Soraya Moreno Palácio

Toxicity assessment from electro-coagulation treated-textile dye wastewaters by bioassays.

In this study the pollutant removal from a textile dyeing wastewater has been investigated by using the electro-coagulation technique with iron electrodes. In order to obtain optimal values of the system state variables, a 3(3) full factorial experimental design was applied. The electro-coagulation (EC) process response was evaluated on the basis of COD removal and decolourization values. The electrolysis time and density current were statistically significant for the COD removal and decolourization. Based on the lettuce seeds (Lactuca sativa) and brine shrimp (Artemia salina), the lowest toxicity level was achieved in 5 min of electrolysis time. Due to the remaining high toxicity level above 30 min of electrolysis time, the EC process is not adequate to be used in a single effluent treatment, suggesting that this electrochemical process of up to 5 min could be used as part of a complete effluent treatment system.

Removal of heavy metal from polluted river water using aquatic macrophytes Salvinia sp

Concentrations of trace metallic element as well as macronutrients were measured in water and plants from pond water. The aquatic macrophyte Salvinia sp. was evaluated for its trace metals removal potential in river water under laboratory conditions. The experiment were performed using several healthy acclimatized plants Salvinia sp. The water and grown plants were collected from ponds. For the trace element removals test, 30-35 grams of fresh aquatic plants were grown in river water into a greenhouse for ten weeks. Control plants were also grown during the experiment. Every two weeks, both plants and water samples were collected. After the end of each experiment, the growth rate was calculated. Trace element concentrations in plants and pond water were obtained using TXRF techniques. Values for the elements (K, Ca, Ti, Fe, Cr, Mn, Cu, Zn and Sr) concentrations in plant dry weight have been obtained after deducting metal contents of control plants. For each trace element, the aquatic Salvinia sp. plant showed to possess different affinity for the incorporation of the metals in its biomass. Results suggest the use of aquatic macrophytes Salvinia sp. for metal abatement in dilute wastewaters.

Optimised photocatalytic degradation of a mixture of azo dyes using a TiO2/H2O2/UV process

The aim of the present study was to optimise the photocatalytic degradation of a mixture of six commercial azo dyes, by exposure to UV radiation in an aqueous solution containing TiO(2)-P25. Response surface methodology, based on a 3(2) full factorial experimental design with three replicates was employed for process optimisation with respect to two parameters: TiO(2) (0.1-0.9 g/L) and H(2)O(2) (1-100 mmol/L). The optimum conditions for photocatalytic degradation were achieved at concentrations of 0.5 g TiO(2)/L and 50 mmol H(2)O(2)/L, respectively. Dye mineralisation was confirmed by monitoring TOC, conductivity, sulfate and nitrate ions, with a sulfate ion yield of 96% under optimal reactor conditions. Complete decolorisation was attained after 240 min irradiation time for all tested azo-dyes, in a process which followed a pseudo-first kinetic order model, with a kinetic rate constant of approximately 0.018 min(-1). Based on these results, this photocatalytic process has promise as an alternative for the treatment of textile effluents.

Evolutive follow-up of the photocatalytic degradation of real textile effluents in TiO2 and TiO2/H2O2 systems and their toxic effects on Lactuca sativa seedlings

Textile industry wastes raise a great concern due to their strong coloration and toxicity. The objective of the present work was to characterize the degradation and mineralization of textile effluents by advanced oxidative processes using either TiO2 or TiO2/H2O2 association and to monitor the toxicity of the products formed during 6 h irradiation in relation to that of the in natura effluent. The results obtained demonstrated that the TiO2/H2O2 association was more efficient in the mineralization of textile effluents than TiO2 alone, with high mineralized ion concentrations (NH4+, NO3-, and SO42-) and significant organic matter reduction rates (represented by the COD and TOC). The toxicity of the degradation products to lettuce seeds (Lactuca sativa) was not significant, since percent germination was not significantly affected and neither was root and sprout percent growth. However, while the TiO2/H2O2 association was more toxic in the first hours of irradiation and less so in the end of the 6 h irradiation, the toxicity of TiO2 increased only slightly in the end of the experiments. Comparatively, the photogenerated products of both the TiO2 and the TiO2/H2O2 association were less toxic than the in natura effluent.

