Potential of a low-cost bentonite for heavy metal abstraction from binary component system

A low-cost and easily obtainable Nigerian bentonite (UAB) was utilized for the removal of heavy metals (Nickel and Manganese) from a binary system. The bentonite was used without chemical modification in order to keep the process cost low. A Fourier transform infrared spectrum was utilized to determine the surface functional groups responsible for adsorption. Scanning electron microscopy revealed a porous surface of UAB. Batch adsorption methodology was applied to study the effect of pH, initial metal ion concentration, adsorbent dose, adsorbent particle size, ligands (citric acid and EDTA), contact time and temperature on the adsorption process. The isotherm data were analyzed using the Langmuir, Freundlich, Temkin and Scatchard isotherm. Scatchard plot analysis revealed the heterogeneous nature of UAB. Kinetic parameters were tested using the pseudo-first order, pseudo-second order, intraparticle and film diffusion models. The presence of film diffusion mechanism was found to play a major role in the adsorption process. Thermodynamic studies revealed an endothermic, spontaneous and physical adsorption process. Importantly, over 90% of both metal ions were desorbed from the bentonite in desorption studies. The results indicated the potential of UAB as a low-cost and eco-friendly adsorbent for the removal of Ni(II) and Mn(II) ions from aqua media.