Engineering GO-pAmOx: A Polyoxazoline-Functionalized Graphene Oxide Composite for Selective Removal of NSAIDs and Organic Pollutants from Water

Organic wastewater compounds (OWCs) employed in human activities are, nowadays, commonly detected in surface water, groundwater, and drinking water. In particular, pharmaceuticals have caused great concern because after their consumption, traces of metabolites are excreted and reach the water resources either directly or after inefficient treatment. Despite this, these compounds are not regulated in drinking water, and existing toxicity data are inadequate to assess potential risks from chronic low-dose exposure. Considering the necessity to find new efficient, reusable, and biocompatible systems to remove organic pollutants from wastewater, the adsorption process has been found to be the most effective and economical because it is simple, highly efficient, regenerative, and scalable and does not produce intermediates that can increase the toxicity of the parent contaminants. Prompted by these reasons, in this research, an adsorbed medium composed of graphene oxide and an amine-oxazoline-based polymer (poly(2-(3-(amino)propyl))-2-oxazoline) was synthesized and employed in several adsorption experiments targeting nonsteroidal anti-inflammatory drugs such as ibuprofen (1), aspirin (2), ketoprofen (3), and benzoic acid (4). The specific interaction between acidic moieties of drugs and basic domains of the polymer has been investigated by targeting both acid compounds and pharmaceutical products free of carboxylic groups. Also, the influence of several parameters, including initial concentration, liquid-phase composition, pH, and reusability, has been investigated. Results show that the maximum adsorption capacity for ibuprofen (1), aspirin (2), ketoprofen (3), and benzoic acid (4) for experiments conducted in water, at the maximum initial concentration explored (90 mg L–1) and at natural pH equilibrium (pH ∼ 4), are, respectively, 37.4, 27.5, 43.5, and 26.0 mg g–1. These findings suggest that the prepared GO-pAmOx material has significant potential for adsorbing these drugs in water and good versatility for all investigated acid compounds and maintains high reusability. Notably, the reduction in adsorption capacity after ten adsorption cycles was only 1%.

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