Biosorptive removal of Cu(II), Ni(II) and Pb(II) ions from aqueous solutions using coconut dregs residue: Adsorption and characterisation studies

• Coconut dregs residue exhibited superior adsorption capacity.
• Coconut dregs residue can be used as an alternative low-cost biosorbent.
• Functional groups favour metal ion binding through complexation mechanism.

The efficacy of coconut dregs residue, a by-product from coconut milk production factory, to adsorb Cu(II), Ni(II) and Pb(II) ions from aqueous solutions was investigated. The effects of experimental parameters such as solution pH, contact time and initial metal concentration on adsorption process were examined in batch experiments. The equilibrium data were best described by the Langmuir isotherm model, while the dynamical data followed the pseudo-second order kinetic model. The Freundlich constant (n) and separation factor (RL) values suggest that the metal ions were favourably adsorbed onto biosorbent. The affinity of the biosorbent for metal ion was in the order of Pb(II) > Cu(II) > Ni(II), both in single- and multi-metal systems. The characterisation studies were carried out using scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDX) and Fourier transform infrared spectrometer (FTIR). Complexation between metal ions and binding sites of the biosorbents was the main adsorption mechanism. Coconut dregs residue removed Cu(II) better than bamboo derived activated carbon, a commercial activated carbon, from electroplating effluent.

SEM images of coconut dregs residue at 5000× magnification before adsorption of metal ion (a), and after adsorption of Cu(II) (b), Ni(II) (c), and Pb(II) (d).Figure optionsDownload as PowerPoint slide