Biomassa residual para remo����o de ��ons uranilo

Activities related to nuclear industry, production of phosphoric acid and hospitals have generated considerable volumes of radioactive waste containing uranyl ions. Banana pith was characterized by Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy and was investigated as a biosorbent for uranyl ions from nitric solutions by batch experiments. Influences of adsorbent size, kinetics and equilibrium adsorption were studied. The biosorption of the uranyl ions followed pseudo-second-order kinetics. The adsorption isotherm data were closely fitted to the Freundlich equation.

Prepara����o de membranas de acetato de celulose organomodificadas para adsor����o dos ��ons Cu(II), Cd(II), Mn(II) e Ni(II)

Cellulose acetate polymeric membranes had been prepared by a procedure of two steps, combining the method of phase inversion and the technique of hydrolysis-deposition. The first step was the preparation of the membrane, and together was organomodified with tetraethylortosilicate and 3-aminopropyltrietoxysilane. Parameters that exert influence in the complexation of the metallic ion, as pH, time of complexation, metal concentration, had been studied in laboratory using tests of metal removal. The membranes had presented resistance mechanics and reactivity to cations, being able to be an alternative for the removal, daily pay-concentration or in the study of the lability of metals complexed.

Remo����o de ��ons Zn2+, Cd2+ e Pb2+ de solu����es aquosas usando comp��sito magn��tico de ze��lita de cinzas de carv��o

For this study, magnetic composite of zeolite-magnetite was prepared by mixing magnetite nanoparticles suspension with synthetic zeolite. The nanoparticles in suspension were synthesized by precipitating iron ions in a NaOH solution. The zeolite was synthesized from coal fly ash by alkaline hydrothermal treatment. The magnetic composite was characterized by XDR, SEM, magnetization measurements, IR, and BET surface area. Batch tests were carried out to investigate the adsorption of metal ions of Zn2+, Cd2+ and Pb2+ from aqueous solution onto magnetic composite. Adsorption isotherms were analyzed using Freundlich and Langmuir equations. The adsorption equilibrium data fitted well to the Langmuir equation with maximum adsorption capacities in the range of 28.5-127 mg g-1.

Aplica����o da casca de arroz na adsor����o dos ��ons Cu2+, Al3+, Ni2+ e Zn2+

The potential use of rice husk as biosorbent to remove Cu2+, Al3+, Ni2+ and Zn2+ ions from aqueous solutions was investigated under both noncompetitive and competitive conditions. The biosorbent was used in the form of particles with size smaller than 0.5 μm and in the concentration of 500 mg L-1 (dry weight). The experiments were performed using batch adsorption technique for concentrations of 10, 30 and 70 mg L-1 of metal ions at pH 4.0 and 5.0. The chemical speciation of metals in the experimental conditions used in this work was predicted by the software Visual MINTEQ 2.6.

Estudos fotoluminescentes em compostos de ��ons terras raras coordenados por um derivado carbaz��lico

[RE(czb)3(H2O)2] complexes (where RE = Eu3+, Tb3+, Gd3+; and czb = 4-(9H-carbazol-9-yl)benzoato) have been synthesized and characterized. The Gd3+ complex was used to determine the triplet state energy of the czb ligand. Photoluminescence measurements of the complexes have been carried out under UV excitation. The Tb3+ complex exhibited a strong green luminescence indicating an efficient antenna effect, whereas the Eu3+ complex showed low red luminescence and the Gd3+ complex a blue-green luminescence from the ligand. The luminescence lifetimes and quantum yields have also been measured for the evaluation of the spectroscopic behavior of the complexes.

Pr��-concentra����o de Cr(III) e an��lise de especia����o de cromo empregando montmorilonita saturada com ��ons pot��ssio

The clay mineral montmorillonite-K10 (MT), treated under acidic medium and saturated with potassium ions (MTK), was employed in sorption and desorption studies aiming the preconcentration of Cr(III) and the speciation analysis of chromium. The sorption process of Cr(III) was close to 100%, suggesting that MTK was a good material for Cr(III) preconcentration, although, the maximum recovery in HNO3 solution was near 89%. On the other hand, Cr(VI) practically was not retained in MTK, suggesting this material as an appropriate mineral phase to be used in speciation analysis of chromium in aqueous medium.

