Synthesis and Modification by Carbonization of Styrene–Ethylene Glycol Dimethacrylate–Lignin Sorbents and their Sorption of Acetylsalicylic Acid

Abstract

This paper deals with the synthesis and studies of new polymer microspheres properties based on ethylene glycol dimethylacrylate (EGDMA), styrene (St), and various quantities of commercial kraft lignin (L). In the first stage of the investigations, the conditions of the synthesis process were optimized by selecting a proper amount of poly (vinyl alcohol), which was a suspension stabilizer. Next, based on EGDMA + St + L, new polymers were synthesized by the suspension polymerization method. The chemical structure of the materials was confirmed by means of the Attenuated Total Reflectance—Fourier Transform Infrared (ATR-FTIR) analysis. The evaluation of the synthesized materials includes susceptibility to swelling in solvents of different character (polar and nonpolar), porous structure of microspheres, and their thermal resistance. Morphology has been specified by the scanning electron microscope and automated particle size, as well as shape analyzer. The obtained pictures confirmed the spherical shape of the materials. The microspheres porosity was characterized using the low-temperature nitrogen adsorption. To increase the porosity (partially blocked by the large lignin molecule), the microspheres (EGDMA + St + 4L copolymer) were impregnated with the aqueous solution of the activating substance (sulphuric acid, nitric acid, phosphorous acid, and silver nitrate) and then carbonized at 400 °C. After the carbonization process, the increase in the specific surface area was observed. The microspheres were porous with a specific surface area up to 300 m2/g. The materials had a desirable feature for their potential use in chromatography, which was confirmed by the results of GC analysis with the acetylsalicylic acid. These materials are an interesting alternative in the field of more environmentally friendly, ecological, and biodegradable polymeric sorbents in comparison to the commonly applied styrene-divinylbenzene (St-DVB) copolymers.