Insights into the synthesis of hydrogels containing glycerol-based macromonomers for wastewater treatment: Focus on the efficient extraction of caffeine and mercury

The present study explores the production of microparticulate hydrogels for the selective adsorption of caffeine and mercury in wastewater treatment. Modified glycerol macromonomers, obtained through esterification reactions of glycerol with acrylic acid (n-ACG AA) and methacrylic acid (n-ACG MA), were successfully employed for the synthesis of these versatile materials using inverse suspension polymerization. The impact of different parameters, such as initiator, suspension agents, and monomers concentrations, and reaction time, on the final hydrogel characteristics – including morphology, swelling degree, and reaction yield – was assessed. Ultimately, microparticulate hydrogels (∼110 µm) with distinct absorption capacities were synthesized. Among the hydrogels produced, the n-ACG AA hydrogel exhibited an absorption capacity of 542% (w/w). This hydrogel was synthesized under optimized conditions using n-ACG AA (20 wt%), acrylic acid (50 wt%), bis-acrylamide (30 wt%), and 5% Span-60. The n-ACG MA hydrogel displayed an absorption capacity of 445% (w/w) and was synthesized with n-ACG MA (20 wt%), acrylic acid (50 wt%), bis-acrylamide (30 wt%), and 5% Span-80. Lastly, the hydrogel resulting from the combination of n-ACG AA and sodium acrylate (n-ACG AA/SA) demonstrated the highest absorption of 760% (w/w). It was synthesized with n-ACG AA (20 wt%), sodium acrylate (50 wt%), bis-acrylamide (30 wt%), and 5% Span-60. To evaluate the adsorption capacity of the materials, equilibrium adsorption isotherm assays were performed. The maximum adsorption capacity observed in caffeine assays was 91.55 mg g−1 for the n-ACG AA hydrogel. In mercury assays, the best capacity was found to be 369.75 mg g−1 with the hydrogel synthesized using n-ACG AA macromonomer combined with sodium acrylate. For both adsorbates, the Freündlich model was proven to be the most suitable for describing the adsorption isotherms. These results reveal the potential application of modified glycerol-based hydrogels in wastewater treatment processes. [Display omitted] •Modified glycerol-based hydrogels show promising potential for water treatment.•Hydrogels exhibited a remarkable absorption capacity, reaching up to 760%.•Hydrogels demonstrated high performance in removing caffeine and mercury from water.•Remarkable adsorption capacity for caffeine (92 mg g−1) and mercury (386 mg g−1).