Removal of Methylene Blue Dye from Aqueous Solution using Cotton (Gossypium Spp.) Leaf as an Adsorbent

Abstract

Synthetic dyes like methylene blue (MB) when released into water bodies, are highly toxic, persistent, and have low biodegradation, which is dangerous to the environment and the people. In this paper, we have used cotton (Gossypium spp.) leaf powder, a readily available and low-cost agricultural waste, as a new biosorbent for the effective extraction of methylene blue from aqueous solutions. Fourier-transform infrared spectrophotometry (FTIR) and scanning electron microscopy (SEM) were used to characterise the adsorbent and the presence of key functional group (–OH, –COOH), and a porous surface structure that bound the dye. To test the impact of solution pH, contact time, and the initial dye concentration, nearly all experiments were run in batch adsorption. Optimal absorbance was realized at pH 7, with adsorption that rose proportionally to contact time and dye concentration attain its optimum at 300 minutes. The pseudo-first-order model gave the best fit to kinetic data (R²= 0.99), implying that the rate-limiting step was physiosorption. The Langmuir isotherm was most suitable as the adsorption equilibrium character: R² was close to 1 (0.99), illustrating monolayer adsorption with the highest adsorption capacity of 75.00 mg/g. The results illustrate that cotton leaf powder is a potential, sustainable, and environmentally friendly adsorbent to be used to decolorize methylene blue dye in wastewater. The research offers a good avenue to the valorisation of agricultural residues in low-cost water treatment systems.