Ethylenediamine Copper Research Articles

The relationship between molecular weight of bacterial cellulose and the viscosity of its copper (II) ethylenediamine solutions

There are difficulties in measuring the molecular weight (Mw) of bacterial cellulose (BC) using Gel Permeation Chromatography (GPC) analysis. Additionally, the Mark-Houwink-Sakurada equation cannot be used to predict the Mw of BC as no Mark-Houwink-Sakurada constant specific to BC is available. In this study, a systematic approach is developed to establish the relationship between the Mw of BC and the viscosity of its copper (II) ethylenediamine (CED) solutions. Impurities contained in the raw BC are examined and appropriate purification procedures are designed for their removal before the above two measurements are conducted. The Mw of BC is obtained by measuring the Degree of Polymerization of its corresponding cellulose acetate (CA), derived from degraded BC, using GPC analysis, and the viscosity of the CED solutions of the BC is measured using a BS/U Tube viscometer. In this paper, the Mark–Houwink–Sakurada constants (K=0.3752 mL/g and α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha$$\\end{document}=1.4532) specific for BC are determined to relate the Mw of BC with the intrinsic viscosity of its CED solutions. It is also found that the Mw of BC is proportional to the dynamic viscosity (i.e.,ηBC=0.0183Mw1.3069\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\eta _{BC} =0.0183Mw^{1.3069}$$\\end{document}) and the flow time (i.e., tBC=1.3809\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$t_{BC} =1.3809$$\\end{document}Mw1.3062\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{1.3062}$$\\end{document}) of its CED solutions. These BC-specific relationships can help determine the Mw of BC from the rheological properties of its CED solutions.

Gold Extraction from Oxide Ore using Copper Ethylenediamine Thiosulfate

Gold Extraction from Oxide Ore using Copper Ethylenediamine Thiosulfate

Study on Synergistic Strengthening of Gold Extraction with Copper Ethylenediamine Thiosulfate Using Pyrite and Nickel Ions

Gold leaching using the copper–ethylenediamine–thiosulfate (Cu2+-en-S2O32−) system, which contains copper–ethylenediamine complexes, instead of the use of copper–ammonia catalysis, is environmentally friendly and cost-effective. In this study, pyrite and Ni2+ were added to the Cu2+-en-S2O32− system to clarify their individual and combined influence on gold leaching. The result obtained showed that when pyrite and Ni2+ were separately added to the system, the dissolution of gold was significantly inhibited. However, the disappearance of the negative impacts of these two substances when they were simultaneously added to the system revealed that they exhibited a synergistic effect on gold dissolution. Notably, Ni2+ weakened the promotional effect of pyrite on the formation of a Cu-containing passivation layer on the gold surface. Furthermore, the separate addition of Ni2+ and pyrite increased the corrosion potential of gold; thus, gold dissolution was inhibited. However, when added together, they brought about a decrease in the corrosion potential of gold, while increasing its dissolution rate. These findings provide a reference for the efficient extraction of pyrite-associated gold, which can be applied to improve the green extraction process of gold.

New insight into enhancing sulfurization of azurite with ethylenediamine and its response to xanthate adsorption

Organic amine salt is an efficient sulfurization accelerator for copper oxide minerals. In fact, its underlying function mechanism is scarce. In this study, the evolution of sulfurized products of azurite under ethylenediamine (EDA) regulation and its response to the xanthate adsorption and surface hydrophobicity were investigated. ToF-SIMS, ICP-OES, XPS and total nitrogen analyses showed that pretreatment with EDA promoted the additional formation of copper sulfide products on azurite, and the sulfurization efficiency increased by 17%. The solution chemistry and transition state search analyses revealed that EDA changed the sulfurization reaction pathway by the formation of copper ethylenediamine ion (Cu(en)n2+, n = 1, 2) resulting in the increase of the reaction energy barrier from 55.12 kcal/mol to 197.83 kcal/mol. Therefore, the deposition rate of copper sulfide on azurite was slowed down, thus creating stable solution environment for the dense adhesion of products, which was observed by FESEM. The increasing copper sulfide products created favorable conditions for the stable adsorption of SBX on azurite, ultimately improving the surface hydrophobicity of azurite. These results may provide a deeper understanding for EDA promoting the sulfurization of copper oxide minerals.

