Preparation process optimization and study on mechanical property of food waste/fly ash/acrylamide composite hydrogel

Resource utilization of food waste and fly ash has been a significant challenge for managing the environment, building a ‘waste-free city’ and achieving the ‘dual-carbon’ goal. In the present study, a high-strength food waste/fly ash/acrylamide composite hydrogel was developed by combining food waste and fly ash into functionalized particles using free radical cross-linking polymerization, with acrylamide used as the monomer, N, N′-methylene bisacrylamide as the cross-linking agent and sodium persulphate as the initiator. After one-factor experiments by changing the dosages of acrylamide, N, N′-methylene bisacrylamide, sodium persulphate, fly ash and polymerization temperature, the process conditions for the hydrogel to have the optimum mechanical property were obtained using response surface optimization. The experimental results showed that Young’s modulus of the produced hydrogels was as high as 2913 kPa at the dosages of acrylamide, N, N′-methylene bisacrylamide, sodium persulphate and fly ash of 4.349, 0.012, 0.540 and 1.181 g, respectively. Subsequently, the morphology and structure of the hydrogels were characterized using a Fourier transform infrared spectrometer, scanning electron microscope and X-ray diffractometer. The results showed that the interactions among polymer chains in the network structure of the hydrogel, the filling of fly ash and the hydrogen bonding combined to give the hydrogel excellent mechanical property. Meanwhile, Young’s modulus of composite hydrogel increased by 30.16% compared to that of the single-phase food waste hydrogel.