Jane Zoppas Ferreira

Removal of cadmium and cyanide from aqueous solutions through electrodialysis

The discharge of galvanic industry wastewaters containing heavy metals and cyanide is one of the largest sources of water pollution. The use of the electrodialysis technique for the treatment of a synthetic wastewater containing approximately 0.0089 mol L-1 cadmium and 0.081 mol L-1 cyanide was studied using a five-compartment electrodialysis cell. The results demonstrate that the removal of cadmium and cyanide depends on the applied current density and it is limited by the precipitation of cadmium on the cation-exchange membrane in the diluate central cell compartment.

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.

Preparation and physical characterization of a sulfonated poly(styrene-co-divinylbenzene) and polypyrrole composite membrane

The properties of cation-exchange membranes based on polymeric composites of sulfonated poly(styrene-co-divinylbenzene) and polypyrrole (Ppy) are discussed. The amount of Ppy in the composites depends on the oxidant solution concentration used in the synthesis. Comparing composite membranes, the highest electronic conductivity and the best thermal stability were obtained for the composite membrane with the greatest content of Ppy. The membranes were thermally stable up to 250°C. As could be seen by SEM, Ppy is homogeneously distributed in the sulfonated poly(styrene-co-divinylbenzene) matrix. Consequently, composite membranes swell in water much less than base membrane alone. Ion-exchange capacity (IEC) does not change with pyrrole polymerization.

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.

Evaluation of the electrodialysis process for the treatment of metal finishing wastewater

in alkaline pH was treated by electrodialysis. The treatment was conducted in a laboratory cell and in a pilot plant unity. The experiments were carried out using Nafion and Selemion membranes. Results showed most of the metallic ions to have an anionic nature, due to the formation of coordination complexes. Each metallic ion showed a different rate of extraction from the treated solution, depending on the galvanostatic or potentiostatic operation mode. Zn, Ni and Cu have shown higher extraction under galvanostatic control. For Al, higher extraction was observed when the experiment was conducted in a potentiostatic mode. Fe ions exhibited an unexpected behavior, not being removed in the same way as the other ions. The best extraction results were obtained within 2-3 h of treatment.

Electrochemical study of the interactions between trivalent chromium ions and Nafion® perfluorosulfonated membranes

Abstract The trivalent chromium transport through Nafion ® 117 cation-exchange membrane was studied by electrochemical impedance spectroscopy (EIS). Results showed the presence of an interfacial charge transfer component characterising the exchange of Cr 3+ ions between the solution and the membrane and a bulk diffusion component relative to the transport of the chromium ions through the membrane. This bulk diffusion component was explained as a coupling between the diffusion of Cr 3+ ions and a chemical reaction due to the formation of a transient coordination complex of Cr 3+ ions and the sulfonate groups. A dependence on the pH of the solution was also observed, suggesting a mixed diffusion of Cr 3+ and H + inside the membrane phase.

Ultrafiltration/Nanofiltration for the Tertiary Treatment of Leather Industry Effluents

Biologically treated effluents from the leather industry pose severe problems for the environment due in part to both the inorganic charge and the high nitrogen content associated with the organic charge. Pressure-driven membrane processes, namely ultrafiltration/nanofiltration (UF/NF) technology, were investigated for their selective retention of the organics and permeation of the inorganic fraction. Permeation experiments were carried out with two model solutions representative of a treated tannery effluent. UF and NF of these model solutions were assessed in terms of both their inorganic/organic fractionation capability and their permeation productivity. The UF membranes with MWCOs ranging from 10,000 to 1000 Da yield retentate streams enriched in organic compounds and permeate streams enriched in salts. Despite their high capacity for pure water permeation, they displayed low permeation fluxes, as the result of concentration polarization and fouling phenomena. NF 200 and NF 270 membranes associated fractionation capability with high permeation rates. Furthermore, these membranes demonstrated the highest permeate fluxes -30 kg/h/m(2) and 16 kg/h/m(2) for different model solutions, at the transmembrane pressure of 8 bar. Although these membranes had lower hydraulic permeabilities relative to the other membranes tested, they exhibited the best characteristics in terms of minimization of colloidal fouling.

New Sol-gel Formulations to Increase the Barrier Effect of a Protective Coating Against the Corrosion and Wear of Galvanized Steel

This study proposes a new pretreatment method that uses alkoxide precursors with a plasticizing agent; the purpose of this study is to improve the electrochemical and mechanical properties of a galvanized steel surface. Galvanized steel was covered with a hybrid film obtained from a sol that consisted of two alkoxide precursors, 3 - (trimethoxysilylpropyl) methacrylate (TMSM) and tetraethoxysilane (TEOS), with nitrate cerium in a concentration of 0.01 M and a polyethylene glycol (PEG) plasticizer. The hybrid coatings were obtained by dip-coating method with various concentrations of plasticizer (0, 20, 40 and 60 g.L-1). The hybrid films were analyzed by scanning electron microscopy (SEM), profilometry, contact angle measurements, a tribometer with the type-setting ball on the plate and electrochemical tests. The addition of the plasticizer into the hybrid films improves the corrosion resistance behavior compared to the sample without the plasticizer. The addition of 20 g.L-1 of plasticizer showed the best performance in the electrochemical tests. The mechanical behavior results indicated that higher PEG concentrations resulted in films with enhanced durability.

Removal of anionic surfactants by nanofiltration

Abstract This work addresses the assessment of nanofiltration (NF) in terms of membrane characteristics, operating transmembrane pressure and feed composition for the maximal removal of anionic surfactants in wastewater from a detergent industry. Model solutions of linear alkylbenzene sulphonates (LAS) and sodium lauryl ether sulphates (SLES) covering a wide range of SLES/LAS ratios are used as surrogates of the wastewaters with 0.43 g l−1 of methylene blue active substances (MSAS). The NF experiments are carried out in a unit equipped with NF-90, NF-200 and NF-270 membranes (FilmTec Corp., USA). The applied pressure varied from 15 to 25 bar. The rejection coefficients to total organic carbon (TOC) are practically independent of pressure and are higher than 95% for all model solutions and higher than 92% for the wastewater. The SLES solutions have the highest permeation fluxes of 20–33, 121–207 and 242–371 kg h−1 m−2 for NF90, NF200 and NF270 membranes, respectively. The permeation fluxes for the other mo...

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.