Preparation Of Gel Materials Based On Acrylate Polymer And Its Adsorption Studies For Heavy Metal Ions

The treatment of wastewater containing heavy metals is a thorny problem around the world, recently. The adsorption has been attracted great attention in the treatment field of wastewater containing heavy metals, due to its advantages of fast kinetics, high adsorption capacities and easy operation. In this paper, three highly efficient polyacylate hybride hydrogels were prepared for systemmaticly sorption of toxic Pb2+ and Cd2+ from water. The major contents are as follows:1. A serial of graphene oxide enhanced sodium acrylate (AANa) and acrylamide (AM) copolymer hybrid hydrogels P(AANa-co-AM)/GO were prepared via dispersion polymerization. The prepared P(AANa-co-AM)/GO samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectrometry (FT-IR), Scanninig electron microscopy (SEM) and Thermogravimetric analysis (TGA), and the tensile strength, swelling ratio were also tested, and the adsorption performance of P(AANa-co-AM)/GO hydrogels for Pb2+ and Cd2+ were systematiclly investigated. The results indicate that the addition of 1.0wt% GO enhanced significantly the tensile strength and removal effcicncies of Pb2+ and Cd2+. The P(AANa-co-AM)/GO hydrogel synthesized with AA:AM=1:1, and 0.8wt% of crosslinker (N, N-methylene bisacrylamide, MBA) feed amount has a relatively higher removal effcicencies for Pb2+ and Cd2+, and possess a suitable swelling ratio of 282.2 g/g. The the optimal adsorption solution pH lies at 4.0-5.0 for Pb2+ and 4.0-6.0 for Cd2+; the existing of Mg2+ and Ca2+ (0.01?0.05mol/L) has a significant effect on the adsorption of Cd2+. The adsorption kinetics of Pb2+ and Cd2+ onto P(AANa-co-AM)/GO followed the pseudo-second order model and the adsorption isotherm followed the Langmuir model, the maximum adsorption capacities were calculated to be 452.25 and 196.38 mg/g for Pb2+ and Cd2+ at 298K, respectively. The P(AANa-co-AM)/GO hydrogel sorbent can be reused at least 4 times. The adsorption mechanism of Pb2+ and Cd2+ were analyzed by Energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) characterization. The fixed-bed column adsorption of Pb2+(80 mg/L) showed that the P(AANa-co-AM)/GO can purify effectively wastewater containing low concentration of Pb2+ and realized the in-situ regeneration of P(AANa-co-AM)/GO sorbent.2. The granular crosslinked PAANa hydrogel (gc-PAANa) was prepared via inverse suspension polymerization, and the asprepared gc-PAANa sample was characterized by SEM, FT-IR and TGA, and its swelling ratio was also tested. The gc-PAANa was used to remove Pb2+ from aqueous solution. The results indicate that gc-PAANa possesses good granhular micro-pores structures and a equilibrium swelling ratio of 71.6 g/g. The gc-PAANa can achive a good adsorption result in the pH range of 3.0?5.0, the equilibrium adsorption capacity of Pb2+ can reached over 198.5 mg/g for 200 mg/L of Pb2+. The adsorption kinetics of Pb2+ on PAANa followed the pseudo-second order model and the adsorption isotherm followed the Langmuir model, the maximum adsorption capacity was calculated to be 466.98 mg/g at 293K. The gc-PAANa can be reused at least 4 times by acid desorption. The adsorption mechanism for Pb2+ was analyzed by XPS characterization.3. The crosslinked PAANa coated Fe3O4 magnetic hybrid hydrogel (PAANa@Fe3O4) was prepared via dispersive solution polymerization combined with calcium ions surface-crosslinking. The prepared sample was characterized by XRD, FT-IR, SEM and TGA, and the magnetic separation effect was also tested. The characterization results showed that the PAANa@Fe3O4 has a diameter of 50?100?m with good magnetic response. The adsorption results revealed that the PAANa@Fe3O4 displayed good adsorption performance for Pb2+ and Cd2+ in the range of pH=2-6. The removal efficiencies of Pb2+ and Cd2+ can reached 99.87% for Pb2+(200 mg/L) and 94.13% for Cd2+(100 mg/L) when the sorbent dosage were 1.0 and 1.6 g/L at pH=5.0, respectively. The adsorption kinetics of Pb2+ and Cd2+ onto PAANa@Fe3O4 followed the pseudo-second-order model, and the adsorption isotherm followed the Langmuir model, the maxuimum adsorption capacities were calculated to be 427.93 mg/g for Pb2+ and 288.58 mg/g for Cd2+ at 293 K. The treatment of practical electrolytic pulp wastewater with complex components showed that the PAANa@Fe3O4 can effectively remove Pb2+ and Cd2+.