Takuma TSURITANI
Metal adsorption from aqueous solution by Ca-Alginate-Bentonite beads
Kazunori SATO, Teoh Wah TZU
Excessive heavy metal ions in waste water must be removed because they are highly toxic. Calcium Alginate is good canditate biosorbent because it is untoxic and has high adsorption capability. However, calcium alginate has a problem of limited adsorption capability caused by decrease of intraparticle diffusion due to low porosity after drying process.
In this study, Bentonite which has swelling property and cation exchange capacity was added into calcium alginate beads to improve the intraparticle diffusion of cations and increase heavy metal adsorption capability. The aim of this study is to investigate capability and mechanism of Ni(¶), Cd(¶) and Pb(¶) adsorption onto Ca-Alginate-Bentonite beads (1.5A-4B) by isotherm study (Langmuir isotherm) and kinetics study.
From the result of Langmuir isotherm, adding Bentonite increased saturation adsorption amount(Ni(¶):3.4 mmolˇ¦m-2, Cd(¶):4.2 mmolˇ¦m-2, Pb(¶):5.8 mmolˇ¦m-2 ) and improved capacity for heavy metal ions adsorption of alginate. Furthermore, from kinetics study, pseudo-second order kinetics rate was increased. In addition, the morphology of 1.5A-4B beads after adsorption experiment by SEM showed that pores were identified on the beads surface contributed by the addition of Bentonite. It is believed that these pores improved intraparticle diffusion of heavy metal ions in alginate beads.
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