Electrochemical analysis of the dissolution of gold in a copper–ethylenediamine–thiosulfate system

Abstract Thiosulfate gold leaching is a green gold extraction technology. Here, the effects of thiosulfate, copper ion, ethylenediamine, and polarization voltage on the dissolution of gold in this system were investigated by an electrochemical method. The results showed that the addition of thiosulfate promoted the dissolution of gold, but increasing the thiosulfate concentration had a little additional effect. The addition of ethylenediamine also increased the dissolution of gold, but the dissolution resistance of gold increased after adding ethylenediamine. The dissolution of gold increased, the diffusion resistance increased, and the dispersion effect increased upon increasing the copper ion concentration. The copper–ethylenediamine–thiosulfate system did not display passivation (or only weak passivation) upon increasing the polarization voltage, which indicates that the system was relatively stable. The influence of three factors on the dissolution of gold followed the order thiosulfate > copper ion > ethylenediamine.

Tetrahydrated bis(monoaqua-bis(ethylenediamine)copper(II))-diaqua-bis(ethylenediamine)copper(II) dicitrate: Preparation, crystal structure, Raman and FTIR spectra and paramagnetic behavior

The crystals of the first copper(II) ethylenediamine complex containing citrate anion have been prepared and characterized. Despite the archetypical character of the copper(II) ethylenediamine complexes, some structural peculiarities were found to be interesting since they are quite rare even among the mentioned type of the complex compounds i.e. a presence of both mono and diaqua-bis(ethylenediamine)copper(II) cations together in the same crystal structure, intramolecular hydrogen bonding of the citric anion, cis,trans-configuration of the citric anion and the disordered C-C bond of the ethylenediamine molecule in the monoaqua-bis(ethylenediamine)copper(II) cation, which in fact is a co-existence of two energetically close δδ and δλ conformers. The Raman as well as FTIR spectra were recorded and discussed. Finally, the magnetic measurements have shown paramagnetic behavior of the prepared complex in a wide range of temperatures.

Evaluation of self-prepared absorbable hemostatic cellulose fibrils.

To evaluate the effectiveness and safety of self-prepared absorbable hemostatic fibrils.A kind of absorbable hemostatic fibrils were prepared by self-developed patent technique. The physical form and molecular structure of the fibrils and a marketed product Surgicel were characterized by general observation and infrared spectroscopy; the carboxyl content, pH value and relative molecular mass of fibrils were determined by potentiometric titration method, pH meter and copper ethylenediamine method, respectively. The behavior of the fibrils and Surgicel in contact with blood was observed by inverted microscope, the cytotoxicity was evaluated by agarose diffusion cell assay . The external iliac artery hemorrhage model and the back muscle infiltration model in rats were established. The hemostatic effectiveness of the fibrils was investigated by hemostasis time and blood weight, and the degradation and biosafety of fibrils were investigated by observation photography, immune organ weighing, hematology and coagulation index measuring, and histopathological examination. The fibrils and Surgicel had similar molecular structures. Compared with the raw material regenerated cellulose, the typical carboxyl stretching vibration absorption peak of -COOH appeared near in both fibrils and Surgicel. The carboxyl content of the two materials was about 20%, and the pH value was about 3. The relative molecular mass of the fibers after oxidation was 4466±79, which was close to that of Surgicel(>0.05). After contacting with blood, the volume of fibrils and Surgicel expanded, and absorbed blood of dozens of times as their own weight. The results of agar diffusion test showed that the fibrils had no cytotoxicity. The results of animal experiments showed that the hemostasis completed within and there was no significant difference in blood weight and speed of hemostasis between two products (both >0.05). The fibrils could be degraded 1 week after being implanted to the bleeding sites of the muscle. There were no pathological effects on the appearance, body weight, food intake, immunological tissue thymus, spleen, lymph nodes, hematology and coagulation indexes of the rats, and no obvious abnormality found in the histopathological examination. The prepared absorbable hemostatic fibrils have excellent biological safety and effectiveness.

