(231b) Enhanced Removal of Pharmaceutical Compounds from Aqueous Solution Using Deep Eutectic Solvents -Impregnated Graphene Oxide

The World Health Organization has designated antimicrobial resistance (AMR) as a "silent pandemic," with an annual mortality rate that could soar to 10 million by 2050. A prominent factor contributing to AMR is the persistence of antibiotics in aquatic environments, threatening marine ecosystems and human health.

Traditional water treatment methodologies actually not effectively mitigating these pollutants. This study innovates with deep eutectic solvents (DESs) as impregnating agent on graphene oxide (GO) to significantly enhance the removal of antibiotics from water bodies.

Graphene oxide, promising candidate among carbonaceous adsorbents, provides an extensive surface area and superior adsorption characteristics, serves an ideal framework for adsorption process. Nevertheless, the effectiveness of GO as a standalone adsorbent in eliminating organic pollutants from water is limited. This is primarily due to its pronounced hydrophilicity, stemming from the oxygen-containing groups on its basal plane and edges. It can be overcome by incorporating nanomaterials on the GO surface. However, the reported formulations include the consumption of highly volatile and toxic conventional solvents, presenting severe risks to human health and the environment. In response to this challenge, modifying GO with green solvents plays a pivotal role in environmental conservation. Ionic liquids (ILs) and deep eutectic solvents (DESs) are particularly noteworthy in this category as compared to organic solvents. ILs lose a liquid state when immobilized on the surface of GO by maintaining polarity and low volatility. Therefore, DESs, based on the wise selection of constituents, flourish with advantages, such as simple preparation, cost-effectiveness, low toxicity, and outstanding biocompatibility and biodegradability.

Most of the research has focused on applying DESs as extraction solvents. However, due to their liquid nature, DESs cannot be used as adsorbents independently due to instability in the water phase. This limitation can be overcome by immobilizing DESs onto the surface of GO materials. This immobilization or grafting not only enhances mass transfer but also improves adsorption interactions and the overall adsorption capacity of the materials. It is attributed by DESs tunable properties and environmental sustainability. This synergistic combination is relatively unexplored avenue in removal targeted pollutants in pharmaceuticals field.

A straightforward impregnation method used to synthesize DES-impregnated GO materials and subjected to employ various characterization techniques such as Fourier-Transform Infrared Spectroscopy (FTIR), UV-Vis Spectroscopy, Total Organic Content (TOC), Scanning Electron Microscopy (SEM), and X-ray Diffraction (XRD). A batch adsorption study was conducted to optimize contact time, pH, and adsorbent dosage, aimed to maximize removal efficiency.

The research findings are significant, demonstrating that both pristine and DES-impregnated GO materials exhibit remarkable adsorption efficiency, with removal rates of 86.75 mg/g and 98.40 mg/g, respectively, for a targeted antibiotic. The adsorption behavior closely follows a pseudo-first-order kinetic model and the Langmuir isotherm, indicative of monolayer adsorption on a uniformly distributed surface. Moreover, the thermodynamic parameters demonstrated that the adsorption process for selected pollutant is endothermic and spontaneous in nature. Chemical regeneration of adsorbent GO@ThyLevA using a ethanol provided significant adsorption capacities after 4 successive adsorption-desorption cycles for the antibiotics removal. These results underscore the potential of this novel approach in water treatment, contributing significantly to addressing the AMR challenge.