Biopassivation Method for the Preservation of Copper and Bronze Artefacts

A biopassivation method has been proposed as a new ecological and sustainable solution for preserving copper-based artefacts using selected microorganisms. This technology is based on the natural capacity of some fungi to form copper oxalates on the corroded surface of copper alloys. Existing unstable and pulverulent corrosion products are converted into an insoluble and chemically stable biopatina that provides the treated surfaces with a stabilization of the corrosion process and an aesthetically attractive green color. This treatment allows to stabilize the active corrosion induced for example by copper chlorides and to prevent green staining of surrounding materials (stone pedestal, wall…) due the leaching and loss of pulverulent and water-soluble corrosion products (i.e. copper sulfates). The behavior and performance of the proposed treatment have been followed during natural aging procedures, which have shown that this method stabilizes the corrosion process while having less chromatic variation compared to more traditional protective systems. The application protocol was then validated on real cases such as outdoor sculptures and archaeological objects. Based on these results, a ready-to-use kit is now proposed to conservators.

The atacamite family of minerals – a testbed for quantum spin liquids

Polymorphism of Cu2(OH)3Cl coupled with partial substitution of Jahn–Teller active Cu2+ by other divalent metal cations gives rise to the complex mineralogy of the atacamite family of secondary basic copper chlorides. Herbertsmithite, Cu3Zn(OH)6Cl2, in which Zn substitutes for one quarter of the Cu atoms, provides a lattice of corner-sharing triangles of paramagnetic Cu2+ (spin ½) cations, rendering the mineral a perfect realization of a kagome antiferromagnet. Geometric frustration of conventional antiferromagnetism is expected to give rise to exotic ground states, with dynamic magnetic structures that might turn out to be physical realizations of quantum spin liquids. In this paper, a synopsis of the key topological, compositional and behavioural features of minerals in the atacamite family is given, with emphasis on the kagome character of the resulting lattice of Cu2+ cations.

Features of the structure active centers of industrial catalysts for the oxidative chlorination of ethylene

The active phase of CuCl2, HСuСl2, H2СuСl4 and two grades of industrial ethylene oxidation chlorination catalysts (EOC) such as deposited catalyst X1 (Harshow), with copper chlorides supported on an alumina surface, and a permeated MEDC-B catalyst immobilized in the internal pores of the firm of the company Sud-Chemie. Catalyst were analyzed by the method of thermoemission electronic raster (VEGA3NTSCAN) microscopy and X-ray fluorescence energy dispersion spectroscopy (EDX-7000). It is shown that the active catalyst centers of CuCl2 have different crystalline structure from the amorphous active phase of H2CuCl2, H2CuCl4 on the surface of the catalysts. On the surface of X1 Harshow copper chlorides are uniformly distributed throughout the volume of the carrier catalyst γ-Al2O3 in the form of amorphous portions [CuCl4]-2, [CuCl2]-1. At the same time, on the surface of the catalyst MEDC-B, the active centers have a separate cluster immobilized crystalline structure of the active phase, which differs from the composition of the carrier γ-Al2O3.

Induction of Micronuclei in Mice Bone Marrow Cells by Cobalt and Copper Chlorides

The aim of our research was to investigate the genotoxic effects of cobalt chloride and copper chloride in mouse bone marrow cells using the micronucleus (MN) assay. The three different concentrations of cobalt chloride (11.2, 22.5 and 45 mg kg-1) and copper chloride (1.17, 2.35 and 4.70 mg kg-1) were injected intraperitoneally to mice for 24 and 48 hours. It was observed that both of these heavy metals induced a significant increase in frequency of micronucleated polychromatic erythrocytes (MNPCE) at different concentrations in mice for 24 and 48 hours when compared with the control. Furthermore, the significant reduction for the polychromatic erythrocyte/normochromatic erythrocyte (PCE/NCE) ratio which is indicative of bone marrow cytotoxicity was observed in bone marrow cells which were treated with copper chloride at all concentrations for 24 and 48 hours. No reduction of the PCE/NCE ratio was observed both 24 and 48 hours after all the doses of cobalt chloride tested as compared to the negative control. These results lead us to the conclusion that copper chloride may have genotoxic and cytotoxic properties due to induction in the frequency of MN and a reduction in PCE/NCE ratio in bone marrow cells of mice, whereas cobalt chloride induced only genotoxic effect in mice bone marrow

Mid-IR and Raman Spectral Properties of Clinoatacamite-Structure Basic Copper Chlorides

Basic copper chloride Cu2(OH)3Cl and Cu2(OD)3Cl polycrystalline sample were successfully synthesized in the same single phase of clinoatacamite-structure, and the latter’s mid-infrared absorption spectra (4000-400cm–1) and Raman spectra (4000-95cm–1) were first, to the best of our knowledge, measured respectively by FTIR spectroscopy and Micro-Raman spectroscopy to study the corresponding relationship between their spectral properties and crystal structure. Through the comparative analysis of the four spectra we definitely assign or tentatively suggest the vibration modes of OH/D groups in the trimeric hydrogen bond environment, (H/DO)–Cu–(OH/D), Cl–Cu–Cl. These results can be propitious to their low temperature spectral properties which must help to understand the underlying physics of their exotic geometric frustration phenomenon.