CHROME VI REMOVAL FROM SYNTHETIC WATER LEVEL LABORATORY, USING LAYERED DOUBLE HYDROXIDES (HDL)

Abstract

Four types of double layered hydroxides (HDL) were synthesized with Al / Mg molar ratio
of 4:1, using analytical and technical grade reagents. Batch essays were conducted in which
it was determined that the adsorption capacity of chromium VI is proportional to the initial
concentration, to the four adsorbents (α = 0,05; F> F critical). It was also determined that it
is viable the use of lower cost technical grade reagents for the synthesis, since the adsorbents
have similar level of efficiency, both with sintetic water (distilled water with competing ions:
80 ppm HCO3
-, 100 ppm Cl-, 120 ppm SO4= and different concentrations of Cr VI) and
industrial water. In batch equilibrium tests with synthetic water it was established a 54% of
adsorption; with industrial water about 19% was obtained, both at 120 minutes. The isotherm
model that fits the adsorption behavior is Freundlich which indicates a multilayer adsorption.
Adsorption kinetics is consistent with the pseudo-first order model, which is a physical
adsorption and ion exchange. In a fixed bed column with synthetic water 70% removal of chromium VI was achieved. When industrial water was treated the removal reached to
98.4% and thus the values remained below the permissible limit for discharge to drain. The
using of HDL in a fixed bed column at pH 2,8 significantly decreases chromium VI from
the effluent in chrome industry appliances. Is recommended the Use of HDL to treat highly
polluted effluents and to transfer them to a solid matrix, easily manageable for environmental
managers.