| In recent years, large amount of heavy metals such as copper, iron, lead, mercury and cadmium ions were discharged into the air, water and soil in the process of the mining,smelting, which leaded series of environmental pollution problems. In addition, heavy metals were not biodegradable and tended to accumulate in living organisms, which leaded directly to threat to the health of human beings. Therefore, it was great significant to carry out the treatment of heavy metal pollution.Based on hard and soft acid-base theory and "soft-soft, hard-hard" rule of thumb,chelating resins that contain sulfur were soft base adsorbent and had a good adsorption performance towards heavy metals such as Cu(II), Pb(II) and Hg(II) and other soft acid type metal ions. And sulfur-containing chelating resin was strongly bonded to metal ions, it was widely used in the separation and enrichment of trace metal ions. Amides adsorbent had good acid and alkali resistance, better absorption, simple preparation, and degradation products of non-polluting, which had attracted more and more attention of scholars. Two kinds of novel chelating resins(THCMPS and EDTAMPS) which were based on chloromethylated bead(CMEPS) were synthesized by different modification methods. The materials were comprehensively analyzed with regard to characteristic functional groups and porous structure parameters(BET and BJH models), the sorption capability of the resin for heavy metal ions were investigated.The THCMPS was prepared via a reaction of carbon disulfide and amine resin(AMEPS),utilizing CMEPS as precursors of AMEPS and DMF as swelling agent. The results shows that the grafting rate could reach 67.9%, the maximum sorption capacity of copper ion was 81.57mg·g-1 and the optimum adsorption pH of copper ion was in the range of 4-7. Analysis of the adsorption results demonstrated that the adsorption process was better fitted by Langmuir adsorption equation than Freundlich or Temkin equation. The kinetics of this process was found to follow the pseudo-second-order kinetic model. The changes in thermodynamic parameters, particularly the standard enthalpy(?H), the standard entropy(?S) and the Gibbs free energy(?G) were calculated. The chelating resin was repeatedly used for five times and reserved 87.02% of initial adsorption capacity.The EDTAMPS was prepared via a reaction of ethylenediaminetetraacetic acid anhydride and AMEPS, utilizing CMEPS as precursors of AMEPS and DMF as swelling agent. The adsorption effect of the EDTAMPS for Cu(II), Cd(II) and Ni(II) was:Cd(II) >Cu(II) >Ni(II). The adsorption properties of the resin on Cd(II) improved with increasing the pH, the pH reached 3 and tended to balance, the effect of pH on Cu(II)adsorption performance was little, and the adsorption performance of Ni(II) increased slightly with the increase of pH. The kinetics of this process were found to follow the pseudo-second-order kinetic model and the chemisorption played a major role in the process of the adsorption. Thermodynamic parameters ?H>0, ?S>0 and ?G<0 showed that the adsorption process of the resin for Cu(II), Cd(II) and Ni(II) was spontaneous entropy production process, adsorption process was endothermic and elevated temperature was conducive to adsorption. The resin had good reuse, and the adsorption rate decreased slightly after 3 times of repeated use. Adsorption process primarily as complex heavy metal ions was the amide group.The research results showed that the two kinds of new chelating resins prepared by this paper had good adsorption properties, and it had good application prospects in the treatment of low concentration waste-water containing heavy metal ions. |
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