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PubMed2005

Oxidation behaviors of metallic copper particles in NO reduction mechanism of copper/activated carbons.

The reduction of nitric oxide (NO) over Cu/ACFs, prepared by copper electroplating, has been studied. It is found that copper content on the ACFs increases with increasing plating time (up to 45 wt%), while the textural properties including specific surface areas and total pore volumes decrease. As an experimental result, the NO reduction efficiency is increased in all of the Cu/ACFs, and it is confirmed that NO is converted into nitrogen and oxygen on the Cu/ACF surfaces (at 500 degrees C). Especially, the Cu metals on the ACF surfaces scavenge oxygen by oxidizing themselves into Cu2O and finally CuO as a reductant. It is indicated that copper metals on the Cu/ACFs play a major role in the NO removal in this system.

Carbon↗
PubMed2006

Chemical discrimination by a kinetic model of organic photooxidation in a heterosupramolecular assembly.

The photooxidation of range of common organic pollutants in a dye-sensitised photoelectrochemical cell (DS-PEC) is reported. A photoanode was prepared by the chemisorption of a photosensitiser, cis-bis-(2,2)-bipyridine)-(4,4'-bis-(methyl)phosphonato-2,2'-bipyridine)ruthenium(II) dichloride ([Ru(bpy)2(dmpbpy]2+), to a nanoporous nanocrystalline TiO2 thin film on a conducting glass substrate. The photoanode was coupled to a platinum electroplated fluorine doped tin oxide glass substrate in a two electrode assembly and the cell cavity was filled with an aqueous solution of organic pollutants and irradiated with lambda>420 nm to give a measurable photocurrent. In addition to the ability of this cell to photooxidise a range of chemically diverse organic pollutants, the application of a kinetic model to observed photocurrent transients allowed the study of interfacial electron transfer processes. Through the mathematical fit of a five-parameter double exponential decay function, evidence to support numerous interfacial reactions for the oxidation process were identified. Rapid oxidation of species in close proximity to the photooxidation centre was proposed as the kinetically fast interfacial process with a first-order rate constant of the order 0.4 s(-1). The slower process was attributed to the diffusion of oxidisable species from the solution bulk to the surface prior to oxidation with a first-order rate constant of the order 0.01 s(-1). Theoretical profiling of the kinetic events supported the biphasic assignment of interfacial processes and indicated that non-exhaustive oxidation occurs for the solution concentrations examined.

Journal Article↗
PubMed2004

Role of the mixing conditions and composition of galvanic sludges on the inertization process in clay-based ceramics.

Hydroxide-metal sludges from electroplating industry are a potential source of environmental contamination due to their high content of heavy metals. The incorporation of these residues in a ceramic matrix can be a promising way to suppress the harmful effect of metals normally present in those sludges. This work reports the role of the mixing time between the waste and ceramic materials and of the calcination step on the fixing level of several metal-containing species (Al, Zn, Ni, Fe, Ca, Cu, Cr) after sequential leaching in different media (aqueous, acetate and citrate). A strong and/or long mixing process will promote the deagglomeration of the coarser agglomerates and then will increase the reactivity of remaining grains towards the ceramic material during the calcination. As a consequence, inertization is improved for fired samples. With non-calcined samples leaching increases as a result of increasing dispersability/availability of species.

Aluminum Silicates↗
PubMed2004

Removal and recovery of nickel(II) from aqueous solution by loofa sponge-immobilized biomass of Chlorella sorokiniana: characterization studies.

