-Heavy metal removal by adsorption using rice husks as a bioadsorbent was evaluated as an alternative for wastewater treatment. Batch equilibrium experiments and kinetic sorption studies were performed using monocomponent solutions of Ni(II), Cd(II), Zn(II), Pb(II) and Cu(II) in surface samples of in natura (RH) and calcined rice husks (RHA). RHA showed higher potential for removing lead and copper. Experimental data for adsorption isotherms of lead and copper were adjusted by Langmuir, Freundlich and Dubinin-Radushkevick (D-R) models, being better represented by the Langmuir model. The calcination of RH increased its surface area, improving its adsorption properties. From a morphological analysis obtained by SEM and diffraction patterns (XRD), a longitudinal fibrous and amorphous structure was observed for RH. TGA results indicated a total mass loss of around 60% for RH and 24.5% for RHA.
-This study evaluated the kinetic adsorption of Pb and Cu ions using rice husk ash as adsorbent in a fixed bed. The maximum adsorption capacities obtained for lead and copper ions in the fixed bed were 0.0561 and 0.0682 mmol/g (at 20 °C), respectively. The thermodynamic studies indicated that the lead adsorption process was exothermic and spontaneous, while the copper adsorption process was endothermic and spontaneous. Characterization results indicated the presence of several functional groups, amorphous silica and a fibrous and longitudinal structure of rice husks. Rice husk ash (RHA) from northern Brazil can be used as a bioadsorbent for the individual removal of Pb(II) and Cu(II) ions from metal-containing effluents.
O Brasil é um dos maiores produtores e consumidores de pimentas do mundo, com destaque para a região Amazônica, cujo consumo de pimentas faz parte do hábito alimentar. Nesse sentido, objetivou-se com este trabalho realizar a caracterização morfoagronômica e físico-química de seis acessos de pimentas largamente comercializadas em feiras livres do estado de Roraima. Dessa forma, os frutos foram avaliados quanto ao comprimento, diâmetro, cor, teor de sólidos solúveis totais (SST), pH, acidez total titulável (ATT), bem como caracterização de ácidos graxos majoritários. Os resultados demonstraram que tanto as características morfoagronômicas quanto as físico-químicas apresentaram diferenças significativas pelo teste de Tukey a 5% de probabilidade. Para as análises físico-químicas, observou-se que os frutos do acesso CA apresentaram maior razão SST/ATT, indicando que esse acesso possui maior potencial para o consumo in natura. No teor de sólidos solúveis totais, os acessos diferiram estatisticamente, entretanto, os frutos do acesso OP apresentaram maior desempenho, sendo, portanto, indicados para processos de industrialização. Por fim, esse trabalho confirma a presença de substâncias bioativas nos frutos das pimentas que podem auxiliar na queima calórica e, consequentemente, no controle de massa corporal. No entanto, mais dados seriam necessários para a quantificação dessas substâncias.
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