with 2.22 and 3.66 mg protein/mL, respectively. While inhibition of α-glucosidase was not observed, the IC50 values against α-amylase ranged from 8.81-18.42 mg protein/mL, with SPH displaying the highest activity. The stability of FPHs following simulated gastrointestinal digestion (SGID) showed an irregular trend. Overall, the findings suggest that marine-derived protein hydrolysates may serve as good sources of natural nutraceuticals with antioxidant and antidiabetic properties.

New Insights Into Application Relevant Properties of Cu2+-Doped Brushite Cements.

Doping of brushite cements with metal ions can entail many positive effects on biological and physicochemical properties. Cu2+ ions are known to exhibit antibacterial properties and can additionally have different positive effects on cells as trace elements, whereas high Cu2+ concentrations are cytotoxic. For therapeutical applications of bone cement, a combination of good biocompatibility and sufficient mechanical properties is required. Therefore, the aim of this study was to investigate different physicochemical and biological aspects, relevant for application, of a brushite cement with Cu2+-doped β-tricalcium phosphate, monocalcium phosphate monohydrate and phytic acid as setting retarder. Additionally, the ion release was compared with a cement with citric acid as setting retarder. The investigated cements showed good injectability coefficients, as well as compressive strength values sufficient for application. Furthermore, no antibacterial effects were detected irrespective of the Cu2+ concentration or the bacterial strain. The cell experiments with eluate samples showed that the viability of MC3T3-E1 cells tended to decrease with increasing Cu2+ concentration in the cement. It is suggested that these biological responses are caused by the difference in the Cu2+ release from the hardened cement depending on the solvent medium. Furthermore, the cements showed a steady release of Cu2+ ions to a lesser extent in comparison with a cement with citric acid as setting retarder, where a burst release of Cu2+ was observed. In conclusion, despite the anticipated antibacterial effect of Cu2+-doped cements was lacking and mammalian cell viability was slightly affected, Cu2+-concentrations maintained the physicochemical properties as well as the compressive strength of cements and the slow ion release from cements produced with phytic acid is considered advantageous compared to citric acid-based formulations.

Hydrothermal synthesis of pore-expanded hydroxyapatite for enhanced Cu2+ adsorption from aqueous solutions

This paper describes the hydrothermal synthesis of a pore-expanded hydroxyapatite (PE-HAp) from fine–grained calcareous sludge using a cetyltrimethylammonium bromide (CTAB) as a template and 1,3,5-trimethylbenzene (TMB) as a pore expander for the removal of Cu2+ ions from aqueous solutions. The PE-HAp was characterized using XRD, SEM, DTA/TGA and BET surface analysis. Adsorption behavior was assessed using Langmuir, Freundlich, Dubinin–Radushkevich, Temkin and Sips isotherms. In a solution with an initial Cu2+ concentration of 200 mg L-1 and a pH of 5.0, the highest Cu2+ removal efficiency was achieved using PE-HAp synthesized at a hydrothermal temperature of 180 °C at a concentration of 15 g/L over a period of 60 min. Using Langmuir isotherms, the highest single-layer adsorption capacity value was 9.90 mg g-1. Gibbs free energy (ΔG°), changes in enthalpy (ΔH°), and changes entropy change (ΔS°) revealed that the adsorption of Cu2+ on PE-HAp was spontaneous and exothermic. The PE-HAp synthesized in this study is a promising material for the removal of Cu2+ from aqueous solutions.

Resistances and Physiological Responses of Impatiens uliginosa to Copper Stress

The phytoremediation of soil and water that has been significantly contaminated with metals has potential ecological and economical ramifications, as well as the advantages of high efficiency, and is an environmentally friendly method of ecological pollution control. This study aimed to examine the impact of varying concentrations of Copper (Cu2+) (0, 5, 10, 15, 20, and 25 mg·L−1) on the growth, development, physiology, biochemistry, mineral elements, and features of Cu2+ enrichment of Impatiens uliginosa. This plant is endemic to Yunnan Province in China and is a wetland species. The results showed that the root lengths, stem diameters, plant height, and stem and leaf biomass of I. uliginosa showed a phenomenon of “low promotion and high inhibition,” while the root biomass showed a trend of gradual decreasing. At the early stage of Cu2+ stress (day 6), the activities of peroxidase and catalase and the contents of malondialdehyde (MDA) of I. uliginosa were directly proportional to the concentration of Cu2+. As the treatment time increased, the activation of a defense mechanism in vivo enabled I. uliginosa to adapt to the high Cu2+ environment, and the content of MDA gradually decreased. As the concentration of Cu2+ increased, its contents in the roots, stems, and leaves also gradually increased. In particular, when the concentration of Cu2+ reached 25 mg·L−1, its contents in the roots of I. uliginosa increased by 39.16-fold compared with that of the control group (CK). The concentration-dependent influence of the contents of iron (Fe) and zinc (Zn) in the roots and leaves were observed. Low concentrations of Cu2+ promoted iron content in roots and leaves, and vice versa, while Zn content decreased with the increasing concentration of Cu2+. It was conclusively shown that I. uliginosa has the potential to remediate low concentrations of Cu2+ pollution in water and is a textbook ornamental plant to remediate bodies of water that are polluted with Cu2+.

