Application of CuNi bimetallic nanoparticle as an adsorbent for the removal of heavy metals from aqueous solution

Currently, bimetallic nanoparticles, composed of two different metal elements, have drawn great interest in drinking water treatment among various types of nanoparticles. Bimetallic nanoparticles have a greater surface area which increases their adsorption power as compared to those of monometallic nanoparticles. In the present study, we investigated the sorption behaviour of CuNi bimetallic nanoparticle and its ability to remove Cd2+, Pb2+ and Zn2+ions from aqueous solutions. The structural and chemical analysis of synthesised nanoparticle was determined using Scanning Electron microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray Spectra (EDS), powder X-ray diffraction (PXRD) and surface area studies. Batch mode adsorption studies were conducted and various physico-chemical parameters such as contact time, pH, initial metal ion concentration, and adsorbent dosage level were studied. The result revealed that the adsorption of heavy metals follows the order: Zn2+>Pb2+>Cd2+. The percentage removal of all ions were strongly dependent on the pH and the removal efficiency is enhanced in higher pH values. The optimum pH for the removal of cadmium was 9, and for the removal of zinc and lead, it was 7. The optimum dose of adsorbent for the removal of zinc was 0.4 g, and the dose of adsorbent for the removal of lead and cadmium was 0.5 g. The adsorption isotherms were described by Freundlich and Langmuir isotherm models. Pseudo-first and second-order models were used to evaluate the mechanism of adsorption, and the results showed that the adsorption reaction was fitted very well to the Langmuir isotherm model and the pseudo-first-order kinetic model. In addition, the synthesised CuNi bimetallic nanoparticle showed a high efficiency in adsorption than Cu nanoparticle. This may be due to the increased surface area of the bimetallic nanoparticle as compared to their monometallic counterpart and the synergic effect between the two metals. The results illustrated that the synthesised nanoparticle can be used as an efficient sorbent for the removal of heavy metals from aqueous solutions.