The biosorption process for the removal of nickel(II) by loofa sponge-immobilized biomass of Chlorella sorokiniana (LIBCS), a newly developed immobilized biosorbent, was characterized. Effects of environmental factors on metal uptake capacity of LIBCS were studied and compared with free biomass of C. sorokiniana (FBCS). Nickel(II) removal by LIBCS was found to be influenced by pH of the solution, initial metal concentration, and biomass concentration. The biosorption of nickel(II) ions by both LIBCS and FBCS increased as the initial concentration of nickel(II) ions increased in the medium. No loss to biosorption capacity of LIBCS for nickel(II) was found due to the presence of loofa sponge, indeed as compared to FBCS an increase of 25.3% was noted in the biosorption capacity of LIBCS. Maximum biosorption capacities for FBCS and LIBCS were found as 48.08 and 60.38 mg nickel(II)/g, respectively, whereas the amount of nickel(II) ions adsorbed on the plain loofa sponge was 6.1mg/g. During these biosorption studies, LIBCS exhibited excellent physical and chemical stability without any significant release/loss of microalgal biomass from loofa sponge matrix. The kinetics of nickel(II) removal was extremely fast reaching at equilibrium in about 15 min for LIBCS and 20 min for FBCS. The biosorption equilibrium was well described by the Langmuir and Freundlich adsorption isotherms. The biosorption capacities were found to be solution pH dependent and the maximum adsorption was found at a solution pH 4-5. The LIBCS could be regenerated using 75 mM HCl, with up to 98% recovery. The LIBCS were shown to be robust and stable with little decrease in the nickel(II) uptake capacity when used in consecutive seven biosorption-desorption cycles. Continuous removal of nickel(II) from electroplating effluent by LIBCS packed in fixed bed column bioreactor confirm the possibility of developing a biological treatment process for the removal of toxic metals from authentic wastewater.

Adsorption↗
PubMed2004

Nickel hydroxide ageing time influence on its solubility in water acidified with sulphuric acid.

Nickel hydroxide samples freshly settled as well as stored over 1 month, 2 months and 6.5 years were examined for their solubility rate in diluted H2SO4 solutions of pH 1.9 and 2.8 as a function of time. Samples with a longer ageing history dissolved less readily than freshly settled ones. It was determined that the resistance to dissolving rose with sample ageing time and the solubility of the 6.5 years stored sample was particularly low. X-ray examination evidenced that during storage the crystallinity of Ni(OH)2 subsequently rose. The parallelity of both time-dependent phenomena allows the conclusion that with nickel hydroxide ageing the transformation of disordered nickel hydroxide species into crystalline Ni(OH)2 (without phase changes) is responsible for increasing nickel hydroxide resistance to dissolving in acidic solutions. Such decrease of nickel hydroxide solubility with ageing in case of waste nickel hydroxide, is worth to notice in a view of environment protection against pollution with electroplating waste.

Crystallography, X-Ray↗
PubMed2005

Extraction kinetics of heavy metal-containing sludge.

In order to remove and recover copper, zinc, cadmium, and chromium from the wastewater treatment sludge generated by an electroplating process, the heavy metal extraction kinetics was studied in a batch reactor using two different extraction agents (nitric and citric acid) at constant agitation speed (150 rpm) and solid to liquid ratio (10 g/L), but varying acid concentrations (0.02-0.10 N), temperatures (25-85 degrees C in nitric acid solution, 25-95 degrees C in citric acid solution), and sludge particle sizes. The shrinking-core model and empirical kinetic model were adopted to analyze the experimental data. Although both models could fit the experimental kinetic data well, the obtained parameters of the shrinking-core model did not show reasonable trends varying with the experimental variables while the empirical model parameters showed significant trends. The experimental and modeling results showed that the metal extraction rates increased with acid concentration, temperature, but decreased with increasing particle size. Nitric acid was found to be more effective than citric acid to extract the heavy metals from the sludge. The extraction activation energies obtained in this study suggested that both a physical diffusion process and a chemical reaction process might play important roles in the overall extraction process.

Citric Acid↗
PubMed2006

Safe immobilization of Cr(III) in heat-treated zeolite tuff compacts.

The possibility to remove chromium ions from a simulated electroplating wastewater by a discontinuous ion-exchange process based on phillipsite-rich Neapolitan yellow tuff (NYT) has been investigated. The immobilization of the pollutant cation in the resulting sludge through a heat-treatment has been realized, demonstrating that compacts made of Cr-loaded NYT powder, fired at temperatures of 1000 degrees C or over, are safe materials with negligible Cr3+ leaching. The set up overall process allows, in addition, a volume reduction of the waste with associated lower disposal costs or, better, the obtainment of a ceramic material, whose physical and mechanical properties are comparable to those of similar ordinary ceramics, such as bricks. In summary, the proposed strategy looks at the polluted sludge as a resource to be exploited, instead of a dangerous material to safely dispose of.

Cations↗
PubMed2006

Special applications of fluorinated organic compounds.

The applications of fluorinated organic compounds (FOCs) as finishing agent for fabrics, components of extinguishing agents, electroplating bathes, lubricating oils, oxygen carriers in blood substitutes have been discussed. Recent achievements in methods of the fluorination and general principles of the synthesis of useful perfluorinated organic compounds are given as well.

