A study on adsorption of Pb(II), Cr(Ш) and Cu(II) from aqueous solution by peanut husk

Peanut husk has been used in this work for removing Pb(II), Cr(Ш) and Cu(II) from aqueous solution. Batch adsorption studies were carried out under different pH, initial concentration of metal ions, interfering metal ions, time and temperature. Adsorption was poor in strongly acidic solution but was improved in alkaline medium and continuously increased with rise in pH. The presence of one metal decreased the removal of the other metal ions. The adsorption processes were more akin towards second-order equation. The suitability of the adsorbent was tested by fitting the adsorption data with Langmuir and Freundlich isotherms, which gave good fits with both isotherms. For an adsorbent amount of 2 g/L and initial metal ions 10 mg/L, the maximum monolayer values of Pb(II), Cr(Ш) and Cu(II) was 4.59 mg/g, 3.34 mg/g and 2.96 mg/g. The adsorption was in the order Pb(II) > Cu(II) > Cr(Ш). The values of the thermodynamic parameters, ΔH, ΔS and ΔG, indicated the interactions to be thermodynamically favorable. KEY WORDS: Peanut husk, Heavy metals, Sorption isotherm, Kinetics Bull. Chem. Soc. Ethiop. 2008, 22(1), 19-26.