Individual and competitive adsorption of ibuprofen and caffeine from primary sewage effluent by yeast-based activated carbon and magnetic carbon nanocomposite

Pharmaceuticals enter water bodies mainly through urban effluents harmful to the biota, inducing microbial resistance, and impacting hydric security. Activated carbon has been used for effluent treatment and associated with ferromagnetic nanoparticles can facilitate the separation of this adsorbent from an aqueous medium and improve the adsorption capacity. A yeast-based carbon (YC) prepared from the residue of the ethanol industry and a magnetic composite prepared from YC (NP-YC) were used to remove ibuprofen (IBU) and caffeine (CAF) from deionized water and primary sewage effluent (PE). A minimum of 51 and 90 mg/g of IBU and CAF were removed by NP-YC, respectively, whereas YC removed a minimum of 107 and 106 mg/g for such contaminants. The removal of both contaminants was favored for competitive studies using NP-YC as adsorbent (removals >70% for deionized water, and >60% and >75% for IBU and CAF, respectively, for PE). The values of q_max obtained for YC in the competitive assays were about the sum of both q_max for the individual experiments suggesting that each molecule adsorbs in a different site. Successive adsorption cycles using the same mass of adsorbent removed higher amounts of IBU and CAF by exposing the adsorbents to new volumes of a solution containing equal or increasing concentrations of contaminants than those exposed to a single high concentration solution. This behavior is probably due to the driving force effect. It suggests that the reuse of synthesized adsorbents was possible without previous desorption, increasing the usability of the synthesized adsorbents.