Preparation And Absorptive Characteristics Of Polyphenylene Sulfide Based Functional Fiber

Ion exchange fiber has been widely used in environmental protection, water treatment, and cleaner production. According to the requirement for application in rigorous environment, ion exchange fiber with desired properties should be explored, such as good mechanics, thermal stability and chemical stability. Polyphenylene sulfide (PPS) fiber is considered as a new type specialty synthetic fiber with excellent mechanical strength, chemical and thermal stability, it could be used in many areas, such as filter felt for high-temperature filtration and chemical corrosive fluids. In recently years, PPS fiber has been modified by melt-spinning and hyperbranched, however, few of chemical modification was reported in the literature. In this paper, a series of ion exchange fibers based on PPS fiber had been prepared, and its adsorption capacity for heavy metal was investigated. The main content was as follows:(1) Chloromethylated polyphenylene sulfide (CMPPS) fiber was prepared by Friedel-Crafts reaction. Due to high degree of crystallinity and lower reactivity of PPS fiber, a series of swelling agents were chosen to swell the PPS fiber, The highest swelling rate was achieved in 1,2-dichloroethane. In the present study, chloromethylation reaction of PPS fiber carried out in air, N2, CO2 atmosphere were also investigated. The results indicated that the chorine content of CMPPS fiber was high when reaction carried out under inert gas atmosphere. Compared to air atmosphere, the reaction carried out in hydrothermal reaction vessel could reduce the reaction time, saving agent and improve the chorine content of CMPPS fiber. The result showed that it was an efficient method that chloromethylation reaction of PPS fiber can be carried out in hydrothermal reaction vessel.(2) A series of novel weak basic ion exchange fibers were prepared via the functionalization of CMPPS fiber with methylamine (MA), ethylenediamine (ED), diethylenetriamine (DE), triethylenetetramine (TE). FT-IR, elemental analysis, TG-DTG, SEM, XRD were used to analyze and characterize its physicochemical structure and properties. The results shown that the functional fibers had high functional group contents (PPS-MA 4.85 mmol/g, PPS-ED 5.21 mmol/g, PPS-DE 5.85 mmol/g for and PPS-TE 6.89 mmol/g, respectively). The result of TG-DTG showed that these functional fiber exhibited excellent thermostability. The functional groups of fiber were decomposed between 300 and 400℃, and PPS skeleton had no decomposition until 500℃. The Cr(VI) adsorption capacity of the PPS-ED and PPS-DE fibers in the aqueous was investigated. The effect of various parameters, such as pH, initial concentration, contact time and temperature, had been evaluated. The results showed that the weak basic fibers had outstangding adsorption capacity for Cr(VI), the maximum adsorption capacity of PPS-ED and PPS-DE fiber were 220.41 mg/g and 300.99 mg/g, respectively. The adsorbed Cr(VI) on fiber could be conveniently eluted by aq. NaOH, and the adsorption capacity of fiber was not changed significantly after six adsorption-desorption cycles.(3) The novel strong basic anion exchange fiber (MZPPS) was prepared via the introduction of N-methylimidazolium group on PPS matrix. By the Box-Behnken experiments design, the optimum preparation conditions of MZPPS fiber were found as follows:reaction temperature 50℃, reaction time 8.3 h, and N-methylimidazolium/CMPPS fiber ratio (3.4:1). In this case, exchange capacity of the MZPPS fiber was 3.89 mmol/g. The structures of anion exchange fiber were charactered through FT-IR, and the content of functional groups was evaluated by chemical titration and elementary analysis. The strong basic exchange fiber presented high thermostability according to TG-DTG and good chemical stability under the experimental conditions.The Cr(VI) adsorption ability on the functionalized fiber from the aqueous was investigated by batch adsorption as well as column studied. The effect of different parameters, such as pH, adsorbate concentration, contact time and temperature, had been evaluated. The MZPPS fiber could be used at the wide pH range 1-12 and was very suitable to remove Cr(VI) at a low concentration level. Adsorption process well fitted in Langmuir adsorption isotherm model, and thermodynamic parameters of Cr(VI) adsorption were also calculated. Maximum adsorption of Cr(Ⅵ) on the fiber was 224.0 mg/g at pH 4.5. Adsorption of anion on the fiber with N-methylimidazolium functional groups was sufficiently fast, and adsorption reached equilibrium within 30 min. Cr(VI) adsorption was found to be effective and selective from solutions in the presence of having amounts of competitive anions,such as Cl-and SO42-.The MZPPS fiber was also found to be effective for the removal of As(Ⅴ). For the adsorption of As(Ⅴ), the maximum adsorption was observed at pH 8.6, and maximum adsorption was 81.3 mg/g. Adsorption process was rapid and completed within 15 min, reaching a removal efficiency above 99%. Adsorption process was well fitted in pseudo-second-order equation. The propertity of MZPPS fiber was not changed significantly after five-adsorption-desorption cycles.(4) A novel weak acid ion exchange fiber (WAPPS) was prepared by oxidizing CMPPS fiber with HNO3 solution, and the physicochemical properties and adsorption performance of WAPPS fiber were characterized. Exchange capacity of weak fiber was up to 2.04 mmol/g, the WAPPS fiber presented high thermal stability according to TG-DTG. The static adsorption capacity of fiber for Cu2+ was 31.55 mg/g.