Effect of pH, Temperature, and Lead Concentration on the Bioremoval of Lead from Water Using Lemna Minor

Abstract

This study examined the ability of the aquatic plant Lemna minor (duckweed) to remove soluble lead under various laboratory conditions. In a batch process L. minor was exposed to different pH values (4.5–8.0) and temperature (15–35°C) in presence of different lead concentrations (0.1–10.0 mg L−1) for 168 h. The amount of biomass obtained in the study period on a dry weight basis, the concentrations of lead in tissue and in medium and net uptake of lead by Lemna all have been determined in each condition. The percentages of lead uptake ratios (PMU) and bioconcentration factors (BCF) were also calculated for these conditions. Bioaccumulated lead concentrations and the PMU were obtained at lowest pH of 4.5, and at 30°C. The highest accumulated lead concentration was found at pH 4.5 as 3.599 mg Pb g−1 in 10.0 mg L−1. It decreased to pH 6.0, but it did not change at pH 6.0–8.0 range. The maximum lead accumulation was obtained at 30°C as 8.622 mg Pb g−1 in 10 mg L−1 at pH 5.0, and the minimum was at 15°C as 0.291 mg g−1 in 0.1 mg L−1. Lead accumulation gradually increased with increasing lead in medium, but the opposite trend was observed for PMU. Lead accumulation increased up to 50 mg L−1, but did not change significantly in the 50.0–100.0 mg L−1 range. The lead uptake from water was modeled and the equation fit the experimental data very well.