The gelling and metal-chelating properties of alginate were combined to develop an adsorbent for heavy metal removal. Biopolymer beads
composed of fly ash and sodium alginate proved to be an effective adsorbent for removal of Zn(II) ions from aqueous solutions. The effect
of initial pH (2–10), bead dose (10–80), agitation time (1–24 h), beads composition (0.1g–0.7 g fly ash) and Zn(II) ions initial concentration
(5–30 mg L-1
) on the adsorption process, as well as to what extent the adsorption data obey Langmuir and Freundlich adsorption isotherms
were investigated. The maximum adsorption was found 84.20 % within 8 h and after that reaches equilibrium. The adsorption of Zn(II) ions
is quite sensitive to pH of the suspension and shows an optimum uptake value at pH 6.0. Maximum adsorption occurred for 40 beads and in
case of composition, beads composed of 0.5 g fly ash has shown good results. It is clear from the experimental results that the pH plays an
important role in adsorption of zinc ions. The average size, bulk density and swelling ratio of beads calculated are; 0.12 cm, 0.34 g mL-1
and 28.65 respectively. The synthesized beads were also characterized by FTIR, XRD, SEM, TGA/DTA and other methods.
Key words: biopolymer beads; sodium alginate; adsorption; isotherm models; wastewater
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