Miriam Gimenes

Sorption kinetics and equilibrium for the removal of nickel ions from aqueous phase on calcined Bofe bentonite clay.

In this paper the kinetics and dynamics of nickel adsorption on calcined Bofe bentonite clay were studied. The clay was characterized through EDX, surface area (BET) and XRD analysis. The influence of parameters (pH, amount of adsorbent, adsorbate concentration and temperature) was investigated. Kinetic models were evaluated in order to identify potential adsorption process mechanisms. The Langmuir and Freundlich models were utilized for the analysis of adsorption equilibrium. Thermodynamic parameters were assessed as a function of the process temperature. The kinetics data were better represented by the second-order model. The process was found to be strongly influenced by the factors studied. The Bofe clay removed nickel with maximum adsorption capacity of 1.91 mg metal/g of clay (20 degrees C; pH 5.3) and that the thermodynamic data indicated that the adsorption reaction is spontaneous and of an exothermal nature. The Langmuir model provided the best fit for sorption isotherms.

Removal of nickel on Bofe bentonite calcined clay in porous bed.

Bentonite clays have been showing good adsorbing characteristics and are used as an alternative material in the removal of heavy metals. The purpose of this study is to evaluate the removal of nickel on Bofe bentonite calcined clay in porous bed. Firstly, a study was conducted to define the operation outflow, based on the minimum mass transfer zone (MTZ) obtained, useful (q(U)) and total adsorbed (q(T)) removal amounts and total nickel removal percentage (Rem (%)). Assays of nickel adsorption on clay were conducted according to a 2(2) factorial design with three central points to evaluate the effect of the particle diameter and initial adsorbate concentration on variables q(U), q(T) and Rem (%). Tests to obtain the adsorbent physical and chemical characteristics were performed on samples of Bofe clay in natura, calcined, and calcined submitted to nickel adsorption. This clay was characterized according to the following techniques: Energy Dispersive Spectroscopy (EDS), Thermogravimetry (TG), Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), Fourier Transformed Infrared Spectroscopy (FTIR), Physisorption of N(2) (BET), Helium Picnometry and Scanning Electron Microscope (SEM) with metal mapping.

Abelhas (Apoidea) visitantes de flores de Comolia ovalifolia DC Triana (Melastomataceae) em uma área de restinga na Bahia

The flowers of Comolia ovalifolia present poricidal anthers and their pollen serve as protein source to a specific group of bees, able to extract the pollen from the anthers through vibration. From January to December /2001, we observed the flowering of C. ovalifolia and the activity of the most frequent bees throughout the year. The peaks of flowering of C. ovalifolia occurred in March and from September to November/2001. The flowers of C. ovalifolia were visited by 16 species of bees, being the most frequent Centris leprieuri (Spinola), Xylocopa subcyanea Perez, Centris sp., Euglossa sp. and Florilegus similis Urban. Among these, C. leprieuri was the most frequent visitor in the flowers (89%) and its foraging period overlapped with the blooming of C. ovalifolia. This bee presented adequate size and efficient behavior in pollen collection and transfer to the stigma, being considered an effective pollinator of the flowers.

Interactions between bees and Ludwigia elegans (Camb.) Hara (Onagraceae) flowers at different altitudes in São Paulo, Brazil

Populations of Ludwigia elegans (Carnb.) Hara were examined in Aluminio (600m) and Campos do Jordao (1520m), in the State of Sao Paulo. Flowers of both populations are self-incompatible and dependent on bees for pollination. Flowers of Ludwigia elegans at the Aluminio site were visited by about 30 different species of bees, and those at Campos do Jordao by 10. These results can be related to climatic differences at the two sites, especially temperature, due to their difference in altitude. Inspite of the difference in the absolute number of bee species seen at each site, Tetraglossula anthracina (Michener, 1989) (Colletidae) can be considered a specialized and efficient pollinator in both areas, since it visited these flowers frequently and showed many morphological and behavioral adaptations for pollen and nectar collection.

Pollination of Cambessedesia wurdackii in Brazilian campo rupestre vegetation, with special reference to crepuscular bees

Abstract Cambessedesia wurdackii Martins (Myrtales: Melastomataceae) is presumably endemic to the Chapada Diamantina, Bahia State, Brazil. A majority of the species of this family are pollinated by diurnal bees that buzz the floral anthers to collect pollen. The present work examined the interactions between C. wurdackii and visiting bees, focusing on temporal, morphological, and behavioral features, especially in regards to the crepuscular bees Megalopta sodalis (Vachal) (Hymenoptera: Halictidae) and Ptiloglossa off. dubia Moure (Hymenoptera: Colletidae). The study was undertaken in an area of campo rupestre montane savanna vegetation located in the Chapada Diamantina Mountains of Bahia State, Brazil, between August/2007 and July/2008. Flowering in C. wurdackii occurred from April through July, with a peak in May. A total of 592 visits by diurnal and crepuscular bees to the flowers of C. wurdackii were recorded, with a majority of the visits made by M. sodalis and P. dubia (92%) near sunrise and sunset. The anthers of C. wurdackii are arranged in two tiers, which favors cross pollination. The morphological, temporal and behavioral characteristics of M. sodalis and P. dubia indicated that they were potential pollinators of C. wurdackii, in spite of the fact that the colorful and showy flowers of this species are more typical of a diurnal melittophilous pollination syndrome.

