| With the acceleration of industrial growth, the discharge of heavy metals into water has become more and more severe, and the chromium pollution phenomenon is significantly serious in aqueous solution. As hexavalent chromium is more poisonous and harmful, it is quite necessary for its efficient disposal. Chemical precipitation, electrolysis method and other traditional methods have been applied for the decontanmination of chromium-containing wastewater treatment and have certain limitations. Taking all factors into consideration, adsorption method with highly efficient ability for the treatment of heavy metal wastewater has become the optimal choice, and exhibits a broad prospect in the future. Consequently, it is of great practical significance for the preparation of adsorbent with high efficiency, energy saving and recyclable properties of materials for chromium-containing wastewater treatment.The amidoxime modified fibers(PANMW-AO) were prepared by the surface modification to polyacrylonitrile(PAN) fibers under microwave irradiation. Synthesis conditions were optimized by orthogonal experiment. Both fibers before and after modification were characterized by fourier transform infrared spectroscopy(FTIR), scanning electron microscope(SEM), X-ray energy dispersion spectrometer(EDS) and X-ray photoelectron spectrometer(XPS), and their mechanical performance were tested, additionally. The results indicated that the optimum preparation conditions for the preparation of modified fibers were found at reaction temperature of 105 °C, ratio of reactants(the mass ratio of hydroxylamine hydrochloride and sodium carbonate) of 4:3, reaction time of 7 min, and bath ratio of 40:1. Microwave irradiation method can greatly shorten the reaction time, while the mechanical properties of the modified fiber were retained to the most degree to meet the requirements of practical application.The static adsorption experiment of the modified fibers was performed by using Cr(Ⅵ) as the processing target. The influences of p H value, adsorption time, initial concentration of Cr(Ⅵ) and adsorption temperature were investigated thoroughly. Meanwhile, the adsorption performances of modified fibers with other heavy metal ions as well as its regeneration properties were also discussed. The adsorption isothermal models and dynamic models have been employed to simulate the experimental data and the parameters of the models were accessed accordingly. Additionally, the adsorption mechanism of the modified fibers for Cr(Ⅵ) was analyzed. The experimental results showed that the process of modified fiber adsorbing Cr(Ⅵ) fits the Langmuir isotherm model and the secondary reaction kinetics model better which indicated the adsorption process was mainly chemical adsorption and obeyed the monolayer molecule adsorption.Using the modified fibers as adsorption material, the dynamic adsorption process of chromium-containing waste water was studied in organic glass. Dynamic experiments showed that the optimum operating conditions were found at a loading degree of the modified fibers of 0.5 g and the hydraulic retention time of 1 min. Through fitting the experimental data by Thomas model and Yoon-Nelson model, the results indicated that two models were all suitable to describe the dynamic adsorption performance of the modified fibers for Cr(Ⅵ). These will provide reliable design parameters for the modified fibers to apply in the chromium-containing waste water. |
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