Surface chemistry evaluation of some solid wastes from olive-oil industry used for lead removal from aqueous solutions

In this paper three different olive oil wastes used for heavy metal removal from aqueous solutions: olive stone (OS), the two-phase olive mill solid (OMS) and olive tree pruning (OTP) were compared about chemical characterization and lead biosorption capacities. A detailed description of the surface acidity/basicity of all the samples was studied by continuous potentiometric titrations. The acid-base properties of the solids were well described by simplified chemical equilibrium models, in terms of discrete sites and continuous distributions. That study evidenced that carboxylic group is the main active site present in these olive oil wastes and constitutes the highest percentage of titratable sites (greater than 50%). The Langmuir isotherm model was used to characterize the interaction of Pb(II) ions with the olive oil wastes and a realistic uptake mechanism which can be used to assess and predict the binding (adsorption) capacity of the materials studied was formulated. (C) 2008 Elsevier B.V. All rights reserved.