Interaction between polyacrylamide super absorbent polymers and heavy metal ions

In order to study the adsorption capacity of super absorbent polymers to heavy metals, the polyacrylamide super absorbent polymers were put into standard solutions of Cu(NO3)2 and Pb(NO3)2. The interaction between super absorbent polymers and Cu2+ and Pb2+was investigated. The results indicated that water absorbency of the super absorbent polymers decreased with the increase of the concentration of Cu2+ and Pb2+. There was a significant power function relationship between water absorbency and ion concentration. Ions adsorption amounts increased significantly with the increase of the concentration of Cu2+ and Pb2+. The maximum adsorption amounts of Cu2+ and Pb2+ were 131.72 and 242.68 mg/g, respectively. The adsorption process of super absorbent polymers was in accordance with the Freundlich isotherm equation. The adsorption amounts of Cu2+ and Pb2+ of the super absorbent polymers increased over time, and the adsorption speed decreased gradually. The kinetic curves of adsorption can be described by quasi two-level dynamic equation. In the same mass concentration, both adsorption amounts and adsorption speed of Pb2+ were higher than those of Cu2+. Gels released Cu2+ and Pb2+ very fast, reaching balance in one hour. The desorption rate was not high in deionized water, but in 1 mol/L HNO3 solution, the desorption rates of Cu2+ and Pb2+ were all higher than 85%. After three times of replication, super absorbent polymers’ equilibrium amounts of adsorption to Cu2+ and Pb2+ were about 75% and 78% of the first time. These results indicate that super absorbent polymers have practical value in wastewater treatment and remediation of soil containing heavy metals.