Synthesis of Dual-Responsive Alginate-Inspired Hydrocomposites for the Absorption of Blue Methylene

Dual-responsive hydrogel composites, hydrocomposites (HC), composed of magnetite particles and alginate, which undergo drastic changes in volume in response to pH and magnetic fields, were prepared and employed for the removal of methylene blue (MB) from the aqueous environment. The use of magnets allowed for the control of the MB absorption mechanism and the removal of HCs following their application in water, thereby preventing secondary contamination. The HC capacity for water absorption was found to be dependent on the amount of magnetite and could be altered with the application of a magnetic field. In a 25 mg/L MB solution at pH 6.3 and 8, 20 mg of HC removed 97.7% of MB. The presence of 1% magnetite (w/w) is sufficient for composites to be guided by magnetic stimuli, and the resulting material could be reused at least four times through a simple treatment process. Graphic Abstract