BIOSORPTION OF Pb2+, Cd2+, & Ni2+ FROM WATERS BY ...

Sorption (%)
100.0
80.0
60.0
40.0
20.0
0.0
10.0 20.0 50.0
100.0
biosorbent amount (mg)
200.0
Pb
Cd
Ni
Figure 3.17. Effect of biosorbent amount on biosorption of Pb 2+ , Cd 2+ , and Ni 2+ by
Scenedesmus protuberans (10.0 mL solution of 250.0 mg/L, solution pH
of 6.0, sorption time of 60 min, and different amounts of biomass)
3.3. Desorption Studies for Oocystis sp. and Scenedesmus protuberans
For the evaluation of the efficiency and feasibility of a metal removal procees,
the regeneration and reusability of the biosorbent should be considered. In addition to
this, the recovery of the metals which has either an economical importance or a vital
role in the environment should be emphasized. Hence, the desorption of metal ions
bound on the biosorbent is applied to re-solubilise biosorbent-bound metals by suitable
eluant or desorbing solution. Therefore, biosorbent can be utilized in multiple sorption –
desorption cycles. A common example method for the desorption of heavy metal from
the biomass is the treatment of biomass after sorption cycle in acidic pH. Increasing the
acidity of the metal-loaded biosorbent suspension leads to separation of metal cations
from biosorbent by protons from the binding sites (Mehta and Gaur 2005).
Notwithstanding, at extremely low pH values, the biomass can be damaged. On the
other hand, organic and mineral acids, bases, salts, and metal chelators have been
studied for their ability on the desorption of metals (Kuyucak and Volesky 1989, Hu
and Reeves 1997, Esteves and Valdman 2000). Hence, as the different eluents should be
screened for their ability for both maximum recovery of metal ions and the protection of
biomass after sorption-desorption cycle (Mehta and Gaur 2005).
Ni
Cd
Pb
48