Remo����o de ��ons Pb2+ de solu����o de bateria automotiva por caulinita modificada com ��xido de mangan��s

Nine absorbents were prepared using a mixture of Amazonian kaolinite and MnO2 at three temperatures (600, 700 and 900 ��C) in order to retain Pb2+ ions contained in the battery solutions. The batch experiments carried out with the batteries used water for 3 h and the kinetic isotherm was fitted with the pseudo-second order Lagergren equation. Findings show that synthesized adsorbents AD4, AD5 and AD7 performed well in reducing the Pb2+ ion content from 0.36 to 0.00 mg g-1. The better performance for removing the Pb2+ ions occurred for adsorbents synthesized in the temperature range from 600 to 700 ��C.

Extra����o/pr��-concentra����o de ��ons cobre no ponto nuvem explorando a forma����o de complexos com DMIT [4,5-dimercapto-1,3-ditiol-2-tionato]

The present study proposes a method for cloud point preconcentration of copper ions at pH 2.0 based on complexes formed with [4,5-dimercapto-1,3-dithyol-2-thionate] and subsequent determination by flame atomic absorption spectrometry (FAAS). Under optimal analytical conditions, the method provided limits of detection of 0.84 and 0.45 ��g L-1, by preconcentrating 12.0 and 24.0 mL of sample, respectively. The method was applied for copper determination in water samples, synthetic saliva, guarana powder, tea samples and soft drinks and the accuracy was assessed by analyzing the certified reference materials Dogfish Liver (DOLT-4) and Lobster Hepatopancreas (TORT-2).

Decaimento de ��ons cianato e a forma����o de carbamato de etila

Cyanate ion stability was studied in aqueous/ethanolic solutions, pH = 4.5 (CH3COOH/NaCH3COO), at different temperatures. Following the decay [(OCN)-] versus time, in the presence of excess C2H5OH, the rate constant for this reaction (k1) was calculated as (2.5 �� 0.3) x 10-4 s-1 at 25 ��C, for 0 < [C2H5OH] < 13.7 x 10-1 mol L-1. For [C2H5OH] &gt; 2.0 mol L-1 a decrease in the numerical value of k1 was observed, reaching 5.2 x 10-5 s-1 when [CH3CH2OH] = 13.7 mol L-1. Variations in the kinetic parameter values &#916;H1��, &#916;S1�� and &#916;G1�� for the cyanate ion decay reaction were observed for solutions at different ethanol concentrations.

Pol��meros impressos com ��ons: fundamentos, estrat��gias de preparo e aplica����es em qu��mica anal��tica

Chemical imprinting technology has been widely used as a valuable tool in selective recognition of a given target analyte (molecule or metal ion), yielding a notable advance in the development of new analytical protocols. Since their discovery, molecularly imprinted polymers (MIPs) have been extensively studied with excellent reviews published. However, studies involving ion imprinted polymers (IIPs), in which metal ions are recognized in the presence of closely related inorganic ions, remain scarce. Thus, this review involved a survey of different synthetic approaches for preparing ion imprinted adsorbents and their application for the development of solid phase extraction methods, metal ion sensors (electrodes and optodes) and selective membranes.

Determina����o da demanda qu��mica de oxig��nio em ��guas por espectrofotometria simult��nea dos ��ons cr��mio(III) e dicromato

Prop��e-se metodologia anal��tica para a determina����o da demanda qu��mica de oxig��nio(DQO) em ��guas e efluentes pouco polu��dos, pela espectrofotometria simult��nea dos ��ons cr��mio(III) e dicromato, ap��s a cl��ssica oxida����o sulfocr��mica das amostras, �� quente e catalisada por ��ons Ag+. Demonstra-se que a inter-rela����o entre as concentra����es de DQO, de cr��mio(III) formado e de dicromato residual permite simplificar a resolu����o num��rica do sistema - de multicomponente, envolvendo as concentra����es desses dois ��ons, e medidas de absorb��ncia em pelo menos dois comprimentos de onda para monocomponente, envolvendo diretamente a concentra����o em DQO, e medida de absorb��ncia num ��nico comprimento de onda.

