Development of a seaweed-based fixed-bed sorption column for the removal of metals in a waste stream

Adil Bakir

    Research output: Types of ThesisDoctoral Thesis

    Abstract

    Fucus vesiculosus, Polysiphonia lanosa, Ulva lactuca and a seaweed waste material resulting from the industrial processing of Ascophyllum nodosum were screened for Zn(II), Ni(II), Al(III) and Sb(III) removal in dried form, in both single and multi-metal systems. The Ascophyllum waste material, which is referred to as Waste Ascophyllum Product (WAP), was also screened in wet form. WAP was shown to be efficient at removing Zn(II), Ni(II) and Al(III) in both single and multi-metal systems. Removal efficiencies (RE) for dried WAP were 93, 96 and 68% for Zn(II), Ni(II) and Al(III) respectively in single metal systems. Polysiphonia lanosa was found to be more effective at removing Sb(III) than WAP with a RE of 86%. In multi-metal systems, Sb(III) was found to adversely affect the sorption of Zn(II), Ni(II) and Al(III) by WAP, while P. lanosa removed Sb(III) in multi-metal systems. The antagonistic effect of Sb(III) on the sorption of the other metals by WAP was investigated using FTIR, XPS and conductimetric titrations. The results demonstrated that Sb(III) was able to bind on a larger and more diversified number of binding sites, preventing the uptake of Zn(II), Ni(II) and Al(III) by both P. lanosa and WAP. Maximum uptake capacity values (q max) were calculated using the Langmuir, Freundlich and the combined Langmuir-Freundlich sorption isotherms. Q max values were very high in the case of WAP for the sorption of Zn(II), Ni(II) and Al(III) at 134.05, 114.94 and 99.7 mg/g biosorbent. The respective q max value for P. lanosa and Sb(III) was lower at 47.44 mg/g biosorbent. Fixed-bed column studies using WAP and P. lanosa immobilised in agar resulted in high removal efficiencies (RE), with 90, 90, 74% for Zn(II), Ni(II) and Al(III) respectively for WAP/agar and 67% for Sb(III) for P. lanosa/agar removal over 3 hours. Agar was found to contribute to the RE. The regeneration and reuse of the biosorbents was achieved using 0.1M HCl with very little loss in metal reuptake efficiency over five sorption cycles. Scale-up of the laboratory column was carried out, with a high RE observed for all metals under investigation. Mathematical and COMSOL modelling were effective tools for representing experimental data and predicting concentration breakthroughs over time.
    Original languageEnglish
    Awarding Institution
    Supervisors/Advisors
    • Fitzgerald, Edmund J., Supervisor
    Publication statusSubmitted - 2010

    Keywords

    • Removal of metals

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