Synthesis of a rod-based porous coordination polymer from a nucleotide as a sequential chiral inductor

We report the two-step synthesis of a novel chiral rod-based porous coordination polymer (PCP). The chemical approach consists of the use of a previously prepared bis(ethylenediamine) copper monomer [Cu(en)]2(NO3)2 [where en = ethylenediamine] reacting with the cytidine 5′-monophosphate (CMP) nucleotide. The bis(ethylenediamine) copper compound—stabilized by axial coordination of nitrate counter-anions—reacts in the presence of sodium salt of CMP to yield right-handed copper(II) chains of P helicity with formula [Cu2(en)2(CMP)2]·5H2O (1). The axial coordination of the CMP2- ligands through the N3 and O2 sites (free nitrogen and carbonyl groups) of the cytosine nucleobase and oxygen atoms of phosphate moieties, ensure stabilization of the neutral chiral polymer. The supramolecular organization involves strong hydrogen bonding interactions to build supramolecular chains of the same helicity. The resulting PCP constitutes one of the few examples of CMP compounds exhibiting coordination involving both nucleobase and phosphate moieties, where a highly stable metal complex is used as precursor for the rational construction of rod-based hydrogen metal-organic frameworks (HMOFs). Furthermore, it shows the intrinsic capability of biomolecules to act as chiral transfer systems.

Crystal structure and Hirshfeld surface analysis of a copper(II) complex with ethyl-enedi-amine and non-coordinated benzoate.

In the title compound, di-aqua-bis-(ethyl-enedi-amine-κ2 N,N')copper(II) bis-(2-nitro-benzoate), [Cu(C2H8N2)2(H2O)2](C7H4NO4)2, two di-aqua-bis-(ethyl-enedi-amine)-copper(II) cations and four nitro-benzoate anions are present in the asymmetric unit. All four anions are 'whole-mol-ecule' disordered over two sets of sites. The major components have refined occupancies of 0.572 (13), 0.591 (9), 0.601 (9) and 0.794 (10). The CuII ions exhibit slightly distorted octa-hedral geometries. In the crystal, cations and anions are connected to each other via N-H⋯O and O-H⋯O hydrogen bonds, forming a two-dimensional network parallel to (200). The inter-molecular contacts in the crystal were further analysed using Hirshfeld surface analysis, which indicates that the most significant contacts are O⋯H/H⋯O (42.9%), followed by H⋯H (35.7%), C⋯H/H⋯C (14.2%), C⋯C (2.9%), C⋯O/O⋯C (2.2%), N⋯H/H⋯N (0.9%) and N⋯O/O⋯N (0.3%).

Improvement on Measuring the Intrinsic Viscosity of Cellulose by the Copper Ethylenediamine Method

Improvement on Measuring the Intrinsic Viscosity of Cellulose by the Copper Ethylenediamine Method

Biological properties of electrospun cellulose scaffolds from biomass

Nowadays the development of sustainable technologies for the effective production of polymeric materials that can be used as biomaterials will be of importance. In this work, cellulose (CEL) was purified from potato peel waste (PPW) and used to produce electrospun nanofibers for tissue engineering applications. The purified CEL was solubilized in copper ethylenediamine (Cuen) and the electrospun nanofibers was produced through electrospinning technique in diameter range of 250–500 nm at electrical field strength of 20 kV. To confirm the applicability of the electrospun CEL scaffolds in tissue engineering, in vitro BALB-3T3 fibroblastic cell adhesion and cell proliferation tests were employed in this study. Cell viability was evaluated by staining with ethidium bromide (EtBr) and acridine orange (AO) to evaluate the possible effects of cytotoxicity of the CNF scaffolds. Fluorescence studies confirmed that BALB-3T3 viable cells attached and spread throughout the CEL scaffold. The attachment and spreading of viable cells suggests that electrospun CEL scaffolds support growth of BALB-3T3 fibroblasts cells and suggests that PPW can be a useful source of raw material for the production of scaffolds for tissue engineering.

