The Preparation Of Low-cost Activated Carbon Fibers And Its Application In Dye Wastewater Purification

Many organic dyes were widely used in textile, paper-making, printing, coating,rubber and food industries. The presence of dyes even at low concentration in water resources caused harmful effects on human health and living environment. Therefore,how to treat the dye wastewater effectively become more and more important. In this study, activated fibrous carbon materials(ACFs) were prepared from various precursors by different physical and chemical methods. The obtained products were characterized by X-ray diffraction(XRD), transmission electron microscope(TEM),scanning electron microscopy(SEM), nitrogen adsorption-desorption measurement and Fourier transform infrared spectroscopy(FT-IR). The adsorption properties of different products were tested towards different dye wastewaters.Mesoporous carbon nanofibers(MCNFs) assembled by nanoparticles were synthesized using ferric-nitrilotriacetate(Fe-NTA) nanofibers as the precursors. The obtained MCNFs were first used for the adsorption of MB and MO, respectively. The MCNF samples with long fibrous morphology(about 150 nm in diameter), pore size was 3-4nm and the specific area was about 392.3 m2 g-1. The influence of pH on the removal of MB and MO by MCNFs was studied. The maximum adsorption capacity of MCNFs on MO and MB were 137.25 mg g-1 and 110.99 mg g-1, respectively.Taking into account the small specific surface area of the MCNF materials, the activated carbon fibers assembled by nanospheres(NC-1) were prepared by nikel-nitrilotriacetate(Ni-NTA) annealing under enclosed condition and further treatment of NC-1 obtained carbon fibers assembled with hollow nanospheres(NC-2).The specific surface area of NC-2 reached 422.3 m2 g-1, and the adsorption capacity of MB increased to 147.23 mg g-1. The obtained data were fitted by kinetics and isotherm models. The adsorption of MB by MCNFs and NC-2 were both well described by the pseduo-second-order kinetic model and Langmuir isotherm model.The MCNFs and NC-2 had good adsorption properties for MB, but the raw materials used in the preparation of these materials were more expensive and the synthesis process were more complicated. Therefore, the ACFs were prepared using cotton waste and cortaderia selloanaas flower spikes(CSFS) as raw materials by different physical and chemical methods. The obtained products were prepared from cotton waste by closed calcination and acid leaching methods, and the obtained ACFs were employed for the MB adsorption. The optimum conditions for adsorption of MB were evaluated by changing various parameters such as ionic concentrations, solution pH, contact time and temperature. The results indicated that the adsorption capacity of MB onto ACFs reached the maximum when the pH value was 7, and decreased with the increase of the concentration of Ca2+ and Na+. The equilibrium data for MB adsorption was fitted to the Langmuir, and the maximum monolayer adsorption capacity for MB were 594.3 mg g-1, 643.3 mg g-1 and 697.1 mg g-1, respectively.Novel carbon fibers were first prepared from CSFS under enclosed condition at 500 oC, the obtained products were used for the adsorption of MB. SEM images showed that the obtained cortaderia selloanaas carbon fibers(CSCF) can keep the same morphology with CSFS and no obvious breakage or scattered. The equilibrium experimental data were analyzed by the Langmuir, Freundlich, Temkin,Dubinin-Radushkevich(D-R) and Harkins-Jura(H-J) models. The equilibrium data for two dyes adsorption were fitted to the Langmuir. The calculated thermodynamic results(?G? < 0, ?H? > 0, ?S?> 0) showed that the adsorption process of MB onto CSFS and CSCF were spontaneous and endothermic in nature.