Abstract
Composites based on nanosized particles of magnetite and natural microsized zeolite were prepared and their efficiency to adsorb arsenate from aqueous systems was evaluated through kinetic data and adsorption isotherms, considering the proportion of magnetic iron oxide, composite:solution ratio and zeolite particle size. A well-crystallized nanomagnetite with an averaged particle size of 50 nm when supported on zeolite was obtained; the nanomagnetite enhances the arsenate adsorption of zeolite. The composite prepared with a nanomagnetite:zeolite mass ratio of 0.43:1 and 0.30:1 presented on zeolite milled 20 and 120 min, respectively, showed a similar adsorption capacity as that observed for pure magnetite. Supported nanomagnetite prevents risks of the nanoparticles contamination. The smaller the mean particle size of zeolite the lower the mass proportion of nanomagnetite in the composite required to reach the maximum adsorptive efficiency. Acidic conditions improve arsenate remotion, in agreement with the development of positive surface charge in the composite.
Highlights
The geological characteristics and mining activities may often impart critical natural and anthropogenic contamination of ground and underground waters
The starting materials, the synthetic magnetite and the natural silicate are relatively affordable, making the composite attractive to be used in industrial scale
From the technological point of view, the use of composites formed with the magnetic iron oxide allows the adsorbent to be magnetically removed from the water medium
Summary
The geological characteristics and mining activities may often impart critical natural and anthropogenic contamination of ground and underground waters. The increasing level of arsenic on the Earth surface has been leading to serious environmental problems, but these are the cause of great concerns about their direct effects on individuals, either those living in remote small communities or in densely populated urban areas of big cities.[1,2] In northern Chile, especially in the Antofagasta region (located approximately from 21o28’ to 25o40’ S), the occurrence of arsenic in ground and underground fresh waters is steadily increasing, as a consequence of the intensive mining activities. Arsenic contents in water of that region are commonly two to four times higher[3,4] than that upper limit (0.01 mg L-1) established
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