Navegando por Assunto "Serra de Maicuru - PA"

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Acesso aberto (Open Access)
Aplicação de Al-PILC na adsorção de Cu2+, Ni2+e Co2+ utilizando modelos físico-químicos de adsorção
(2007) GUERRA, Denis de Jesus Lima; AIROLDI, Claudio; LEMOS, Vanda Porpino; ANGÉLICA, Rômulo Simões; VIANA, Rúbia Ribeiro
Smectite sample from the Serra de Maicuru area (Pará state, northern Brazil, Amazon region) were used for the pillaring process with Al13. Aluminum pillared clay (Al-PILC) was characterized by XRD, SEM and EDS. the textural analysis using nitrogen adsorption-desorption isotherms. The aim of this paper is to study in how Al-PILC adsorb heavy metals. The adsorption of Cu2+, Ni2+, Co2+ ions from aqueous solution in room temperature by Al-PILC have been carried out. The Langmuir, Freundlich and Temkin adsorption isotherm models have been applied to fit the experimental data, with the first model well adjusted with r = 0.999. The one-surface Langmuir equation provided the best fit to the data. The Freundlich equation presented limitations in rises concentrations, but acceptable values of parameters were obtained (Kf and n) with the use of the three models. The parameters were used to calculate the amount adsorbed Nf, a function constant Cs.
Acesso aberto (Open Access)
Evolução mineralógica e geoquímica de lateritos sobre rochas do complexo de Maicurú - Pará
(Universidade Federal do Pará, 1990-08-17) LEMOS, Vanda Porpino; COSTA, Marcondes Lima da; http://lattes.cnpq.br/1639498384851302
The study on the mineralogical and geochemical evolution of the laterites formed from the weathering of the aika-Iine-ultramafic-carbonatite rocks of the Maicuru complex, Pará, were based in the sampling of laterites (about 223 samples), including lateritic profiles (on the apatitite, glimmerite, pyroxenite, biotitite, dunite and syenite) and surface (crust and soils) materials. This study permited to conclude that after dissolution of the carbonates, complete alteration of the pyroxenes and anphiboles in to smectites and micas (biotite and phlogopite) in to vermiculite, and incipient alteration of the fluorapatite, occurred: enrichement of the REE, probabig in the form of carbonate-hidroxi; moderate losses in Si, Ca, Mg, Na, K, Mn, Zn, Y, Sr and P; and retention of Al, Ni, Co, Cu, main-tmined in smectite and vermiculite, Fe, Ti, Nb, represented bg ilmenomagnetite, titanite and perovskite (Ti and Nb), and Zr, lodged in the ilmemomagnetite and titanite structures. In the transitional and phosphatic-clageg hor)zons interface occured the degradation of smectite and vermiculite and dissolution of fluorapatite and perovskite, while titanite and ilmenomagnetíte remain inaltered. In this wag the following products were obtained: Kaolínite, goethite, anatase and aluminous phosphates (wavelite, wardite and crandallite group). Hence, was observed: moderate enrichment in Ti, Nb and Zr, depletion in rare earth elements, especially in the LREE; retention of Al and Fe; and expressive losses in other elements analyzed, relative to the lower levels of the Profiles. In the intermediary levels of the phosphatic-clayey horizon the transformation of the titanite into anatase, took place with retention of Nb and Zr in its structures and the liberation of REE, Ca, Sr and Na, which were in part retained as crandallite group and wardite phosphates. In the phosphatic-clayey and crust horizons interface oxidation of ilmenomagneti-te occurred, with latter evolution into maghemite and anatase. From this level was possible to verify into the lateritic profiles: a great enrichment in Y, REE, (mainly LREE, due to high concentration in crandalite group), Ti, Nb, Fe and Zr, represented by anatase and maghemite; moderate enrichement of Cu, as turquoise, Sr and Zn, acomoded in structure of the crandallite group; Mn contained in the ilmenites and as hgdroxides (which fixed fractions of Co); intense lixiviation of Si, Kr Ca and Mg, moderate lixiviation of Na e Ni; and little lixiviation of P. The chondrite normalized REE patterns for the parent rocks indicated a preferable enrichment in LREE relative to the HREE. This behavior as reflected along the profiles, but stand out mainly in the outcropping crust, samples where there is abundance of crandalite group phosphates. Eventually, the enrichment of HREE in the phosphatic-clayey horizon and in some samples formation of the crust was observed, probably due to churchite. The laterites show favorable economic perspectives for phosphates, titanium and rare earth elements.