Aderval S. Luna

Kinetic modeling and equilibrium studies during cadmium biosorption by dead Sargassum sp. biomass

A basic investigation on the removal of cadmium(II) ions from aqueous solutions by dead Sargassum sp. was conducted in batch conditions. The influence of different experimental parameters; initial pH, shaking rate, sorption time, temperature and initial concentrations of cadmium ions on cadmium uptake was evaluated. Results indicated that cadmium uptake could be described by the Langmuir adsorption model, being the monolayer capacity negatively affected with an increase in temperature. Analogously, the adsorption equilibrium constant decreased with increasing temperature. The kinetics of the adsorption process followed a second-order adsorption, with characteristic constants increasing with increasing temperature. Activation energy of biosorption could be calculated as equal to 10 kcal/mol. The biomass used proved to be suitable for removal of cadmium from dilute solutions. Its maximum uptake capacity was 120 mg/g. It can be considered an optimal result when compared to conventional adsorbing materials. Thus Sargassum sp. has great potential for removing cadmium ions especially when concentration of this metal is low in samples such as wastewater streams.

An evaluation of copper biosorption by a brown seaweed under optimized conditions

A basic investigation into the removal of copper ions from aqueous solutions by Sargassum sp. was conducted in batch conditions. The influence of different experimental parameters such as initial pH, shaking rate, sorption time, temperature, equilibrium conditions and initial concentrations of copper ions on copper uptake was evaluated. Results indicated that for shaking rates higher than 100 rpm no significant changes in copper accumulation were observed, as well as for pH values between 3.0 and 5.0. No marked effect on the biosorption of copper was detected for temperatures between 298 and 328K. The Langmuir model better represented the sorption process, in comparison to the model of Freundlich. The process followed a second-order kinetics and its calculated activation energy was 5.2 kcal/mol. Due to its outstanding copper uptake capacity (1.48 mmol/g biomass) Sargassum sp. proved to be an excellent biomaterial for accumulating and recovering copper from industrial solutions.

Assessment of apically extruded debris produced by the single-file ProTaper F2 technique under reciprocating movement

OBJECTIVE This study was designed to quantitatively evaluate the amount of dentin debris extruded from the apical foramen by comparing the conventional sequence of the ProTaper Universal nickel-titanium (NiTi) files with the single-file ProTaper F2 technique. STUDY DESIGN Thirty mesial roots of lower molars were selected, and the use of different instrumentation techniques resulted in 3 groups (n=10 each). In G1, a crown-down hand-file technique was used, and in G2 conventional ProTaper Universal technique was used. In G3, ProTaper F2 file was used in a reciprocating motion. The apical finish preparation was equivalent to ISO size 25. An apparatus was used to evaluate the apically extruded debris. Statistical analysis was performed using 1-way analysis of variance and Tukey multiple comparisons. RESULTS No significant difference was found in the amount of the debris extruded between the conventional sequence of the ProTaper Universal NiTi files and the single-file ProTaper F2 technique (P>.05). In contrast, the hand instrumentation group extruded significantly more debris than both NiTi groups (P<.05). CONCLUSIONS The present results yielded favorable input for the F2 single-file technique in terms of apically extruded debris, inasmuch as it is the most simple and cost-effective instrumentation approach.

Competitive biosorption of cadmium(II) and zinc(II) ions from binary systems by Sargassum filipendula

The present work describes our study on the competitive biosorption of Cd(II) and Zn(II) ions onto Sargassum filipendula from single component and binary systems. Results showed that S. filipendula was an efficient biosorbent for the removal of Cd(II) and Zn(II) ions from an aqueous solution. The equilibrium experimental data for the single component system for the two metallic species fitted well to Langmuir and Langmuir-Freundlich isotherm models. Seven isotherm models were tested with the equilibrium data for modeling of the binary system. Based on the sum of squares error, the Langmuir-Freundlich isotherm model showed the best fit to the binary adsorption data. The influence of the additional cation on the behavior of the biosorption of Cd(2+) and Zn(2+) was analyzed comparing single component and binary isotherms. It was observed that Zn(2+) had a relevant effect on the Cd(2+) biosorption, but the interference of Cd(2+) on the sorption of Zn(2+) was considerably less intense.

