Preparation And Characterization Of Novel Thiol Fiber Materials For Removal Of Mercury(Ⅱ) From Water

Thiol-containing materials were known as good mercury adsorption materials. They were signed as good selectivity and high adsorption capacity. The paper prepared a novel thiol fiber material (cys-PAN) with L-cysteine monohydrochloride (L-CMHC) as the modification reagent, and polyacrylonitrile (PAN) fiber as the starting material. The effects of reaction temperature, reaction time, mass concentration of L-CMHC, mass ratio between PAN fiber and L-CMHC were studied through orthogonal experiments and single-factor experiments. It showed that the optimum reaction conditions were:reaction temperature125℃-130℃, reaction time4.5h, mass concentration of L-CMHC0.04g/mL, mass ratio between PAN fiber and L-CMHC1:0.5-1. The synthesis of10g fiber was carried out under the optimum reaction conditions, and the weight gain rate was up to34%. In order to characterize the structure of cys-PAN, FT-IR and Raman spectra was employed. In the FT-IR spectra, the stretching vibration peak of-CN (2243cm-1) decreased obviously in the cys-PAN fiber’s spectra. It said that-CN the reaction took place in-CN groups. In the Raman spectra, the appearance of two novel peaks,2425cm-1(-SH) and683cm-1(C-S), represented that cys-PAN fiber was a novel thiol fiber. TGA test and tensile force test results indicated that cys-PAN was a kind of materials with good thermal stability and mechanical strength. The thiol content of cys-PAN was1.56mmol/g as measured by indirect iodimetry.The research studied the performance of cys-PAN for the removal of Hg(Ⅱ). The effect of pH on adsorption indicated that the adsorption capacity increased obviously with the increase of pH at pH1.0-3.0, and changing weakly with pH at pH5.0-7.0. Isothermal adsorption experiments showed that the adsorption capacity increased with the increasing initial Hg(Ⅱ) concentration. The isothermal adsorption behaviors could be represented well by Langmuir and Freundlich isothermal adsorption equations, and the adsorption process belonged to heterogeneous single molecular layer adsorption. The maximum adsorption capacity at30℃and35℃were459mg/g and518mg/g, which obtained from the fitting of Langmuir isothermal equation. Adsorption kinetic experiments said that the adsorption equilibrium took about120min and240min at the initial Hg(Ⅱ) concentration of50mg/L and100mg/L. The desorption experiments showed that the mixed solution of thiourea and hydrochloric acid could elute the adsorbed Hg(Ⅱ) perfectly, and more than98%Hg(Ⅱ) was eluted from cys-PAN fiber, when the volume ratio between thiourea (5%, m/v) and hydrochloric acid (1mol/L) was1:0.667-1.5. And the cys-PAN fiber maintained good form and performance after several adsorption-desorption experiments. Desorption kinetic experiments demonstrated that the stripping ratio was above80%after40min, when the volume ratio between thiourea (5%, m/v) and hydrochloric acid (1mol/L) was1:1, and Hg(Ⅱ) was fully stripped at90min. The FT-IR spectra of cys-PAN fiber before and after adsorption described the removal of Hg(Ⅱ) was due to the interaction between Hg(Ⅱ) and-SH.The study showed that the novel cys-PAN fiber was a kind of good material with high thiol content, high mechanical strength and good thermal stability. The characterization of cys-PAN for the removal of Hg(Ⅱ) indicated that it has a broad application prospect in the field of Hg(Ⅱ) contained waste water purification.