*4.1. Antibiotics*

Antibiotics are found today in relatively high amounts in ecosystems due to their increasing use. In fact, many studies have been carried out to examine the possibilities of biosorption for the removal of antibiotics. Recently, new articles confirm this use. An example of this is the antibiotic dicloxacillin, biosorption studies with this antibiotic that were performed with Indian almond (*Terminalia catappa*) leaf biomass. The maximum adsorption capacity was 71.94 mg/g. The optimal pH for this biosorption was 6.0. For the intermolecular interaction such as hydrogen bonds, van der Waals forces could be the main interaction for the dicloxacillin and the surface properties of this biosorbent [129]. Four sulfonamide antibiotics were also recently investigated. Extracellular polymeric substances (EPS) extracted from *Klebsiella* sp. J1 were used for this purpose and with e fficiencies that reached 142.86 mg/g. In this case, the hydrophobic interaction between EPS and sulfonamides seemed to dominate the adsorption process. There was the maximum proportion of sulfonamides at molecular states when the solution pH was 4.0–5.0, and the molecular states of sulfonamides were favorable for hydrophobic groups to effectively play a role during adsorption process [130].

Biomass from *Dialium guineense* seed waste was modified with sodium hydroxide and tested as biosorbent for ciprofloxacin. This biomass, modified in this way, exhibited a maximum uptake capacity of 120.34 mg/g at pH = 6.0, higher than some reported adsorbents for this antibiotic [131]. Another antibiotic that was recently evaluated for its elimination by biosorption was oxytetracycline. This antibiotic was e ffectively removed using a reed-based-beads biosorbent (an enhanced adsorbent from Tunisian reed). The maximum biosorption capacity obtained was 15.78 mg/g at pH = 6.0. In this experiment, an initial mixture of 165.54 μmol/L of oxytetracycline and 362.16 μmol/L of Cd(II) was used, demonstrating the e ffectiveness of this material to simultaneously remove two pollutants. The biosorption of Cd(II) cations took place through electrostatic attraction between them and the biosorbent, and the biosorption of oxytetracycline could take place via π-π stacking, as well as hydrophobic interactions [52].
