Avaliação do efeito da concentração de carbonato na eletrodeposição de cobre sobre discos de aço-carbono

Mild steel blankets were covered with electrolytic copper thin layer, from cyanide bath, being evaluated the influence of the carbonate concentration in the physiochemical properties of those deposits. The cell voltage decreased as the current intensity decreased, but the adherence of the deposit was not enhanced, showing that the increment of carbonate concentration causes substantial problems. Chemical solubilization reactions of air-bearing carbon dioxide and oxidation of free cyanide ions through dissolved oxygen evolved in the anodic processes contribute to the copper plating to occur in an inefficient way. The best optimal conditions require a carbonate concentration below 50 g L-1.

Estudo do comportamento eletroquímico de substâncias complexantes utilizando eletrodo de cobre

Copper electrode can be used for determination of complexing compounds through complexation reactions between Cu(II) and the analites. In this work some studies with three compounds were performed: glycine (precursor of glyphosate synthesis), herbicide glyphosate and aminomethylphosphonic acid (main metabolite of glyphosate). These compounds are complexing agents for Cu electrodes. Through simple experiments (cyclic voltammetry and corrosion studies) the applicability of the copper electrode as electrochemical sensor for complexing compounds in flow systems was presented.

Efeito de substâncias empregadas para remoção de cobre sobre o teor de compostos secundários da cachaça

High copper content is of great concern among producers of sugar-cane spirits who frequently use filters instead of cleaning the stills. This study compared the efficiency of activated carbon, ion-exchange-polymeric resin, and activated-carbon/iron-oxide magnetic composite for copper reduction without removing excessive organic compounds that are important for the beverage's quality. Resin was the most efficient copper adsorbent, removing fewer organic compounds. The composite also removed copper; however, it also removed large amounts of organic compounds. Activated carbon didn't remove sufficient copper to reduce its concentration to less than 5 g L-1, and it removed large amounts of higher alcohols and esters.

Emprego de sílica gel organicamente modificada e impressa ionicamente para pré-concentração seletiva on-line de íons cobre

The present work purposes the preparation of a silica gel sorbent organically modified with 2-aminoethyl-3-aminobutylmethyldimethoxysilane (AAMDMS) and imprinted with Cu2+ ions by means surface imprinting technique and its use for selective on-line sorbent preconcentration of Cu2+ ions with further UV-VIS spectrophotometric determination by flow injection analysis. The Cu2+-imprinted silica gel, when compared with non imprinted silica gel and silica gel, showed from the binary mixture of Cu2+/Ni2+ relative selectivity coefficient (k') of 6.84 and 5.43 and 6.64 and 19.83 for the mixture Cu2+/Pb2+, thus demonstrating higher selectivity of Cu2+-imprinted silica gel towards Cu2+ ions. Under optimized condition, the on-line preconcentration method provided detection limit of 3.4 μg L-1 and linear range ranging from 30.0 up to 300.0 μg L-1 (r = 0.995). The accuracy of method was successfully assessed by analyzing different kind of spiked water samples with recovery values ranging from 92.2 up to 103.0%.

Evaluación de la toxicidad de cobre en suelos a través de biomarcadores de estrés oxidativo en eisenia foetida

Copper toxicity in soil was evaluated using biomarkers of oxidative stress (catalase enzyme activity, superoxide dismutase and lipid peroxidation) in the earthworm Eisenia foetida. Agricultural topsoils from mining areas of the Aconcagua river basin were collected. Total copper concentrations were in the range of 94-959 mg kg-1, while the exchangeable copper concentrations were in the range of 46-2225 µg kg-1. Earthworms exposed to soil with exchangeable copper concentrations above 32 µg kg-1 showed an increase in catalase activity. Parameters of antioxidant activity were more sensitive than the weight change and thus can be used as appropriate biomarkers in Eisenia foetida.

Avaliação da influência de sulfetos solúveis na complexação do cobre em águas superficiais empregando métodos voltamétricos

In this work a sulfide quantification protocol using voltammetric methods was developed to evaluate the effect of dissolved sulfides on copper complexation. On the basis of pH, sulfide release from the dissociation of specific metal sulfide complexes can be electrochemically measured and then removed (as H2S) by a N2 purge. Cathodic stripping square wave voltammetry (CSSWV) was conducted to quantify Cu sulfides complexes which dissociate at pH < 5.0 during the process of acid titration.

Reciclagem do crômio de resíduos químicos provenientes da determinação de carbono oxidável em fertilizantes orgânicos

This work proposes a separation, recovery and reuse procedure of chemical residues with chromium. This residue was generated by the determination of oxidizable carbon in organic fertilizers samples. The Cr(VI) of the residue was reduced with ethanol and precipitated with NaOH. The Cr(OH)3 precipitate was separated and oxidized to dichromate ions with hydrogen peroxide. This solution was used another time in organic carbon determination. The uses of recycled dichromate solution were appropriated in four successive recycling. The accuracy was proven using potassium hydrogen phthalate and ten organic fertilizer samples. The organic carbon results, determined with recycled solutions, were similar the conventional solution.

