D-OPTIMAL OPTIMIZATION OF MICROWAVEASSISTED SYNTHESIS OF MORINGA OLEIFERA POD ACTIVATED CARBON AND APPLICATION TO METHYLENE BLUE ADSORPTION

Activated carbon was optimally produced from Moringa oleífera pod (AMOP), with the aid of microwave, based on the D-Optimal Design under the Response Surface Methodology of the Design Expert software (6.0.8). Process factors selected were time (20-60 mins), temperature (200-450 °C), and impregnation ratio (IMR) (1:1-1:5), while the responses selected were yield, Methylene Blue Number (MBN) and Iodine Value Number (IVN). Adsorption, kinetic and diffusion mechanism of Methylene Blue (MB) adsorption on the AMOP were investigated. Suitability of types 1 -6 of pseudo-second-order (PSO) equation was analysed. Surface properties of the AMOP were characterized using Fourier Transform Infrared Spectroscopy (FTIR) and physicochemical analysis. The optimum conditions (20 mins, IMR of 1:1, and 450 °C) obtained for the activation/carbonization gave 22.11% yield, 78.53 mg/g MBN and 96 mg/g IVN. The FTIR spectra showed changes in the functional groups on the AMOP after the activation/carbonization process. Maximum adsorption capacity of AMOP for MB adsorption was 98.46 mg/g. The process fit well to Type3 of PSO (R2 >0.9). The process's adsorption rate was controlled by diffusion mechanism. This study showed that Moringa oleifera pod is a viable precursor for the production of effective activated carbon.