Adsorption thermodynamics of some basic dyes uptake from aqueous solution using Albizia lebbeck shells

Abstract

The efficiency of Albizia lebbeck shell for the adsorption of auramine yellow (AY), basic malachite green (BMG) and basic violet (BV) dyes from aqueous solution has been studied in a batch system. The effects of contact time, adsorbent dosage, initial dye concentration, solution pH and temperature have been investigated and the optimum conditions were determined. Thermodynamic parameters such as enthalpy change (ΔH o ), entropy change (ΔS o ) and free energy change (ΔG o ) were studied and the values were -53,475.648 Jmol -1 , -138.345 Jmol -1 K -1 and -11,557.125 Jmol -1 respectively for the adsorption of auramine yellow and -12,6730.302 Jmol -1 , -389.012 Jmol -1 K -1 and -8,859.648 Jmol -1 respectively for the adsorption of basic malachite green indicating exothermic, non-spontaneous and feasible processes for AY and BMG at tested low and high temperatures of 303k and 323k. However, the enthalpy, entropy and free energy changes’ values for the adsorption of basic violet were 19,030.746 Jmol -1 , 83.639 Jmol -1 K -1 and 18,335.371 Jmol -1 respectively indicating endothermic, spontaneous and infeasible process at 303k but feasible at 323k. Surface characterization of the adsorbent based on scanning electron microscopy (SEM) were studied before and after adsorption, and the results indicate that the adsorbent could be effective due to its large number of external cavities on the surface. Therefore, Albizia lebbeck  shells could serve as an effective adsorbent for the removal of organic colorants from textile wastewater prior to disposal since it has 94.2, 72.4 and 85.3% adsorption efficiency values for the removal of AY, BMG and BV respectively. Keywords: Adsorption, Albizia lebbeck Shells, Basic Dyes, Thermodynamics