Evaluation of hybrid neutralization/biosorption process for zinc ions removal from automotive battery effluent by dolomite and fish scales.

This work focused in the evaluation of Oreochromis niloticus fish scales (FS) as biosorbent material in the removal of Zn from a synthetic effluent based on automotive battery industry effluent and, further, a hybrid neutralization/biosorption process, aiming at a high-quality treated effluent, by a cooperative use of dolomite and FS. For this, a physicochemical and morphological characterization (i.e. SEM-EDX, FTIR, XRD, and TXRF) was performed, which helped to clarify a great heterogeneity of active sites (phosphate, carbonate, amide, and hydroxyl) on the biosorbent; also the inorganic constituents (apatites) leaching from the FS was identified. Biosorption results pointed out to a pH-dependent process due to changes in the functional group's anionic character (i.e. electrostatic interactions), where an initial pH = 3 favored the Zn uptake. Kinetic and equilibrium studies confirmed the heterogeneous surface and cooperative sorption, wherein experimental data were described by Generalized Elovich kinetic model and the favorable isotherm profile by Langmuir-Freundlich isotherm ( qmax = 15.38 mg g-1 and 1/n>1 ). Speciation diagram of Zn species along with the leached species demonstrated that, for the studied pH range, the biosorption was the most likely phenomena rather than precipitation. Finally, the hybrid neutralization/biosorption process showed great potential since both the Zn concentration levels and the pH reached the legislation standards (CZn = 4 mg L-1; pH = 5). Hence, based on the characterization and biosorption results, a comprehensive evaluation of the involved mechanisms in such complex system helped to verify the prospective of FS biosorbent for the Zn treatment from solution, in both individual and hybrid processes.

Thin and thick target PIXE analyses to assess the mechanism of Cu2+ removal by Egeria densa.

In this work the PIXE technique was used to study the mechanism of metal sorption by dead biomass. Several batch copper-sorption experiments were performed by using Egeria densa biomass. PIXE measurements were performed in solid and liquid samples. Element concentrations in biosorbent samples were determined using the Clara software. Based on the mass balance among the major elements in the liquid and solid phases before and after the Cu-removal experiments, an ion exchange process is suggested as the main mechanism.

Assessment of metal sorption mechanisms by aquatic macrophytes using PIXE analysis.

In this work, a study of the metal sorption mechanism by dead biomass has been performed. All batch metal biosorption experiments were performed using the aquatic macrophyte Egeria densa as biosorbent. Divalent cadmium and zinc solutions were used to assess the sorption mechanisms involved. Using a suitable equilibrium time of 2h and a mixture of 300 mg biosorbent and 50 mL metal solution at pH 5, monocomponent sorption experiments were performed. In order to determine the residual amounts of metals in the aqueous solutions and the concentrations of removed metals in the dry biomass, Particle Induced X-ray Emission (PIXE) measurements in thin and thick target samples were carried out. Based on the strong experimental evidence from the mass balance among the major elements participating in the sorption processes, an ion exchange process was identified as the mechanism responsible for metal removal by the dry biomass.

Performance evaluation of a photo-Fenton process applied to pollutant removal from textile effluents in a batch system.

In this work, the performance of a photo-Fenton process-based textile effluent treatment was investigated using both solar and artificial light sources. A full 3(3) factorial experimental design was applied for the optimisation with respect to three parameters: initial pH, amounts of Fe(2+) (0.01-0.09 g L(-1)) and H(2)O(2) (1-7 g L(-1)). The photo-Fenton process response was evaluated on the basis of chemical oxygen demand (COD) removal and decolourisation. The optimum conditions of the photo-Fenton process were attained at concentration values of 0.05 g Fe(2+) L(-1) and 6.0 g H(2)O(2) L(-1) and pH 3, for both solar and artificial light sources. The effects of initial pH, and Fe(2+) and H(2)O(2) concentrations were evaluated. From the monitoring of TOC, COD, turbidity and decolourisation over time, the progress of the mineralisation of dyes was analysed, forming nitrate, ammonia nitrogen and nitrite. Low amounts of residual peroxide and iron, which were below the limit allowed by Brazilian environmental legislation, were attained after 360 min of irradiation time for both artificial and solar sources. An operational cost of US$ 6.85 per m(3) of treated effluent was estimated using solar irradiation.

Adsorption of Zn(II) and Cd(II) ions in batch system by using the Eichhornia crassipes.

