Removal of Cu2+ and Cd2+ from aqueous solution by Bentonite clay modified with binary mixture of Goethite and Humic Acid.
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Date
2010
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Publisher
Springer
Abstract
Pre-modification of bentonite clay with
goethite, humic acid, and a binary mixture of goethite
and humic acid reagents increased its cation exchange
capacity from 95 to 105.32, 120.4, and 125.8 meq/
100 g of bentonite clay, respectively. The effective
pre-modification of bentonite clay with goethite,
humic acid, and goethite–humic acid reagents was
confirmed from their Fourier transform infrared
spectra which suggested that modification was effective on the AlAlOH and Si–O sites for goethite and
humic acid modification and AlAlOH for goethite–
humic acid modification. The presence of 0.001 M
NaNO3 electrolyte increased the adsorption capacity
of bentonite clay. Temperature was observed to favor
the adsorption of Cu2+ and Cd2+ onto both the raw
and modified bentonite clay samples. The goethite–
humic acid-modified bentonite gave the best adsorption capacity of ≈10 and 16 mg/g at 30 and 50°C,
respectively, for both metal ions. The inner sphere
complexation mechanism was suggested for the
adsorption of both metal ions onto the modified
adsorbents. Modifying bentonite clay with a binary
mixture of goethite and humic acid reduced the
selectivity of bentonite clay for either Cu2+ or Cd2+.
Preadsorbed goethite and humic acid on bentonite
clay will further reduce the mobility of heavy metal
ions in soils and in aquatic environments