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PubMed2005

Extraction and recovery of chromium from electroplating sludge.

This work reports a study of the extraction and recovery of chromium from the wastes (class I dangerous) generated by a galvanic manufacturer. Commercial HCl at room temperature was employed, and the conditions of the extraction process were optimized according to a sequential experimental design, which also included the acid concentration and contact time as variables. The best extraction conditions (80% v/v; 30 min; 97.6% Cr) for the chromic sludge were chosen in order to make the recovery process economically feasible. After each extraction, the residue was submitted to leaching essays, to assess environmental risks. It was found that sludge could be characterized as no longer dangerous. In the recovery study, a simple and low-cost technique was evaluated for selectivity based on an oxidation step with hydrogen peroxide. A 2(3) factorial design to assess the influence of oxidation time (min), temperature ( degrees C) and peroxide amount (mol/L) was employed. The best conditions, yielding a chromium recovery of about 92%, were a time of 60 min, a temperature of 60 degrees C and 2.1 mol/L peroxide. Additional essays revealed that the same result could be obtained with more economic conditions (40 min, 1.4 mol/L peroxide and 60 degrees C). This technique proved not only effective in comparison with existing alternatives, but also low costing.

Chromium↗
PubMed2004

In situ speciation studies of copper in the electroplating sludge under an electric field.

Speciation of copper in the electrokinetic treatments of an industrial sludge was studied by in situ extended X-ray absorption fine structural (EXAFS) and X-ray absorption near-edge structural (XANES) spectroscopies in the present work. The least-square fits (LSF) of the XANES spectra indicated that the main copper species in the sludge were Cu(NO)(3) (82%) and adsorbed copper (Cu/SiO(2)) (17%). Copper in the sludge possessed a Cu-O bond distance of 1.97A with a coordination number (CN) of 3.8. In the second shells, the bond distance of Cu-(O)-Si was 3.03A with a CN of 1.5. Most of Cu/SiO(2) was dissolved in the aqueous phase since little Cu-(O)-Si species in the sludge was found after 180 min of the electrokinetic treatments. About 69% of total Cu(II) was dissolved into the aqueous phase and 51% of which was migrated to the cathode under the electric field (5V cm(-1)) for 180 min.

Copper↗
PubMed2000

Adsorption studies on Citrus reticulata (fruit peel of orange): removal and recovery of Ni(II) from electroplating wastewater.

The ability of fruit peel of orange to remove Zn, Ni, Cu, Pb and Cr from aqueous solution by adsorption was studied. The adsorption was in the order of Ni(II)>Cu(II)>Pb(II)>Zn(II)>Cr(II). The extent of removal of Ni(II) was found to be dependent on sorbent dose, initial concentration, pH and temperature. The adsorption follows first-order kinetics. The process is endothermic showing monolayer adsorption of Ni(II), with a maximum adsorption of 96% at 50 degrees C for an initial concentration of 50 mg l(-1) at pH 6. Thermodynamic parameters were also evaluated. Desorption was possible with 0.05 M HCl and was found to be 95.83% in column and 76% in batch process, respectively. The spent adsorbent was regenerated and recycled thrice. The removal and recovery was also done in wastewater and was found to be 89% and 93.33%, respectively.

Absorption↗
PubMed2001

Thermal behaviour of chromium electroplating sludge.

Galvanic sludge is classified as a hazardous waste and incineration is one of the techniques used for its treatment. The aim of this work is to study the thermal behavior of a galvanic sludge which contains only chromium as a restriction metal. Simultaneous DTA/TG coupled with mass spectrometer tests were performed to characterize the thermal behavior of the sludge. Besides thermal analysis, sludge samples were heated in a specially designed furnace and these samples were submitted to X-ray diffraction. Vapor from the heated sludge was condensed and the particles were analyzed by EDS microprobe coupled in a scanning electron microscope. The slag formed after the calcination of the galvanic sludge was mainly composed of a mixture of calcium phosphate and fluoride. and minor concentrations of metals. A total weight loss of 34% was observed. The greatest part of this weight loss corresponds to CO2, H2O and SO2. H2O is liberated in the temperature range of 500-1,250 degrees C. CO2 in the range of 500-750 degrees C and SO2 near 1,000 degrees C. Chromium evaporation was not observed in relevant quantities, about 99.6% of the Cr remained incorporated in the slag.

Air Pollutants↗
PubMed1999

Genotoxicity and radioresistance in electroplating workers exposed to chromium.

