Chemical Engineering Journal 157 (2010) 357–365 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej Biosorption of Cu(II), Cd(II) and Pb(II) by Acacia leucocephala bark powder: Kinetics, equilibrium and thermodynamics Venkata Subbaiah Munagapati, Vijaya Yarramuthi, Siva Kumar Nadavala, Subba Reddy Alla, Krishnaiah Abburi ∗ Biopolymers and Thermophysical Laboratories, Department of Chemistry, Sri Venkateswara University, Tirupati 517 502, A.P., India article info Article history: Received 31 July 2009 Received in revised form 7 November 2009 Accepted 10 November 2009 Keywords: Biosorption Acacia leucocephala bark Heavy metals Isotherm Kinetics Thermodynamics abstract The kinetics, equilibrium and thermodynamics of the biosorption of Cu(II), Cd(II) and Pb(II) onto Acacia leucocephala bark powder from aqueous solution were investigated at different experimental conditions. The biosorption characteristics of Cu(II), Cd(II) and Pb(II) ions on the bark powder was investigated with respect to well-established effective parameters including the effect of pH, initial metal ion concentration, biosorbent dosage, contact time and temperature. Optimum adsorption of Cu(II), Cd(II) and Pb(II) took place at pH values of 6.0, 5.0 and 4.0, respectively. Further, the biosorbent was characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The Langmuir and Freundlich equilibrium adsorption models were studied and observed to fit well. The Langmuir model gives a better fit than the Freundlich model. The kinetic studies indicated that the biosorption process of the metal ions followed well pseudo-second-order model. The thermodynamic parameters Gibbs free energy (G ◦ ), enthalpy (H ◦ ), and entropy (S ◦ ) changes were also calculated, and the values indicated that the biosorption process was exothermic and spontaneous. It was concluded that A. leucocephala bark powder can be used as an effective, low cost, and environmentally friendly biosorbent for the removal of Cu(II), Cd(II) and Pb(II) ions from aqueous solution. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Heavy metals can enter a water supply from either industrial activities such as microelectronics, electroplating, battery manu- facture, metallurgical, and fertilizer industries or acid rain breaking down soils and releasing heavy metals into streams, lakes, rivers, and groundwater. Heavy metals are taken into the body via inhala- tion, ingestion, and skin adsorption. Most are extremely harmful to humans, animals and plants mainly because of their accumulation in the body [1–4]. Cadmium is introduced into the water from smelting, metal plating, cadmium–nickel batteries, phosphate fertilizers, mining, pigments, stabilizers, alloy industries and sewage sludge [5]. The harmful effects of Cd(II) include acute and chronic metabolic disorders, such as itai-itai disease, renal damage, emphysema, hypertension and testicular atrophy. Copper is one of the major contaminants emanating from electrical, electroplating, and metal finishing industries. It is often found in high concentrations near mines, landfills and waste disposal sites. In human beings cop- per toxicity causes itching and dermatization, keratinization of ∗ Corresponding author. Tel.: +91 9393621986. E-mail address: abburikrishnaiah@gmail.com (K. Abburi). the hands and soles of feet [6,7]. Severe gastro-intestinal irrita- tion and possible changes in the liver and kidney occur due to intake of excessively large doses of copper [8]. Inhalation of cop- per spray increases the risk of lung cancer among exposed workers [9]. Lead is a particularly hazardous heavy metal because once it gets into human body. It disperses throughout the body immedi- ately and causes harmful effects wherever it lands. For example, it can damage the red blood cells and limit their ability to carry oxy- gen to the organs and tissues. It can also affect the nervous system, kidneys and hearing [10]. In particular unborn babies and young children are at risk of health problems from lead poisoning because their smaller bodies make them more susceptible to absorbing lead ions. Lead compounds are known as metabolic poison and enzyme inhibitor [11]. The most widely used methods for heavy metal removal from wastewaters include chemical precipitation and filtration, electro- chemical treatments, reverse osmosis, ion exchange, evaporation, preconcentration, adsorption and biosorption. Among these meth- ods, biosorption is an emerging and attractive method which involves sorption of dissolved substances by a biomaterial. In addition, the main advantages of this technique can be ordered as follows: the reusability of biomaterial, low operating cost, improved selectivity for specific metals of interest, removal of heavy metals from effluent irrespective of toxicity, short operation 1385-8947/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.cej.2009.11.015