Size-exclusion chromatography with on-line viscometry of various celluloses with branched and linear structures

We analyzed softwood and hardwood bleached kraft pulps (SBKP and HBKP, respectively), and Japanese cedar (Cryptomeria japonica) celluloses prepared from wood powders using delignification, hemicellulose removal, and dilute acid hydrolysis. For sample preparation, each sample was dissolved in 8% (w/w) lithium chloride/N,N-dimethylacetamide (LiCl/DMAc), after the sample was soaked in ethylenediamine (EDA) and the EDA was exchanged with DMAc through methanol. These solutions were diluted to 1% (w/v) LiCl/DMAc and subjected to size-exclusion chromatography (SEC) combined with multiangle laser light scattering and viscometry analyses. SEC/multiangle laser light scattering and SEC/viscometry use different principles to determine the molecular structures of polymers dissolved in LiCl/DMAc. Both methods showed that SBKP celluloses with high molar masses had branched structures, whereas HBKP celluloses had linear structures as like cotton, bacterial, tunicate, and algal celluloses. Conventionally, viscosity-average molar masses or viscosity-average degrees of polymerization of SBKP and HBKP are obtained by capillary viscometry using a 0.5 M copper ethylenediamine hydroxide (cuen) solution. Because SBKP and HBKP have different cellulose structures (branched and linear molecules, respectively), their viscosity-average molar masses and viscosity-average degrees of polymerization should not be calculated using the same Mark–Houwink–Sakurada equation.

Ecofriendly preparation of graphene sheets decorated with an ethylenediamine copper(ii) complex composite modified electrode for the selective detection of hydroquinone in water

A reduced graphene oxide decorated copper(ii) ethylenediamine complex composite modified electrode was applied for the electrochemical determination of hydroquinone.

Synthesis, spectroscopic, and X-ray structural study of aqua-bis(thymine-N1,N4)-ethylenediamine copper(II)dihydrate [Cu(Thy)2(en)(H2O)].2H2O

ABSTRACTA new compound of thyminato anions and ethylenediamine with five-coordinate Cu(II) is synthesized. Elemental analysis and spectroscopic techniques (IR, UV-visible) were used to characterize this compound and its crystal structure was determined by single-crystal X-ray diffraction. The crystal structure consists of the neutral mononuclear complex [Cu(Thy)2(en)(H2O)].2H2O. The environment around Cu(II) ion exhibits a square pyramidal geometry with two nitrogen atoms of ethylenediamine and two other nitrogen atoms of the monodentate monoanions of thymine building the equatorial plane. The oxygen atom from H2O molecule occupies the apical position. The complex displays a hydrogen-bonded network. The IR and UV-visible spectra were used to correlate the description of complex.

Hierarchical reduced graphene oxide supported dealloyed platinum–copper nanoparticles for highly efficient methanol electrooxidation

Exploiting highly efficient electrocatalysts through simple methods is very critical to the development of energy conversion technologies. Herein, we develop a hierarchical reduced graphene oxide supported dealloyed platinum–copper nanoparticle catalyst (Pt–Cu/RGO) by a facile one-step electrodeposition of graphene oxide in the presence of H2PtCl6 and copper ethylenediamine tetraacetate. The nanostructure and composition were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman spectroscopy. Meanwhile, the electrocatalytic performance was investigated by cyclic voltammetry and chronoamperometry, showing that the Pt–Cu/RGO catalyst not only equips with an outstanding electrocatalytic activity for the methanol oxidation reaction (2.3 times that of commercial Pt/C catalyst), but also shows a robust durability and superior tolerance to CO poisoning. The excellent electrocatalytic performance could be attributed to the three-dimensional hierarchical structure, porous dealloyed nanoparticles and synergistic effect between each component.

Bio-based polymer from heterogeneous catalytic polymerization of vegetable oils

AbstractRecently, printing ink ingredients have been provided from vegetable oils as a renewable, non-toxic, and biodegradable resource. In this work, to produce bio-based polymer potentially exploitable in printing ink vehicles, tris(ethylenediamine)nickel(II) nitrate and bis(ethylenediamine)copper(II) nitrate complexes were synthesized, characterized, and then used as heterogeneous catalysts for polymerization of soybean oil. Also, nickel and copper oxide catalysts were fabricated through thermolysis of the mentioned complexes and, after characterization, were employed for the polymerization reaction. The results showed that the presence of nickel and copper complex catalysts favored the reaction progress as the viscosity of the reaction product was increased 4 and 1.3 times, respectively, compared with polymerization without a catalyst. Also, the results obtained from using nickel and copper oxides indicated that these metal oxides do not have a significant effect on the reaction process.

