Exploring the potential of waste biomass of olive as an additive for layered double hydroxide/polyurethane as an effective and safe agent for the adsorption of drug residues: a bioremediation approach†

The increasing use of antibiotics worldwide and their presence in wastewater pose a risk to human health and the environment, even in minute amounts, making them potentially new and dangerous pollutants of the ecosystem. Drug resistance and changes in the biological cycle are two of the negative consequences of chemical pollution. The development of affordable, practical, and recyclable adsorbents is imperative because of the significant threat that the rise in antibiotic residues poses to aquatic and ecological settings. The accumulation of pharmaceutical compounds in aqueous solutions has been lessened by a number of strategies, including adsorption onto the surface of agricultural wastes. Bioactive substances such as vitamins, carotenoids, and polyphenols are abundant in pomace, including minerals, proteins, cellulose, lignin, and pectin. All of these substances exhibit sorption characteristics with respect to pharmaceutical compounds in addition to their many other positive health effects. X-Ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) analysis and particle size analysis were used to thoroughly examine olive pomace (O-Pom), layered double hydroxide (LDH), polyurethane (PU) and LDH/PU/O-Pom composites. FTIR spectroscopy of O-Pom and LDH/PU/O-Pom before and after the adsorption of cefotaxime was performed and the results were discussed. Next, the effects of several parameters, including pH, adsorbent amount, concentration, and contact time, on wastewater treatment efficiency were investigated. We studied nonlinear adsorption isotherm models at pH 5 using O-Pom and O-Pom-LDH/PU, which showed maximum adsorption capacities (q_max) of 163.23 mg g⁻¹ for O-Pom and 250 mg g⁻¹ for LDH/PU/O-Pom. By identifying the most suitable isotherm, error functions are used to assess the validity of the adsorption mathematical models against experimental data, as precise adsorption equilibrium information is essential for adsorption analysis and design. Additionally, we compared the investigated models with the corrected Akaike information criterion (AIC) to confirm that more fitting models were used in the isotherm study. The model that best fitted according to the AIC calculated for O-Pom was the Freundlich model, and the AIC values were 69.23 and 63.91 for O-Pom and LDH/PU/O-Pom, respectively. In addition, ethanol was used as a regeneration agent for the tested adsorbent loaded with cefotaxime. It retained a high removal percentage up to the fourth cycle. Additionally, kinetic experiments were carried out. The MTT assay results of normal Vero cells indicate that at the highest concentration of 1000 μg mL⁻¹, LDH/PU, O-Pom, and LDH/PU/O-Pom resulted in cell viabilities of 66.7 ± 1.1%, 61 ± 1%, and 61.8 ± 1.3%, respectively, suggesting their low cytotoxicity and potential suitability for water treatment applications without significant health risks. LDH/PU/O-Pom demonstrated the highest antibacterial activity against both Gram-positive and Gram-negative bacteria, with E. coli being the most sensitive (MIC, 60 μg mL⁻¹) and B. cereus being the least susceptible (MIC, 250 μg mL⁻¹), which was attributed to differences in bacterial cell surface structures, indicating its potential as an effective water treatment agent. According to the cost analysis, the synthesis of LDH/PU/O-Pom involves a cost of 0.927 USD per g of the adsorbent, which is reasonable for large-scale industrial use. Greenness profile calculations of proposed chemical methods have become more popular worldwide. Many green chemistry calculation methods are now known to be used to evaluate the greenness of a method where many parameters, including quantity, toxicity, power, waste, miniaturization, and automation, are considered to determine how environmentally friendly an analytical methodology is. The analytical eco-scale (AES) method, the analytical method volume intensity (AMVI) method and the analytical GREENness (AGREE) calculator method were used for this assessment.