<p>The present work reports the synthesis of various nanocomposites based on polyacrylic acid (PAA), including PAA–Fe₃O₄, PAA–Fe₃O₄–Citric acid, PAA–Fe₃O₄–Glutamic acid, and PAA–Fe₃O₄–Ascorbic acid. The objective of synthesizing these nanocomposites was to effectively remove Indole (IND) and Quinolone (QUI) from gas oil. To achieve this, PAA–Fe₃O₄ was first synthesized using radical polymerization, followed by the co-precipitation of Fe salts in an alkaline environment. The expected functional groups were successfully incorporated into the surface of all composites. The presence of Fe₃O₄ within the PAA matrix was confirmed, enabling effective magnetic separation. The study employed the Response Surface Methodology (RSM)-Box-Behnken design (BBD) to assess the impact of adsorption period, initial concentration, and adsorbent dosage on the performance of four distinct PAA-based magnetic adsorbents in removing nitrogen-containing compounds IND and QUI from gas oil. The results indicated that the PAA–Fe₃O₄–Citric acid composite exhibited high removal efficiencies for IND and QUI, achieving maximum adsorption rates of 96% and 94%, respectively. Kinetic adsorption studies for all prepared adsorbents revealed that the adsorption processes were well described by the second-order model and followed the Langmuir isotherm model. Additionally, thermodynamic analyses of the adsorption process showed that it was both endothermic and spontaneous. Thus, PAA-based composites demonstrate significant potential for the removal of nitrogen-containing compounds.</p>