Animals↗
PubMed2006

Activated carbons and low cost adsorbents for remediation of tri- and hexavalent chromium from water.

Hexavalent chromium is a well-known highly toxic metal, considered a priority pollutant. Industrial sources of Cr(VI) include leather tanning, cooling tower blowdown, plating, electroplating, anodizing baths, rinse waters, etc. The most common method applied for chromate control is reduction of Cr(VI) to its trivalent form in acid (pH approximately 2.0) and subsequent hydroxide precipitation of Cr(III) by increasing the pH to approximately 9.0-10.0 using lime. Existing overviews of chromium removal only cover selected technologies that have traditionally been used in chromium removal. Far less attention has been paid to adsorption. Herein, we provide the first review article that provides readers an overview of the sorption capacities of commercial developed carbons and other low cost sorbents for chromium remediation. After an overview of chromium contamination is provided, more than 300 papers on chromium remediation using adsorption are discussed to provide recent information about the most widely used adsorbents applied for chromium remediation. Efforts to establish the adsorption mechanisms of Cr(III) and Cr(VI) on various adsorbents are reviewed. Chromium's impact environmental quality, sources of chromium pollution and toxicological/health effects is also briefly introduced. Interpretations of the surface interactions are offered. Particular attention is paid to comparing the sorption efficiency and capacities of commercially available activated carbons to other low cost alternatives, including an extensive table.

Adsorption↗
PubMed2006

Biosorption of chromium and nickel by heavy metal resistant fungal and bacterial isolates.

Microorganisms play a significant role in bioremediation of heavy metal contaminated soil and wastewater. In this study, heavy metal resistant fungi and bacteria were isolated from the soil samples of an electroplating industry, and the bioaccumulations of Cr(VI) and Ni(II) by these isolates were characterized to evaluate their applicability for heavy metal removal from industrial wastewaters. The optimum pH and temperature conditions for both the growth and heavy metal removal were determined for each isolate. The optimal pH for fungal isolates was lower (5-5.2) than that for bacterial isolates (7). The observed effect(s) of pH was attributable mainly to organism-specific physiology because in all the tested cases the cellular growth positively correlated with heavy metal removal. Batch and tolerance experiments provided information for solid retention time (SRT) design and the lethal tolerance limits for the isolated microorganisms. Experimental results indicated that expanded SRTs (stationary phase) can be recommended while using the fungal and bacterial Cr-resistant isolates for removing chromium. In the case of Ni-resistant bacterial isolate, a non-expanded SRT was recommended for designing continuous-flow completely stirred (CFCS) bioreactor so that a mid-log phase of cellular growth can be kept during the bioaccumulation process. The tolerance data with a high range of heavy metal concentrations revealed the Cr-resistant isolates, especially the fungal one, could tolerate chromium toxicity at up to 10,000 mg L(-1) chromium. Result indicates the applicability of the isolated Micrococcus sp. and Aspergillus sp. for the removal of chromium and nickel from industrial wastewater.

Adsorption↗
PubMed2003

Nickel carcinogenesis.

Human exposure to highly nickel-polluted environments, such as those associated with nickel refining, electroplating, and welding, has the potential to produce a variety of pathologic effects. Among them are skin allergies, lung fibrosis, and cancer of the respiratory tract. The exact mechanisms of nickel-induced carcinogenesis are not known and have been the subject of numerous epidemiologic and experimental investigations. These mechanisms are likely to involve genetic and epigenetic routes. The present review provides evidence for the genotoxic and mutagenic activity of Ni(II) particularly at high doses. Such doses are best delivered into the cells by phagocytosis of sparingly soluble nickel-containing dust particles. Ni(II) genotoxicity may be aggravated through the generation of DNA-damaging reactive oxygen species (ROS) and the inhibition of DNA repair by this metal. Broad spectrum of epigenetic effects of nickel includes alteration in gene expression resulting from DNA hypermethylation and histone hypoacetylation, as well as activation or silencing of certain genes and transcription factors, especially those involved in cellular response to hypoxia. The investigations of the pathogenic effects of nickel greatly benefit from the understanding of the chemical basis of Ni(II) interactions with intracellular targets/ligands and oxidants. Many pathogenic effects of nickel are due to the interference with the metabolism of essential metals such as Fe(II), Mn(II), Ca(II), Zn(II), or Mg(II). Research in this field allows for identification of putative Ni(II) targets relevant to carcinogenesis and prediction of pathogenic effects caused by exposure to nickel. Ultimately, the investigations of nickel carcinogenesis should be aimed at the development of treatments that would inhibit or prevent Ni(II) interactions with critical target molecules and ions, Fe(II) in particular, and thus avert the respiratory tract cancer and other adverse health effects in nickel workers.

