Malachite Surface Research Articles

Bench-scale flotation of chrysocolla with n-octanohydroxamate

Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, atomic absorption spectroscopy (AAS) and X-ray photoelectron spectroscopy (XPS) have been employed to characterise the surface layer and compound formation during the interaction of n-octanohydroxamate with chrysocolla and malachite surfaces. The flotation response of a single mineral chrysocolla–quartz sand sample and mixed chrysocolla–malachite–quartz sand sample using n-octanohydroxamate collector has been investigated. Recoveries of 95% were achieved in bench-scale flotation testing, with the best Cu grades achieved at pH>9. Long conditioning times adversely affected flotation performance. Moderate recovery of impurity minerals in the mineral and sand was also observed.

A Rational Approach for Controlled Adsorption of Metal Ions on Bovine Serum Albumin−Malachite Bionanocomposite

In this article, we demonstrate the preparation of a new bionanocomposite by surface modification of malachite [Cu2(OH)2CO3] nanoparticles with bovine serum albumin (BSA). The conformation of protein in BSA−malachite nanocomposite has been analyzed by employing fluorescence and Fourier transform infrared (FT-IR) spectroscopic methods. The BSA molecule loses its tertiary and secondary conformation partially in BSA−malachite nanocomposite. For the first time, bare malachite nanoparticles and BSA−malachite nanocomposite have been used for the adsorption of a series of toxic and precious metal ions from single- and multicomponent aqueous solution. We report a reversal in adsorption behavior of selected metal ions upon surface modification of malachite nanoparticle with BSA. Among different metal ions studied here, the “harder” ions (according to HSAB principle), likely, Cu2+, Ni2+, Cr3+, and Zn2+, were preferably adsorbed on bare malachite surface but show less adsorption on BSA−malachite nanocomposite. After...

Calcium Carbonate on Bronze Finds

The removal of calcareous accretions from archaeological bronzes can be a difficult step in their conservation. Chemical cleaning with chelating agents might be an alternative to mechanical methods. In this study the use of the chelating agent sodium tripolyphosphate (STPP) was examined to determine whether it is effective in discriminating between calcium carbonate and copper patina, and non-corrosive to copper alloys in the presence of air. Comparative experiments with STPP and disodium ethylenediamine-tetraacetate (Na2-EDTA) were carried out on synthetic malachite, cuprite, calcium carbonate, naturally polished malachite surfaces and sheets of bronze and brass. In addition to the properties of the chelating agent, the solubility of the salts and the pH values of the solutions are crucial factors in the removal of compounds of low solubility. The quantity of metal ions dissolved, estimated by atomic absorption spectral analysis and scanning electron microscopy, showed that the calcareous accretions could be removed satisfactorily, but STPP also dissolved constituent parts of the patina, such as malachite and cuprite, and may harm bronze or brass. Compared to Na2-EDTA, STPP is less effective in dissolving calcium carbonate. It is less harmful to the patina and base metal, but may lead to patination of the underlying metal.

Interactions between sulphide minerals and alkylxanthates 7. A vibration and X-ray photoelectron spectroscopic study of the interaction between covellite and alkylxanthate ions and the non-sulphide mineral malachite and ethylxanthate ions in aqueous solution

The reactions between covellite, CuS, and malachite, CU 2CO 3(OH) 2, and aqueous and acetone solutions of potassium ethylxanthate and decylxanthate have been studied. X-ray photoelectron spectroscopy (XPS) has been used to determine the oxidation state of copper in the surfaces of the minerals. The XPS measurements showed that copper is present as copper(I) and copper(II) on the surfaces of covellite and malachite respectively. Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy has been used for qualitative analysis of the alkylxanthate species present on the mineral surfaces after treatment with an aqueous solution of potassium alkylxanthate. Solid copper(I) alkylxanthate is the predominating alkylxanthate species formed on covellite. Very small amounts of dialkyl dixanthogen are found on the covellite surfaces as well. Solid copper(I) alkylxanthate is sorbed on the covellite surfaces according to a dissolution—precipitation mechanism in which copper(I) species are dissolved from the covellite surface, a concentration gradient of copper(I) species is formed around the covellite particles and copper(I) alkylxanthate is precipitated back on the covellite surface in the presence of a suitable concentration of alkylxanthate ions. No experimental evidence for the formation of chemisorbed complexes of alkylxanthate ions on covellite surfaces was found. Solid copper(I) alkylxanthate and dialkyl dixanthogen are both present in large quantities on malachite surfaces after treatment with an aqueous solution of potassium alkylxanthate, as expected for a copper(II) mineral.