A gestão do conhecimento aplicada à reciclagem de componentes automotivos através do tratamento das informações contidas em documentos de patentes

This article evaluates the technologies adopted for recycling and reuse of automobile components, through the analysis of patents documents. The automobile batteries recycling is the main topic, followed by the automatic disassembly of vehicles, tires recycling and polyurethane recycling. None document approached recycling of steel and aluminum or ceramics products. The reduced number of technologies for the recycling of the polymeric compounds (including polyurethane) indicates that a bigger number of research and inventions must be elaborated in the next years, aiming at to the reduction of costs of processes and adequacy to the more restricted environmental legislation.

Respuesta fisiológica de Euglena gracilis al estrés por cobre

The objective of this study was to evaluate the toxic effect of Cu2 + in the physiological development of E. gracilis. The results showed that E. gracilis had an effect on the dose-dependent growth to the concentration of metal. The exposure of E. gracilis metal at doses of 0.8 and 1.6 mM of Cu2+ showed a significant negative effect on the stability of DNA and photosynthetic pigments involved in capturing light in the antenna complex after 144 h of exposure to the metal.

Caracterização cromatográfica de compostos orgânicos presentes nos resíduos sólidos provenientes de indústria de reciclagem de papel e sua aplicação na produção de briquetes de carvão vegetal

Recycling of paper in industrial scale has become an established practice worldwide. In this work, organic compositions of three different kinds of sludge generated in recycle paper industry were studied, and the incorporation of one of those sludge in briket was also investigated. The characterization of organic compounds in sludge samples and briket was performed using Gas Chromatography coupled with Mass Spectrometry after a Soxhlet extraction. Different chemical classes were identified in each type of sludge, but just the sludge composed by cellulose residue did not presented polyaromatic hydrocarbons. Four formulations of sludge incorporated with charcoal for briket production were evaluated.

Análise de especiação de cobre e zinco empregando voltametria de redissolução anódica com pulso diferencial

This work describes methodologies for speciation analysis of the metals copper and zinc as total, total dissolved, labile, as well as complexation capacity (conditional stability constants and available ligand concentration), using the same technique, differential pulse anodic stripping voltammetry (DPASV). Several supporting electrolytes were tested, and the results showed that KNO3 and HNO3 resulted in voltamograms without interferences as well as excellent resolution for the total and labile fractions. The methodology using the DPASV technique allows a simple and low cost analysis of copper and zinc speciation, with high precision and sensitivity, with limits of quantification (LOQ) of 1.8 nmol L-1 for copper and 2.1 nmol L-1 for zinc.

Extração sequencial de zinco e cobre em solos tratados com lodo de esgoto e composto de lixo

This work aimed to access the contents and chemical forms and to estimate mobility and availability of cooper and zinc in samples from two soils (Haplortox and Paleudult) previously treated with doses of sewage sludge (SS) and municipal solid waste compost (MSWC), besides a control treatment. Largest percentages of Cu and Zn were determined in the organic matter fraction. Zn showed higher percentages of soluble and exchangeable fractions than Cu. Treatments with SS showed higher potential of Cu and Zn availability. Modifications in soil attributes due to residue application affected metal mobility and availability indexes.

Fracionamento de cobre em proteínas do plasma, músculo e fígado de tilápia do Nilo

Copper fractionation in plasma, muscle and liver of Nile tilapia was performed after protein separation by 2D-PAGE. SR XRF analysis indicated the presence of copper in three protein spots of plasma, and in two protein spots of muscle and liver, respectively. Copper ions were found to be distributed mostly in proteins that had a molar mass of less than 54 kDa and greater than 13 kDa and a pI in the 5.3-9.3 range. The copper concentration bound to these proteins was determined by GFAAS which showed concentrations in the 1.20-4.82 mg g-1 range.

Reciclagem do lixo de informática: uma oportunidade para a química

Recycling and sustainable development are increasing in importance around the world. In Brazil, the new National Policy on Solid Wastes has prompted discussion on the future of electronic waste (e-waste). Brazil generates the greatest amount of e-waste among Latin American countries. Nevertheless complete recycling, including end processing of e-waste, does not occur in Brazil. This paper discusses the physical and chemical technologies currently used worldwide and in Brazil for printed circuit board recycling, with emphasis on metal recovery and plastic processing. The goal is to put in evidence the important role that chemistry can play in developing cheaper processes to recycle e-waste.

Extração/pré-concentração de íons cobre no ponto nuvem explorando a formação de complexos com DMIT [4,5-dimercapto-1,3-ditiol-2-tionato]

The present study proposes a method for cloud point preconcentration of copper ions at pH 2.0 based on complexes formed with [4,5-dimercapto-1,3-dithyol-2-thionate] and subsequent determination by flame atomic absorption spectrometry (FAAS). Under optimal analytical conditions, the method provided limits of detection of 0.84 and 0.45 µg L-1, by preconcentrating 12.0 and 24.0 mL of sample, respectively. The method was applied for copper determination in water samples, synthetic saliva, guarana powder, tea samples and soft drinks and the accuracy was assessed by analyzing the certified reference materials Dogfish Liver (DOLT-4) and Lobster Hepatopancreas (TORT-2).