2.4. Influence of particle size in the removal efficiencyIn order to determinate the influence of the particle size in theremoval efficiency, two different particle sizes (1 and 2 mm) wereused for banana cortex in experiments for the removal of lead insolution without reload. In order to perform these experiments,the methodology described in Section 2.3 was used except forthe reloading of the solution eluted. The result of this assessmentwas used to decide the best conditions to be applied in other metalsassays.2.5. Analytical testsMetal concentration measurements during the experimentalassessments were performed by atomic absorption using a standardcalibration curve including 1.5, 2.5, 5 and 10 mg/L of everymetal. Those concentrations were selected in agreement the Mexicanlegislation (NOM-001-ECOL-1996), establishing the maximumpermissible limit in waste water discharges and onto nationalgoods (<0.025 mg/L; Cd < 0.005 mg/L and Cu < 2 mg/L). The conditionsfor the measurement for Pb were: lamp 5 mA; wavelength324.8 nm; air flow 13.5 L/min; flame air/acetylene; acetylene flow2 L/min. For Cd, similar condition was used except for the wavelengthfixed, for this case, at 228.8 nm and, in the case of Cu, a4.5 mA lamp was used at 324.8 nm. Biosorption capacity for everymaterial was calculated byq ¼VðCi Cf Þm ð1Þwhere Ci is the initial metal concentration in solution (mg/L); Cf isthe final metal concentration (mg/L); V is the total volume used in
every load plus reload (L) and m is the mass of the biosorbent (g).
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