Biosorption for heavy metal removal and recovery from dilute solutions by immobilized nonviable biomass

Zhang, Yue (2005) Biosorption for heavy metal removal and recovery from dilute solutions by immobilized nonviable biomass. University of Southampton, Doctoral Thesis.

Abstract

The biosorption of Cu(II), Pb(II), Zn(II) and Ni(II) was investigated both individually and from mixed metal ion solutions in batch and packed-bed flow-through column experiments using the hydrophilic polyurethane immobilised biomass matrix.

Initial work tested the biosorption stability of immobilised Sphagnum moss in bath experiments.  The polyurethane immobilisation technique helped moss maintain around 90% of its biosorption capacity over 10 repetitive cycles of biosorption/desorption using HC1 as a desorbent with typically more than 95% metal ion recovery from each cycle.  Factors which it was thought might affect the performance of biosorption were also explored, including solution pH, other metal ions, organic materials and biomass particle size.

Further batch experiments using Sphagnum moss look at sequestration of Cu(II), Pb(II), Zn(II) and Ni(II) both individually and from mixed metal ion solutions.  The data were evaluated using the Langmuir isotherm equation, and it was concluded that care must be taken in presentation and interpretation of results when this modelling approach is applied at low concentrations. Repetitive metal loading cycles also gave lower values for biosorption capacity compared to the maximum potential value, due to equilibrium effects.  Biosorption from a multi-component metal system showed that lead and copper competed equally for binding sites and much more effectively than zinc and nickel. Equations ere derived to predict the percentage effect on a given metal ion of other metals in a multi-metal system based on their behaviour in the relevant single and binary systems.

Biosorption column experiments were carried out on multicomponent mixtures of Cu(II), Pb(II), Zn(II) and Ni(II) using immobilised Sphagnum moss, seaweed Ascophyllum nodosum, sunflower waste, and whole plant maize.  Columns with seaweed held 0.68 mmol g^-1 metal, followed by Sphagnum moss (0.30 mmol g^-1) and sunflower waste (0.26 mmol g^-1).  Binding by maize was poor at 0.02 mmol g^-1 metal and it was considered unsuitable as a biosorbent. Titration experiments revealed differences in the number of acidic functional groups on the different types of biomass and a recommendation was made that a simple titration experiment should be the first step for biosorbent screening.

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