Effect of Inorganic Salts on Synthesis of Poly(glycidyl methacrylate) Microspheres, Their Functionalization with Poly(ethyleneimine) and Evaluation of Its Use for Removal of Acid Red 27, Acetaminophen and Nitrites

Poly(glycidyl methacrylate) (PGMA) is a polymer containing epoxy groups in its side chains, which makes it a suitable platform for the development of functional materials. In this study, crosslinked PGMA-based microspheres were synthesized by suspension polymerization using N,N′-methylenebisacrylamide as a crosslinker, and the effect of incorporating inorganic additives (InAds) (NaCl, CaCO₃, and MgO nanoparticles) during synthesis was evaluated. In all cases, solid microspheres were obtained, exhibiting variations in particle size, sphericity, and aggregation depending on the type and amount of InAds. Thermal stability was characteristic of crosslinked PGMA (i.e., a single broad thermal transition in ~80–110 °C), while water absorption remained within a narrow range (80–120% for t = 40 min). In addition, the number of epoxy groups per gram of sample was 4.83 ± 0.02 mmol g⁻¹. Selected microspheres were subsequently functionalized with polyethyleneimine (PEI) to obtain graft polymers (PGMA–PEI) and evaluated for the adsorption of three model contaminants: Acid Red 27 (AR-27), nitrites, and acetaminophen. PGMA–PEI showed high affinity toward AR-27 and nitrites, achieving high removal efficiencies at acidic and neutral pH, with rapid adsorption kinetics consistent with a pseudo-second-order model, attributed to electrostatic interactions between protonated amine groups and anions. At pH 11, anion desorption was promoted, enabling partial material regeneration. The results highlight the potential of PGMA–PEI microspheres for the removal of AR-27 (maximum retention ~0.25 mg of dye/g of polymer) and nitrites (maximum retention ~0.023 mg of ${NO}_2^{-}$/g of polymer), whereas acetaminophen removal was not evidenced.