Kinetic, isotherm and thermodynamic studies of the biosorption of zinc (II) from solution by maize wrapper

The removal of Zn2+ from dilute aqueous solution using maize (Zea mays) wrapper as the biosorbent is reported in this paper. Batch experiments were carried out to assess biosorption kinetic and equilibrium behaviour of Zn2+ by varying parameters such as pH, contact time and initial metal ion concentration at 27 degrees C. The analysis of residual metal ions was determined using atomic absorption spectrophotometer. The pH study shows that the initial pH would play a vital role in the biosorption of the Zn2+ from solution. The optimum pH obtained was in the range pH 5 - 7, therefore pH 6 was used for other studies. The kinetic study shows that uptake of Zn2+ increased with time and that maximum biosorption was obtained within 60 min of the process. The result obtained showed that the pseudo-first order model correlated with the experimental data better than the pseudo-second order model examined in this study. Freundlich and Langmuir isotherm models were used to analyse the experimental data of the biosorption process. The Freundlich and Langmuir equations obtained are log = 0.643 log C-e + 1.1177 and 1/ = 0.0411/C-e + 0.009, respectively. The correlation factors are 0.9971 and 0.9889, respectively. The free energy change for the biosorption of Zn2+ at 27 degrees C, initial concentration of 100 mg L-1 and pH 6 is -7.663 kJ mol(-1) within 60 min. These results indicate that maize wrapper has potential for the removal of Zn2+ from industrial wastewater.