Rapid characterization of transgenic and non-transgenic soybean oils by chemometric methods using NIR spectroscopy

Near infrared (NIR) spectroscopy and multivariate classification were applied to discriminate soybean oil samples into non-transgenic and transgenic. Principal Component Analysis (PCA) was applied to extract relevant features from the spectral data and to remove the anomalous samples. The best results were obtained when with Support Vectors Machine-Discriminant Analysis (SVM-DA) and Partial Least Squares-Discriminant Analysis (PLS-DA) after mean centering plus multiplicative scatter correction. For SVM-DA the percentage of successful classification was 100% for the training group and 100% and 90% in validation group for non transgenic and transgenic soybean oil samples respectively. For PLS-DA the percentage of successful classification was 95% and 100% in training group for non transgenic and transgenic soybean oil samples respectively and 100% and 80% in validation group for non transgenic and transgenic respectively. The results demonstrate that NIR spectroscopy can provide a rapid, nondestructive and reliable method to distinguish non-transgenic and transgenic soybean oils.

Negligible Expression of Arsenic in Some Commercially Available Brands of Portland Cement and Mineral Trioxide Aggregate

INTRODUCTION This study was designed aiming to determine and compare the amount of arsenic in some brands of mineral trioxide aggregate (MTA) and Portland cement. METHODS In the present study, arsenic species (As[III], As[V], and dimethylarsinic acid) were separated by high-performance liquid chromatography (HPLC) using a strong anion exchange column and converted into arsines by online HG. The instrumental coupling, HPLC-HG-AFS, was applied to 0.2 g of each cement that was prior digested in a solution of HCl, HNO(3), and HBF(4). Data were expressed as a part per million, and the preliminary analysis of the raw pooled data revealed a bell-shaped distribution. Statistical analysis was performed using one-way analysis of variance for multiple comparisons. RESULTS In all chromatograms obtained, only type III arsenic could be detected. The minimum amount of arsenic was detected in samples of white MTA ProRoot (3.3 x 10-4) and the maximum in the samples MTA Bio Angelus (Angelus, Londrina, PR, Brazil) (8.6 x 10-4). In the Gray MTA (Angelus), gray ProRoot MTA (Tulsa/Dentsply, Tulsa, OK) and CP Juntalider (Brasilatex Ltda, Diadema, SP, Brazil) did not detect any trace of arsenic. The values of arsenic found in CP Irajazinho (Votorantim Cimentos, Rio Branco, SP, Brazil) and white MTA Angelus were intermediaries to minimum and maximum values. The nonparametric test Kruskal-Wallis showed statistically similar results among all cements tested (p > 0.5). CONCLUSIONS Overall, the present study showed that all cements showed insignificant amounts of type III arsenic as well as no trace of arsenic DMA and type V could be detected.

Lack of correlation between sealer penetration into dentinal tubules and sealability in nonbonded root fillings

AIM To determine the correlation between leakage and sealer penetration into dentinal tubule. METHODOLOGY The root canal of 60 mandibular central incisor teeth were prepared and filled under standardized conditions. Teeth were placed into a device to assess glucose penetration using 15 psi pressure application. After 1 h, glucose concentrations in the lower chamber were measured using an enzymatic reaction. Each specimen was then sectioned horizontally at 3, 6 and 8 mm from the apex, and a standard metallographic preparation was performed. The coronally facing surface of each slice was examined in a high-resolution stereomicroscope and under Confocal Laser Scanning Microscope. For each slice, the external outline of the root canal, the internal circumference of the root canal walls and the areas along the canal walls where the sealer had penetrated into the dentinal tubules (sealer tags) were outlined and measured. Afterwards, the percentage of the sealer penetration in each section was calculated. The Spearman correlation test was used to verify the correlation between the variables studied (glucose leakage and sealer penetration into dentinal tubules). RESULTS The means and standard deviations of glucose leakage were 0.744 g L(-1) (±0.5), and the percentage of the dentinal tubule sealer penetration varied between teeth from 5.6% to 42.21%, with an average of 13.7 ± 17.2%. The Spearman correlation test revealed no significant correlation between the two factors analysed (P = 0.082). The r(2) value was equal to 0.12. CONCLUSIONS There was no significant correlation between sealability sealer penetration into dentinal tubules. The lack of correlation reported is of relevance as sealer penetration into dentinal tubules has been used as an advantageous property during the launch of new root filling materials and techniques.

