| With the development of industry, the heavy metal pollution has been more serious due to the over release of heavy metal ions into water, which brings huge damage to environment and human health. Therefore, it's of great significance for treatment of heavy metal pollution. Methods for removing heavy metal form water include chemical precipitation, membrane separation, and adsorption, and so on. Adsorption is promising due to its high efficiency, easy handling and low cost effectiveness. Considering the shortcoming of current adsorbents, the research of this paper is aiming to find a kind of adsorbent with high efficiency of heavy metal adsorption and selectivity which is easily prepared and controlled.2-Hydroxyethyl acrylate and 2-acrylamido-2-methy propane sulfonic acid (HEA/AMPS) based hydrogel was synthesized by gamma radiation, and characterized for the structure and partial behavior. The removal behaviour of heavy metal ions including Pb2+, Cd2+, Cu2+, Cr3+, Fe3+ from aqueous solution by the prepared HEA/AMPS chelating copolymer was examined with batch experiment, and the adsorption mechanism was studied. The results are shown as following:1. Polymer hydrogel with HEA and AMPS as monomers was successfully prepared by Co-y radiation at low temperature. The characterization results of hydrogel showed that hydrogel was porous with plenty of macropores, and the thermal stability of hydrogel was correlated to the AMPS content. The FT-IR spectrum and XPS spectrum of hydrogel confirmed the hydrogel as copolymer of HEA and AMPS. The results of swelling experiments showed that, the equilibrium degree of swelling increased with the increase of AMPS content in hydrogel, nearly lineation. The equilibrium degree of swelling of hydrogel prepared with the volume percentage of water 70% was larger than the others. The water absorbing quality of hydrogel was affected by all of HEA, AMPS and water.2. The heavy metal uptake capacity of hydrogel mostly increased with the increase of AMPS content, not as lineation. However, in the case of Cr3+, the adsorption capacity dropped when the AMPS content increase from 40% to 50%. The volume percentage of water also influenced the heavy metal adsorption capacity.3. In the experiment of effect of pH on Pb2+, Cr3+, Cd2+, Cu2+ adsorption, the heavy metal uptake capacity of hydrogel increased with the increase of solution pH, resulting from the decrease of electrostatic rejection at high pH. However, the maximum of Fe3+ adsorption capacity appeared at pH=2, coursed by reaction of electrostatic and hydrolysis of Fe3+. The heavy metal uptake capacity of hydrogel declined with the increase of solution temperature, indicating that the adsorption process of hydrogel was exothermic reaction.4. The metal uptake reached sasturation when the initial heavy metal concentration was over 1g/L. The adsorption isotherm fit Langmuir mode. The metal uptake increased with adsorption time, equilibrium of adsorption was reached at time for 24h in the case of Pb2+, Cd2+, Fe3+ and Cu2+, except for Cr3+, that of which was reached at time for 5h. The adsorption kinetics followed pseudo-second-order kinetic mode.5. The results of selective adsorption showed that when the heavy metal concentration was 200mg/L or 500mg/L, the priority order in multi-component adsorption was Cr3+>Cu2+>Cd2+>Pb2+. Trivalent ions showed higher selectivity than bivalent ions, as a result of higher charge density of trivalent ions which was good for ion exchange.6. The heavy metal adsorption of hydrogel mainly based on chemical adsorption and physical adsorption as auxiliary. Chemical adsorption relied on active group of hydrogel, while physical adsorption relied on the structure of hydrogel. The active group for heavy metal adsorption was-NHCO-and-SO3H in AMPS. The mechanism of heavy metal adsorption was chelation with N and ion exchange with-SO3H. |
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