Spent Coffee Grounds as Adsorbents for Pesticide Paraquat Removal from its Aqueous Solutions

Spent coffee grounds were evaluated for adsorption efficiency in the removal of pesticide paraquat from its aqueous solutions. The influence of the adsorbent mass, agitation time, paraquat concentration and pH have been investigated in the batch sorption mode. Adsorption capacity (mg/g) has been found to be 27.87 ± 1.57 mg/g, while the removal efficiency has resulted of 32.25 ± 1.79 %. Adsorption rate was found to be very fast, whereby the time required for equilibrium adsorption occurred within first 20 minutes. The process behavior was predicted using the second-order kinetic model. On the basis of the observed data, further process optimization may be greatly facilitated, thus it is considered that coffee waste may be exploited well for pesticides removal purposes. Keywords—Adsorption, coffee residues, paraquat, pesticides.