Coffee waste as potential adsorbent for the removal of basic dyes from aqueous solution

We evaluated the adsorption performance of coffee waste (CW), collected from coffee shops, for the removal of two basic dyes, toluidine blue (TB) and crystal violet (CV), from aqueous solutions. Batch adsorption experiments were conducted under different conditions including contact time, initial concentration of dye, pH, sorbent dosage and temperature. The Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) isotherms were tested to examine the adsorption behavior. The equilibrium data were well fitted by Langmuir isotherm model. The kinetic study indicates that adsorption follows the pseudo second-order model. The maximum adsorption capacity was found to be as high as 142.5 mg/g for TB and 125 mg/g for CV, which makes CW a prospective adsorbent for the removal of basic dyes from aqueous solution.