6.1 Batch Mode
The batch mode adsorption is carried out by putting the adsorbent in the solution and
allowing it to adsorb for a specified period of time. Shift in the adsorption equilibrium due to the influence of various parameters such as temperature, pH, concentration of the adsorbate and adsorbent and time can be studied in batch mode.
Agitated batch adsorption is recommended for efficient adsorption processes as it
makes the biosorbent available throughout the reactor vessel. Small flasks can be
agitated by placing them in a rotary shaker incubator or by using impellors or
turbines.
6.2 Continuous Mode
Continuous mode of biosorption is carried out in columns packed with biosorbents.
The raw or processed biosorbents are packed tightly inside a glass column, and the
adsorbate is passed continuously through the column. The effluent concentration is
monitored, and breakthrough curve is plotted to evaluate the effectiveness of the
biosorption process. Mode of operation of column may be either top to bottom or
bottom-up process. Flow rate of the adsorbate is maintained throughout the process.
The column may be a fixed bed [31] column in which the adsorbent is tightly
packed or a fluidized bed column in which the adsorbent is loosely packed or
immobilized in beads. When fluidized bed column is used, adsorbate is sent in
through the bottom and collected at the top.
7 Factors Influencing Biosorption
In the treatment of waste water containing ions of minerals, there are various factors
that influence the equilibrium of the biosorption process.
7.1 Temperature
Effect of temperature on biosorption is inconsistent with different authors. Some
reported increase in the rate of adsorption with increase in temperature [34], while
some reported decrease in rate of adsorption with increase in temperature [29]. From
most of the works, temperature is not known to affect the biosorption equilibrium
[43–46].
Material and Process Selection for Biosorption
251
The batch mode adsorption is carried out by putting the adsorbent in the solution and
allowing it to adsorb for a specified period of time. Shift in the adsorption equilibrium due to the influence of various parameters such as temperature, pH, concentration of the adsorbate and adsorbent and time can be studied in batch mode.
Agitated batch adsorption is recommended for efficient adsorption processes as it
makes the biosorbent available throughout the reactor vessel. Small flasks can be
agitated by placing them in a rotary shaker incubator or by using impellors or
turbines.
6.2 Continuous Mode
Continuous mode of biosorption is carried out in columns packed with biosorbents.
The raw or processed biosorbents are packed tightly inside a glass column, and the
adsorbate is passed continuously through the column. The effluent concentration is
monitored, and breakthrough curve is plotted to evaluate the effectiveness of the
biosorption process. Mode of operation of column may be either top to bottom or
bottom-up process. Flow rate of the adsorbate is maintained throughout the process.
The column may be a fixed bed [31] column in which the adsorbent is tightly
packed or a fluidized bed column in which the adsorbent is loosely packed or
immobilized in beads. When fluidized bed column is used, adsorbate is sent in
through the bottom and collected at the top.
7 Factors Influencing Biosorption
In the treatment of waste water containing ions of minerals, there are various factors
that influence the equilibrium of the biosorption process.
7.1 Temperature
Effect of temperature on biosorption is inconsistent with different authors. Some
reported increase in the rate of adsorption with increase in temperature [34], while
some reported decrease in rate of adsorption with increase in temperature [29]. From
most of the works, temperature is not known to affect the biosorption equilibrium
[43–46].
Material and Process Selection for Biosorption
251