Cleide Sandra Tavares Araújo

Development of a flow system for the determination of cadmium in fuel alcohol using vermicompost as biosorbent and flame atomic absorption spectrometry.

In this study a method for the determination of cadmium in fuel alcohol using solid-phase extraction with a flow injection analysis system and detection by flame atomic absorption spectrometry was developed. The sorbent material used was a vermicompost commonly used as a garden fertilizer. The chemical and flow variables of the on-line preconcentration system were optimized by means of a full factorial design. The selected factors were: sorbent mass, sample pH, buffer concentration and sample flow rate. The optimum extraction conditions were obtained using sample pH in the range of 7.3-8.3 buffered with tris(hydroxymethyl)aminomethane at 50 mmol L(-1), a sample flow rate of 4.5 mL min(-1) and 160 mg of sorbent mass. With the optimized conditions, the preconcentration factor, limit of detection and sample throughput were estimated as 32 (for preconcentration of 10 mL sample), 1.7 microg L(-1) and 20 samples per hour, respectively. The analytical curve was linear from 5 up to at least 50 microg L(-1), with a correlation coefficient of 0.998 and a relative standard deviation of 2.4% (35 microg L(-1), n=7). The developed method was successfully applied to spiked fuel alcohol, and accuracy was assessed through recovery tests, with recovery ranging from 94% to 100%.

Characterization and use of Moringa oleifera seeds as biosorbent for removing metal ions from aqueous effluents

Moringa oleifera seeds were investigated as a biosorbent for removing metal ions from aqueous effluents. The morphological characteristics as well as the chemical composition of M. oleifera seeds were evaluated using Fourier Transform Infrared (FT-IR) Spectroscopy, Thermogravimetric Analysis (TGA), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The FT-IR spectra showed the presence of lipids and protein components. Scanning electron micrographs showed that Moringa seeds have an adequate morphological profile for the retention of metal ions. The results suggest that M. oleifera seeds have potential application in Cd(II), Pb(II), Co(II), Cu(II) and Ag(I) decontamination from aqueous effluents.

Moringa oleifera Lam. seeds as a natural solid adsorbent for removal of AgI in aqueous solutions

This work describes the sorption potential of Moringa oleifera seeds for the decontamination of AgI in aqueous solutions. Infrared spectroscopy was used for elucidating possible functional groups responsible for uptaking AgI. Sorption studies using AgI standard solutions were carried out in batch experiments as functions of adsorbent mass, extraction time, particle size and pH. The AgI was quantified before and after the removal experiments using flame atomic absorption spectrometry. Furthermore, based on adsorption studies and adsorption isotherms applied to the Langmuir model, it was possible to verify that M. oleifera seeds present a high adsorption capacity. The optimum conditions were: 2.0 g of adsorbent with particle size of 75-500 µm, 100 mL of 25.0 mg L-1 AgI, extraction time of 20 min and pH at 6.5. The results show that Moringa oleifera seeds can be used for removing AgI in aqueous solutions.

Bioremediation of Waters Contaminated with Heavy Metals Using Moringa oleifera Seeds as Biosorbent

Water is not only a resource, it is a life source. It is well established that water is important for life. Water is useful for several purposes including agricultural, industrial, household, recreational and environmental activities. Despite its extensive use, in most parts of the world water is a scarce resource. Ninety percent of the water on earth is seawater in the oceans, only three percent is fresh water and just over two thirds of this is frozen in glaciers and polar ice caps. The remaining unfrozen freshwater is found mainly as groundwater, with only a small fraction present above ground or in the air. Thus, almost all of the fresh water that is available for human use is either contained in soils and rocks below the surface, called groundwater, or in rivers and lakes.

Characterization of Pequi (Caryocar brasiliense) Shells and Evaluation of Their Potential for the Adsorption of PbIIIons in Aqueous Systems

In this study pequi (Caryocar brasiliense) shells were evaluated in relation to their potential for the adsorption of PbII ions in aqueous systems. The adsorbent was characterized by point of zero charge (PZC), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and PbII ions were detected by flame atomic absorption spectrometry (FAAS). The adsorption parameters studied were solution pH, adsorbent mass, contact time and the optimum adsorption conditions were found to be 7.0, 50 mg and 30 min, respectively, using 15 mL of the metal solution. A study on the adsorption kinetics and isotherms was performed applying the optimized conditions. The adsorption process followed a pseudo-second-order model. The experimental adsorption data were fitted to the Langmuir and Freundlich isotherm adsorptions and a very good fit to the Langmuir linear model was observed. The maximum adsorption capacity was found to be 35.52 mg g-1.

Analytical Strategies for the Determination of Arsenic in Rice

Arsenic is an element of concern given its toxicological significance, even at low concentrations. Food is a potential route of exposure to inorganic arsenic and in this regard arsenic in rice is associated with soil contamination, fertilizer application, and the use of arsenic-containing irrigation water. Therefore, there is a need to investigate the regional rice crops with a view to future discussions on the need for possible regulatory measures. Several studies have reported high concentrations of arsenic in rice grown in soils irrigated with contaminated water; however, procedures used, including sample pretreatment and preconcentration steps, have to be followed to ensure sensitivity, accuracy, and reproducibility. Arsenic is a difficult element to measure in complex matrices, such as foods, because the matrix must be destroyed at an elevated temperature without the loss of the analyte or contamination. This review summarizes the major methods for the determination of arsenic in rice samples. The main purpose of this review is to provide an update on the recent literature concerning the strategies for the determination of arsenic and to critically discuss their advantages and weaknesses. These difficulties are described along with recent developments aimed at overcoming these potential issues.