Ambrósio Florêncio de Almeida Neto

Removal of Cadmium(II) and Lead(II) ions from aqueous phase on sodic bentonite

before and after chemical modification and thermal activation was characterized by different techniques including X-ray diffraction, thermal analysis, Fourier transform infrared, surface area, helium pycnometry, cation exchange capacity and scanning electron microscopy. Pseudo-first order, pseudo-second order and intra-particle diffusion models were used to analyze the kinetic curves. Equilibrium data were analyzed using Langmuir and Freundlich models. The thermodynamic study indicated that lead adsorption process is endothermic and interactions between clays and solutions of lead occurred spontaneously, while cadmium adsorption revealed an exothermic and spontaneous nature. The maximum removal efficiencies were 97.62% for Cd(II) using

Equilibrium and Thermodynamic Studies of Zinc Adsorption on Expanded Vermiculite

Because of industrial growth, large amounts of effluents are generated, which need to be treated. Among the micropollutants usually present in industrial effluents, heavy metals are especially dangerous to aquatic environment because they are bioaccumulated along the food chain. This work aims to study the removal of zinc ions in aqueous solution by adsorbing them onto expanded vermiculite. In addition, equilibrium and thermodynamics studies were carried out to verify the spontaneity and the characteristics of the process. Langmuir, Freundlich and Dubinin–Radushkevichs models were applied to the data obtained from isotherms at temperatures of 273, 293, 313 and 333 K. Furthermore, experiments in static system were carried out to choose a suitable eluent to this process, to find the metal concentration and identify a method for effective recovery of the adsorbent. This adsorption process was found to be spontaneous, favourable, endothermic and physical. The best eluting agent was ethylenediaminetetraacetic acid (0.1 M); however, for cycle adsorption experiments the best agent was CaCl2 (0.1 M).

Modification of Sodium Bentonitic Clay Used in Zinc Ion Adsorption

In this study, it was evaluated the potential use of commercial sodium bentonitic clay, called Fluidgel, chemically and thermally treated, as an adsorbent in the removal of zinc ions from aqueous effluents. The chemical treatment was carried out with 10 g of clay dispersed in 100 mL of acetic acid 4 %. The heat treatment was obtained by calcination at 750 °C for 24 hours in muffle. The adsorption experiments were performed in thermostatic bath system and fixed bed, both based on preliminary study of metallic cationic speciation. The kinetics of zinc ions adsorption by acid-treated clay was rapid, requiring a minimum time of 60 min to reach equilibrium. The adsorbed amount and percentage of total zinc removal, at equilibrium time, was 0.06 mmol/g and 45 %, respectively, using the acid-treated clay. There was no removal of zinc by Fluidgel calcined clay in bath system, but in fixed bed it was obtained the total amount of zinc removal of 0.11 mmol/g and 41 % of percentage of removal.

ESTUDO DO COMPORTAMENTO DA EFICIÊNCIA DE DEPOSIÇÃO DA LIGA CO-W UTILIZANDO PLANEJAMENTO EXPERIMENTAL.

RESUMO Uma das formas que mais contribui para o desgaste dos metais e sem duvida a corrosao. O controle e estudo para minimizar os efeitos causados por esse processo sao essenciais. A eletrodeposicao e um dos metodos mais importantes de deposicao metalica para a producao comercial de peliculas protetoras. O desenvolvimento de banhos estaveis com adequados niveis de pH, temperatura, concentracao de reagentes e densidade de corrente sao de fundamental importância para obter depositos de boa qualidade e resistente a corrosao. Este trabalho estudou o efeito da concentracao de sulfato de cobalto, temperatura do banho e densidade de corrente para obtencao de deposito da liga Co-W. Para o estudo proposto, dentro da faixa de variaveis utilizadas, a maior porcentagem de deposicao encontrada foi de 86,61%, utilizando concentracao de sulfato de cobalto 0,3 mol/L, temperatura de 25°C e densidade de corrente igual a 10 mA/cm 2 . As ligas obtidas apresentaram boa aderencia e brilho metalico.

OBTENÇÃO E CARACTERIZAÇÃO DE LIGAS DE FE-W DESTINADAS À PROTEÇÃO ANTICORROSIVA

Neste trabalho foram sintetizadas, por eletrodeposicao, ligas de tungstenio usando o ferro como metal indutor. Os ensaios de eletrodeposicao foram realizados segundo um planejamento experimental 2 com 3 pontos centrais, de modo que foi analisada a influencia da densidade de corrente eletrica, concentracao do ferro no banho eletrolitico e temperatura sobre a eficiencia de eletrodeposicao. As melhores ligas obtidas foram caracterizadas utilizando microscopia eletronica de varredura (MEV), difracao de Raios X (DRX) e espectroscopia de absorcao de infravermelho (FTIR). A maior eficiencia de deposicao obtida foi de aproximadamente 50% e as ligas caracterizadas apresentaram alto grau de pureza e baixa cristalinidade, sendo predominantemente amorfas.

ADSORÇÃO DE PRATA E COBRE POR ARGILA BENTONÍTICA: CARACTERIZAÇÃO DO ADSORVENTE PRÉ E PÓS PROCESSO

A remocao e recuperacao de metais toxicos de efluentes aquosos tem gerado grande interesse para pesquisas cientificas. Nesse contexto, o processo de adsorcao se mostra bastante promissor, possibilitando atingir niveis aceitaveis dessas substâncias nos meios aquosos, gerando, assim, a necessidade de estudar o potencial de novos adsorventes. Nesse trabalho, foi avaliada a argila bentonitica para remocao de ions de prata e cobre em mistura binaria. A argila foi caracterizada antes e apos a adsorcao, para verificar a ocorrencia de possiveis modificacoes no solido, causadas pela presenca dos ions metalicos. Dentre as analises empregadas estao a difracao de Raio-X (DRX), a microscopia eletronica de varredura (MEV), a fisissorcao de N2 para obtencao da area superficial pelo metodo de BET (BET), analises termogravimetricas e termodiferenciais (TG/DTG e DTA), espectroscopia na regiao do infravermelho por Transformada de Fourier (FT-IR), e picnometria a gas Helio. Os resultados obtidos demonstraram que nao ocorrem grandes alteracoes nas propriedades estruturais da particula, mesmo apos o processo de adsorcao.