Determination of High Concentration Copper Ions Based on Ultraviolet—Visible Spectroscopy Combined with Partial Least Squares Regression Analysis

With the rapid development of industrialization, the problem of concentration determination based on the copper production process has been widely concerned, and the accurate determination of high-concentration copper ions (Cu2+) is of great significance for enterprise production, resource utilization, and pollution prevention. The characteristics of different spectrophotometric methods for the determination of Cu2+ are discussed, and it is found that these methods are suitable for the determination of trace or low concentration of Cu2+ (0.5 μg/L–5 mg/L), whereas for the determination of high Cu2+ concentration pre-treatments such as dilution, complexation, and coloring are required. In this study, a method based on ultraviolet-visible spectroscopy (UV-Vis) combined with partial least squares regression analysis (PLS) was proposed for the determination of high copper ions (&gt;100 mg/L), which performs rapid and accurate determination of high Cu2+ concentration by preprocessing and feature extraction of UV-Vis spectral data, followed by model construction with PLS analysis, which is easy to operate and applicable to a wide range of concentrations. The correlation coefficient (R2), mean relative error (MRE), and root mean square error (RMSECV) of the model prediction of Cu2+ concentrations were 0.99946, 0.006343, and 11.237 mg/L, respectively, indicating that the accuracy of the model prediction is very high. This study not only provides an efficient method for the precise determination of high Cu2+ concentration but also enables the simultaneous determination of Cu2+, Co2+, and Ni2+ ions, which provides a new technical means for environmental monitoring and pollution prevention.

Potential effects of Cu2+ stress on nitrogen removal performance, microbial characteristics, and metabolism pathways of biofilm reactor

Sequencing batch biofilm reactors (SBBR) were utilized to investigate the impact of Cu2+ on nitrogen (N) removal and microbial characteristics. The result indicated that the low concentration of Cu2+ (0.5 mg L−1) facilitated the removal of ammonia nitrogen (NH4+-N), total nitrogen (TN), nitrate nitrogen (NO3−-N), and chemical oxygen demand (COD). In comparison to the average effluent concentration of the control group, the average effluent concentrations of NH4+-N, NO3−-N, COD, and TN were found to decrease by 40.53%, 17.02%, 10.73%, and 15.86%, respectively. Conversely, the high concentration of Cu2+ (5 mg L−1) resulted in an increase of 94.27%, 55.47%, 22.22%, and 14.23% in the aforementioned parameters, compared to the control group. Low concentrations of Cu2+ increased the abundance of nitrifying bacteria (Rhodanobacter, unclassified-o-Sacharimonadales), denitrifying bacteria (Thermomonas, Comamonas), denitrification-associated genes (hao, nosZ, norC, nffA, nirB, nick, and nifD), and heavy-metal-resistant genes related to Cu2+ (pcoB, cutM, cutC, pcoA, copZ) to promote nitrification and denitrification. Conversely, high concentration Cu2+ hindered the interspecies relationship among denitrifying bacteria genera, nitrifying bacteria genera, and other genera, reducing denitrification and nitrification efficiency. Cu2+ involved in the N and tricarboxylic acid (TCA) cycles, as evidenced by changes in the abundance of key enzymes, such as (EC:1.7.99.1), (EC:1.7.2.4), and (EC:1.1.1.42), which initially increased and then decreased with varying concentrations of Cu2+. Conversely, the abundance of EC1.7.2.1, associated with the accumulation of nitrite nitrogen (NO2−-N), gradually declined. These findings provided insights into the impact of Cu2+ on biological N removal.

