In the present study, spent tea leaves (STL) were used as a new non-conventional and
low-cost adsorbent for the cationic dye (methylene blue) adsorption in a batch process
at 30 °C. Equilibrium sorption isotherms and kinetics were investigated. The
experimental data were analyzed by the Langmuir, Freundlich and Temkin models of
adsorption. The adsorption isotherm data were fitted well to the Langmuir isotherm and
the monolayer adsorption capacity was found to be 300.052 mg/g at 30 °C. The kinetic
data obtained at different initial concentrations were analyzed using pseudo-first-order,
pseudo-second-order and intraparticle diffusion equations. The results revealed that the
spent tea leaves, being waste, have the potential to be used as a low-cost adsorbent for
the removal of methylene blue from aqueous solutions.