Waste coffee-grounds as potential biosorbents for removal of acid dye 44 from aqueous solution

Waste coffee-grounds (CG) with micro- and macropores are a potential biosorbent for the removal of organics or heavy metal ions from aqueous solutions. In several studies, CG was used as adsorbent for removal of heavy metal ions and organics (phenolic compounds). We investigated the potential application of CG as biosorbents for the removal of acid dye (Acid Red 44). To evaluate objectively the adsorption performance of the CG, conventional adsorbent (DA, Degussa alumina) was also tested and our previous reported data for mesoporous materials compared. In adsorption kinetics, experimental data followed the pseudo-second-order kinetic model and intraparticle diffusion was rate-controlled. The maximum uptake (Q_m) capacity of CG proved half of DA, but its adsorption rate was fast (less than 1 h). Namely, Q_m of CG is 27.8mg/g, and smaller than that of mesoporous adsorbents. However, coffee-ground biosorbent still possesses economical advantages compared to inorganic adsorbents.