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A bentonite from the Northeast Brazilian region was modified with lanthanum (NT-25La) using an ion exchange process. Lanthanum incorporation in the natural clay, as well as the properties of the clay materials, were confirmed by X-ray diffraction, X-ray fluorescence, specific surface area and scanning electron microscopy (SEM/EDX). Phosphate adsorption equilibrium and kinetic tests were performed at different temperatures. The adsorption data have shown that NT-25La reaches equilibrium between modified clay and phosphate solution within 60 min of contact. The phosphate retention at room temperature reached 95%, when initial phosphate concentration in solution was 5 mg L(-1). A kinetic-order variable model provided satisfactory fitting of the kinetic data. Adsorption of phosphate was best described by a Langmuir isotherm, with maximum phosphate sorption capacity of 14.0 mg g(-1). Two distinct adsorption mechanisms were observed that may influence the adsorption processes. The investigation pointed out that the phosphate adsorption occurs via physisorption processes and that the use of NT-25La provides a maximum phosphate sorption capacity higher than many commercial adsorbents., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Industrial effluents discharged in water bodies without proper treatment contribute to water pollution by potentially toxic metal ions. Considering that the legislation for discarding of such effluents is getting more and more rigorous, the development of efficient processes for the treatment of industrial effluents is of great interest. A study on the capacity of metal retention by silylated-modified clays was carried out with the aim to evaluate the efficiency of this application. K10 clay was modified with 3-mercaptopropyltrimethoxysilane (MPS) and tested in batch removal processes. We investigated the sorption process, obtaining isotherms and kinetics of adsorption and the influence of pH, the desorption process and the metal recovery. It was observed that the modified clay presents fast retention and good capacity of both adsorption and desorption. The use of K10/MPS as adsorbent shows to be more adequate in effluent final polishment, after a conventional treatment, or when Ni(II) initial concentration in the effluent is low enough to permit its adequate removal by conventional methods.