Adsorption mechanism modeling using lead (Pb) sorption data on modified rice bran-insoluble fiber as universal approach to assess other metals toxicity

The binding capacity of Pb on modified rice bran-insoluble fibers RBIF-0.2, RBIF-1.25, and RBIF-2.0 (0.2%, 1.25%, and 2.0% H 2 SO 4 with 1.25% KOH) having the variable specific surface area and cation-exchange capacity was evaluated. The Pb binding in terms of maximum binding capacity (BC max ) with RBIF increased with pH (2-7). However, the presence of sodium and calcium reduced the binding of Pb to RBIFs. Further, adsorption kinetics followed pseudo-second-order kinetic model when fitted to real Pb sorption data. However, sorption mechanism data (scanning electron microscopy images) were well fitted to Langmuir model instead of Freundlich and Dubinin-Radushkevich that suggests monomolecular adsorption of Pb to RBIF (