Fe (ii) adsorption on Ucides Cordatus crab shells

Abstract

Recebido em 13/5/10; aceito em 12/1/11; publicado na web em 29/3/11In this study Ucides cordatus crab shells were utilized as Fe (II) sorbent as material of low cost and simple preparation. Values of pH of standard solution, biosorbent mass, particles size, contact time (t c ) and initial concentration of the standard solution were optimized. The best conditions were pH = 2.00, t c = 840 min and M c = 0.25 g. The kinetic pseudo first-order model displayed the best description of the adsorption process and the equilibrium study showed that the Langmuir model better describes the adsorption of the Fe (II). There is great affinity between the Fe (II) and the biosorbent.

Assessment of Cadmium and Lead Adsorption in Organic and Conventional Coffee

“…Azouaou et al 6 concluded that the Langmuir's isotherm model was in agreement with the experimental data obtained in the cadmium adsorption experiment on untreated coffee grounds. Porpino et al 12 also concluded that the iron adsorption by crab shell followed the model proposed by Langmuir. This variation depends on the analyzed material, because the adsorption process is linked to the adsorbent's free sites, where links with the metal occur, influencing both whether the process occurs in mono or multilayers.…”

“…For the calculations, the same formulas employed by Porpino and Barreto 12 were used. The lead and cadmium adsorbed amount per adsorbate gram, Qe, was calculated using Eq.…”

“…The best definition of the kinetic model is by determining the highest correlation coefficient (R 2 ), and the proximity of the calculated and experimental Qe value. 12 The pseudo-first and -second order models' linear forms are shown in Figs. 2B and 2C.…”

“…The KF value allowed identifying the adsorbent ability to retain the metal. 12 Therefore, the cadmium adsorbing ability in conventional coffee was greater than that in organic coffee (97.03, in conventional coffee, against 0.02, in organic one). The n value indicated the heterogeneity of the adsorption sites, 18 thus the process in organic coffee, which had the largest value of n (1.0934), occurred with greater diversity, making it less favorable compared to conventional.…”

Biossorção de cobre utilizando-se o mesocarpo e o endocarpo da macadâmia natural e quimicamente tratados

“…C eq q eq = 1 q m b + C eq q m em que: b -constante que indica a intensidade da biossorção q m -capacidade que indica a quantidade máxima adsorvida log q eq = log K f + 1 n log C eq em que: K f -constante de Freundlich, que está relacionada com a capacidade de biossorção n -constante que indica a intensidade de biossorção Se os valores de n estiverem na faixa 1 < n < 10, indicam uma biossorção favorável (Porpino et al, 2011).…”