Release Rate Of Cu Research Articles

Copper/Silver Bimetallic Nanoparticles Supported on Aluminosilicate Geomaterials as Antibacterial Agents

This study aims to understand how properties of modified aluminosilicate geomaterials influence the antibacterial performance of nanocomposites when prepared with bimetallic nanoparticles (NPs). Copper/silver (Cu/Ag) bimetallic NPs were synthesized in the presence of imogolite (Imo), montmorillonite (Mtt), or zeolite (Zeo) using a simple one-pot method and characterized for their crystal phases, micro- and nanomorphologies, particle size, elemental composition, and electrophoretic mobility. The antibacterial activity was evaluated through minimum inhibition concentration assays of NPs and nanocomposites for Gram (−) Escherichia coli and Gram (+) Staphylococcus aureus bacteria. Deposition of metallic Cu0, Ag0, and cuprite NPs was confirmed in Zeo_Cu/Ag and Imo_Cu/Ag nanocomposites, whereas only Cu0 and Ag0 were identified in Mtt_Cu/Ag. The bimetallic NPs were more uniformly distributed on Zeo and Mtt than Imo. Particle sizes of 28.1 ± 5.0, 9.4 ± 2.3, 10.1 ± 1.7, and 12 ± 1.3 nm were determined for Cu/Ag NPs, Imo_Cu/Ag, Mtt_Cu/Ag, and Zeo_Cu/Ag, respectively. The release rate of Cu and Ag ions from Zeo_Cu/Ag was higher than those of pristine Cu/Ag NPs and the other two nanocomposites. The antimicrobial action of bimetallic NPs and nanocomposites was dose-dependent in relation to the concentration of concerned materials and their stability in the medium. The physicochemical characteristics of Zeo resulted in a homogeneous distribution and low oxidation and agglomeration of Cu/Ag NPs, consequently increasing the antibacterial activity. Results of this study highlight the benefits of using a geomaterial support to achieve high antibacterial activity of bimetallic NPs, which could help reduce the consumption of pure Cu/Ag salts in NP-based antibacterial applications.

Effect of soil particle size on the kinetics of Cu release from field-contaminated soils: Experiments and a quantitative model

Predicting the kinetics of heavy metal release from the field-contaminated soils requires the consideration of the chemical and physical heterogeneity of soil composition, such as multiple soil adsorbents, heterogeneous binding sites, and varying soil particle sizes. In this study, we conducted kinetic experiments to investigate kinetics of copper (Cu) release from different size fractions of two field-contaminated soils. The morphology and elemental distribution of different size fractions of soil particles were measured with scanning electron microscopy (SEM) and spherical aberration corrected scanning transmission electron microscopy (Cs-STEM). A kinetics model considering both variations of soil adsorbents and particle sizes was developed. Overall, different size fractions of soil particles showed highly heterogeneous physical and chemical properties. The reactive soil adsorbents (e.g., soil organic matter (SOM)) and Cu concentrations increased with the decrease of the particle size, and the rate of Cu release from soil particles also increased with the decrease of the particle size. The kinetics model described the experimental kinetics data from different size fractions of soil particles reasonably well. More significantly, the model was able to predict Cu release from the bulk soil samples based on Cu kinetic reactions with different size fractions of soil particles. SOM appeared to be the most dominant adsorbent for Cu under our experimental conditions, and, among different SOM binding sites, bidentate sites involving carboxylic and phenolic functional groups were the most significant. Our results suggested that a unified modeling framework, which specifically considers the chemical heterogeneity of soil binding sites and variations of particle sizes, is promising for predicting kinetic reactions of metals with heterogeneous soil particles in the field.

Tribological and biological behaviors of laser cladded Ti-based metallic glass composite coatings

