The adsorption of methylene blue from wastewater by Moringaoleifera pods and kernels wastes using the response surface methodology

Abstract

In recent decades, researchers have focused more on the use of many types of biomaterials from various organisms and agricultural by-products for wastewater treatment. In this study, we are using Moringaoleifera pods powder (MOPP) and Moringaoleifera kernels powder (MOPK) for the removal of industrial Methylene blue (MB) dye from aqueous solutions. The adsorption process of MB onto MOPP and MOKP follows the pseudo-second-order model. First of all, the adsorbents were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscope (SEM). The second objective was the optimization process of Moringaoleifera wastes seeds (MOPP and MOKP) for the removal of methylene blue dye (MB), using Box-Behnken under the Response Surface methodology. The optimal conditions were X1 = 2.5 g/L of adsorbent, X2 = 40 ppm of concentration of MB and X3 = 10.03 of pH with removal efficiency which reaches 98.12% for MOPP and X1 = 2.5 g/L of adsorbent, X2 = 30 mg/L of concentration of MB and X3 = 7.43 of pH with removal efficiency which reaches 96.94% for MOKP. The model envisaged for the optimal design has been well verified by the experimental data, with R2/R2adj equal to 0.99 and 0.74, respectively for MOPP, then for MOKP 0.90 and 0.73. Finally, the analysis of variance (ANOVA), confirmed that MOPP and MOKP had a high-efficiency adsorbent capacity with the MOPP as the best biosorbent than MOKP and that the chosen model is valid. The two materials could be adopted as efficient and cost-effective adsorbents.