Marco Antônio Siqueira Rodrigues

TRANSPORT OF TRIVALENT AND HEXAVALENT CHROMIUM THROUGH DIFFERENT ION-SELECTIVE MEMBRANES IN ACIDIC AQUEOUS MEDIA

ABSTRACT The aim of this work was to evaluate the transport of trivalent and hexavalent chromium through anion- and cation-selective membranes using two-and three-compartment electrodialysis cells. Tests were done with acidic solutions of trivalent chromium ions, Cr3+, and hexavalent chromium ions, Cr2O2 7. In each situation the transport of metallic ions through the membrane was evaluated. In the tests with trivalent chromium, Nafion 417 and Selemion CMT cation-selective membranes were used, and in the tests with hexavalent chromium, Selemion AMT membrane was used. The influence of SO2 4 ions and of the concentration of H+ ions in the solutions was also analyzed. Results showed the oxidation of the Cr3* ion at the anode and the reduction of the Cr2 7; ion at the cathode. The maximum yield in the process was reached when hexavalent chromium solutions were used in the absence of sulfate ions and a Selemion AMT membrane in a three-compartment cell.

Anxiety-like behaviour in mice exposed to tannery wastewater: The effect of photoelectrooxidation treatment.

The leather industry is a major producer of wastewaters and releases large quantities of many different chemical agents used in hide processing into the environment. Since the central nervous system is sensitive to many different contaminants, our aim was to investigate the neurobehavioral effects of exposure of mice to tannery effluents using animal models of depression and anxiety, namely forced swim and elevated plus-maze. In order to propose a clean technology for the treatment of this effluent, we also investigated the exposure of mice to effluents treated by photoelectrooxidation process (PEO). Adult male Swiss albino mice (CF1 strain) were given free access to water bottles containing an effluent treated by a tannery (non-PEO) or PEO-treated tannery wastewater (0.1 and 1% in drinking water). Exposure to tannery wastewater induced behavioural changes in the mice in elevated plus-maze. Exposure to non-PEO 1% decreased the percentage of time spent in the open arms, indicating anxiety-like behaviour. Exposure to tannery wastewater did not alter immobility time in the forced swim test, suggesting that tannery effluents did not induce depression-like behaviour in the mice. These behavioural data suggest that non-PEO tannery effluent has an anxiogenic effect, whereas PEO-treated tannery effluents do not alter anxiety levels.

Influence of ligand exchange on the treatment of trivalent chromium solutions by electrodialysis

The effect of ligand type and the aging of the solution in the transport of trivalent chromium through Nafion 450 ion-exchange membranes was studied. Chromium chloride and sulfate solutions were employed in order to evaluate the transport number and the percent extraction of trivalent chromium ions. Results showed that the aging of the solution has a significant influence in the transport of chromium ions through the membrane, which is attributed to the changes observed in the chromium complexes due to the characteristic ligand exchange reactions. Higher values for the chromium transport parameters were obtained for chloride solutions.

High-impact polystyrene/polyaniline membranes for acid solution treatment by electrodialysis : Preparation, evaluation, and chemical calculation

In this study different membranes were produced, aiming to evaluate their use in electrodialysis. These membranes were produced using conventional polymer (high-impact polystyrene) and polyaniline. The membrane characterization was done by FTIR spectroscopy, scanning electron microscopy (SEM), and thermogravimetry (TGA). The studies of the zinc and proton extraction ionic transport through the membranes were evaluated using a three-compartment cell. The results obtained using the produced membranes were compared to the results obtained with the commercial membrane Nafion 450. It was found that a synthesized membrane can be used to recover zinc in acid media. In addition, a preliminary computational essay about the structures of PAni and CSA is presented.

The effect of sanitary landfill leachate aging on the biological treatment and assessment of photoelectrooxidation as a pre-treatment process

The sanitary landfill leachate is a dark liquid, of highly variable composition, with recalcitrant features that hamper conventional biological treatment. The physical-chemical characteristics of the leachate along the landfill aging, as well as their effects on the efficiency of the conventional treatment, were evaluated at this paper. The feasibility of photoelectrooxidation process as an alternative technique for treatment of landfill leachates was also determined. Photoelectrooxidation experiments were conducted in a bench-scale reactor. Analysis of the raw leachate revealed many critical parameters demonstrating that the recalcitrance of leachate tends to increase with time, directly influencing the decline in efficiency of the conventional treatment currently employed. The effects of current density and lamp power were investigated. Using a 400 W power lamp and a current density of 31.5 mA cm(-)(2), 53% and 61% efficiency for the removal of ammoniacal nitrogen and chemical oxygen demand were respectively achieved by applying photoelectrooxidation process. With the removal of these pollutants, downstream biological treatment should be improved. These results demonstrate that photoelectrooxidation is a feasible technique for the treatment of sanitary landfill leachate, even considering this effluents high resistance to treatment.

Exposition to tannery wastewater did not alter behavioral and biochemical parameters in Wistar rats.

There are scarce data on the neurotoxicity in mammalian induced by tannery wastewaters. Previously, the anxiogenic effect of tannery wastewater was demonstrated in mice, while wastewater submitted to photoelectrooxidation (PEO) process treatment did not affect the anxiety state. Considering that species may response differently to xenobiotics, the aim of the present work was to study the effects of exposure to tannery wastewaters (non-PEO or PEO-treated) on behavioral and neurochemical markers in another species of laboratory animals, specifically Wistar rats. Male Wistar rats were given free access to water bottles containing non-PEO or PEO-treated tannery wastewaters (0.1, 1 and 5% in drinking water). During the exposure, behavioral tests of anxiety (elevated plus-maze, neophobia, open field and light-dark box), depression (forced swimming) and memory (inhibitory avoidance, novel object and discriminative avoidance) were performed. On the 30th day, brain structures were dissected out to evaluate cellular oxidative state (hippocampus, cerebellum and striatum) and acetylcholinesterase activity (hippocampus and striatum). Exposure to tannery effluent with or without photoelectrochemical treatment did not alter any behavioral and neurochemical parameters evaluated. Our data indicate that Wistar rats may not be an adequate species for ecotoxicological studies involving tannery effluents and that POE treatment did not generate other toxic compounds.

