Environmental Engineering Reference
In-Depth Information
bicarbonate solution to release the carboxylic groups. MMSCB 2 exhibited an
increase in its adsorption capacity for Cd
2+
(43.6 mg g
-1
) in relation to SCB 2.
Carboxylic groups from MMSCB 1 were modified with triethylenetetramine
through two different synthesis routes, according to the methodology
described by Gurgel and Gil [92]. In the first synthesis route MMSCB 1 was
activated with 1,3-diisopropylcarbodiimide (DIC) and in the second route with
acetic anhydride and afterwards both were modified with triethylenetetramine.
Finally, the obtained samples were called MMSCB 3 and 5. MMSCB 3 and 5
showed a mass gain of 19.9 and 57.1%, respectively. The concentrations of
amine groups in the samples MMSCB 3 was 2.0 and the sample 5 was 2.1
mmol g
-1
. The nitrogen content in the sample MMSCB 3 was 5.8, whilst in the
sample 5, it was 4.4%. The maximum adsorption capacities of MMSCB 3 and
5 for Cd
2+
were found to be 69.4 and 158.7 mg g
-1
, respectively. The
xanthation of sugarcane bagasse was investigated for the separation of
cadmium, lead, nickel, zinc and copper ions from their aqueous solutions by
Homagai
et al.
[95]. The optimum pH for Cd
2+
, Pb
2+
, Ni
2+
, Zn
2+
and Cu
2+
biosorption was found to be 5, 4, 4, 6 and 5, respectively. The sorption kinetics
of the tested metallic ions was fast, reaching the thermodynamics equilibrium
within 20-40 min. The maximum capacity of the Cd
2+
adsorption, evaluated in
terms of the dry gel, was 219.2 mg g
-1
.
Belhalfaoui
et al.
[96] studied the removal of Cd
2+
from aqueous solution
using samples of sodic succinylated cellulose. These samples are particularly
effective in removing cadmium from distilled water and spiked groundwater,
with a maximum uptake of 185.2 and 178.6 mg g
-1
, respectively. Furthermore,
the material proved to be efficiently regenerated by NaCl solution.
Novel biosorbent wheat bran was successfully utilized for the removal of
cadmium from wastewater [97]. The maximum removal capacity of Cd
2+
was
87.2% and it was obtained at the following conditions: pH 8.6, initial
concentration of Cd
2+
of 12.5 mg L
-1
and a temperature of 20 ºC. Results show
that when the temperature increases from 20 to 40 ºC the maximum adsorption
capacity is decreased from 0.7 to 0.6 mg g
-1
.
Low cost wheat bran was also
used as adsorbent for Cd
2+
from aqueous solution by Nouri
et al.
[98]. Based
on the adsorption capacity (15.7 mg g
-1
), the authors concluded that the use of
wheat bran as an adsorbent is much more economical, effective and viable.
Experimental results indicated that the sulphuric acid-treated wheat bran has a
strong affinity for Cd
2+
ions and its adsorption capacity decreases from 101.0
to 62.5 mg g
-1
, when the solution temperature increases from 25 to 70 ºC,
which shows that the adsorption process is exothermic [99].
Search WWH ::
Custom Search