Kinetic study of a single and binary biosorption of cadmium and lead onto the dead acquatic plant Lemna Gibba

Biosorption of heavy metals by a dead aquatic plant

Abstract

Cadmium and lead are recognized as toxic heavy metals even at low concentrations. Thus, their removal is required. The present paper deals with the use of a natural low-cost and environmentally friendly material as a bioadsorbent obtained from a dead  aquatic plant (Lemna gibba). The biosorption of Cd and Pb individually or in combination was studies under different experimental conditions such as time effect (0-240 min), concentration of metal ion (0.1 and 1 mg/L), adsorbent dose (0.10, 0.25 and 0.50 g) to examine the operational factors impact on heavy metals removal effectiveness. The dead biomass was characterized by FTIR to provide information about the functional groups responsible of biosorption. Inductively coupled plasma atomic emission spectroscopy was employed to perform quantitative measurement of Cd and Pb (ICP-OES). For the kinetic investigation, pseudo-first order and pseudo-second order, models were used.

The experimental results demonstrated that lead and cadmium adsorption onto Lemna gibba powder occurred quickly, with equilibrium being reached in 120 minutes and 30 minutes, respectively. At 0.1, the greatest removal efficiencies were 84.01%  of  Pb and 93%  of Cd  . At  1 mg/L, 73.82%,  and  88% of  Pb and Cd  were removed respectively. After 180 minutes, both metals were effectively eliminated (90%) from the binary system that was contaminated with 0.1 mg/L of each metal. At 1 mg/L for each element, Pb was removed 86% after 90 minutes, and Cd clearance was less (54%).