Correlation between heavy metal ions (copper, zinc, lead) concentrations and root length of Allium cepa L. in polluted river water

O presente trabalho foi realizado utilizando a cebola comum (Allium cepa L.) como bioindicador da toxicidade de metais pesados em agua de rio. As aguas de teste foram coletadas em dois locais: na nascente e na foz do rio Toledo. Os bulbos de A. cepa L. foram cultivados em agua de teste com nove niveis de concentracao de cobre, zinco e chumbo de 0,1 a 50 ppm. Em laboratorio a influencia destes liquidos de teste em crescimento de raiz foi examinada durante cinco dias. Em todos os liquidos de teste o metal dissolvido contido foi medido pela tecnica TXRF. Para liquidos de teste contendo 0,1-ppm de Cu dissolvido o crescimento da raiz foi reduzido em 50%. Entretanto, ocorreu a mesma reducao para 1-ppm de Zn dissolvido. Para Pb dissolvido, o metodo do Allium teste revela toxidade acima de 0,1 e 0,5 ppm para a nascente e a foz do rio Toledo, respectivamente.

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.

Application of high resolution X-ray emission spectroscopy on the study of Cr ion adsorption by activated carbon.

In this work granular activated carbon has been chosen as an absorbent in order to investigate the Cr(VI) reduced by adsorption experiments. Several batch chromium-sorption experiments were carried out using 0.25 g of granular activated carbon in 50 mL aqueous solution containing approximately 70 and 140 mg L(-1) of Cr(VI) and Cr(III), respectively. Cr-Kbeta fluorescence spectra of Cr adsorbed in a carbon matrix and Cr reference materials were measured using a high-resolution Johann-type spectrometer. Based on evidence from the Cr-Kb satellite lines, the Cr(VI) reduction process has actually happened during metal adsorption by the activated carbon.

Analysis of Trace Elements in Groundwater Using ICP-OES and TXRF Techniques and Its Compliance with Brazilian Protection Standards

In this work, an assessment of groundwater quality and its compliance with Brazilian environmental protection standards was carried out. Ground waters from the Serra Geral aquifer are currently used for human consumption at the western region of the Brazilian state of Paraná. Ground water samples from 10 wells covering the entire Toledo municipality rural region were collected and analysed by two highly accurate and sensitive spectrometric techniques: inductively coupled plasma–optical emission spectrometry (ICP-OES) and total reflection X-ray spectrometry (TXRF). Among all detected elements, 18 elements (As, Ba, Br, Ca, Pb, Cl, Co, Cu, Cr, Fe, P, S, Mn, Ni, K, Ti, V and Zn) were measured by the TXRF technique while three elements (B, Mg and Na) were measured by ICP-OES. Trace element concentration levels were then compared with Brazilian environmental legislation (BEL). From the results obtained, concentrations of chromium, iron, arsenic, selenium, manganese and barium were detectable in some wells at slightly above the maximum limits allowed by the BEL.

Optimization of the Iron Electro-Coagulation Process of Cr, Ni, Cu, and Zn Galvanization By-Products by Using Response Surface Methodology

An electrocoagulation laboratory scale system was studied for the removal of inorganic pollutants from a mixture of galvanic process-based by-products. Response surface methodology based on a five-level, four-variable central composite rotatable design was employed for optimization with respect to four important variables—reaction time, agitation velocity, current density, and pH. The electrocoagulation process response was evaluated on the basis of chemical oxygen demand (COD), turbidity, total suspended solid, and element concentration values. Interaction effects between reactor operating variables and response variables were evaluated by using 3-D response surface analysis Second-order models were validated by ANOVA. Predicted yields were in a good agreement with the experimental ones. The reactor optimal performance was achieved at 35 min reaction time, 170 rpm agitation velocity, 97.7 Am−2 current density, and 6.5 initial pH. Under these conditions 100% color and turbidity, 90% COD and total suspended solids, 100% chromium and nickel, and almost 99% zinc and copper were removed. A pseudo-first-order rate model was applied to describe the metal removal kinetics. The EC treatment of heavy metal solutions proved to be more cost-effective than the conventional one, indicating clearly that the method of electro-coagulation is a very promising alternative for industrial applications.

Biodegradability and toxicity assessment of a real textile wastewater effluent treated by an optimized electrocoagulation process.

In this work, the application of an iron electrode-based electrocoagulation (EC) process on the treatment of a real textile wastewater (RTW) was investigated. In order to perform an efficient integration of the EC process with a biological oxidation one, an enhancement in the biodegradability and low toxicity of final compounds was sought. Optimal values of EC reactor operation parameters (pH, current density and electrolysis time) were achieved by applying a full factorial 33 experimental design. Biodegradability and toxicity assays were performed on treated RTW samples obtained at the optimal values of: pH of the solution (7.0), current density (142.9 A m−2) and different electrolysis times. As response variables for the biodegradability and toxicity assessment, the Zahn–Wellens test (Dt), the ratio values of dissolved organic carbon (DOC) relative to low-molecular-weight carboxylates anions (LMCA) and lethal concentration 50 (LC50) were used. According to the Dt, the DOC/LMCA ratio and LC50, an electrolysis time of 15 min along with the optimal values of pH and current density were suggested as suitable for a next stage of treatment based on a biological oxidation process.