In order to improve the wear resistance of pure Ti, three kinds of metallic glass composite coatings (MGCCs) with the compositions of Ti45Zr5Cu41Ni9, Ti45Zr5Cu41Ni6Sn3 and Ti51Zr5Cu41Sn3, were deposited on pure Ti by laser cladding. It is found that the order of amorphous phase percentage is Ti51Zr5Cu41Sn3 > Ti45Zr5Cu41Ni6Sn3 > Ti45Zr5Cu41Ni9. Compared to the pure Ti substrate, the wear resistances of three coatings were significantly improved in simulated body fluid (SBF) solution. The wear resistance of MGCCs in SBF solution is in the order of Ti45Zr5Cu41Ni6Sn3 > Ti45Zr5Cu41Ni9 ≥ Ti51Zr5Cu41Sn3, which is attributed to the combination of fine grain strengthening and well corrosion resistance. XPS results imply that these coatings enable to induce the deposition of calcium phosphate which is excellent responsible for the bone formation. The CCK-8 test and cell adhesion experiments show that compared to pure Ti, the Ti51Zr5Cu41Sn3 coating was free of cytotoxicity, while Ti45Zr5Cu41Ni9 and Ti45Zr5Cu41Ni6Sn3 coatings have obvious cytotoxicity in vitro due to the high release rate of Cu and Ni ions from coatings. It is suggested that the Ti51Zr5Cu41Sn3 coating had not only well wear resistance, but also excellent biocompatibility.

The effect of enzymes on release of trace elements in feedstuffs based on in vitro digestion model for monogastric livestock

BackgroundThis experiment was conducted to study the effect of different feed enzymes (phytase, xylanase, β-glucanase) on release rate of trace elements (Fe, Cu, Mn and Zn) in 6 commonly used feedstuffs (corn, wheat, barley, soybean meal, wheat bran, wheat middlings) by using an in vitro model, simulating the digestive processes in stomach for 2 h and then in small intestine for 6 h at 39 °C.ResultsPhytase raised (P < 0.05) the release rate of Cu and Zn in corn, Cu, Zn and Mn in wheat, Cu in barley, Cu, Zn and Mn in soybean meal, Zn, Fe in wheat bran and Zn, Fe, Mn in wheat middlings. The release rate of various trace elements in feedstuffs was increased after xylanase addition. Compared with the control group, the release rate of soluble Cu in corn, wheat, barley and soybean meal, soluble Zn in corn, wheat and wheat middlings and soluble of Mn in corn, wheat, barley and wheat bran increased (P < 0.05) after xylanase treatment. After the treatment of β-glucanase, the release rate of soluble Cu in corn, wheat and wheat bran, soluble Fe in barley, soybean meal and wheat bran and soluble Mn in corn and wheat bran all increased (P < 0.05) compared with the control group. In each feedstuff, after corresponding enzyme treatment, the contents of phytic acid, xylan and β-glucan were significantly lower than those of the control group (P < 0.05).ConclusionsResults showed that bound trace elements in feedstuffs can be released by feed enzymes. It may be necessary to take the trace elements in feedstuffs into account in the actual feed preparation including feed enzymes.

Production of food-grade multiple emulsions with high encapsulation yield using oscillating membrane emulsification

Food-grade water-in-oil-in-water (W/O/W) multiple emulsions with a volume median diameter of outer droplets of 50–210μm were produced by injecting a water-in-oil (W/O) emulsion at the flux of 30Lm−2h−1 through a 10-μm pore electroplated nickel membrane oscillating at 10–90Hz frequency and 0.1–5mm amplitude in 2wt% aqueous Tween® 20 (polyoxyethylene sorbitan monolaurate) solution. The oil phase in the primary W/O emulsion was 5wt% PGPR (polyglycerol polyricinoleate) dissolved in sunflower oil and the content of water phase in the W/O emulsion was 30vol%. The size of outer droplets was precisely controlled by the amplitude and frequency of membrane oscillation. Only 3–5% of the inner droplets with a mean diameter of 0.54μm were released into the outer aqueous phase during membrane emulsification. A sustained release of 200ppm copper (II) loaded in the inner aqueous phase was investigated over 7 days. 95% of Cu(II) initially present in the inner water phase was released in the first 2 days from 56-μm diameter multiple emulsion droplets and less than 15% of Cu(II) was released over the same interval from 122μm droplets. The release rate of Cu(II) decreased with increasing the size of outer droplets and followed non-zero-order kinetics with a release exponent of 0.3–0.5. The prepared multiple emulsions can be used for controlled release of hydrophilic actives in the pharmaceutical, food, and cosmetic industry.