Nitrogen promoted electron transfer to create highly active Cu2+ and Mn3+ sites for efficient catalytic ozonation of Ammonia over copper and nitrogen co-doped Cryptomelane-Type manganese oxide at ambient temperature

Eliminating ammonia (NH3) from high-humidity exhaust gases by catalytic oxidation is a great challenge, especially at low temperatures. Herein, Cu and N co-doped cryptomelane-type manganese oxide (Cu-N-OMS-2) catalysts with high active Cu2+ and Mn3+ sites were synthesized and tested for catalytic ozonation of NH3 at 30 °C. The optimal Cu0.05-N2-OMS-2 catalyst exhibited 93.8 % NH3 conversion, 91.7 % O3 conversion, and 92.1 % N2 selectivity when the relative humidity (RH) was 40 %, whereas OMS-2 only demonstrated 39.3 %, 44.0 % and 83.1 %. Additionally, NH3 and O3 conversion at high RH could be recovered with just a basic water-washing, indicating that Cu0.05-N2-OMS-2 catalyst possessed outstanding renewable properties. The results of characterization revealed that N doping increased the amount of Cu fixed on the catalyst surface and promoted the electron transfer from Cu to Mn, resulting in an increase in electron-poor Cu2+ and electron-rich Mn3+ in Cu-N-OMS-2. In dry conditions, the Mn3+ sites provided O3 with electrons to form adsorbed oxygen species and •O2–, which were essential for oxidation of adsorbed NH3. The electron-poor Cu2+ sites combined with H2O and O3 to form Cu-OH and •HO3, which facilitated the generation of •OH and •O2–, thereby improving the stability under humid conditions. This study provides a new theoretical guidance for the efficient removal of NH3 in industrial exhaust gases.

A novel highly dispersed calcium silicate hydrate nanosheets for efficient high-concentration Cu2+ adsorption

Currently, the low cost and effective purification toward heavy metal ions in wastewater has garnered global attention. Herein, we used hydrothermal method to prepare highly dispersed calcium silicate hydrate in fluorite tailings. And the stacking thickness of calcium silicate hydrate layered morphology was less than 5 nm. For high concentration Cu2+ purification investigation in wastewater, we found that the equilibrium adsorption capacity reached 797.92 mg/g via the CSH with 3:2 Ca/Si molar ratio, be 1.43–21.8 times than that of reported data. Therein, the metal-metal exchange and deposition are the primary pathways for Cu2+ adsorption, and electrostatic attraction is the secondary pathway. And the relative ∼100 % removal rate of high-concentration Ni2+ and Cr3+ ions were confirmed via CSH prepared from different tailings. This method offers a cost-effective way to utilize tailings for preparing highly efficient adsorbents toward HMIs removal in wastewater.

Ionic Liquid-Assisted Production of Biochar with High Cu2+ Removal Efficiency: Effect of Pyrolysis Temperature and CaCO3 Content in Biomass

Ionic Liquid-Assisted Production of Biochar with High Cu2+ Removal Efficiency: Effect of Pyrolysis Temperature and CaCO3 Content in Biomass

Photoluminescent Carbon Quantum Dots from Dichrostachys glomerata Pods with Antioxidant and Cu2+ Chelating Properties

AbstractThis work presents the facile and single‐step hydrothermal synthesis of carbon quantum dots (CQDs) using the Dichrostachys glomerata extract as raw material. CQDs with the highest photoluminescence (PL) were obtained after heating the extract in 4 M NaOH at 200 °C for 7 h. The obtained CQDs exhibit an average size of ca. 4.7 nm, a green‐yellow PL emission independent on the excitation wavelength with contributions located at 478 and 562 nm, a monoexponential decay of their PL lifetime and a PL quantum yield of 18 %. These results indicate that the surface functionalization of sp2 clusters in CQDs is uniform. The antioxidant properties of CQDs were also investigated. CQDs can effectively reduce free radicals like superoxide or oxidants like KMnO4. Moreover, CQDs show a high Cu2+ chelating activity, which is attributed to the abundant carboxylate functions on their surface and may therefore be of high interest in therapeutic applications related to Cu2+ ions overload.

Acid-washing-alkali-fusion pretreated red mud for fabricating Cu-based BEA zeolite for NH3-SCR

The utilization of red mud as a solid waste to fabricate high-value-added products was a critical approach to reduce its storage. This research successfully synthesized a series of Cu-based BEA zeolite NH3-SCR catalysts with the acid-washing-alkali-fusion pretreated red mud as the Al source. XRF, XRD and N2 adsorption–desorption characterized the textual information of all samples. The H2-TPR, XPS, and UV–Vis DRS characterized the electronic structure of Cu. The highest Cu2+ content was obtained in Cu-BA0.5-H among all samples. The Cu-BA0.5-H processed the excellent low-temperature NO removal performance of ca. 99 % in 200 °C ∼ 300 °C when NH3/NO was 1. Finally, the in-situ DRIFTS analysis was carried out regarding the NH3 adsorption, NO + O2 adsorption, and co-adsorption to evaluate the possible reaction route. It was confirmed that the SCR reduction over Cu-BA0.5-H in SCR reactions followed the E-R mechanism, but different critical intermediate species depended on the reaction temperatures. It was deduced that the acid-washing-alkali-fusion pretreatment made the non-water-soluble components containing Si and Al into soluble components and further affected NO removal performance of the fabricated catalysts. Our research provided a novel approach for converting red mud into high-value products and unravelled the possible mechanism for NH3-SCR.