Comparison of the root-end seal provided by bioceramic repair cements and White MTA

AIM To compare the ability of Ceramicrete, BioAggregate and white ProRoot MTA (mineral trioxide aggregate) to prevent glucose leakage through root-end fillings. METHODOLOGY After root canal instrumentation, the apical 3 mm of maxillary incisors were resected and retropreparations, 3 mm in depth, were created with ultrasound. Root-end cavities were filled with the tested materials (15 roots per group). All roots were mounted in a double-chamber system to assess glucose penetration using 15 psi pressure application. After 1 h, glucose concentrations in the lower chamber were measured following an enzymatic reaction. Four roots were used as controls. One-way anova verified differences in glucose leakage between groups and Tukey test performed multiple comparisons. Significance was set at α = 5%. RESULTS There was a significant difference between the three materials (anova, P < 0.05). Ceramicrete had significantly lower glucose penetration than BioAggregate (Tukey, P < 0.05). There was no difference between the two bioceramic cements and white MTA (P > 0.05). CONCLUSIONS Both endodontic bioceramic repair cements displayed similar leakage results to white MTA when used as root-end fillings materials. Ceramicrete had significantly lower glucose penetration.

Chemical vapor generation—electrothermal atomic absorption spectrometry: new perspectives☆

Abstract Volatile species of Ag, Cu, Cd, and Zn were generated at room temperature by the addition of sodium tetrahydroborate (III) to an acidified solution of the analytes. The vapor-phase species were rapidly transported to a pre-heated graphite tube, the surface of which was previously treated with Ir as a permanent chemical modifier. The volatile species were trapped at the Ir treated tube surface, and the further heating of the furnace permits their determination by atomic absorption spectrometry. A univariate approach was used to achieve optimized conditions and derive the figures of merit. The limits of detection based on a 3σ b criterion were 10 (1); 0.006 (6×10 −4 ); 28 (2.8) and 1.1 (0.11) ng (μg ml −1 ) for Ag, Cd, Cu and Zn, respectively. Precision of replicate measurements was typically approximately 10% R.S.D. Using a transfer line as short as possible should minimize losses of analyte during the transport to the graphite furnace. The overall efficiency of the volatile species generation and trapping process estimated for silver was 13%.

Classification of edible oils and modeling of their physico-chemical properties by chemometric methods using mid-IR spectroscopy.

This research work describes two studies for the classification and characterization of edible oils and its quality parameters through Fourier transform mid infrared spectroscopy (FT-mid-IR) together with chemometric methods. The discrimination of canola, sunflower, corn and soybean oils was investigated using SVM-DA, SIMCA and PLS-DA. Using FT-mid-IR, DPLS was able to classify 100% of the samples from the validation set, but SIMCA and SVM-DA were not. The quality parameters: refraction index and relative density of edible oils were obtained from reference methods. Prediction models for FT-mid-IR spectra were calculated for these quality parameters using partial least squares (PLS) and support vector machines (SVM). Several preprocessing alternatives (first derivative, multiplicative scatter correction, mean centering, and standard normal variate) were investigated. The best result for the refraction index was achieved with SVM as well as for the relative density except when the preprocessing combination of mean centering and first derivative was used. For both of quality parameters, the best results obtained for the figures of merit expressed by the root mean square error of cross validation (RMSECV) and prediction (RMSEP) were equal to 0.0001.