Preparation of cellulose adsorbent based on banana peel waste (Musa paradisiaca): Green activation and adsorption of Rhodamine B from the aquatic environment

In this study, the successful development of an adsorbent based on banana peel (Musa paradisiaca) activated using lime juice (Citrus aurantifolia) has been reported. The physicochemical parameters of the adsorbent were investigated using an XRD instrument, which showed that the crystal structure of the banana peel (BP) and green activated banana peel (ABP) had a 2θ peak between 18 and 25°, which is the typical peak of cellulose 1. The FTIR spectra showed that green activation of BP specifically changes BP's structure. A bonded O–H group is seen at a wavelength of 3300 cm⁻¹, a peak at 2921 cm⁻¹ is assigned to C-H stretching, the peak at 1615 cm⁻¹ is typical for C[dbnd]O stretching, the peak at 1598 cm⁻¹ is the characteristic peak of C-C aromatic skeletal vibration and the peak at 1034 cm⁻¹ is from the C-O-C and C-C stretch. The FESEM image showed that the morphology of ABP looks rougher and more porous than the morphology of BP. BET-BJH data showed the weak interactions during adsorption can lead to a higher adsorption capacity because these interactions are reversible. The adsorption of RhB with a maximum initial concentration was 70 mg L⁻¹ on 0.2 g of ABP at pH 6, in 10 min at 323 K. The adsorption mechanism followed a pseudo-second-order kinetic model, while the isotherm adsorption followed the Freundlich model. Thermodynamic analysis revealed that the adsorption process is exothermic and spontaneous, as indicated by the enthalpy value of −25.342 kJ mol⁻¹ and entropy of 0.572 kJ mol⁻¹. In summary, this adsorbent can effectively eliminate coloured pollutants from wastewater.