[Effect of competitive interference on the biosorption of lead (II) by Hydrilla verticallata]

Using submerged aquatic plant is a cheap and clean technique to remediate heavy metals in wastewaters. Batch experiments were conducted to assess the biosorption characteristics of Pb (II) ions by fresh tissues of Hydrilla verticallata. The biosorption of Pb(II) was examined for single, binary and ternary solutions at different initial concentrations and different pH values. The experimental results showed that the biosorption capacity increased with increasing pH from 2.0 to 6.0. The biosorption value reached 44.65 mg/g when initial lead concentration was 250 mg/L and pH = 5. Both Cu (II) and Zn(II) ions were found to have an adverse effect on the biosorption of Pb(II) for binary and ternary solutions. In Pb-Cu binary metal solution, when both initial concentrations of lead and copper ions were 250 mg/L, the biosorption capacity for lead ions was decreased to 49.29% of that in single lead ion solution. The biosorption equilibrium data for the Pb-Cu binary metal solution fitted the Langmuir competitive model well (R2 = 0.966). The theoretical q(max) value (58.02 mg/g) was in excellent consistent with that obtained experimentally, and the average relative error between calculated q(e) and experimental q(e) values was only 15.6%. Comparison between biosorption of Pb (II) and Cu (II) by H. verticallata in the binary solution could lead to the conclusion that H. verticallata has no preference of Pb(II) over Cu(II).