Air Pollutants↗
PubMed2004

Evaluation of distribution, mobility and binding behaviour of heavy metals in surficial sediments of Louro River (Galicia, Spain) using chemometric analysis: a case study.

Contents of total and extractable heavy metals, carbonates, MnO and Fe2O3, organic matter, and matrix components such as SiO2, Al2O3, CaO, Na2O, MgO, TiO2, K2O and P2O5 are used along with principal component analysis (PCA) for studying distribution, mobility and binding behaviour of Cd, Cr, Cu, Ni and Pb in the Louro River (Galicia, Spain). Eleven surficial sediment samples were taken along the beds of the river course. Total metal concentrations were obtained after microwave-assisted digestion whilst extractable metal contents were obtained following a three-stage sequential extraction scheme (i.e. soluble, reducible and oxidisable fractions). Loading plots of heavy metals bound to carbonates, Fe-Mn oxides, organic matter and aluminosilicates allowed determination of binding behaviour. Correlations found indicate that Pb and Cu are mainly discharged from urban wastes, whereas Cr and Ni are from electroplating and galvanizing industries. The occurrence of diffuse pollution sources along the river can account for the binding behaviour of Cd. Metal mobility decreased in the order: Cd > Pb > Cu > Ni > Cr. Despite total contents indicating moderate-to-high heavy metal pollution in this river, metals are mostly distributed in the residual fraction, hence showing a low risk of mobility.

Journal Article↗
PubMed2006

Endocrine and metabolic responses of Anguilla anguilla L. caged in a freshwater-wetland (Pateira de Fermentelos--Portugal).

The present short-term in situ study was carried out in a freshwater-wetland--Pateira de Fermentelos--considered an enlargement of Cértima River, in the centre of Portugal. This ecosystem is an important fishing and recreation place, receiving effluents from different origins namely, electroplating industrial effluents containing heavy metals, domestic wastes, as well as pesticides and fertilizers resulting from agriculture activities. The aim of the present research work was to monitor the effects induced by the contaminants present in Pateira de Fermentelos water, using Anguilla anguilla L. (European eel) as a bioindicator. The eels were caged for 48 h at four Pateira de Fermentelos sites, differing in their distances to the main known pollution source (Cértima River): A (close to the lagoon entrance), B, C and D (the farthest from the Cértima River). A reference site was selected near the Cértima river spring. The following parameters were measured: liver ethoxyresorufin-O-deethylase (EROD) and alanine transaminase (ALT) activities, plasma levels of cortisol, 17beta-estradiol (E2), thyroid-stimulating-hormone (TSH), free thyroxine (T4), free triiodothyronine (T3), as well as glucose and lactate. The erythrocytic nuclear abnormalities (ENA) frequency was also scored as a genotoxicity indicator. The results revealed increased plasma cortisol and glucose concentrations at all exposure sites, displaying a similar response pattern. Plasma T3 showed a significant decrease only at site A when compared to reference site, whereas plasma E2 increased at sites B and D when compared to all the other sites, including reference site. The present results indicate the Pateira de Fermentelos water contamination, demonstrating the usefulness of the adopted strategy.

Alanine Transaminase↗
PubMed2004

Heavy metals (Ni, Cr, Cu) in the Karoon waterway river, Iran.

Environmental pollution is a world-wide problem, heavy metals belonging to the most important pollutants. The progress of industries has led to increased emission of pollutants into ecosystems. Karoon is the biggest and only navigable river in the South of Iran. Along the Karoon industrial units such as piping, steel, paint making, agriculture, paper mill, fish cultivation, abbottiors, electroplating industries drain their wastewater into the river. In this study, the concentrations of heavy metals (Ni, Cr, Cu) in the Karoon river have been determined. Samples were collected from 16 stations along the river, in winter and spring 1996. Heavy metal concentrations were measured by graphite furnace atomic absorption spectrometry. The minimal and maximal concentrations of these metals in winter were 69.3-110.7, 1.7-118.3, and 5.5-70.3 microg/l, for Ni, Cr, and Cu, respectively. The minimal and maximal concentrations of these metals in spring were 41.0-60.7, 0.7-19.8, and 0.5-28.7 microg/l, for Ni, Cr, and Cu, respectively. The results show that the pollution has increased along the river, down to the estuary at the Persian Gulf.