Determination of intrinsic viscosity-molecular weight relationship for cellulose in BmimAc/DMSO solutions

For simply and accurately determining molecular weight of cellulose, an ionic liquid mixed with a co-solvent, 1-butyl-3-methylimidazolium acetate/dimethyl sulfoxide (BmimAc/DMSO) (1:1, w/w) was used and dissolved cellulose well at ambient temperature. During the dissolution process no degradation of cellulose was observed, and all the resultant cellulose/BmimAc/DMSO solutions were transparent and stable. These advantages make it as an ideal solvent system to build a new characteristic method of cellulose’s molecular weight by the measurement of the intrinsic viscosity [η], which is significantly better than the currently used solvent systems. [η] of solutions of nine cellulose samples was measured by using rheometer with cylinder fixture and Ubbelohde viscometer, respectively. The [η] values obtained by these two methods were well consistent. The degree of polymerization (DP) of these cellulose samples was determined by Copper (II) ethylenediamine method. Then the molecular weight and its distribution of representative samples were cross-checked by gel permeation chromatography for soluble derivatives of cellulose. As a result, a relationship DP = 134 [η]1.2 was built, suitable for DPs in the range of 220–1400. The uncertainty of this relationship was estimated to be 5 %. This work provided a simple, accurate and reliable method for determining [η] and the molecular weight of cellulose.

Cu–EDTA-modified APTMS-Fe3O4@SiO2 core–shell nanocatalyst: a novel magnetic recoverable catalyst for the Biginelli reaction

A novel copper–ethylenediamine tetracarboxylate modified core–shell magnetic catalyst is introduced.

Time-Resolved Continuous-Wave and Pulse EPR Investigation of Photoinduced States of Zinc Porphyrin Linked with an Ethylenediamine Copper Complex

Electron spin dynamics of the photoexcited state of a new porphyrin system built of a zinc porphyrin molecule with a linked complex of copper ion (ZnPCu) was studied using electron paramagnetic resonance (EPR) methods. The time-resolved continuous-wave and echo-detected EPR data show that electron spins of the ZnPCu system are polarized. The shape of the EPR spectrum and the echo-detected nutation spectroscopy data indicate that there is a relatively small spin–spin interaction between two subunits, namely, less than the zero-field splitting parameter of the excited triplet ZnP molecule. Results have been interpreted assuming that the S = 1 Zn porphyrin subunit electron spins are polarized via the triplet mechanism and this polarization is transferred to the S = 1/2 copper subunit via a flip-flop process induced by the exchange interaction between these subunits. The formation of the integral spin polarization in the triplet–doublet system as a function of the value and type of the triplet–doublet interaction was analyzed.

Molecular mass and molecular-mass distribution of TEMPO-oxidized celluloses and TEMPO-oxidized cellulose nanofibrils.

Native wood cellulose was oxidized by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation, and the fibrous TEMPO-oxidized celluloses (TOCs) thus obtained were disintegrated in water to prepare TOC nanofibrils (TOCNs). The carboxyl groups of TOCs and TOCNs were methyl-esterified, and the methylated samples were dissolved in 8% LiCl/N,N-dimethylacetamide for size-exclusion chromatography/multiangle laser-light scattering (SEC-MALLS) analysis to obtain their molecular-mass (MM) values and MM distributions (MMDs). The results showed that remarkable depolymerization occurred in TOCs and TOCNs and depended on the oxidation and sonication conditions. Because single peaks without bimodal patterns were observed in the MMDs for all of the TOC and TOCN samples, depolymerization may have randomly occurred on whole cellulose molecules and oxidized cellulose molecules in the microfibrils during these treatments. Compared with the MM values obtained by SEC-MALLS, the intrinsic viscosities of TOCs dissolved in 0.5 M copper ethylenediamine solution provided lower MM values owing to depolymerization during the dissolution and postreduction processes.