Sustainable Adsorbents: Characterisation of Banana Stem-Based Materials for Reactive Black 5 Dye Removal

Abstract

Banana stems are agricultural plant waste from one of Asia's most popular fruits, which is grown primarily in India, Thailand, China, Indonesia, and Malaysia. Since coal-derived activated carbon is expensive and has limited availability, agricultural waste such as banana stems has been seen as an affordable and abundant alternative. Activated carbon banana stem (ACBS) was prepared by soaking with phosphoric acid (H₃PO₄) and heating in a furnace at 400°C for 1 hour. Both raw banana stem (RBS) and activated carbon banana stem (ACBS) were characterized using proximate analysis, Scanning Electron Microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and Brunauer–Emmett–Teller (BET). The results showed that ACBS had higher ash (25.45%) and fixed carbon (36.4%) contents, and lower moisture (2.3%) and volatile matter (35.85%) contents than RBS. Analysis of the surface morphology using SEM indicated that the ACBS was more porous than the RBS, thereby enhancing its adsorption capacity. BET analysis revealed that the surface area, pore volume, and average pore diameter of the ACBS (475.7 m²/g, 0.4491cm3/g, and 3.776 nm) were significantly greater than those of the RBS (1.886 m²/g, 0.0047 cm³/g, and 9.882 nm), demonstrating effective pore development during activation. The results showed that ACBS was more effective at removing Reactive Black 5 (RB5) dye, with a removal efficiency of 99.11%, compared to RBS, which had only 6.4%.