Heavy Metals Uptake by Dried Caulerpa lentillifera - The Joint ...

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The 2 nd Joint International Conference on “Sustainable Energy and Environment (SEE 2006)” E-043 (P) 21-23 November 2006, Bangkok, Thailand V ( Ci − C f ) q = (1) m where q is amount of metal uptake per unit mass of biomass (mol kg -1 ), C i is initial concentration of heavy metal (mol m -3 ), C f is final concentration of heavy metal (mol m -3 ), V is volume of the solution (m 3 ), m is dry mass of the algae (kg). 3. RESULTS AND DISCUSSION 3.1 Effect of initial metal concentration on biosorption Initial metal concentration was found to have significant effect on the biosorption capacities of caulerpa lentillifera. Figs 1 and 2 illustrate the variation in the sorption capacity (q) as a function of initial heavy metal concentrations between 0.1 and 10 mM where it was found that a higher initial concentration provided a higher sorption capacity. This was because the initial metal ion concentration provides an important driving force to overcome all mass transfer resistances of Cu 2+ and Pb 2+ between the aqueous and solid phases [6]. This is the fundamental of the equilibrium between the sorption capacity and the final heavy metal concentration in the liquid phase, and this equilibrium is a very important factor that limits the sorption process. q (mmol g -1 ) 0.16 0.14 0.12 0.1 0.08 0.06 Cu 0.1 mM Cu 0.2 mM Cu 0.3 mM Cu 0.8 mM Cu 1 mM Cu 3 mM Cu 5 mM Cu 10 mM 0.04 0.02 0 0 10 20 30 40 50 60 70 time (min) Fig. 1 Effect of initial Cu 2+ ions concentration on biosorption by caulerpa lentillifera (pH 5, agitation speed: 150 rpm, temperature 20 o C adsorbent dose 0.5 g) q (mmol g -1 ) 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Pb 0.1 mM Pb 0.2 mM Pb 0.3 mM Pb 0.8 mM Pb 1.0 mM Pb 3.0 mM Pb 5.0 mM Pb 10 mM 0 10 20 30 40 50 60 70 time (min) Fig. 2 Effect of initial Pb 2+ ions concentration on biosorption by caulerpa lentillifera (pH 5, agitation speed: 150 rpm, temperature 20 o C adsorbent dose 0.5 g) 3.2 Effect of adsorbent dose on biosorption The effects of adsorbent concentration on the removal of heavy metal ions from aqueous were investigated using three different adsorbent concentrations. The extent of biosorption is proportional of specific area which is defined as the portion of the area available for biosorption to the total area on the sorbent [6]. Adsorbent concentration was varied from 0.1 to 1g/30 mL of synthetic 2
The 2 nd Joint International Conference on “Sustainable Energy and Environment (SEE 2006)” E-043 (P) 21-23 November 2006, Bangkok, Thailand waste water. The effect of biomass on the sorption kinetics of heavy metal ion was studied at pH of 5.0 and 0.1 mM initial Cu 2+ and Pb 2+ concentrations. The results for the adsorption of Cu 2+ and Pb 2+ are presented in Figs. 3 and 4, respectively, which indicated that the equilibrium concentrations for both metals decreased with increasing biomass doses for a given initial Cu 2+ and Pb 2+ concentration. This result was anticipated because increasing adsorbent doses provided a greater surface area which could accommodate a higher quantity of heavy metals, and due to the equilibrium limitation, the quantity of metals being adsorbed for a certain unit surface area of adsorbent decreased [7,8]. 0.008 0.007 0.006 q (mmol g -1 ) 0.005 0.004 0.003 0.002 0.001 0 0.1 g/30 ml of synthetic solution 0.25 g/30 ml of synthetic solution 0.5 g/30 ml of synthetic solution 1.0 g/30 ml of synthetic solution 0 10 20 30 40 50 60 70 time (min) Fig. 3 Effect of adsorbent dose on Cu 2+ biosorption by caulerpa lentillifera (pH 5, agitation speed: 150 rpm, temperature 20 o C initial Cu 2+ concentration 0.1 mM) 0.018 0.016 q (mmol g -1 ) 0.014 0.012 0.01 0.008 0.006 0.1g/30 ml of synthetic solution 0.25g/30 ml of synthetic solution 0.5g/30 ml of synthetic solution 1.0g/30 ml of synthetic solution 0.004 0.002 0 0 10 20 30 40 50 60 70 time (min) Fig. 4 Effect of adsorbent dose on Pb 2+ biosorption by caulerpa lentillifera (pH 5, agitation speed: 150 rpm, temperature 20 o C initial Pb 2+ concentration 0.1 mM) 3.3 Adsorption kinetic The kinetics of Cu 2+ , Cd 2+ and Pb 2+ biosorption on the algal biomass were determined with two different kinetics models [9,10]. The first model is the pseudo-first-order rate Lagergren model, expressed as: dqt 1 e t / dt = k ( q − q ) (2) where k 1 is the rate constant of first-order biosorption (min -1 ) and q e and q t denote the amounts of the biosorption at equilibrium and at time t (mg/g), respectively. Integration by applying the boundary condition q=0 at t=0 and q t =q t at t=t, gives: 3
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Heavy Metals Uptake by Dried Caulerpa lentillifera - The Joint ...

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