Optimization of Heavy Metals Removal from Aqueous Solution Using Synthesized Chromic Oxide and Chromic Oxide – Lophira Alata Carbonized Sawdust Nanoparticles

Abstract

This research was designed to ascertain the removal efficiency of Cd²⁺ and Pb²⁺ ion in aqueous system with the use of chromic oxide nanoparticle (CN) and chromic oxide-lophiraalata carbonised sawdust nanocomposite (CLN) synthesized by co-precipitation and thermal degradation methods. The physicochemical characterization of the synthesized chromic oxide nanoparticle and chromic oxide-lophiraalata carbonised sawdust nanocomposite (CN and CLN) were evaluated using x-ray diffractograms (XRD), scanning electron microscope (SEM) and Fourier Transform infrared spectrophotometer (FTIR). The obtained CN and CLN were crystalline, amorphous, smooth and spherical in shape with very small particles inapparently soft agglomerates with a size of 7.7 and 12.05 nm respectively. The amount of Cd²⁺ and Pb²⁺ ions before and after treatment of the polluted water was evaluated using atomic absorption spectrometer (AAS). The adsorption property of CN and CLN was studied using isotherm models and Response Surface Methodology (RSM) Analysis. The isotherm models revealed that the adsorption process of Cd²⁺ and Pb²⁺ ions onto CN and CLN was a physical process (physiosorption), favorable and exothermic. The energy of affinity for Pb²⁺ ions on both nanoparticles was higher. The response surface methodology analysis for CN revealed that the cadmium ions were slightly more adsorbed and removed from the heavy metal polluted water compared to lead ions. This observation was in agreement with the k_F values obtained from Freundlich isotherm in which the k­_F value for cadmium ions (59.52) was higher than that of lead (51.99). However, the response surface methodology analysis for CLN revealed that the Pb²⁺ ions were more adsorbed compared to Cd²⁺ ions with optimum adsorption capacities of 191.50 and 66.20 mg/g respectively. These values also agreed with the K_F values obtained from Freundlich isotherm. This implies that CLN was more effective in the removal of Pb²⁺ ions.

Keywords: Chromic oxide, Nanoparticle, Optimization, Response Surface Methodology, Isotherm

DOI: 10.7176/JNSR/10-2-06

Publication date: January 31^st 2020