Modeling of biosorption of Pb(II) and Zn(II) ions onto PaMRH: Langmuir, Freundlich, Temkin, Dubinin-Raduskevich, Jovanovic, Flory-Huggins, Fowler-Guggenheim and Kiselev comparative isotherm studies

Biosorption of Pb2+ and Zn2+ onto Phosphoric Acid Modified Rice Husk (PAMRH) was carried out. The equilibrium adsorption data of Pb2+ and Zn2+ for initial concentration ranging from 10 – 200 mg g-1 were fitted into Langmuir, Freundlich, Temkin, Dubinin-Raduskevich, Jovanovic, Flory-Huggins, FowlerGuggenheim and Kiselev isotherm models. The comparative isotherm studies however, unraveled the adsorption capacities of PAMRH and a great affinity of the adsorbent (PAMRH) for Pb2+ than Zn2+. The studies showed that the adsorption Modeling of Biosorption of Pb(Ii) and Zn(Ii) Ions onto Pamrh: Langmuir, Freundlich, Temkin, Dubinin-Raduskevich, Jovanovic, Flory-Huggins, Fowler-Guggenheim and Kiselev Comparative Isotherm Studies http://www.iaeme.com/IJMET/index.asp 1049 editor@iaeme.com capacities obtained from isotherm models for Pb2+ are relatively higher than that of Zn2+. Comparatively, based on the correlation coefficients (R2) obtained from both Pb2+ and Zn2+ linear plots, the equilibrium data fitted to the isotherm models in the following order: Langmuir > Kiselev > DKR > Temkin > Freundlich > Jovanovic > Flory-Huggins > Fowler-Guggenheim. A maximum monolayer adsorption capacity of 138.89 mg g-1 was obtained from Langmuir adsorption isotherm for Pb2+ and 121.95 mgg-1 for Zn2+. Biosorption isotherm modeling shows that the uptake of these divalent heavy metals ions (Pb2+ than Zn2+) onto PAMRH took place at specific localized sites on the surface and the saturation coverage corresponds to complete occupancy of these sites. The mean adsorption free energy, E per molecule evaluated from DKR model was less than 8 kJmol-1 indicating a physisorption mechanism and electrostatic attraction. This study revealed vividly that PAMRH is a better and promising eco-friendly low cost adsorbent for both Pb2+ and Zn2+ Keywords: Biosorption, Isotherm modeling, Heavy metals, PAMRH.