Monitoring of copper adsorption on biochar using spectral induced polarization method

Copper contaminant generated from mining and industrial smelting poses potential risks to human health. Biochar, as a low-energy and cost-effective biomaterial, holds value in Cu remediation. Spectral Induced Polarization (SIP) technique is employed in this study to monitor the Cu remediation processes of by biochar in column experiments. Cation exchange at low Cu2+ concentrations and surface complexation at high Cu2+ concentrations are identified as the major mechanisms for copper retention on biochar. The normalized chargeability (mn) from SIP signals linearly decreased (R2 = 0.776) with copper retention under 60 mg/L Cu influent; while mn linearly increases (R2 = 0.907, 0.852) under high 300 and 700 mg/L Cu influents. The characteristic polarizing unit sizes (primarily the pores adsorbing Cu2+) calculated from Schwartz equation match well with experimental results by mercury intrusion porosimetry (MIP). It is revealed that Cu2+ was driven to small pores (∼3 μm) given high concentration gradient (influent Cu2+ concentration of 700 mg/L). Comparing to activated carbon, biochar is identified as an ideal adsorbent for Cu remediation, given its high adsorption capacity, cost-effectiveness, carbon-sink ability, and high sensitivity to SIP responses – the latter facilitates its performance assessment.

An array of femtoliter wells for sensitive detection of copper using click chemistry

Sensitive detection of copper ion (Cu2+), which is of great importance for environmental pollution and human health, is crucial. In this study, we present a highly sensitive method for measuring Cu2+ in an array of femtoliter wells. In brief, magnetic beads (MBs) modified with alkyne groups were bound to the azide groups of biotin-PEG3-azide (bio-PEG-N3) via Cu+-catalyzed click chemistry. Cu+ in the click chemistry reaction was generated by reducing Cu2+ with sodium ascorbate. Following the ligation, the surface of the MBs was modified with biotin, which could be labeled with streptavidin-β-galactosidase (SβG). The MBs complex was then suspended in β-galactosidase substrate fluorescein-di-β-d-galactopyranoside (FDG), and loaded into the array of femtoliter wells. The MBs sank into the wells due to gravity, and the resulting fluorescent product, generated from the reaction between SβG on the surface of the MBs and FDG, was confined within the wells. The number of fluorescent wells increased with higher Cu2+ concentrations. The bright-field and fluorescent images of the wells were acquired using an inverted fluorescent microscope. The detection limit of this assay for Cu2+ was 1 nM without signal amplification, which was 103 times lower than that of traditional fluorescence detection assays.

Comparative effectiveness of carbon nanoparticles and biochar in alleviating copper stress in corn (Zea mays L.)

The application of carbon nanoparticles (CNPs) and biochar in agriculture for improving plant health and soil quality and alleviating metal stress offers alternative approaches to meet the ever-increasing demand for food. However, poor understanding of their roles in improving crop production under Cu stress represents a significant obstacle to their wide application in agriculture. To clarify how CNPs and biochar affect corn (Zea mays L.) seed germination, seedling growth, plant health, and nutrient uptake under different Cu stress levels, soil-less Petri-dish and greenhouse soil-based bioassays were conducted. The results revealed that CNPs and biochar stimulated corn seed germination and seedling growth. Besides, they were effective in immobilizing Cu2+ sorption in sandy soil and alleviating Cu stress for plant growth, as shown by the increased plant height and dry biomass. The plant nutrient uptake efficiency (NUE) was significantly increased by CNPs, with a maximum increase of 63.1% for N and 63.3% for K at the highest Cu2+ stress level (400 mg Cu2+ L−1). In contrast, non-significant effects on NUE were observed with biochar treatments regardless of Cu stress levels. Interestingly, CNPs significantly increased plant uptake of Cu in the Petri dish test, while biochar inhibited plant uptake of Cu under both experimental conditions. Principle component analysis (PCA) and Pearson correlation analysis indicated that CNPs mitigated Cu stress mainly by elevating antioxidant enzyme activities, enhancing plant photochemical efficiency, and increasing plant uptake of N and K, while biochar was more likely to reduce bioavailability and uptake of Cu in the plant. These findings have great implications for the application of CNPs and biochar as plant growth stimulators and de-toxicity agents in agriculture.