Modelling and Optimization of Methylene Blue Adsorption onto Magnesium Oxide Nanoparticles loaded onto Activated Carbon (MgONP-AC): Response Surface Methodology and Artificial Neural Networks

Abstract

Abstract A unique nano-adsorbent was made ready in the laboratory by using magnesium oxide nanoparticles (MgONP) synthesized by a simple chemical precipitation step loaded onto commercial activated carbon (MgONP-AC). Adsorption studies were conducted for its adsorption potential towards a cationic dye i.e. methylene blue (MB). X-ray diffraction (XRD) analysis of the synthesized MgONP exhibits Periclase phase (JCPDS No: # 96-900-0501) with crystallite size of 20.11nm. MgONP exhibits a cubic crystal structure in Scanning electron microscopy (SEM) analysis. Low band gap value of 4.8eV for the MgONP, in comparison with bulk form of MgO (7.8eV) indicates the surface reactivity of synthesized MgONP, attributed to the oxygen vacancies present known as F centres. Both XRD & SEM images of the synthesized MgONP-AC confirm that MgO had retained its nano size in the composite. To study the impact of experimental variables such as agitation time, pH, MgONP-AC dosage, MB concentration and temperature on % MB removal, response surface methodology (RSM) based central rotatable composite experimental design was employed. At 90 min. of agitation time, the variables investigated are pH (4-8), mass of MgONP-AC (0.2-0.6 g/L), initial MO concentration (10-30 mg/L) and temperature (283-323 K). The desirability function value of 0.787 on the STATISTICA version 8.0 showed the optimum MB removal of 94.34% at pH 5.91, MgONP-AC dosage 0.47 g/L, initial concentration of MB in solution 15mg/L and temperature 313 K..