Comparison of toxicity and release rates of Cu and Zn from anti-fouling paints leached in natural and artificial brackish seawater

Biocide-containing anti-fouling paints are regulated and approved according to the added active ingredients, such as Cu. Biocide-free paints are considered to be less environmentally damaging and do not need an approval. Zn, a common ingredient in paints with the potential of causing adverse effects has received only minor attention. Laboratory experiments were conducted in artificial brackish seawater (ASW) and natural brackish seawater (NSW) to quantify release rates of Cu and Zn from biocide-containing and biocide-free labeled eroding anti-fouling paints used on commercial vessels as well as leisure boats. In addition, organisms from three trophic levels, the crustacean Nitocra spinipes, the macroalga Ceramium tenuicorne and the bacteria Vibrio fischeri, were exposed to Cu and Zn to determine the toxicity of these metals. The release rate of Cu in NSW was higher from the paints for professional use (3.2–3.6 µg cm − 2 d − 1 ) than from the biocide leaching leisure boat paint (1.1 µg cm − 2 d − 1 ). Biocide-free paints did leach considerably more Zn (4.4–8.2 µg cm − 2 d − 1 ) than biocide-containing leisure boat paint (3.0 µg cm − 2 d − 1 ) and ship paints (0.7–2.0 µg cm − 2 d − 1 ). In ASW the release rates of both metals were notably higher than in NSW for most tested paints. The macroalga was the most sensitive species to both Cu (EC 50 = 6.4 µg l − 1 ) and Zn (EC 50 = 25 µg l − 1 ) compared to the crustacean (Cu, LC 50 = 2000 µg l − 1 Zn, LC 50 = 890 µg l − 1 ), and the bacteria (Cu, EC 50 = 800 µg l − 1 and Zn, EC 50 = 2000 µg l − 1 ). The results suggest that the amounts of Zn and Cu leached from anti-fouling paints may attain toxic concentrations in areas with high boat density. To fully account for potential ecological risk associated with anti-fouling paints, Zn as well as active ingredients should be considered in the regulatory process.

Chalcopyrite leaching: The rate controlling factors

Abstract The processes that determine the rate of chalcopyrite leaching are central to understanding how chalcopyrite (CuFeS2) behaves under the environmentally adverse conditions of acid rock drainage. To this end the effect of the acid anion on chalcopyrite leach rates using a variety of acidic media (H2SO4, HClO4, HCl and H2SO4 with 0.25 M NaCl) under carefully controlled solution conditions (pH 1 and 2, Eh 750 mV (SHE) and 75 °C) has been examined. These conditions have been chosen to enable sufficient leach rates for accurate experimental determination and to compare to the previous mechanistic analysis carried out by Harmer et al. (2006) . Extensive surface analysis of leach residues demonstrated that variations in the surface speciation could not be responsible for the observed variations in leach rate. The rate of Cu release, however, was found to be first order with respect to Fe3+ activity and inversely proportional with respect to H+ activity to the power of 0.7: 1 S dC dt = ( 2.0 ± 0.2 ) a Fe 3 + a H + 0.7 where S is the relative surface area, C is concentration of Cu in the solution (M), t is the time (h), 2.0 is the rate constant (M0.7 h−1) and a Fe 3 + and a H + are Fe3+ and H+ activities, respectively (M). The rate model was further validated against additional leaches carried out in H2SO4 media with the initial addition of Fe3+ (8 mM as Fe2(SO4)3) at 75 °C under various pH and Eh regimes. The only condition under which this rate model was found not to hold was at simultaneously low a Fe 3 + and high a H + , that is at pH 1 and a Fe 3 + 5 × 10 - 5 M , where the concentration of dissolved O2 may be leach rate determining.

In Situ Observation of Whole Lake Gross Primary Productivity: Response to and Recovery from Copper Algaecide Application

The fortuitous presence of in situ equipment capable of high-resolution (time/space) measures of O2 and total dissolved inorganic carbon (TDIC) enabled the response and recovery of a small pond to copper algaecide application to be monitored. Algaecide application to the pond significantly impacted the gross primary productivity (GPP) of the pond over a timescale of less than 4 days. By day 3–4 (postapplication), GPP had recovered to preherbicide levels and net ecosystem productivity (NEP) returned to a positive value. This indicated a timescale for copper algaecide impact on GPP of the order 1+ day and duration of impact of the order 3 days. Observed timescales for GPP recovery (3–4 days) indicate that algaecide effectiveness is not significantly controlled by mixing processes in this pond but is most likely influenced by the rate of removal of Cu to the sediment and the rate of Cu release from the chelating agent in K-tea. Observed recovery timescales for GPP (3–4 days) occurring during minimal inflow also indicate that significant nutrient recycling (internal loading) occurs to fuel the recovery of GPP. Thus, as an agent for the overall reduction in primary productivity of a polymictic pond ecosystem, a single copper application may not have a significant long-term impact on primary productivity.

