A Review on the Adsorption Isotherms and Design Calculations for the Optimization of Adsorbent Mass and Contact Time

Adsorption is a widely
used chemical engineering unit operation
for the separation and purification of fluid streams. Typical uses
of adsorption include the removal of targeted pollutants like antibiotics,
dyes, heavy metals, and other small to large molecules from aqueous
solutions or wastewater. To date several adsorbents that vary in terms
of their physicochemical properties and costs have been tested for
their efficacy to remove these pollutants from wastewater. Irrespective
of the type of adsorbent, nature of the pollutant, or experimental
conditions, the overall cost of adsorption depends directly on the
adsorption contact time and the cost of the adsorbent materials. Thus,
it is essential to minimize the amount of adsorbent and the contact
time required. We carefully reviewed the attempts made by several
researchers to minimize these two parameters using theoretical adsorption
kinetics and isotherms. We also clearly explained the theoretical
methods and the calculation procedures involved during the optimization
of the adsorbent mass and the contact time. To complement the theoretical
calculation procedures, we also made a detailed review on the theoretical
adsorption isotherms that are commonly used to model experimental
equilibrium data that can be used to optimize the adsorbent mass.