Paulo Sérgio Parreira

Granulometry and Moisture Influence for In Situ Soil Analysis by Portable EDXRF

The objective of this work was to verify the granulometry and the moisture influence in results when soils samples are measured for identification and quantification of metal, on field, employing portable Energy Dispersive X‐Ray Fluorescence (PXRF) equipment. For granulometry, the obtained concentration values for Ti, Fe and Zr, are equivalent for the samples grinded for one minute and the samples grinded and sieved. This result indicates that, for in situ analysis of this soil, it is sufficient to grind the dried sample before measurement. For moisture, concentration values obtained for the samples dried from 30 to 120 minutes at sun are equivalent. On the other hand, the concentration values obtained for the samples dried during 24 h are higher than the values obtained for the same samples dried at sun. Moisture influences the concentrations values in around 20%.

Elementary chemical analysis in leaves infected by fumagina by X-Ray fluorescence technique

Energy Dispersion X-Ray Fluorescence Technique (EDXRF) was employed to study the effects of the fumagina disease on the elementary chemical composition of the leaves. The experimental set up consisted of a Mo X-ray tube (Ksubµ = 17.44 keV) with Zr filter and a Si (Li) detector. The measurements were performed with the infected and healthy leaves of citric plants. The elements Ti, Mn, Fe, Cu and Zn were quantified, with an average DL of 69, 12, 8, 4 and 4 µg.g-1 respectively. The obtained concentration for Fe varied from 44 to 192 µg.g-1 in healthy leaves and from 363 to 704 µg.g-1 in infected leaves with fumagina .

Sorption and desorption of silver ions by bentonite clays

Anthropogenic activities have increased the concentration of metal species in the environment. The toxicity of silver ions to aquatic and terrestrial organisms has required monitoring by analytical methods, besides actions to promote its control as pollutant. Sorption and desorption processes are directly related to the mobility and availability of metal ions in the environment. In this context, clay minerals can be used for pre-concentration, removal and recovery of silver ions from aqueous solution. Herein, two bentonite clays (BaVC-1 and SWy-2) were characterised and applied to investigate the sorption and desorption of silver ions. Isotherms were fitted to the dual-mode Langmuir-Freundlich model to qualify and quantify sorption sites and evaluate the mobilisation process. The maximum sorption capacity was 743 and 849 meq kg−1 for BaVC-1 and SWy-2, respectively. Hysteresis index (HI) and mobilisation factor (MF) suggest that the desorption of silver ions in BaVC-1 is about four times more conducive compared to that in SWy-2, although both materials have demonstrated a great potential for Ag+ pre-concentration from aqueous solutions.

Sorption-desorption of antimony species onto calcined hydrotalcite: surface structure and control of competitive anions

Calcined hydrotalcite can be applied to remove anionic contaminants from aqueous systems such as antimony species due to its great anion exchange capacity and high surface area. Hence, this study evaluated antimonite and antimonate sorption-desorption processes onto calcined hydrotalcite in the presence of nitrate, sulfate and phosphate. Sorption and desorption experiments of antimonite and antimonate were carried out in batch equilibrium and the post-sorption solids were analyzed by X-ray fluorescence (EDXRF). Sorption data were better fitted by dual-mode Langmuir-Freundlich model (R2>0.99) and desorption data by Langmuir model. High maximum sorption capacities were found for the calcined hydrotalcite, ranging from 617 to 790meqkg-1. The competing anions strongly affected the antimony sorption. EDXRF analysis and mathematical modelling showed that sulfate and phosphate presented higher effect on antimonite and antimonate sorption, respectively. High values for sorption efficiency (SE=99%) and sorption capacity were attributed to the sorbent small particles and the large surface area. Positive hysteresis indexes and low mobilization factors (MF>3%) suggest very low desorption capacity to antimony species from LDH. These calcined hydrotalcite characteristics are desirable for sorption of antimony species from aqueous solutions.

Preliminary analysis of Brazilian archaeological ceramics by non‐destructive analytical technique

Portable System of Energy Dispersive X‐ray Fluorescence was used to analyze of pre‐colonial pottery from northeast of Brazil. In 43 pottery fragments there is a different treatment on the faces in relation to the ceramic paste. The results of two‐dimensional graphs and cluster analyses show the formation of five groups of fragments. This result indicates that the fragments analyzed were manufactured with clay from five different origins. It was possible to observe elements K, Ca, Ti, Mn, Fe, Zn, Br, Rb, Sr, Y, Zr and Pb in the analyzed fragments.