Fabrication of a Magnetic Poly(aspartic acid)-Poly(acrylic acid) Hydrogel: Application for the Adsorptive Removal of Organic Dyes from Aqueous Solution

At present, synthetic dyes have been widely used in several industries such as textiles, rubber, paper, plastic, and leather tanning. The dyes in effluents are among the most aggressive pollutions of all the industrial sectors and can lead to severe water contamination as well as resource waste without proper treatment and recovery. In the present work, magnetic poly(aspartic acid)-poly(acrylic acid) hydrogels (PAsp-PAA/Fe3O4) with semi-interpenetrating networks are successfully prepared. Their physicochemical properties are systematically characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, the Brunauer–Emmett–Teller method, thermogravimetric analysis, and vibrating sample magnetometry. Organic dye methylene blue (MB) and neutral red (NR) adsorption onto the PAsp-PAA/Fe3O4 hydrogel are studied for the first time, and the maximum adsorption capacities of MB and NR are calculated by using the Langmuir model as 357.14 and 370.37 mg·g–1, respectively. The adsorption kinetics can be well described by a pseudo-second-order kinetic model. Furthermore, reusability tests indicate that the hydrogel has good reproducibility. In conclusion, the results demonstrate that the PAsp-PAA/Fe3O4 hydrogel can used as an excellent adsorbent material for removing dye pollutants from wastewater.