Fe₃O₄-doped silk fibroin-polyacrylamide hydrogel for selective and highly efficient absorption of cationic dyes...

Overuse of organic dyes has caused serious threats to the ecosystem and human health. However, the development of high-efficient, environmentally friendly, selective, and degradable cationic dye adsorbents remains a huge challenge. In this work, a novel Fe₃O₄nanoparticles doped silk fibroin-polyacrylamide magnetic hybrid hydrogel (Fe₃O₄@SF-PAAM) was successfully fabricated by combining free radical polymerization to prepare hydrogels andin situco-precipitation to prepare nanoparticles. The obtained Fe₃O₄@SF-PAAM hydrogel shows strong magnetic performance with saturated magnetic of 10.2 emu mg^-1and excellent swelling properties with a swelling ratio of 55867%. In addition, Fe₃O₄@SF-PAAM can adsorb cationic dyes such as methylene blue (MB), crystal violet, and Rhodamine B, but has no adsorption effect on anionic dyes such as methyl orange, congo red, and carmine, indicating that Fe₃O₄@SF-PAAM has good selective adsorption properties for cationic dyes. Interestingly, the adsorption capacity of Fe₃O₄@SF-PAAM was approached 2025 mg g^-1for MB (MB, a typical cation dye) at 25 °C and neutral. Meanwhile, the hybrid hydrogel is reusable, the removal rate for MB is still over 90% after the five adsorption-desorption cycles. The fabricated magnetic hybrid hydrogel is a kind of a highly-efficiency and eco-friendly adsorbent and presents great potential applications in water purification and environmental protection.