Lead (II) and cadmium (II) biosorption on Spirodela polyrhiza (L.) Schleiden biomass

Spirodela polyrhiza biomass was studied as an adsorbent for Pb (II) and Cd (II) removal from aqueous solution. Batch adsorption experiments were carried out to describe the effects of pH, adsorbent dosage, contact time, initial metal concentration and temperature on the metal removal process. The maximum adsorption capacity of Pb (II) and Cd (II) onto S. polyrhiza biomass was found to be 137 and 36.0 mg g−1, respectively at optimum pH of 4.0 and 6.0, contact time of 120 min, and temperature at 20 °C. The Freundlich and Langmuir isotherm models were used to explain the equilibrium data. The Langmuir model best described the data with correlation coefficients (R2) of 0.999 and 0.995 for Pb (II) and Cd (II) adsorption. Kinetic studies revealed that the adsorption process followed pseudo second order model. The calculated thermodynamic parameters showed that the adsorption of Pb (II) and Cd (II) onto the biomass of S. polyrhiza was feasible, spontaneous and exothermic in nature.