RESUMO
ABSTRACT: Iron oxides are environmental indicators and influence on physical and chemical behavior of soils. This research aimed to identify and characterize pedogenic iron oxides in soils of the Acre state, Brazil. The soils developed from sedimentary rocks of the Solimões Formation. Twenty one samples of subsurface horizons were collected from ten soil profiles. Soil samples were analyzed by x-ray diffractometry associated to selective chemical dissolutions. Fe contents in the clay minerals (Fes), in the pedogenic iron oxides (Fed) and in the poorly crystalline oxides (Feo) were determined. The Al3+-substitution and the mean crystal diameter of goethite and hematite were estimated. Soils presented low contents of Fes and Fed. The Fed/Fes ratio indicated soils in the intermediate stage of weathering, with dominance of goethite, hematite and maghemite. This condition of weathering was confirmed by the higher frequency of goethites and hematite with intermediate Al3+-substitution. Goethites have isodimensional forms and hematite have flat plaques forms.
RESUMO: Os óxidos de ferro são indicadores ambientais e influenciam o comportamento físico e químico dos solos. Este trabalho objetivou identificar e caracterizar os óxidos de ferro pedogênicos de solos do estado do Acre, desenvolvidos de rochas sedimentares da Formação Solimões. Vinte e uma amostras de horizontes subsuperficiais de dez perfis de solos foram analisadas por difratometria de raios x associada a dissoluções químicas seletivas. Os teores de Fe total (Fes), dos óxidos de Fe pedogênicos (Fed) e de baixa cristalinidade (Feo) foram determinados; e a Al3+-substituição e o diâmetro médio cristalino da goethita e da hematita foram estimados. Em geral, os solos apresentaram baixos teores de Fes e de Fed. A relação Fed/Fes indicou solos em estágio de intemperização intermediário, com dominância dos óxidos de Fe goethita, hematita e maghemita. Essa condição de intemperismo foi reforçada pela maior frequência de goethitas e hematitas com intermediária Al3+-substituição. As goethitas possuem formas isodimencionais e as hematitas ocorrem como placas achatadas.
RESUMO
The present investigation deals with the utilization of synthetic goethite and two red soils obtained from AHALA-NSAM and NKOLOFANE as adsorbent for the removal of copper from waste water. The synthetic goethite was characterized by IR, XRD and BET where the red soils were characterized by XRD, Chemical Analysis and BET. A series of experiments were conducted in a batch system to evaluate the effect of system variables. The effect of contact time, pH and the initial concentration of copper (II) solution were considered. The results show that the contact time of 180 minutes, 20 minutes and 15 minutes are sufficient to fit the equilibrium for GEO, E1-B1 and NSAM-B2 respectively. The optimal adsorption pH for the adsorption of copper (II) ions is 4.6±1. The maximal quantities adsorbed by every adsorbent were 78 .2 mg/g for GEO, 41.2mg/g for E1-B1 and 32.2mg/g for NSAM-B2. The experimental results obtained have been correlated to four kinetic models including the first order, the second order, Elovich and intra particle diffusion models. The kinetic model that gave the value of the linear correlation coefficient which best fits is that of second order. Three isotherms models amongst which are Langmuir, Freundlich and Tempkin’s have been applied to the experimental data. The Langmuir model best described the adsorption of copper (II) ions in aqueous solution by the three adsorbents.