title: Adsorptive removal of heavy metals from aqueous solution by treated sawdust (Acacia arabica).
abstract: The removal of Cr(VI), Pb(II), Hg(II) and Cu(II), by treated sawdust has been found to be concentration, pH, contact time, adsorbent dose and temperature dependent. The adsorption parameters were determined using both Langmuir and Freundlich isotherm models. Adsorption capacity for treated sawdust, i.e. Cr(VI) (111.61 mg/g), Pb(II) (52.38 mg/g), Hg(II) (20.62 mg/g), and Cu(II) (5.64 mg/g), respectively. Surface complexation and ion exchange are the major removal mechanisms involved. The adsorption isotherm studies clearly indicated that the adsorptive behaviour of metal ions on treated sawdust satisfies not only the Langmuir assumptions but also the Freundlich assumptions. The applicability of Lagergren kinetic model has also been investigated. The adsorption follows first-order kinetics. Thermodynamic constant (k(ad)), standard free energy (DeltaG degrees ), enthalpy (DeltaH degrees ) and entropy (DeltaS degrees ) were calculated for predicting the nature of adsorption. The percentage adsorption increases with pH to attain a maximum at pH 6 and thereafter it decreases with further increase in pH. The results indicate the potential application of this method for effluent treatment in industries and also provide strong evidence to support the adsorption mechanism proposed.
authors.affiliation: Centre for Fire, Explosive & Environment Safety (CFEES), Defence R & D Organisation (DRDO), Brig. S.K. Mazumdar Road, Timarpur, Delhi 110054, India.
authors.forename: Ajay Kumar
authors.initials: AK
authors.lastname: Meena
authors.forename: K
authors.initials: K
authors.lastname: Kadirvelu
authors.forename: G K
authors.initials: GK
authors.lastname: Mishra
authors.forename: Chitra
authors.initials: C
authors.lastname: Rajagopal
authors.forename: P N
authors.initials: PN
authors.lastname: Nagar
mesh_terms: D000045:Acacia; D000327:Adsorption; D006863:Hydrogen-Ion Concentration; D019216:Metals, Heavy / Q000737:chemistry*; D012972:Sodium Hydroxide / Q000737:chemistry; D012996:Solutions; D013464:Sulfuric Acids / Q000737:chemistry; D013696:Temperature; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*; D014934:Wood / Q000737:chemistry*
chemical_list: D019216:Metals, Heavy; D012996:Solutions; D013464:Sulfuric Acids; D014874:Water Pollutants, Chemical; D012972:Sodium Hydroxide; C033158:sulfuric acid