عنوان مقاله [English]
The main objective of the present study was to investigate Cd(II) adsorption by immobilized silica nanopowder within calcium alginate and to determine the isotherm, kinetics, and thermodynamics of the adsorption process. Batch flow mode reactors were used to investigate the effects of initial pH, contact time and metal ion concentration on Cd(II) adsorption. The optimal contact time and initial pH for Cd(II) adsorption were found to be 120 min and 4.0, respectively. Increasing Cd(II) ion concentration from 10 to 1000 mg/L led to increasing adsorbed Cd(II) ions from 5.71 to 100.65 mg/g. The results showed that the Langmuir isotherm model was the best model to describe the experimental data (R2=0.997). The maximum adsorption capacity (qm) for Cd(II) adsorption onto the adsorbent was estimated to be 72.99 mg/g. Based on the mean free energy of adsorption (E) obtained from Dubinin-Radushkevich (D–R) isotherm model, Cd(II) adsorption onto immobilized silica nanopowder follows a chemical mechanism (E=8.451 kJ/mol). The kinetic study indicated that the pseudo-second order model was a more suitable model than the pseudo-first order one for describing Cd(II) adsorption (R2=0.999). Additionally, the negative ∆Hº and ΔGº values demonstrated an exothermic and spontaneous Cd(II) adsorption onto immobilized silica nanopowder.
10. Mata, Y.N., Blázquez, M.L., Ballester, A., González, F., and Muñoz, J.A. (2009). “Biosorption of cadmium, lead and copper with calcium alginate xerogels and immobilized Fucus vesiculosus.” J. of Hazardous Materials, 163, 555-562.
11. Lipski, A.M., Pino, C.J., Haselton, F.R., Chen, I.W., and Shastri, V.P. (2008). “The effect of silica nanoparticle-modified surfaces on cell morphology, cytoskeletal organization and function.” J. of Biomaterials, 29, 3836-3846.
12. Akar, T., Kaynak, Z., Ulusoy, S., Yuvaci, D., Ozsari, G., and Akar, S.T. (2009). “Enhanced biosorption of nickel(II) ions by silica-gel-immobilized waste biomass: Biosorption characteristics in batch and dynamic flow mode.” J. of Hazardous Materials, 163, 1134-1141.
13. Nadavala, S.K., Swayampakula, K., Boddu, V.M., and Abburi, K. (2009). “Biosorption of phenol and
o-chlorophenol from aqueous solutions on to chitosan-calcium alginate blended beads.” J. of Hazardous Materials, 162, 482-489.
14. Najafi, M., Yousefi, Y., and Rafati, A.A. (2012). “Synthesis, characterization and adsorption studies of several heavy metal ions on Amino-Functionalized Silica Nano Hollow Sphere and Silica Gel.” J. of Separation and Purification Technology, 85, 193-205.
15. Ozay, O., Ekici, S., Baran, Y., Aktas, N., and Sahiner, N. (2009). “Removal of toxic metal ions with magnetic hydrogels.” J. of Water Research, 43, 4403-4411.
16. Hua, M., Zhang, S., Pan, B., Zhang, W., Lv, L., and Zhang, Q. (2012) “Heavy metal removal from water/wastewater by nanosized metal oxides: A review.” J. of Hazardous Materials, 211/212, 317-331.
17. Sari, A., and Tuzen, M. (2008). “Biosorption of total chromium from aqueous solution by red algae (Ceramium virgatum): Equilibrium, kinetic and thermodynamic studies.” J. of Hazardous Materials, 160, 349-355.
18. Rahmani, A., Zavvar, Mousavi, H., and Fazli, M. (2010). “Effect of nanostructure alumina on adsorption of heavy metals.” J. of Desalination, 253, 94-100.