Sequestration of Pb(II) and Ni(II) ions from aqueous solution using microalga Rhizoclonium hookeri: adsorption thermodynamics, kinetics, and equilibrium studies

Abstract

In the present study, the microalga Rhizoclonium hookeri (RH) was effectively applied to remove the metal ions [Pb(II) and Ni(II)] from aqueous solution in batch adsorption mode experiments. The adsorption process was influenced by several operating parameters such as initial metal ion concentration, contact time, pH, particle size, adsorbent dose, and temperature. The maximum monolayer adsorption capacity of the RH was found to be 81.7 mg g−1 and 65.81 mg g−1 for Pb(II) and Ni(II) ions, respectively, at optimum conditions. The calculated thermodynamic parameters illustrated that the adsorption process was found to be spontaneous and endothermic in nature. Experimental data were analyzed in terms of pseudo-first order, pseudo-second order, and Elovich kinetic models. The results showed that the removal of Pb(II) and Ni(II) ions followed the pseudo-second order kinetics. The adsorption isotherm data were described using two and three parameter models. The results indicate that the adsorption data were best fitted with the Sips isotherm model. Consequently, the microalga RH with good adsorbability and reusability could be used as an effective adsorbent for the adsorption of Pb(II) and Ni(II) ions from wastewater.