Synergistic effect of adsorption and photo-catalysis on the removal of hazardous dyes using steam exploded banana fiber derived micro-cellulose

Abstract

The utilization of banana fiber derived from micro-cellulose (MC) was exploited as a supporting material for advanced oxidation process (AOP) on the degradation of methylene blue and methyl violet dyes in the presence of H₂O₂-UV in aqueous medium for the first time using green chemistry protocols. Additionally, it was also effectively utilized for the adsorption of methylene blue dye using addition of H₂O₂ in the presence of sunlight. The MC powder was fabricated using an acid alkali process from the pseudo-stem of a banana tree. The as-fabricated MC powder was systematically characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectrometer (EDX), and zero point charge (pH_zpc). The AOP assisted degradation of dye molecules was monitored by using calorimetric techniques as a function of dye concentration and pH in a batch reactor. In a short period of time, the maximum degradation efficiency of 98 % of methylene blue was achieved using MC powder assisted H₂O₂ under UV irradiation at a minimum irradiation time of 120 min at pH 7.0 using dosage of 0.2 g/L. However, in the absence of UV light, the degradation efficiency of MC powder assisted H₂O₂ was only about 5-10 % without UV light irradiation. The dye removal was studied as a function of various operational parameters such as pH (3-11), catalyst dose (0.2-0.6 g/L), and initial dye concentration (100-400 mg/L). In the presence of H₂O₂-sunlight and 0.2 g/L of dosage at pH 7.0 at a minimum contact time of 120 min, MC fiber showed maximum adsorption capacities of 98% and 85% for 100 mg/L and 400 mg/L of methylene blue concentrations. According to the obtained data, the adsorption of methylene blue dye on MC follows the Freundlich isotherm model (R² = 0.9886) and pseudo-first-order kinetic model (R² = 0.9596) due to the higher regression coefficients. This process of dye degradation and adsorption process is a novel one and environmentally benign for an effective removal of hazardous dyes.

Keywords: Adsorption; Banana fiber; Degradation; Methyl violet; Methylene blue; Micro-cellulose.