Chromium↗
PubMed2002

Chemically facilitated chromium(VI) transport throughout an anion-exchange membrane application to an optical sensor for chromium(VI) monitoring.

The Raipore R1030 membrane, an anion-exchange membrane containing ammonium groups as ionogenic groups, was evaluated as the interface of an optical sensor for Cr(VI), and the effect of chemical parameters affecting Cr(VI) transport were studied. Good transport features were obtained, demonstrating the suitability of the Raipore R1030 membrane for this application. Thus, an optical sensor for chromium(VI) monitoring in industrial process waters was developed. The sensor is based on the renewable reagent approach and uses the Raipore R1030 membrane as the interface between the sample and the sensor head, which contains 1,5-diphenylcarbazide as spectrophotometric reagent for chromium. Chromium(VI) crosses the membrane and reacts with the reagent inside the sensor head, resulting in changes in the absorption of light. These changes are monitored in situ through a system of optical fibers. The sensor performance was tested by analysing samples from a waste water treatment plant for effluents from electroplating industries.

Anion Exchange Resins↗
PubMed2000

Acoustic emission monitoring of high speed grinding of silicon nitride

Acoustic emission (AE) monitoring of a machining process offers real-time sensory input which could provide tool condition and part quality information that is critical to effective process control. However, the choice of sensor, its placement, and how to process the data and extract useful information are challenging application-specific questions which researchers must consider. Here we report an effort to resolve these questions for the case of high speed grinding of silicon nitride using an electroplated single-layered diamond wheel. A grinding experiment was conducted at a wheel speed of 149 m s-1 and continued until the end of the useful wheel life. AE signal data were then collected for each complete pass at given grinding times throughout the useful wheel life. We found that the amplitude of the AE signal monotonically increases with wheel wear, as do grinding forces and energy. Furthermore, the signal power contained in the AE signal proportionally increases with the associated grinding power, which suggests that the AE signal could provide quantitative information of wheel wear in high-speed grinding, and could also be used to determine when the grinding wheel needs replacement.

Journal Article↗
PubMed2003

Model experiments on the microbial removal of chromium from contaminated groundwater.

A bacterial consortium with representatives of sulfate-reducing and denitrifying bacteria was selectively enriched. Model experiments under microaerobic conditions showed that it precipitated chromium from Cr (VI)-containing waters (area of a former electroplating factory, Leipzig, Germany) by two different mechanisms: by sulfate reduction and precipitation as sulfide, and by some direct reduction. Sulfate reduction needed fatty acids as organic substrates and resulted at the first stage in no sulfide accumulation. In the absence of the fatty acids but with straw as organic substrate, the direct reduction of chromium was observed without sulfate reduction. In this case Cr (VI)-reduction rate correlated with that of the denitrification.

Bacteria↗
PubMed2001

Comparisons of metal leachability for various wastes by extraction and leaching methods.

The objective of this research was to evaluate three extraction tests, i.e., toxicity characteristic leaching procedures (TCLP), extraction procedure (EP), and American Society for Testing and Materials (ASTM) methods, for their ability to extract metals in chemical sludge and incineration bottom ash, in terms of the precision of analytical results. Typical chemical sludges, including the electroplating and dye-stuff sludges, the municipal solid waste incineration bottom ash, the leather debris, and the steel-mill bottom residue containing Cd, Cr, Cu, Pb, and Zn were prepared for the lysimetry test (dynamic testing) to compare with the extraction results. Results show that for bottom residue and dye-stuff sludge, the concentration of metal leached was almost the same between the lysimetry leaching and the TCLP tests. The metal concentration followed the order: TCLP approximately = EP > ASTM. TCLP and EP exhibited almost the same relative standard deviation (RSD) value. Therefore, the results of the TCLP tests for bottom residue and dye-stuff sludge, which have a low metal content and alkalinity, can be used to estimate the metal concentration leached by typical acid rain in Taiwan; whereas the ASTM extraction test may be a better indicator of the lysimetry test.

Chemistry Techniques, Analytical↗