The prevalence of antibiotics in water creates microbial resistance and has a negative impact on the ecosystem. Biomaterials such as spent tea leaves are rich in functional groups and are suitable for chemical modification for diverse applications. This research proposes the use of spent tea leaves of chamomile (CM), green tea (GT), and peppermint (PM) as structural scaffolds for the incorporation of carboxyl, sulfonyl, and thiol groups to improve the adsorption of Penicillin G (Pe). Adsorbents characterization reported a higher number of acidic functional groups, mainly in thiolated products. Scanning electron microscopy (SEM) analysis showed changes on the surfaces of the adsorbents due to reaction conditions, with a stronger effect on thiolated and sulfonated adsorbents. Elemental analysis by Energy dispersive X-ray spectrophotometry (EDS) corroborated the chemical modification by the presence of sulfur atoms and the increase in oxygen/carbon ratios. Batch experiments at different pH shows a strong pH-dependence with a high adsorption at pH 8 for all the adsorbents. The adsorption follows the trend CMs > GTs > PMs. Thiolation and sulfonation reported higher adsorptions, which is most likely due to the sulfur bridge formation, reaching adsorption percentages of 25%. These results create a new mindset in the use of spent tea leaves and their chemical modifications for the bioremediation of antibiotics.

The presence of sulfur compounds in fossil fuels has been an important concern in recent decades as an environmental risk due to the increase of greenhouse gases in the atmosphere and accentuation of acid rain. This study evaluates modified clays as low-cost and efficient adsorbents for the removal of dibenzothiophene (BT) and 4,6-dibenzothiophene (DBT). Adsorption was investigated in a batch system with synthetic fuels (gasoline and diesel) as a function of type of clay modification, adsorbent dosage, initial concentration of the pollutants, desorption, and isotherm modeling. Maximum adsorption was observed with clays modified with benzyltrimethylammonium ion (BM), achieving a maximum adsorption capacity (qmax) of BT of 11.3 mg/g in gasoline and 31.3 mg/g in diesel. The formation of Van der Waals interaction as well as aromatic forces as the main mechanism is proposed based on the results. A 40% desorption was accomplished in 0.1 N HCl. Adsorbents were characterized by scanning electron microscopy (SEM) and Fourier transform-infrared spectroscopy (FT-IR), indicating their optimum properties as adsorbents in fuels. This work highlights the potential use of reverse polarity clays in the elimination of sulfur compounds from model fuels as a low-cost and environmentally friendly purification technique.