P(AAS-co-AMPS-Na)/SA/laponite composite hydrogel beads with excellent performance prepared by photopolymerization under green LED irradiation for adsorption of malachite green

With the rapid development of industry, water pollution has become one of the important problems that harm the ecological environment and human health. The extensive use and random discharge of dyes have caused serious damage to water resources. Hydrogel bead is a promising material for dye adsorption due to its advantages of rich functional groups and high specific surface area. Here, acrylic acid sodium salt (AAS) and 2acrylamide-2-methylpropanesulfonic acid (AMPS) as monomers, N,N'-Methylene-bis-acrylamide (MBA) as crosslinking agent, sodium alginate (SA) as semi-interpenetrating network component, laponite as nano-clay additive, and single 2 ',4 ',5 ',7 ' -tetrabromofluorescein disodium salt (EY)/ Triethanolamine (TEOA)/ diphenyl iodonium hexafluorophosphate (DPI) as green light polymerization initiating system were combined to prepare composite hydrogel beads within 10 s under green LED irradiation. The composite hydrogels were characterized by infrared spectroscopy (FTIR), thermogravimetric analyzer (TG), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The addition of sodium alginate and laponite can improve the mechanical properties of hydrogel beads. In the adsorption study of malachite green, the influence of time, temperature, dye concentration, pH, ionic strength, and other factors on the adsorption effect were investigated. The adsorption process was consistent with the second-order kinetic process and Langmuir adsorption. At room temperature, the highest adsorption capacity of the hydrogel beads for malachite green reached 829.63 mg/g. The PAAS-SL hydrogel beads maintained a high adsorption effect in the pH range (3-10), and the capacity reached 575.0 mg /g at pH 3, which had a good ability to resist low pH. In the adsorption-desorption experiments, the removal rate of PAAS-SL hydrogel beads for MG is still more than 80 % after 5 cycles. Our research provides a promising strategy for the efficient and rapid preparation of hydrogel beads with excellent properties.