Kinetics of sulfidization of malachite in hydrosulfide and tetrasulfide solutions

The kinetics of sulfidization of malachite in sodium hydrosulfide and tetrasulfide as the sulfidizing agents was investigated in this study. The sulfidization reaction occurred in two stages. The first stage involved the formation of a primary sulfidized layer and the second involved two types of secondary reactions. One was the precipitation of copper ions which diffused through the primary layer, and the other was the oxidation of the sulfidizing agent to oxysulfide species. The influence of the type and concentration of the sulfidizing reagent and solution pH was determined. A significant difference in the surface morphology was observed for malachite treated with these two reagents. With sodium tetrasulfide, a uniform sulfidized layer formed on the particle surface, whereas for sodium hydrosulfide, the malachite surface was coated with loosely adherent precipitates, which might peel-off upon agitation. The results indicate that the extent of the reaction in the second stage was smaller in sodium tetrasulfide than in sodium sulfide.

２，３のフッ素系界面活性剤によるマラカイト表面の疎水化

２，３のフッ素系界面活性剤によるマラカイト表面の疎水化

くじゃく石表面におけるオクタンチオール銅の生成

The bubble-pick-up tests were carried out to show the effectiveness of 1-octanethiol as a collector for malachite. Octanethiol with soft base group has given a good collection at pH 5-10. Octanethiol has adsorbed and/or reacted on the surface of malachite and copper octanethiolate with high hydrophobicity has been formed, which has given strong collecting action. In a concentrated octanethiol solution the reaction of the formation of copper octanethiolate has proceeded inside malachite, but in the case of surface-sulphidized malachite the extent of the reaction has been less. The extent of the formation has also been influenced by the solubility of octanethiol in the solution.

Infrared spectral study of species formed on malachite surface by adsorption from aqueous salicylaldoxime solution

The adsorption of salicylaldoxime from aqueous solution by malachite has been studied and the nature of the adsorbed species has been determined by infrared spectroscopy. At low surface coverage, a basic salt is observed whereas the bis-salicylaldoximato-copper II complex is formed when tridimensional condensation of the adsorbate occurs on the surface. At this stage the surface becomes hydrophobic allowing the mineral to be floated. The kinetics of the adsorption process is first order with respect to the salicylaldoxime concentration. The mechanism of this process is discussed in the light of the spectroscopic results.

Sulfidizing of chromium stainless steels : E. P. Pukhovskii and others. Metallovedenie i Obrabotka Metallov, v.2, no. 5, 1956, pp. 40–43; 5 fig., 3 tables, 1,200 words. (No. 3799, $ 2.90)

The kinetics of sulfidization of malachite in sodium hydrosulfide and tetrasulfide as the sulfidizing agents was investigated in this study. The sulfidization reaction occurred in two stages. The first stage involved the formation of a primary sulfidized layer and the second involved two types of secondary reactions. One was the precipitation of copper ions which diffused through the primary layer, and the other was the oxidation of the sulfidizing agent to oxysulfide species. The influence of the type and concentration of the sulfidizing reagent and solution pH was determined. A significant difference in the surface morphology was observed for malachite treated with these two reagents. With sodium tetrasulfide, a uniform sulfidized layer formed on the particle surface, whereas for sodium hydrosulfide, the malachite surface was coated with loosely adherent precipitates, which might peel-off upon agitation. The results indicate that the extent of the reaction in the second stage was smaller in sodium tetrasulfide than in sodium sulfide.