Synthesis, Characterisation and Application of Capped Chromic Oxide Nanoparticle (CCONP) for the Removal of Cd2+ and Pb2+ ion from Aqueous Solution

Abstract

This research was designed to ascertain the removal efficiency of Cd2+ and Pb2+ ion from aqueous solution using capped chromic oxide nanoparticle (CCONP) synthesized by method of co-precipitation and thermal degradation of chromic hydroxide (Cr(OH)3), stabilized and capped using polyvinyl alcohol (PVA). The physicochemical characterization of the synthesized CCONP was evaluated using x-ray diffractograms (XRD), scanning electron microscope (SEM) and Fourier Transform infrared spectrophotometer (FTIR). The CCONP obtained was more of crystalline than amorphous with very small particles inapparently soft agglomerates with a size of 7.7 nm. The amount of Cd2+ and Pb2+ ions before and after treatment of the aqueous solution was evaluated using atomic absorption spectrometer (AAS). Adsorption experiments were conducted in batches and the adsorption property of CCONP was studied using adsorption isotherm models and optimized using response surface methodology (RSM) Analysis. The adsorption isotherm models revealed that the adsorption process of Cd2+ and Pb2+ ions onto CCONP was a physical process, favorable and exothermic. The energy of affinity for Pb2+ ions on CCONP was higher. The adsorption process for Cd2+ ions on CCONP was spontaneous and the adsorption capacity of CCONP for Pb2+ ions was higher. However, optimisation analysis revealed that the cadmium ions were slightly more adsorbed on CCONP and removed from the aqueous solution compared to lead ions. This observation was in agreement with the Kf values obtained from Freundlich isotherm in which the Kf value for cadmium ions (59.52) was higher than that of lead (51.99).