In this present work, a commercial coffee waste was treated using cationic surfactants cetyltrimethyl ammonium
bromide (CTAB) or cetylpyridinium chloride (CPC) to enhance its adsorption capacity for the removal
of methyl orange dye (MO, anionic dye) from aqueous solutions. A series of experiments were undertaken in
an agitated batch to assess the effect of key parameters such as pH, contact time, adsorbent dose and ionic
strength. Maximum methyl orange dye adsorption onto modified commercial coffee waste (MCWs) was observed
at pH 3.5 with 0.1 g/50 ml of adsorbent dose. Modeling study shows that pseudo-second-order kinetic
model and Langmuir adsorption isotherm model provide better fitness to the experimental data. The maximum
adsorption capacity (62.5 mg/g at 25 °C) was obtained with CPC modified commercial coffee waste. Calculated
thermodynamic parameters G0, H0 and S0 showed that adsorption is spontaneous and exothermic.
The FT-IR analysis showed that possible mechanisms controlling MO adsorption on the MCWs included
electrostatic interactions and hydrophobic interaction.