Lead(II) Adsorption onto Sulphuric Acid Treated Cashew Nut Shell

In this study, sulphuric acid treated cashew nut shell (STCNS) was used as adsorbent for the removal of lead(II) ions from the aqueous solutions. Adsorption studies were performed by varying the solution pH, contact time, and temperature. Experimental data were analyzed by the model equations such as Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherms and it was found that the Freundlich isotherm model fits best with the experimental data at different temperatures studied. The maximum adsorption capacity of lead(II) on STCNS was determined as 408.6, 432, 446.3, and 480.5 mg/g, respectively, at different temperatures (30, 40, 50, and 60 degrees C). The thermodynamic parameters (Delta G degrees, Delta H degrees, and Delta S degrees) were calculated and the thermodynamic properties of lead(II) ions-STCNS system indicate the exothermic process. Adsorption kinetic constants were determined using pseudo-first-order, pseudo-second-order, and the Elovich kinetic models at various temperatures. The adsorption results clearly showed that the adsorption of lead(II) ions onto STCNS followed pseudo-second-order model and the adsorption was both by film diffusion and by intraparticle diffusion. A single-stage batch adsorber was designed using the Freundlich equation.