Daily activity patterns of visits by males of four species of Eulaema (Apidae: Euglossina) to odor baits in a tropical forest fragment in Bahia, Brasil

Several studies have been conducted with bees of the subtribe Euglossina using odor baits as attractants. The objective of this study was to analyze the daily activity pattern of visits by males of four species of Eulaema - Eulaema nigrita Lepeletier, 1841, Eulaema flavescens (Friese, 1899), Eulaema cingulata (Fabricius, 1804) and Eulaema bombiformis (Packard, 1869) - to vanillin and benzyl acetate baits, and their relationship with climatic and environmental factors throughout the day in different months of the year in a tropical forest fragment in Bahia. Eulaema nigrita was the most frequent species on vanillin baits and E. flavescens was the most frequent species on benzyl acetate baits. The highest frequency of visits was observed in February and December. Activities started between 5:00 and 9:00 h. In February and November, visits of E. nigrita to the bait were observed daily, following a bimodal pattern. The same activity pattern was observed for E. bombiformis in December. Males of four species of Eulaema occurred in all remaining months in a unimodal daily activity pattern, with a higher frequency before 9:30 h. The correlation between the visiting activity to odor baits and climatic factors was low. This result can be due to bee flight activity occurring within a range of adequate climatic variation, particularly temperature, which in our study ranged from 23 to 32oC. Daily activity patterns of Euglossina males on odor baits can represent patterns of flower fragrance collection under natural conditions, with visits usually at the time of highest production.

Atividades relacionadas à construção e aprovisionamento de ninhos de Xylocopa subcyanea (Hymenoptera, Apidae) em uma área de restinga na Bahia, Brasil

Bees of the genus Xylocopa Latreille, 1802 are frequent in sandbank ecosystems under accelerated degradation. They nest especially in dead or rotted wood. The nest construction and nest structure of Xylocopa (Schoenherria) subcyanea Perez, 1901 were studied in a sandbank from Bahias north littoral, Brazil. We observed 43 active nests, under different stages of development, in two dead logs. The main activities were excavation of the logs, entering and leaving nest, permanence in the nest entrance, entering with pollen, and nectar dehydration. Preferential times along the day were observed for entering and leaving nest, showing influence of sunrise and sunset times. Abandoned nests were reused by X. subcyanea and Centris tarsata Smith, 1874. Active nests were occupied by four different adult bees. An individual frequently stayed at nest entrance, adopting a defensive behavior. The nest structure was described.

Characterization of the complex metal-clay obtained in the process of lead adsorption

This study aims to characterize the complex metal-clay formed by adsorption of lead. In this work, the bentonite clay named Fluidgel was calcined at 750 oC and was used as adsorbent for lead removal. The characterization of this clay and complex metal-clay was carried out by X-ray diffraction (XRD), Fourier transformer infrared spectroscopy (FTIR), surface area (BET method), scanning electron microscopy (SEM) and chemical composition by energy dispersive X-ray (EDX). The removal of lead from aqueous solution was carried out in a fixed bed. Dynamic experiments were performed to evaluate the effect of flowrate on adsorption efficiency. The experiments were accomplished at room temperature, the clay adsorbent particle diameter was of 0.855 mm and the flow rate varied from 0.6 to 2 mL/min. The feed concentration of lead was about 0.24 mmol/L. Comparing the chemical compositions of the clays obtained by EDX before and after removal of the lead, it was concluded that the ion exchange process might be important to lead removal. From the semi-quantitative analysis of chemical composition in clays with and without adsorbed lead it was observed a reduction of the amount of Ca2+, K+ cations and the disappearance of Na+ cations, which was caused by cation exchange process.

Polinização de Vochysia lucida C. Presl (Vochysiaceae) em uma área de restinga na Bahia

Vochysia species are Neotropical and present flowers that can be visited by bees, hummingbirds, and butterflies. This study aimed to analyze the interactions between the flowers of Vochysia lucida and their floral visitors in an area of restinga in Bahia State, Brazil. V. lucida is an arborescent species and presents inflorescences of the type raceme, with about 100 to 170 flowers. The flowers are zygomorphic, yellow-coloured, and considered mellitophilous. The floral nectar is produced and stored in the spur, which is localized at the calyx. The flowering peak of V. lucida was in November and December. All through the study the flowers opened at 6 h., when the stigma was already receptive. At flower opening the anther was already not more present and the pollen grains were deposited in the wall of the style, occurring secondary presentation of pollen. Petals dropped in the end of the afternoon about 17:00 h. The hummingbirds, although frequent in the flowers of V. lucida, were considered as opportunistic visitors. Among the recorded floral visitors, the large bees were regarded the most efficient pollinators, especially Xylocopa frontalis, because it has suitable morphology and behavior to contact the reproductive structures of the flower, during nectar collections, and for its high visiting frequency.