Treatment of solutions containing nonylphenol ethoxylate by photoelectrooxidation.

In this work the photoelectrooxidation (PEO) was applied in the treatment of a solution containing nonylphenol ethoxylate surfactant (NP4EO). The use of different lamps (125 and 250 W), current density (5 and 10 mA cm(-2)) and treatment time (0, 60, 120, 180 and 240 min) were investigated. The samples were characterized by UV/Vis, total organic carbon (TOC), gas chromatography associated to mass spectroscopy (GC/MS) and ecotoxicity. The reaction kinetics were calculated and the light flux and pH were measured. The results of analysis by UV/Vis show that there is degradation of nonylphenol ethoxylated in the treatment time of 240 min for all configurations, and the configurations that used a 250 W lamp and a current density of 10 mA cm(-2) obtained better results, with a reduction of 83% in TOC, indicating a high mineralization of the surfactant. It was further found in the GC/MS that the configurations that used the 125 W lamp promoted a smaller incident light flux on the solution, and, regardless of the applied current density, it was generated the reaction intermediate nonylphenol, more toxic than the parent compound. The opposite can be observed when a 250 W lamp was used, which produced a higher incident light flux. Based on the degradation products detected, a simplified mechanism for degradation of nonylphenol ethoxylate was proposed. Although a treatment time of 240 min with photoelectrooxidation with different configurations was not effective in the complete mineralization of the compound, a promising process was developed with the treatment using a lamp of 250 W and a current density of 10 mA cm(-2), which generated a solution with less toxicity than the original one.

Toxicological evaluation of landfill leachate using plant (Allium cepa) and fish (Leporinus obtusidens) bioassays.

The disposal of municipal waste in landfills may pose an environmental problem because the product of the decomposition of these residues generates large volumes of leachate, which may present high toxicity. The aim of this study was to assess the toxic and genotoxic effects of a sample of untreated leachate in fish (Leporinus obtusidens) and onions (Allium cepa). The leachate was collected in a landfill located in the region of Vale do Rio dos Sinos, southern Brazil. The fish were exposed to raw leachate, at concentrations of 0.5%, 1.0%, 5%, 10% and 20% for 6 days, while the bulbs of A. cepa were exposed to concentrations of 5%, 10%, 25%, 50% and 100% for 48 h. For fish, the concentrations of 5%, 10% and 20% were lethal, thus indicating high toxicity; however, sublethal concentrations (0.5% and 1.0%) showed no genotoxicity by micronucleus test when compared with the control group. In the bioassays involving onions, high toxicity was observed, with significant reduction of root growth and mitotic index in bulbs exposed to the 100% concentration of the leachate. An increase in the frequency of chromosome abnormalities in the A. cepa root cells in anaphase–telophase was observed in accordance with the increase in the concentration of leachate (5%, 10%, 25% and 50%), with values   significantly greater than the control, at the highest concentration. The results showed that the leachate contains toxic and genotoxic substances, thus representing a major source of environmental pollution if not handled properly.

Genotoxic Potential and Physicochemical Parameters of Sinos River, Southern Brazil

The present study aimed to evaluate the physicochemical parameters and the genotoxic potential of water samples collected in the upper, middle, and lower courses of the Sinos River, southern Brazil. The comet assay was performed in the peripheral blood of fish Hyphessobrycon luetkenii exposed under laboratory conditions to water samples collected in summer and winter in three sampling sites of Sinos River. Water quality analysis demonstrated values above those described in Brazilian legislation in Parobé and Sapucaia do Sul sites, located in the middle and in the lower courses of the Sinos River, respectively. The Caraá site, located in the upper river reach, presented all the physicochemical parameters in accordance with the allowed limits in both sampling periods. Comet assay in fish revealed genotoxicity in water samples collected in the middle course site in summer and in the three sites in winter when compared to control group. Thus, the physicochemical parameters indicated that the water quality of the upper course complies with the limits set by the national guidelines, and the ecotoxicological assessment, however, indicated the presence of genotoxic agents. The present study highlights the importance of combining water physicochemical analysis and bioassays to river monitoring.

Electrodialysis Treatment of Nickel Wastewater

The galvanic processes are one of the main activities contributing to metal discharges into the environment. A large volume of wastewater is generated that contains a high load of salts and metals and it must be treated to recover the chemicals and water and save resources. Nickel is a toxic metal and causes various health problems. According to environmental regulations across the world, nickel concentrations in effluents must be controlled on an acceptable level before the discharge into the environment. The removal of metals by conventional treatment (chemical precipitation) not only does not result in a final effluent with a nickel concentration below the acceptable limit, but it also generates a large volume of galvanic sludge, a hazardous waste material. Several treatment processes have been suggested for the removal of nickel from rinse water, such as electrochemical techniques. This chapter presents the application of electrodialysis (ED) as an alternative that can contribute to comply with legal environmental standards and enable the recovery and reuse of water and chemicals in the nickel electroplating process, helping to minimize the environmental impact associated with the water consumption and generation of waste in the galvanic industry.