In this work, the displacement effects on the sorption capacities of zinc and cadmium ions of the Eichornia crassipes-type biosorbent in batch binary system has been studied. Preliminary single metal sorption experiments were carried out. An improvement on the Zn(II) and Cd(II) ions removal was achieved by working at 30 °C temperature and with non-uniform biosorbent grain sizes. A 60 min equilibrium time was achieved for both Zn(II) and Cd(II) ions. Furthermore, it was found that the overall kinetic data were best described by the pseudo second-order kinetic model. Classical multi-component adsorption isotherms have been tested as well as a modified extended Langmuir isotherm model, showing good agreement with the equilibrium binary data. Around 0.65 mequiv./g maximum metal uptake associated with the E. crassipes biosorbent was attained and the E. crassipes biosorbent has shown higher adsorption affinity for the zinc ions than for the cadmium ones in the binary system.

Analysis of metal concentration levels in water, sediment and fish tissues from Toledo municipal lake by applying SR-TXRF technique.

The main objective of this study was to evaluate the metal content in water and sediment from the Toledo municipal lake, as well as the concentration levels of heavy metals in muscle and liver of four fish species. A digestion procedure was performed in all fish samples. Metal analysis was performed by using the Synchrotron Radiation X-ray Fluorescence technique. The accuracy and validity of the measurements were determined by analysis of certified reference materials. The highest Cr, Cu and Se concentration levels above the maximum tolerance limit according to the Brazilian norms in fish tissue could be associated with the metal uptake and accumulation due to the direct contact with contaminated water and sediment.

Evaluation of trace element levels in muscles, liver and gonad of fish species from São Francisco River of the Paraná Brazilian state by using SR-TXRF technique.

This study is focused on the analysis of an accumulation of inorganic elements in muscles, liver and gonad of seven fish species from São Francisco River located in the Paraná state of Brazil. Concentrations of the elements were determined using the SR-TXRF technique. In the muscles of fish species, negative length dependent relationships were observed for chromium and zinc ion absorption. The obtained results showed that accumulated Cr ions values are above the limits defined in the Brazilian legislative norm on food.

The evaluation of benzene and phenol biodegradation kinetics by applying non-structured models.

The biodegradation kinetics of the aromatic hydrocarbons benzene and phenol as single substrates and as a mixture were investigated through non-structured model analysis. The material balance equations involving the models of Monod and Andrews and representing the biodegradation kinetics of individual substrates in batch mode were numerically solved. Further, utilization of a benzene-phenol mixture was described by applying more sophisticated mathematical forms of competitive, noncompetitive and uncompetitive inhibition models as well as the sum kinetic interactions parameters (SKIP) model. In order to improve the performance of the studied models, some modifications were also proposed. The Particle Swarm Global Optimization method, coded in Maple, was applied to the parameter identification procedure of each model, where the least square method was used as a search statistical criterion. The description of the biodegradation kinetics of a benzene-phenol mixture by the competitive inhibition model was based on the information that the compounds could be catabolized via one metabolic pathway of Pseudomonas putida F1. Simulation results were in good agreement with the experimental data and proved the robustness of the applied methods and models. The developed knowledge database could be very useful in the optimization of the biodegradation processes of different bioreactor types and operational conditions.

Cadmium biosorption by non-living aquatic macrophytes Egeria densa.

In this work the removal potential on Cd(2+ ) by the non-living Egeria densa biomass has been studied. The influence of the metal solution pH, the plant drying and the metal solution temperature, and biosorbent grain size was previously studied in batch systems. The cadmium adsorption rate has increased when the pH was increasing, but at pH 5, the cadmium precipitation has begun to occur, avoiding such high pH values in other tests. The cadmium removal was around 70% at 30 degrees C biomass dried and solution temperatures, assuming as the best temperature conditions. No significant influence was observed in cadmium removal due to the grain size effect. The biosorption kinetic data were well fitted by a pseudo-second order model. The equilibrium time in experiments was around 45 min with a 70% Cd removal. The equilibrium data at pH 5 were described rather better by the Langmuir isotherm than the Freundlich one, with an adsorption rate and maximum metal content values of 0.40 L g(-1) and 1.28 meq g(-1), respectively, for Langmuir model. The kinetic parameter values are near to other biosorbents, indicating that the macrophytes E. densa could be used as biosorbent material in industrial effluent treatment system.

Inhibition effect on the Allium cepa L. root growth when using hexavalent chromium-doped river waters.

The effect of Cr(6+) on Allium cepa root length was studied using both clean and polluted river waters. Seven series of Cr(6+)-doped polluted and non-polluted river waters were used to grow onions. Chromium concentration (Cr(6+)) of 4.2 mg L(-1)(EC(50) value), doped in clean river water caused a 50% reduction of root length, while in organically polluted samples similar root growth inhibition occurred at 12.0 mg Cr(6+) L(-1). The results suggested that there was a dislocation to higher values in toxic chromium concentration in polluted river water due to the eutrophization level of river water.