Waste-based biosorbents as cost-effective alternatives to commercial adsorbents for the retention of fluoxetine from water

Abstract

The goal of this study is to demonstrate that waste-based biosorbents can be cost-effective and green alternatives to commercial adsorbents for the retention of pharmaceuticals. Adsorption kinetics and equilibrium measurements allowed the determination of the adsorption capacity of commercial adsorbents (GAC - granular activated carbon and two synthetic zeolites) and waste-based biosorbents (SCG - spent coffee grounds, pine bark and cork waste) for the retention of fluoxetine from water. For commercial adsorbents, the maximum adsorption capacities followed the order GAC (233.5 mg/g) > zeolite 13× (32.11 mg/g) > zeolite 4A (21.86 mg/g), while for low-cost biosorbents, the sequence was SCG (14.31 mg/g) > pine bark (6.53 mg/g) > cork waste (4.74 mg/g). The economic feasibility of the adsorbents/biosorbents was examined through a detailed cost analysis. Commercial adsorbents present higher costs per gram of fluoxetine removed (6.85 €/g, 3.13 €/g and 1.07 €/g zeolite 4 A, zeolite 13× and GAC, respectively) when compared to low-cost biosorbents (0.92 €/g, 0.41 €/g and 0.16 €/g for pine bark, cork waste and SCG, respectively). It was found that SCG is the most economically viable option for fluoxetine removal, while cork waste, the second less expensive, is the most environmentally friendly biosorbent since its preparation does not generate any solid or liquid wastes. This manuscript demonstrates that the conversion of waste materials into adsorbents has a double environmental benefit for both improving waste management and protecting the environment.