Title : Development andformation of sugarcane bagasse bioadsorbents using Deep Eutectic Solvents (DES)
Abstract:
Currently, a widely documented problem remains regarding the contamination of fluvial sources by pollutants including plasticizers, personal care products, hydrocarbons, dyes, hormones, and, to a large extent, remnants of active ingredients from pharmaceutical products, whose side effects are associated with chronic toxicity sequelae and endocrine disruption in living organisms [1]. In addition, due to the structural complexity of some drugs, their use in the manufacture of medicines and their biotransformed metabolites, it has been observed that they may transform into entities capable of easily persisting in ecosystems, which generates ecotoxicity problems and a long-term sanitary risk [2]. The presence of these contaminants has also been attributed to insufficient infrastructure and the low efficiency of treatment systems commonly used in Colombia, where it is estimated that only about 36% of wastewater is treated [3]. Considering this situation, it becomes necessary to develop solutions that combine effectiveness in the removal of pharmaceutical contaminants with environmental sustainability and economic viability. Under this perspective, the valorization of residues from the agroindustry is presented as an innovative alternative to produce adsorbent materials, promoting practices aligned with the principles of the circular economy.
Accordingly, in the present work sugarcane bagasse was used as a biomaterial for the preparation of bioadsorbents, taking advantage of its abundance and lignocellulosic structure. This residue was milled and dried, and afterwards it was modified using DES based on choline chloride combined with citric acid (BC-HAC), 1,3-propanediol (BC-PROP) and 1,3-butanediol (BC-BUT). These treatments aim to improve properties such as surface area, porosity, and chemical functionalization, thereby increasing its adsorption capacity for pharmaceuticals. The materials were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), point of zero charge (pHPZC), thermogravimetric analysis (TGA), as well as adsorption kinetics and adsorption–desorption isotherms. The obtained results show a morphological profile and the presence of functional groups suitable for the retention of pharmaceuticals, presenting a point of zero charge close to 4.1. The post-treatment morphological changes observed by SEM indicate an improvement in the porosity of the material and its distribution.
Adsorption assays were conducted using three pharmaceuticals: propranolol, tinidazole, and acetaminophen, from which acetaminophen was selected as the model compound. A pH effect study was carried out at pH 2, 4, 7, and 10, obtaining the best retention for acetaminophen at pH 7, where the best-performing material was BC-PROP with a removal of up to 58%, additionally, a dosage effect study was performed for acetaminophen, varying the adsorbent mass at 0.5 g/L, 1.0 g/L, 1.5 g/L, 2.0 g/L, 3.0 g/L, and 4.0 g/L, where it was observed that a higher adsorbent mass leads to greater retention of the pharmaceutical. Peak retention values at 4.0 g/L reached 81.44% for BC-HAC, 90.93% for BC-PROP, 85.43% for BC-BUT, and 77% for BC. Finally, according to the results obtained, the formation of sugarcane bagasse bioadsorbents with DES represents an alternative to be applied in the removal of contaminants, given their biocompatibility and low cost.
