Synthesis of a Novel Hydrogel Nanocomposite Coated on Cotton Fabric for Water–Oil Separation

A new cotton-based hydrogel nanocomposite was successfully prepared by free radical graft copolymerization of acrylamide (AAm) and acrylonitrile (AN) onto fabric followed by insertion of Ag nanoparticles. Ammonium persulfate (APS) was used as an initiator in the presence of a cross-linker, methylene bisacrylamide (MBA). Fourier transform infrared, thermogravimetric analysis, scanning electron microscopy, X-ray diffraction, and transmission electron microscopy were employed to confirm the structure of the hydrogel nanocomposite. Initially, the affecting variables onto graft polymerization (i.e. AAm, AN, MBA, APS, and silver concentrations) were systematically optimized to achieve a hydrogel with swelling capacity as high as possible. The resulted nanocomposite exhibits superhydrophilic and superhydrophobic properties. Therefore, the grafted fabric selectively separated water from oil/water mixtures with high separation efficiency. The influences of filter type, percentage of coated hydrogel on cotton, presence of silver nanoparticles, pH of solution, extracted oil type, as well as hydrogel nanocomposite on the separation efficiency of filters were also studied in detail. Moreover, pH of zero point charge (pHzpc) of the hydrogel nanocomposite was determined by alkaline titration method, and a value of 6.5 was obtained.