| As one of the most important high-performance polymeric materials, poly(p-phenylene terephthalamide) fibers(PPTA) and their composites possess excellent properties, such as high tenacity and modulus, light weight, and low electrical.Therefore, PPTA has been widely used in the fields of aviation, aerospace, military,automobile, ballistic fabrics, mechanical, and petrochemical. However, the increasing production and consumption of PPTA leads to a large quantity of waste materials.PPTA products cannot be easy biodegraded and dissolved due to its aromatic rigid polymer chain, high crystallinity, and poor activity of amide group. In order to avoid waste PPTA to pollution the environment. In this paper, we prepared EDA anchored PPTA through chemical modified method. A series of aramid-based adsorbents were prepared by the functionalization of waste poly(p-phenylene terephthalamide)(PPTA)with different content of ethylenediamine(EDA). The synthetic materials were characterized, and its adsorption properties were studied.In this paper, The adsorbents of PPTA-ECH-EDA-1~PPTA-ECH-EDA-4 was sythesized by adopting the homogeous reaction method with epichlorohydrin and ethylenediamine as the modified agent. In a typical procedure, The sodium salt of dimethyl sulfoxide was prepared by NaH reaction with dimethyl sulfoxide, then the PPTA powder was added to the reaction mixture, a homogeneous solution of sodium salt of PPTA in DMSO was obtained. Epichlorohydrin was added to the DMSO solution of PPTA salt for preparation of PPTA-ECH, viaing a ring-opening reaction of ethylenediamine with the epoxidation of PPTA for sythesized PPTA-ECH-EDA, and stydied the adsorption properties.Their structures were characterized by field emission scanning electron microscopy(FESEM), transmission electron microscopy(TEM),fourier transform infrared spectroscopy(FTIR), thermogravimetric analysis(TG), and elemental analysis. FTIR spectrum indicate that the epoxy groups were succesful introduced onto PPTA and the completed reaction of PPTA-ECH with EDA.Thermogravimetric analysis showed the thermostability of PPTA-ECH-EDA slightly decreased, the final weight loss can indicated the grafting percentage was increased wiht the increase of dosage of modified agent. The FESEM and TEM imagines can observed that the adsorbents are all nanospheres with the diameters range from 20 to70 nm. Elemental analysis were further indicating the successful introduction of functional groups on PPTA.The binding behaviors of PPTA-ECH-EDA for metal ions such as Hg(II), Au(III), Pb(II),Ag(I), Cu(II), Cd(II) and Ni(II) were evaluated. Results showed that PPTA-ECH-EDA exhibited higher adsorption capacity for Hg(II) and Au(III). The influence of pH on the adsorption performance, adsorption kinetics, adsorption isotherms and adsorption selectivity were studied. Kinetic adsorption indicated the pseudo second-order model can reasonable describe the adsorption process for Hg(II) and Au(III), while isotherm adsorption can be well fitted by Freundlich models for Hg(II), Langmuir model can better describe the process of gold adsorption. According to calculating the thermodynamic parameter △G,△H and △S.It could be seen that enthothermic heat of adsorption, the increase of disorder at the solid–solution interface during the adsorption of Hg(II) and Au(III) and the adsorption process is spontaneous. The adsorption mechanism was revealed by X-ray photoelectron spectroscopy(XPS). PPTA-ECH-EDA could be used as an effective adsorbent for removal of Hg(II) and Au(III) from wastewater. The present research also provides a simple and efficient way for the reuse of waste PPTA. |
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