A biomonitoring study was carried out to investigate the genetic risk associated to occupational exposure to chromium. The induction of genetic damage was measured by analysing the frequency of micronuclei (MN) in peripheral blood lymphocytes. In addition to the 40 electroplater exposed workers who participated in the study, a group constituted by 18 volunteer donors, without exposure to chromium, was analysed as a control group. Measures of chromium levels at working place and in erythrocytes and urine were obtained, as indicators of exposure. The results from this study indicate that the blood from exposed workers contained higher levels of chromium, when compared with those obtained in the control group, and that a significant increase in the frequency of both the total number of MN and the number of binucleated cells carrying MN (BNMN) was detected. Furthermore, a good direct relationship was obtained between the amount of chromium present in air, erythrocytes or urine and the frequency of MN. To determine the existence of radioresistance as consequence of chromium exposure, the response of lymphocytes to the in vitro gamma-radiation was studied. The results of this experiment show a lower induction in the increase of the frequency of MN after challenge irradiation in the lymphocytes of chromium exposed workers, which should be indicative of an adaptive response.

Adaptation, Physiological↗
PubMed2003

Identification and leaching characteristics of sludge generated from metal pickling and electroplating industries by Toxicity Characteristics Leaching Procedure (TCLP).

One of India's major concerns is the increasing level of land pollution largely due to the uncontrolled disposal of industrial solid and hazardous waste. With rapid industrialization, the generation of industrial solid and hazardous waste has increased appreciably and the nature of waste generated has become complex. Their impacts on the ecological bodies are noticeable. The article describes the details of studies conducted using Toxicity Characteristics Leaching Procedure, to estimate the toxicity effects of the metals viz., chromium, zinc, manganese, iron, nickel, cobalt and copper by the Zero Headspace Extractor for the sludges generated from effluent treatment plant of steel tube, wire and plating industries on environment constituents like groundwater, surface water and land. Toxicity Characteristics Leaching Procedure determines the mobility of organic and inorganic analytes of liquid, solid or multiphase waste from hazardous solid wastes in the form of primary and secondary extracts. These extracts are mixed in equal volume proportion and analyzed by Direct Reading 2000 spectrophotometer. The amount of heavy metals observed during the studies in the leachates were found and the results were compared with Hazardous Waste categories as per Indian Standards. TCLP regulatory limits given by United States Environment Protection Agency (USEPA) and Germany Leachate Quality Standards and it was observed that they were on higher side, needing a proper preventive concept of sludge management including handling, treatment, recovery and disposal.

Electroplating↗
PubMed2000

Investigation of electroplated conducting polymers as antibody receptors in immunosensors.

Antibodies raised against the conducting polymer, carbazole as a hapten, react to modulate the polymer's electrochemistry. Using cyclic voltammetry the reaction of the antiserum was discovered to influence the polymer matrix's electrochemistry by an amperometric response. It is suggested that these observation form the basis of a direct sensor for immunoassay.

Alkaline Phosphatase↗
PubMed2004

Final decontamination of the filtrates obtained after interaction of two ligand-containing Cu2+ and Zn2+ electroplating solutions.

A cheap and simple way to decontaminate two ligand-containing rinsing waters of metal finishing has been previously suggested. Both the copper diphosphate-containing rinsing wastewater and acidic zinc ammonium-containing rinsing wastewater may be decontaminated by mixing them which results in precipitation of solid solutions of copper-zinc-potassium-ammonium diphosphates. This way of decontamination requires no expensive reagents since only a small amount of H2SO4, is needed for pH adjustment. 80-99.5 % of environmentally dangerous substances, viz. zinc, copper and diphosphate, are removed from the mixture. However, Cu2+ and Zn2+ amounts in filtrates significantly exceed the discharge consent level (DCL). Besides, high concentrations of undesirable diphosphate and ammonium ions, which cause the eutrophication of natural water reservoirs, are present in the filtrates. There are relatively small concentrations of heavy metals: Cu2+ (approximately 0.4 mM dm-3) and Zn2+ (approximately 1 mM dm-3), and relatively large quantities of ligands: P2O7(4-) (approximately 20 mM dm-3) and NH4+/NH3 (approximately 500 mM dm-3) in these filtrates. Our investigation has shown, that decontamination may be easily achieved in industry by using cheap materials or industrial by-products: lime, MgO, phosphogypsum, extractive phosphoric acid and spent steel etching solution. Using lime, Cu2+ and Zn2+ ions may be removed below their DCL. After that, diphosphate ion concentration may be reduced approximately 1000 fold by addition of spent steel etching solution or continuous mixing with phosphogypsum. The amount of NH4+/NH3 may be reduced 20 to 30 fold, the concentration of soluble phosphates -- 5 to 40 fold and both c Cu2+ and c Zn2+ -- lower than their DCL by precipitating barely soluble fine crystalline MgNH4PO46H2O (struvite).

Copper↗