Adsorption of methylene blue dye onto acid-treated tej residue: Kinetic, equilibrium and thermodynamic study

Abstract

Dye-containing wastewater is a very toxic and a major threat to the deterioration of water quality and makes it unsuitable for domestic purposes. This drives low cost and eco-friendly adsorbents from environmental waste have been investigated to treat dye-containing wastewater. In the present study, tej residues (TR) have been successfully employed as a natural and non-conventional low-cost adsorbent for the removal of methylene blue (MB) dye from an aqueous solution. Optimization of maximum operating condition has been carried out by batch mode experiment and the result shows maximum removal efficiency of 82.1821 % at pH 8.0, adsorbent dosage 0.4g, initial dye concentration 20 ppm, contact time 60 min, and temperature 25°C on the acid-treated surface of tej residue. Adsorption kinetics of the adsorbent has been evaluated by pseudo-first-order, pseudo-second-order and intra-particle diffusion, and it is observed that the pseudo-first-order kinetic model is better fitted with a good correlation coefficient, and the equilibrium data fitted well with the Freundlich isotherm model. The Langmuir isotherm model estimates that the maximum adsorption capacity of the monolayer is found to be 215.053 mg/g. Thermodynamics parameters such as ΔG0, ΔH0 and ΔS0 indicate that the sorption process is feasible and exothermic.