Study of adsorption efficiencies of acid-modified banana pseudo stem biomass (BPSB) using methylene blue and rhodamine B as industrial dyes

Abstract

The research explores the adsorptive removal of Methylene Blue (MB) and Rhodamine B (RhB), two industrial dyes, using both dried and acid-modified BPSB. BPSB was chosen as the adsorbent cause it is very cheap to prepare, and banana trees are readily available in Sri Lanka. The investigation, conducted through batch sorption studies, varied operational variables (dye concentration, pH, contact time, temperature and adsorbent dosage) to determine the optimal conditions for maximum dye adsorption. The highest adsorption capacity for MB was observed at a pH of 7 (pH range taken as pH 3–11) and a temperature of 40 °C (temperature range taken as 20–70 oC), with an acid-modified BPSB dosage of 0.3 g (dosage rage was taken 0.1– 0.5 g). The adsorption equilibrium was reached within 2 hours at a dye concentration of 500 ppm (concentration range taken from 100–2500 ppm) (0.1 M HCl acid-modified BPSB 0.3 g used and the adsorption capacity was 487.1 mg/g; 0.1 M HNO3 acidmodified BPSB 0.3 g used and the adsorption capacity was 492.3 mg/g). In contrast, the adsorption capacity of RhB was less influenced by pH variations (pH range taken as pH 3–11), with the most efficient removal occurring at 40 °C (temperature range taken as 20–70 oC) and a similar BPSB dosage and contact time, but at a reduced dye concentration of 300 ppm (concentration range taken from 100– 500 ppm). After running three replicas and calculating the median value, obtained the most accurate results. The adsorbents were characterized using Scanning Electron Microscopy (SEM), which provided detailed imagery of the biomass's surface morphology. Unfortunately, there were no observed changes in surface morphology before and after the adsorption process. The kinetic data fits the pseudosecond-order model very well. The thermodynamic data correlated well with the Langmuir, Freundlich, and Temkin Adsorption Isotherms. The findings of this study highlight the potential of BPSB as an effective and environmentally friendly adsorbent for the treatment of dye-contaminated water. The adaptability of BPSB to various operational conditions, coupled with its low manufacturing costs, instils optimism about its economic feasibility and positions it as a promising candidate for large-scale applications in water purification. BPSB is a natural substance and environmentally friendly. This leads to a green method for water purification. This research adds to the broader conversation on sustainable environmental management by promoting the use of agricultural waste to address water pollution. This finding showcases the innovative progress in water treatment and the continuous endeavours to protect our planet's most crucial resource.