Authors
Abstract
In present communication we report on Cd(II) adsorption using our recently reported material, the guar gum-silica nanocomposite. The equilibrium, thermodynamics and kinetics of Cd(II) adsorption onto composite from aqueous solution were investigated. Optimum experimental parameters were determined to be pH 8, contact time 2 hours, Cd(II) concentration 100 mg/L, temperature 30 o C and adsorbent dose 10 mg. The sorption equilibrium data were modeled using the Langmuir and Freundlich isotherms where the data fitted better to Langmuir model indicating unilayer sorption, the Qmax being 666 mg/g. The kinetic data indicated chemisorption in the rate-controlling step as the pseudo-second-order model was best suited (rate constant of 2.79 × 10-4 gmg -1 min -1 at 100 mg/L Cd 2+ ). The calculated thermodynamic parameters (ΔG°, ΔS°, ΔH°) showed the adsorption to be exothermic and spontaneous with decreased randomness at the solid–solution interface. The adsorbent could be recycled for six successive cycles with 31% loss in its efficiency.
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