TITLE:
Continuous-Flow Removal of Arsenic in Drinking Water by Filtering down through Fe3O4@SiO2 Magnetic Composite
AUTHORS:
Virginia Montero-Campos, Allen Puente-Urbina
KEYWORDS:
Magnetite, Drinking Water, Arsenic, Nanotoxicology
JOURNAL NAME:
Journal of Water Resource and Protection,
Vol.8 No.5,
May
27,
2016
ABSTRACT: Natural contamination of world groundwater supplies with arsenic of
volcanic origin has become a complicated and growing problem given current
shortage of water. Maintenance cost of treatments that are based on ion
exchange and reverse osmosis is considered high, in addition to the high
production of sludge with such methods. On the other hand, efficiency of
treatments employing coagulation/filtration is usually relative, depending on
the method of application. Currently, emerging treatments that use nanotechnology
are gaining relevance, due to their high efficiency and low cost. These methods
are highly selective, with minimum generation of toxic wastes, as long as
particle release into the environment is kept under control to avoid health
risks. The present study developed filters with magnetic nanoparticles of Fe3O4 (magnetite) supported on porous silica (Fe3O4@SiO2)
at a mass ratio of 2:1. The nanoparticles were synthetized by co-precipitation of Fe(II) and Fe(III) using NH4OH(ac) under inert
atmosphere. Average sizes of 15 nm were obtained, measured by means of
Transmission Electronic Microscopy (TEM) and characterized by X-ray Powder
Diffraction (XRD); the magnetic power was qualitatively determined. The
efficiency of the composite material (Fe3O4@SiO2)
was determined in a prototype laboratory with a height of 60 cm and a diameter
of 5 cm, assembled with five filters of the composite material, with 1 g each
filter. The filters were wrapped in resistant water-porous fabric to favor
continuous flow at a ratio of 0.015 L/min. The test was performed with arsenic
solutions at (43.7 ± 2.1 μg/L), similar to the amount present in water supplies
currently treated in Costa Rica. The removal was completed in 7 minutes with 0
N.T.U and less than 10 μg/L arsenic concentration (maximum limit allowed in
Costa Rica), quantified by Atomic Absorption Spectrometry with Hydride
Generation. After the reaction filters, the prototype was assembled with
cleaning filters at a ratio of 1:8. The final way out was through a magnetized
tube to ensure that no nanoparticles were released outside with the water, thus
contributing to nanotoxicology safety for people and the environment.