Lead sorption by waste biomass of hazelnut and almond shell

The potential to remove Pb2+ ion from aqueous solutions using the shells of hazelnut (HNS) (Corylus avellana) and almond (AS) (Prunus dulcis) through biosorption was investigated in batch experiments. The main parameters influencing Pb2+ ion sorption on HNS and AS were: initial metal ion concentration. amount of adsorbent, contact time and pH value of solution. The influences of initial Pb2+ ion concentration (0.1-1.0 mM), pH (2-9), contact time (10-240 min) and adsorbent amount (0.1-1.0 g) have been investigated. Equilibrium isotherms have been measured and modelled. Adsorption of Pb2+ ions was in all cases pH-dependent showing a maximum at equilibrium pH values between 6.0 and 7.0, depending on the biomaterial, that corresponded to equilibrium pH values of 6.0 for HNS and 7.0 for AS. The equilibrium sorption capacities of HNS and AS were 28.18 and 8.08 mg/g for lead, respectively after equilibrium time of 2 h. The adsorption data fit well with the Langmuir isotherm model and the experimental result inferred that adsorption, chelation and ion exchange are major adsorption mechanisms for binding Pb2+ ion to the sorbents. (C) 2009 Elsevier B.V. All rights reserved.