Remo����o de ��ons met��licos de solu����es aquosas, por apatitas sint��ticas, usando o m��todo de troca i��nica em coluna

Foi investigada a remo����o dos ��ons Al3+, Mn2+, Cu2+, Zn2+, Cd2+ and Pb2 +, em solu����o aquosa, por apatitas sint��ticas usando o m��todo de coluna. Sob as mesmas condi����es, hidroxiapatitas foram mais seletivas para a remo����o de c��tions que carboapatitas. Usando hidroxiapatita, a capacidades de troca aumentaram na seguinte ordem: Mn2+ < Zn2+ < Cu2+ < Cd2+ < Al3+ < Pb2+. A seq����ncia acima �� similar a obtida em trabalhos pr��vios, usando o m��todo de batelada. An��lises de DRX e IV indicaram a forma����o de uma fase ��nica atribu��da a uma Pb-apatita.

Influ��ncia dos ��ons K+ e Mg2+ na obten����o de apatitas biomim��ticas

O crescimento da hidroxiapatita - HA, tanto no meio biol��gico quanto em solu����es aquosas como a Synthetic Body Fluid - SBF, ocorre em meio contendo, al��m dos elementos Ca e P, elementos-tra��os essenciais tais como: Mg2+, HCO3-, K+ e Na+. Alguns destes elementos s��o conhecidos como inibidores do crescimento da HA, como Mg2+ e HCO3-. Neste trabalho, estudou-se a influ��ncia dos ��ons K+ e Mg2+ na forma����o de apatitas sobre substratos met��licos de Ti c.p. previamente tratados com NaOH 5M. Os efeitos destes ��ons no recobrimento obtidos, antes e ap��s o tratamento t��rmico a 800��C, foram analisados por microscopia eletr��nica de varredura - MEV, espectroscopia de energia dispersiva de raios-X - EDX, difratometria de raios-X - DRX e espectroscopia no infravermelho - IV e mostraram que o efeito inibit��rio do Mg2+ na forma����o da HA se manifesta ap��s o tratamento t��rmico. Diferentemente, o crescimento cristalino da HA n��o foi afetado pela presen��a do ��on K+. Al��m disso, a forma����o de apatita carbonatada se deu tamb��m em solu����es que n��o continham o ��on CO3(2-) em sua composi����o.

Efeito do ��on malato no processo de oxida����o do ��cido asc��rbico por oxig��nio molecular catalisado por ��ons cobre(II)

Íons cobre(II) catalisam a oxida����o de ��cido asc��rbico por oxig��nio molecular. O mecanismo envolve a coordena����o dos reagentes ao ��on met��lico. Íons malato, quando presentes, tamb��m se coordenam ao cobre(II) e inibem o efeito catal��tico. As constantes cin��ticas espec��ficas (k / mol-1 L min.-1) da rea����o em presen��a de ��ons malato s��o 46,58, 7,11 e 30,00 em valores de pH de 3,5, 4,5 e 5,8, respectivamente. Existe decr��scimo do valor de k com o aumento do pH de 3,5 para 4,5, o que est�� de acordo com a coordena����o mais efetiva do malato ao cobre(II).

Comportamento fotof��sico do antraceno em sistemas micro-heterog��neos argila-surfactantes-��ons met��licos

Argilas constituem uma classe de complexos micro-heterog��neos e podem ser utilizados como substrato para adsor����o. O seu comportamento de sor����o em fase s��lida intensificada pela presen��a de surfactantes, argilas organof��licas, �� um importante fen��meno explorado pela tecnologia ambiental para a remo����o de compostos org��nicos polic��clicos (hidrocarbonetos arom��ticos polic��clicos, HPA) da ��gua, introduzidos no ambiente por fontes antropog��nicas. Este trabalho tem por objetivo estudar o comportamento fotof��sico do antraceno, como modelo de HPA, em sistemas micro-heterog��neos argila-surfactantes-��ons met��licos (M(II)= Cd(II), Cu(II), Hg(II), Ni(II) e Pb(II); surfactantes: CTACl; SDS; TR-X100). Os estudos foram conduzidos pelo monitoramento na mudan��a das propriedades de fluoresc��ncia est��tica e na supress��o da emiss��o do antraceno utilizado como sonda fluorescente. Como supressores foram utilizados os c��tions met��licos: Cd(II), Cu(II), Hg(II), Ni(II) e Pb(II). O perfil do espectro de fluoresc��ncia e os resultados dos ensaios de supress��o da fluoresc��ncia da sonda permitiram inferir na localiza����o do s��tio de solubiliza����o do antraceno nos sistemas micro-heterog��neos estudados e na conseq��ente organiza����o dos mesmos.