Sorption potential of Moringa oleifera pods for the removal of organic pollutants from aqueous solutions Mubeena Akhtar a,∗ , S. Moosa Hasany b , M.I. Bhanger a , Shahid Iqbal c a National Center of Excellence in Analytical Chemistry, University of Sindh, Jamshoro-76080, Pakistan b Pakistan Institute of Engineering and Applied Sciences, PO Nilore, Islamabad, Pakistan c Department of Chemistry, University of Sargodha, Sargodha-40100, Pakistan Received 14 February 2006; received in revised form 8 July 2006; accepted 11 July 2006 Available online 14 July 2006 Abstract Moringa oleifera pods Lamarck (Drumstick or Horseradish) is a multipurpose medium or small size tree from sub-Himalayan regions of north-west India and indigenous to many parts of Asia, Africa, South America, and in the Pacific and Caribbean Islands. Its pods (MOP) have been employed as an inexpensive and effective sorbent for the removal of organics, i.e., benzene, toluene, ethylbenzene and cumene (BTEC) from aqueous solutions using HPLC method. Effect of different parameters, i.e., sorbent dose 0.05–0.8 g, 25 cm -3 agitation time 5–120 min, pH 1–10, temperature 283–308 K and concentration of sorbate (1.3–13) × 10 -3 , (1.1–11) × 10 -3 , (0.9–9) × 10 -3 , (0.8–8) × 10 -3 mol dm -3 , on the sorption potential of MOP for BTEC have been investigated. The pore area and average pore diameter of the MOP by BET method using nitrogen as a standard are calculated to be 28.06 ± 0.8 m 2 g -1 and 86.2 ± 1.3nm respectively. Freundlich, Langumir and Dubinin–Radushkevich (D-R) sorption isotherms were employed to evaluate the sorption capacity of MOP. Sorption capacities of BTEC onto MOP have been found to be 46 ± 10, 84 ± 9, 101 ± 4, 106 ± 32 mmol g -1 by Freundlich, 8 ± 0.1, 9 ± 0.1, 10 ± 0.3, 9 ± 0.1 mmol g -1 by Langumir and 15 ± 1, 21 ± 1, 23 ± 2, 22 ± 3 mmol g -1 by D–R isotherms respectively, from BTEC solutions at 303K. While the mean energy of sorption process 9.6 ± 0.3, 9.2 ± 0.2, 9.3 ± 0.3, 9.5 ± 0.4 kJ mol -1 for BTEC is calculated by D–R isotherm only. Rate constant of BTEC onto MOP 0.033 ± 0.003, 0.030 ± 0.002, 0.029 ± 0.002, 0.027 ± 0.002 min -1 at solution concentration of 1.3 × 10 -3 , 1.1 × 10 -3 , 0.9 × 10 -3 and 0.8 × 10 -3 mol dm -3 and at 303 K have been calculated by employing Lagergren equation. Thermodynamic parameters H -8 ± 0.4, -10 ± 0.6, -11 ± 0.7, -11 ± 0.7 kJ mol -1 , S -22 ± 2, -26 ± 2, -27 ± 2, -29 ± 3 J mol -1 K -1 and G 303 K -0.9 ± 0.2, -1.9 ± 0.2, -2.3 ± 0.1 and -2.6 ± 0.2 kJ mol -1 were also estimated for BTEC respectively at temperatures 283–308 K. The negative values of H, S and G suggest exothermic, stable (with no structural changes at solid–liquid interface) and spontaneous nature of sorption process under optimized conditions. MOP has been used extensively to accrue and then to preconcentrate benzene, toluene and ethylbenzene in wastewater sample. © 2006 Elsevier B.V. All rights reserved. Keywords: Moringa oleifera (drumstick) pods; Sorption; Benzene; Toluene; Ethylbenzene; Cumene 1. Introduction Since last two decades, contamination of groundwater with organic pollutants has become great environmental concern. Var- ious kinds of pollutants have been detected in the environment. Among these, volatile organic compounds (VOCs), e.g., ben- zene, toluene, ethylbenzene, xylene and cumene are important ∗ Corresponding author. Tel.: +92 300 3073027/92 321 6011304; fax: +92 22 2771560. E-mail addresses: profmarao@yahoo.com (M. Akhtar), ranashahid313@gmail.com (S. Iqbal). environmental contaminants because of their high toxicity and widespread occurrence [1,2]. BTEC components are present in aviation fuel (gasoline) and are widely used as industrial solvents and raw materials for the production of different commodities [3]. These may lead to serious safety concerns, when someone comes across these organics [4]. As they are important items of many industries, therefore, it is not practically feasible to elimi- nate these from the environment; however, it is required to keep their concentrations in water as low as possible. Therefore, it is essential to monitor the environment to ensure that their levels may not increase beyond the tolerance levels [4], otherwise they may adversely affect the well being of animal and human life and cause certain physiological disorders and diseases [5]. Among 0304-3894/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2006.07.016