10 Summary
Selection of materials and process for the removal of pollutants from environment
starts with the selection and processing of the biosorbent used. Even though living
microorganisms can be used, dead biomass is usually preferred to be used as
biosorbents. Modification of biosorbents for better adsorption is not possible in
living organisms. The biomass used for biosorption should have appropriate pore
size, surface area, charge and appropriate functional groups on the surface to readily
adsorb the pollutant passed through them. These properties can be incorporated into
the biomass by various pre-treatment processes.
Pre-treatment process used should make the biosorbent more available to the
adsorbate. The pre-treatment process should not complicate the recovery and regeneration process. Pre-treatment process should be determined according to the mechanism of biosorption involved and the type of material adsorbed. Some biosorbents
does not require pre-treatment for removal of some materials. Treatment process
includes drying and grinding, alkali or acid treatment, detergent treatment, carbonization process, boiling and pyrolysis. Grinding to a specific size makes the surface
area of the material appropriate for the biosorption process. Alkali, acid, detergents
and other chemical treatments will enhance the availability of the functional groups
on the surface of the biosorbent for the adsorption process. Boiling helps in the
separation of fibres from plant parts. Pyrolysis makes the biomass into biochar.
Carbonization process removes moisture content and increases carbon content in the
biosorbent used.
Visual characterization of the biosorbent can be done by scanning electron
microscopy. FT-IR can be used to analyse the functional groups and to analyse the
mechanism of the biosorption. X-ray photon spectroscopy, EDAX and ICP-AES/
ICP-OES can be used to estimate the elemental composition of the adsorbent. The
metals that are adsorbed onto the surface can also be estimated by above mentioned
methods. Nitrogen adsorption/desorption studies are used to determine the pore size
and surface area by BET, DFT and BHJ methods.
Mechanism of biosorption also plays a major role in the selection of material for
biosorption. In whole cells used as biosorbents, the biosorption may be intracellular
or extracellular. In case of physical and chemical attraction of the metals to the cell
surface, dead cells can be used as biosorbents. Extracellular polymeric substances
produced by microorganisms have a large diversity of functional groups that can
adsorb various heavy metals and removes them by precipitation or complexation.
The organisms that are capable of sequestrating metals by precipitation and complexation can be used alive. Intracellular biosorption requires active metabolism and
thus requires a live cell. Live cells thus used may take the pollutant as nutrient or
might require separate nutrition provided in the feed.
Biosorption can be carried in either batch mode or continuous mode. Batch mode
is suitable for all types of biosorption process. Advantage of the batch biosorption
process is that the biosorbent along with the pollutant adsorbed on the surface can be
removed easily from the feed. Continuous mode can be used for live cells which can
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K. J. Samuel P N et al.
Selection of materials and process for the removal of pollutants from environment
starts with the selection and processing of the biosorbent used. Even though living
microorganisms can be used, dead biomass is usually preferred to be used as
biosorbents. Modification of biosorbents for better adsorption is not possible in
living organisms. The biomass used for biosorption should have appropriate pore
size, surface area, charge and appropriate functional groups on the surface to readily
adsorb the pollutant passed through them. These properties can be incorporated into
the biomass by various pre-treatment processes.
Pre-treatment process used should make the biosorbent more available to the
adsorbate. The pre-treatment process should not complicate the recovery and regeneration process. Pre-treatment process should be determined according to the mechanism of biosorption involved and the type of material adsorbed. Some biosorbents
does not require pre-treatment for removal of some materials. Treatment process
includes drying and grinding, alkali or acid treatment, detergent treatment, carbonization process, boiling and pyrolysis. Grinding to a specific size makes the surface
area of the material appropriate for the biosorption process. Alkali, acid, detergents
and other chemical treatments will enhance the availability of the functional groups
on the surface of the biosorbent for the adsorption process. Boiling helps in the
separation of fibres from plant parts. Pyrolysis makes the biomass into biochar.
Carbonization process removes moisture content and increases carbon content in the
biosorbent used.
Visual characterization of the biosorbent can be done by scanning electron
microscopy. FT-IR can be used to analyse the functional groups and to analyse the
mechanism of the biosorption. X-ray photon spectroscopy, EDAX and ICP-AES/
ICP-OES can be used to estimate the elemental composition of the adsorbent. The
metals that are adsorbed onto the surface can also be estimated by above mentioned
methods. Nitrogen adsorption/desorption studies are used to determine the pore size
and surface area by BET, DFT and BHJ methods.
Mechanism of biosorption also plays a major role in the selection of material for
biosorption. In whole cells used as biosorbents, the biosorption may be intracellular
or extracellular. In case of physical and chemical attraction of the metals to the cell
surface, dead cells can be used as biosorbents. Extracellular polymeric substances
produced by microorganisms have a large diversity of functional groups that can
adsorb various heavy metals and removes them by precipitation or complexation.
The organisms that are capable of sequestrating metals by precipitation and complexation can be used alive. Intracellular biosorption requires active metabolism and
thus requires a live cell. Live cells thus used may take the pollutant as nutrient or
might require separate nutrition provided in the feed.
Biosorption can be carried in either batch mode or continuous mode. Batch mode
is suitable for all types of biosorption process. Advantage of the batch biosorption
process is that the biosorbent along with the pollutant adsorbed on the surface can be
removed easily from the feed. Continuous mode can be used for live cells which can
256
K. J. Samuel P N et al.