Study On The Removal Performance For Cr(?) On The Ion Exchange Resin D301 Modified By Poly Epichlorohydrin-dimethylamine

Cr(?)is a common toxic element in the environment attribute to its high biotoxicity and carcinogenicity,which has pernicious effects on most organisms and natural waters.Ion exchange resin is a widely used adsorbent due to its high mechanical strength and good regeneration property.In the present paper,a macroporous styrene weakly alkaline anion exchange resin,D301,was used to prepare the composite adsorbent with high specific surface area and good adsorption property through different methods of modification considering the limited adsorption capacity and the poor selectivity of the resin,which was applied to remove Cr(?)from wastewater.The specific surface area,Zeta potential and chemical composition of adsorbents were characterized.The adsorption performance of Cr(?)on the resins before and after modification was investigated,and the corresponding adsorption mechanism was discussed.The main contents and relevant conalusions of the paper were as followed:1.The composite adsorbent EPIDMA-D301 was prepared by supporting poly epichlorohydrin-dimethylamine served as modifying agent onto D301,which was used to remove Cr(?)in wastewater.The results showed that compared with D301,EPIDMA-D301 had better adsorption property for Cr(?)and was less affected by other anions.The adsorption behavior were well fitted with the Pseudo-second order kinetic model and the Langmuir isotherm model,and the maximum adsorption capacity of EPIDMA-D301 was 194 mg/g.Through the BET,Zeta potential,FT-IR and XPS analysis,it was found that the specific surface area,the content of N and Cl element and the surface charge of EPIDMA-D301 increased,as well the functional groups of adsorbents changed,indicating that EPI-DMA has been loaded on D301 successfully.And the results of FT-IR and XPS exhibited that the main adsorption mechanism of Cr(?)on EPIDMA-D301 was the electrostatic attraction between the quaternary ammonium group supported on resins with Cr(?)and the ion exchange between the functional groups of D301 resin with Cr(?).2.The composite adsorbent EDE-D301 was synthesized by immobilizing the monomers including dimethylamine,epichlorohydrin and ethylenediamine considered as modifying agents into D301 through in-situ polymerization method,and its adsorption capacity for Cr(?)was utilized to compare with EPIDMA-D301.The results exhibited that EDE-D301 had much higher adsorption performance for Cr(?),and was less affected by other anions.The adsorption data followed the Pseudo-second order kinetic model and the Langmuir isotherm model,and the maximum adsorption capacity of EDE-D301 was 298 mg/g.Through the BET,Zeta potential,FT-IR and XPS analysis,it was found that in contrast of EPIDMA-D301,EDE-D301 had a higher surface area and the content of N and Cl element of EDE-D301 increased by 3.87%and 5.75%,respectively.The degree of protonation of the adsorbent surface was higher,indicating the modifier in the form of monomers can be impregnated into the pores of D301,which improved the adsorption property of EDE-D301 for Cr(?).The results of FT-IR and XPS showed that the interaction between the functional groups polymerized by monomers and Cr(?)anions and ion exchange was the main adsorption mechanism of Cr(?)onto EDE-D301.3.The fixed-bed column experiments of Cr(?)onto EPIDMA-D301 and EDE-D301 were carried out and the effect of bed depth,flow rate and influent Cr(?)concentration on the breakthrough times were also investigated in order to estimate the adsorption performance for Cr(?)on adsorbents.The results demonstrated that the breakthrough time of adsorbents increased as the bed depth increased,but decreased as the flow rate and influent concentration increased.And the adsorption capacity for Cr(?)onto EDE-D301 was higher than that of EPIDMA-D301,and the time to reach saturation was longer.The fixed-bed adsorption behavior followed well with the Thomas model.Moreover,EDE-D301 still maintained good adsorption performance after four consecutive cycles.The results proved that EDE-D301 can effectively remove Cr(?)from wasterwater,which provided a theoretical basis for device design in practical industrial application.