Lead and cadmium removal from water using duckweed - Lemna gibba L.: Impact of pH and initial metal load

The aim of this study was to investigate the potential of duckweed (Lemna gibba) in heavy metal (Pb and Cd) from water under different pH and metal loads. A total of three (2, 5 and 10 mg/L) strengths of Pb and Cd were used with varying pH (5, 7 and 9) and changes in metal concentration and metal uptake yield of system were recorded. The Pb and Cd removal ranged between 60.1% (2 mg/L at 9 pH) and 98.1% (10 mg/L at 7 pH) and 41.6% (10 mg/L at pH 9) and 84.8% (2 mg/L at pH 7), respectively. The duckweed set-up with pH 7 showed the optimum metal removal. The metal removal rate showed an inverse relationship with pH (r2 > 0.60, for all). Bioconcentration factor (BCF) and metal uptake yield per unit of dry biomass (qm) were recorded: 403-738 and 445-616, respectively for BCFPb and BCFCd. The qm suggest the dose (mg/L) 5 and 10 at pH 5 as the best combinations for the optimum removal. Results, thus suggest that L. gibba can be a suitable candidate for removal of heavy metals from pollutant water bodies.