Biosorption of heavy metals (Cu, Zn, Cd and Pb) by marine algae biomass

Ching, Mei Lan (2010) Biosorption of heavy metals (Cu, Zn, Cd and Pb) by marine algae biomass. Masters thesis, University Malaysia Sabah.


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The use of biological materials or biomass as adsorbent for the removal of heavy metals from aqueous solutions or wastewater is increasingly getting attention. In the present studies, biosorption of heavy metals (i.e Cu, Zn, Cd and Pb) by non living biomass of marine algae, Sargassum sp., was investigated according to batch and column techniques. The experimental variables include contact time, initial metal concentration, biosorbent dosage, metal type, pH, solution composition, biosorbent pre-treatment, flow rate and bed height. The residual concentration of the metals in solution was determined by flame atomic absorption spectroscopy (FAAS). The results showed that the adsorption of all the metals by the biosorbent was rapid and approached maximum within 30 min contact time but attained equilibrium after 120 min. The adsorption obeyed pseudo-2nd order kinetics (R²-1.0) with the rate constant, K₂ following the order Pb > Cu - Zn > Cd. The amount of each metal adsorbed increased proportionally from approximately 980 μg/g to 4900 μg/g while percentage removal was fairly constant (- 98 %) with increase in initial metal concentration from 10 μg/mL to 50 μg/mL. The equilibrium adsorption data fitted better to Freundlich isotherm (R² = 0.97 - 0.99) compared with Langmuir isotherm (R² = 0.74 - 0.88). The calculated maximum monolayer adsorption, q max of the biomass vary according to the type of metal: Cd (16.67 mg/g) > Pb (14.29 mg/g) > Cu = Zn (12.50 mg/g). Percent adsorption increased slightly (i.e 2.32 % - 15.9 %) with increase in the biosorbent dosage from 0.1 to 1.0 g. The adsorption of all the metals increased with increase in pH from pH 2.0 to 4.0, with no further significant increase beyond pH 4.0. Metal removal efficiency was lower in mixed metal solutions compared to single metal solutions. The presence of other metal ions in solution resulted in the reduction of the adsorption of a particular metal in the order Zn > Cu > Cd > Pb, and this was more apparent at high initial metal concentrations. Acid pre-treatment of the biomass resulted in the reduction (14.5 % - 48.8 %) in its efficiency to adsorb the metals. Meanwhile, the results of the column experiments showed that the efficiency of Cu, Zn, Cd and Pb removal decreased with the increase in flow rate but increased with the increase in bed height. Overall, non-living biomass of the locally available marine algae, Sargassum sp., have promising potential as biosorbent for the heavy metals Cu, Zn, Cd and Pb

Item Type: Thesis (Masters)
Uncontrolled Keywords: biomass, biosorbent, heavy metal, aqueous solution, adsorption, marine algae
Subjects: Q Science > QR Microbiology
Divisions: SCHOOL > School of Science and Technology
Date Deposited: 19 May 2014 01:58
Last Modified: 26 Oct 2017 02:23

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