Removal of Cr(VI) from electroplating wastewater using fruit peel of Leechi (Litchi chinensis)

Fruit peel of Litchi chinensis showed remarkable adsorption capacity towards Cr(VI) ions. The effect of temperature, pH, initial Cr(VI) concentration and time was investigated using batch process. The adsorption of Cr(VI) was maximum at pH 2. Fourier transform infrared spectroscopy (FTIR) was used to explore number and position of active functional groups available for the binding of Cr(VI) ions. Thermodynamic parameters like change in standard free energy (ΔG °), enthalpy (ΔH °) and entropy (ΔS °) indicated the spontaneous, endothermic and increased randomness nature of Cr(VI) adsorption. Equilibrium data were well fitted in Langmuir isotherm at 40°C.The value of mean free energy (E = 8.28 kJ mol−1) indicated that adsorption process was chemical in nature. The breakthrough and exhaustive capacities were found to be 30 and 50 mg g−1 respectively. The results indicated that the adsorbent could be used effectively for the removal of Cr(VI) from electroplating wastewater by batch process.