Efficient adsorption of anionic and cationic dyes by PVA/PAA/GO composite hydrogel with three-dimensional porous double network structure

Polyvinyl alcohol (PVA) and polyacrylic acid (PAA) were introduced into graphene oxide (GO) by a water bath method, and PVA/PAA/GO (PPG) with a three-dimensional double network structure was prepared under the action of hydrogen bonding. With the help of a large number of oxygen-containing functional groups and a threedimensional double network structure in the PPG composite hydrogel, the adsorption performance of anionic and cationic dyes was greatly improved, and the adsorption rates of 100 mg center dot L-1 malachite green (MG) and Congo red (CR) within 6 min were 93 % and 55 %, respectively. For comparison, the adsorption rates of MG and CR by graphene hydrogel alone within 30 min were only 10 % and 48 %, respectively. Meanwhile, the free radical polymerization of PAA and PVA also effectively improved the mechanical strength of the graphene hydrogel, and the PPG remained structurally stable under the action of 800 g of gravity. The results of adsorption kinetics showed that the adsorption process of PPG on CR and MG was in accordance with Freundlich adsorption and pseudo-second-order kinetic adsorption. Based on the X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrometer (FTIR) results, the adsorption performance of PPG mainly originated from physical adsorption, electrostatic attraction, hydrogen bonding and pi-pi conjugation.