Characterization and adsorption capacity of a novel high-performance polymeric sorbent synthesized in supercritical carbon dioxide

A novel, pH-sensitive sorbent was synthesized by precipitation polymerization in supercritical carbon dioxide at pressures ranging from 14 MPa to 26 MPa. The copolymers of hydroxymethylacrylamide and acrylic acid were cross-linked by N,N′-methylenebisacrylamide. Aggregate particles with diameters of approximately 200 nm were observed by scanning electron microscopy, and surface area analysis showed that the surface area and pore volume of a sorbent prepared at a pressure of 26 MPa are 50.38 m2/g and 0.101 m3/g, respectively. The polymer has good thermal stability. Additionally, the adsorption behaviors of methylene blue (MB) by the copolymers were evaluated. The effect of reaction pressure, cross-linker ratio, polymer structure, pH values of solution, MB concentration, and adsorption time on adsorption capacity was also investigated. The results revealed that cross-linked copolymer has a high adsorption capacity of 343.23 mg/g for MB under the conditions of pH 9 and crosslinker ratio of 5.8%. The findings show that cross-linked copolymer materials can be used for large-scale dye adsorption.