Bioadsorption of nickel and cadmium ions from a binary solution onto sugarcane bagasse lignin: Kinetic and thermodynamic study

The single and binary adsorption of Cd(II) and Ni(II) from aqueous solution on lignin of sugarcane bagasse, a secondary product of sugarcane industry, has been demonstrated in this work. Experimental parameters affecting the adsorption are studied, such as the lignin dose, pH, contact time and temperature. The optimal values found for these parameters, both binary and single adsorption, are the followings: lignin dose (7g / L), pH (6), contact time (12 hours) and temperature (40°C). Different empirical adsorption models are used for the evaluation of sorption equilibrium data. Experimental results were interpreted considering speciation curves of ions present in the solution. In single and binary system adsorption data are analyzed using the following adsorption isotherms: single, non-modified, extended and modified Langmuir; single, non-modified and modified Redlich–Peterson; single and extended Freundlich; single and multicomponent Langmuir-Freundlich; and Sheindorf–Rebuhn–Sheintuch. The experimental adsorption isotherms are better adjusted to the extended Langmuir model. This study indicates that the lignin is an adsorbent able to remove Ni (II) and Cd (II) in binary systems, having a greater affinity for cadmium.