Kinetic, equilibrium and thermodynamic studies of Ni(II) ions sorption on sulfuric acid treated Lagenaria vulgaris shell

Chemically modified Lagenaria vulgaris shell (ccLVB) was tested as a new sorbent for the removal of Ni(II) from aqueous solution, in batch conditions. The sorption process was very fast reaching equilibrium in about 20 min. Ni(II) sorption is almost invariant in the pH range from 3 to 6. Sorption kinetics followed pseudo-second order, intraparticle diffusion and Chrastil’s models, which suggest that both surface reaction and diffusion were the rate-limiting steps. Equilibria experimental results are well fitted by Langmuir and Temkin sorption isotherm models, indicating mixed adsorption process. The maximum biosorption capacity of ccLVB for Ni(II) was found to be 84.51 mg g-1. The calculated thermodynamic parameters showed that the biosorption of nickel on ccLVB was feasible, spontaneous and exothermic at 25-45oC. The desorption experiments showed that the ccLVB could be reused for five cycles without significant loss in sorption capacity. Release of Na+ ions from the biosorbent during sorption of Ni(II) reveals that the main sorption mechanism is ion exchange. Presented study suggests that ccLVB can be used effectively for the removal of Ni(II) ions from aqueous solution.