Biosorption of Organic Dyes: Research Opportunities and Challenges - Green Chemistry for Dyes Removal from Wastewater - page 314

Blázquez et al. [117] presented a classification with five isotherm shapes for
biosorption in liquid phase. Figure 8.2 shows these five isotherm shapes.
Several different types of isotherms have been presented in the litera-
ture; the isotherm shape depends on the type of biosorbent, the type of
adsorbate, and intermolecular interactions between the adsorbate and
biosorbent [116]. The biosorption isotherms of agricultural wastes gen-
erally belong to type I (which has a convex shape). This shape is associ-
ated with monomolecular layer biosorption of nonporous or microporous
biosorbents. Types II and III depict multimolecular adsorption layer for-
mation and strong and weak adsorbate-biosorbent interaction on macro-
porous adsorbents, respectively. Type IV describes multimolecular layer
Figure 8.2 Characteristic shapes of the biosorption isotherms (Based on Blázquez
et al. [117]).