Preparation of rice husk-derived activated carbon and evaluation of its methylene blue adsorption

Abstract

Activated carbon for the adsorption of the organic dye methylene blue (MB) was synthesised from rice husk through carbonisation, followed by activation using sodium hydroxide (NaOH) at various concentrations and subsequent treatment with nitric acid and citric acid to enhance porosity and increase the surface area. Scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) analyses revealed a significant increase in surface area from 55.47 to 300.20 m²/g after the activation process. Fourier transform infrared (FT-IR) spectroscopy demonstrated pronounced absorption bands in the 2000-to-400-cm- ¹ range, corresponding to characteristic functional groups of activated carbon. The adsorption capacity of the material for MB was influenced by the NaOH concentration used during activation as well as the pH and MB concentration in the solution. The activated carbon sample treated with 0.3 M NaOH and citric acid exhibited the highest MB adsorption capacity, achieving up to 200 mg/g. These findings indicate that this material is suitable for application as an adsorbent for the removal of the organic dye MB from textile industrial wastewater.