.
2.2. Cellulose-derivate material
The different cortexes were
cleaned avoiding any pulp and carpellar membrane, then the different
materials were dried in an oven at 40 C during six days.
Once dried, cortexes were milled using a mortar and screened to
obtain two different particle sizes (1 and 2 mm). The resulting
powders were treated for alkalinization with 0.5 N NaOH during
20 min according Navarro et al. (2006). Then passed through gauze
and rinsed with distilled water four times to eliminate the excess
of NaOH. Finally, the powders were dried again at 40 C. In order
to estimate the effect of alkalinization procedure, control materials
were also produced in the same way except the treatment with
NaOH. Once dried, all the biosorbent powders were kept on a dryer
until its use.
2.3. Biosorption process
In this process, 1.5 g of powder were weighed to fill different
100 mm high, 10 mm i.d. glass columns. Then 25 ml of the heavy
metal solution were added keeping the column close until complete
matrix humidification. After that, the column was open to allow
water flow and pressure was applied on the top of the column
using a syringe. From the elution, a sample (1.0 ml) was obtained,
labeled and stored for analysis and the rest was reloaded into the
column to test the amount of metal adsorbed after more than
one elution, all the experiments were done by triplicate.