Taguchi Design Optimisation of Adsorption of Methylene Blue Dye by Manganese (iv) Oxide Modified Maize Stalk Biochar

Abstract

When wastewater containing methylene blue, a cationic dye is improperly treated or immediately dumped into the environment, it can degrade the quality of water bodies and contaminate the ecological environment. The removal of methylene blue from the aqueous solution is critical and urgent. The present work focuses on the use of maize stalk agricultural waste to prepare an adsorbent for the removal of cationic dye (methylene blue) from an aqueous solution. The prepared maize stalk biochar (MSB) was modified with MnO2 and the modified maize stalk biochar was characterized using Fourier transform infrared (FTIR) spectroscopy. Taguchi technique was employed to determine the optimum conditions for the removal of methylene blue (MB) dye from aqueous solution by MMSB. The factors were adsorbent dose (0.5, 1.0 and 1.5 g/100 mL), initial dye concentration (100, 200 and 300 mg/L), contact time (30, 60, 90 minutes) and pH (4, 6 and 8). Among the investigated process factors, adsorption efficiency was influenced by adsorbent dose and initial MB dye concentration. The optimum parameters were 1 g/100 mL adsorbent dose, 100 mg/L initial dye concentration, 60 minutes contact time and a pH of 8.0. This yielded a removal efficiency of 87.49% with adsorption capacity of 206.53 mg/g. The adsorption kinetics agreed with the pseudo-second-order (R2 of 0.999968) model and fitted a Langmuir isotherm (R2 of 0.9795) representing homogeneous monolayer chemisorption.