Accentuated Adsorption of Cu2+ and Pb2+ from Aqueous Solution Using Activated Macadamia Nutshell

Abstract

The efficiency of activated macadamia nutshell as an adsorbent for removing lead (Pb2+) and copper (Cu2+) from the water was investigated. The treated macadamia nutshell was characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM). Batch mode adsorption experiments were conducted by varying pH, concentration, adsorbent dose and contact time. The kinetics study of sorption indicates that the pseudo-second-order model provides better correlation of the sorption data (R2=0.99) than the pseudo first-order model (R2 = 0.94), confirming the chemisorption of metal ions in solutions on macadamia nutshell. The Freundlich isotherm has a good fit with the experimental data (R2 close to 1) compared to Langmuir isotherm (R2=0.96). This study shows that macadamia nutshell is an available, low cost, effective and environmentally friendly biosorbent for the removal of Cu2+ and Pb2+ ions from aqueous solution. Thermodynamic studies confirmed that the biosorption process was endothermic and the positive value of ΔG° is quite common when an ion-exchange mechanism applies in the biosorption. The positive value of ΔS° suggested an increase in randomness during the biosorption.