Effects of LDPE film on the properties of copper/LDPE composites for intrauterine contraceptive device

Copper/low density polyethylene (LDPE) composites covered with LDPE film on the surface were prepared for intrauterine contraceptive device (IUD). Cu 2+ release rates of the composites were determined by absorbance measurements. The surface characteristics of the composites after incubated for 5 months were investigated by SEM and EDX techniques. The results show that the existence of LDPE film on the surface of the composites decreases the release rate of Cu 2+, especially the burst release of Cu 2+ at initial period. The undesirable deposits, which are observed on the surface of the composite without LDPE film, are not detected on the surface of the composite with LDPE film, indicating that the presence of LDPE film can effectively prevent the formation of deposits on the composite surface. Results obtained from this study suggest that the existence of LDPE film on the composite surface may alleviate the side effects (bleeding, abdominal pain and inflammatory complication) of IUD resulting from the burst release and the deposit formation.

Kinetics of copper desorption from soils as affected by different organic ligands

Desorption of Cu and low molecular weight dissolved organics are the primary factors that impact fate and transport of Cu in soils. To improve predictions of the toxicity and threat from Cu contaminated soil, it is critical that time-dependent desorption behavior be understood. In this paper, the effect of organic ligands citrate, malate, and succinate on the kinetics of Cu desorption from contaminated soils varying widely in soil characteristics was investigated at 25 0 C and the soils used were referred to as clay, calcareous and sandy soils. The amount of Cu released by the used organic ligands varied greatly with physicochemical properties of the soils. The rate of Cu release by different extractants was in the order citric > malic > succinic, which was consistent with the stability constants of Cu complexes with these ligands. The modified Freundlich and the Elovich and Parabolic diffusion models were used to describe dsorption of Cu 2+ from the three studied soils as affected by the organic ligands. All of the models fit the data well with correlation coefficients ranging from 0.83 to 1.00 (P < 0.01). Each Model has a set of assumptions for the different physical and chemical properties of the systems to which they are being applied. The uses of these equations yield different magnitudes for the calculated variable, but the relationships between the soil + organic ligands and their effect (i.e., increase or decrease) on these variables are the same. Such information is critical, since Cu is used in a variety of industrial and manufacturing processes and is one of the most common contaminants found at hazardous waste sites.

Effects of NH 3, O 2, and N 2 co-implantation on Cu out-diffusion and antimicrobial properties of copper plasma-implanted polyethylene

Metal antibacterial reagents are effective in the enhancement of the antimicrobial properties of medical polymers. However, incorporation of metal antibacterial reagents into polymers using conventional methods usually results in unstable antimicrobial effects. Our previous research demonstrates that plasma immersion ion implantation (PIII) can be used to effectively incorporate metal antibacterial reagents such as Cu into polyethylene (PE) in the near surface region up to several hundred nanometers without causing noticeable damage to the polymer matrix. In this work, various gases including NH 3, O 2, and N 2 were plasma-implanted in concert with Cu plasma immersion ion implantation to study the effects of these gas species on the release rate of Cu from the substrate. Our experimental results reveal that the copper depth profiles are not affected significantly by NH 3, O 2, or N 2 co-implantation and these gas elements have similar depth profiles as Cu. Chemical analyses demonstrate that polar functional C O, C O, C N, C N, and C N bonds formed in the substrate play an important role in regulating Cu out-diffusion. Among the three gas species, N 2 shows the best effects in regulating Cu out-diffusion and produces the best long term antibacterial properties. The Cu retention and out-diffusion mechanism in the ion-implanted polyethylene is described.

Copper complexes at N- and C-site of ovotransferrin: Quantitative determination and visible absorption spectrum of each complex

(1) Copper complexes at the two sites of ovotransferrin (Tf) differed markedly in the rate of Cu release by EDTA. (2) During the reaction, λ max of the remaining Cu-Tf complex shifted to red side, while the difference spectrum of Fe nCu 2−nTf vs. Fe nTf in which the N-site had been preferentially occupied with Fe had λ max at blue side from that of Cu 2Tf, 440 nm. (3) From these results, the intrinsic spectrum for Cu-complex at each site was assigned: λ max 450 nm for N- and 430 nm for C-site. (4) The differences in the release rate and the spectrum can be used for the identification of the two domains of Tf and for the analysis of metal-binding behavior of each site.