The reactive species of electrochlorination (E-Cl) in the ultrahigh salinity water (1 %-15 % NaCl) were investigated using pyridine (Pyr) as the model pollutant. No • OH signal can be detected for the E-Cl process in the ultrahigh salinity water. The free radicals are dominantly composed of the reactive chlorine species (RCS) such as Cl • , Cl 2 •− and ClO • . Moreover, the steady concentrations of Cl 2 •− and ClO • , and thus their contributions to the Pyr removal, are higher than that of Cl • . In 15 % NaCl solution, at the current density lower than 3 mA cm −2 , the RCS cannot be generated. Compared with the RCS species, the contribution of free chlorine (FC) to the Pyr removal is slightly higher due to the abundant FC generated during the E-Cl process. However, the reactivity of RCS to Pyr is much higher than that of FC. The second-order reaction rate constants of Cl • , Cl 2 •− , ClO • and FC with Pyr are 4.1 × 10 9 M −1 s −1 , 8.0 × 10 6 M −1 s −1 , 2.2 × 10 5 M −1 s −1 and 1.9 × 10 −3 M −1 s −1 , respectively. Among the background substances, SO 4 2- ions shows the significantly inhibitory effect on the Pyr degradation. Furthermore, the degradation pathway of Pyr was also proposed in the study.
In this study, zirconia-functionalized magnetic core-shell mesoporous carbon composites (Fe3O4@C-ZrO2) were synthesized for the effective removal of Cr(III)-EDTA in high-salinity wastewater. Fe3O4@C-ZrO2 with Fe3O4 as a magnetic core and ZrO2 embedded in a mesoporous carbon skeleton were prepared by the sol-gel method in the nano-casting stage, which can be magnetically separated. The presence of ZrO2 on the adsorbents enhanced the adsorption of Cr(III)-EDTA and the maximum adsorption capacity of Fe3O4@C-ZrO2 was 16.21 mg·g−1 at pH = 3.0, which is remarkably higher than that of Fe3O4@C (3.65 mg·g−1). Fe3O4@C-ZrO2 has a strong anti-interference capability for cations in water, which can exhibit effective adsorption properties in presence of high concentration cations and anions (80 mmol·L−1) and high salt/complexant agent environments. Cr(III)-EDTA removal by adsorption of Fe3O4@C-ZrO2 was mainly through the formation of ternary complexes between ZrO2 in Fe3O4@C-ZrO2 and carboxylic acid groups in Cr(III)-EDTA. The Cr(III)-EDTA saturated Fe3O4@C-ZrO2 can be easily regenerated in 0.1 mol·L−1 NaOH than in 0.1 mol·L−1 HCl and still demonstrated an effective adsorption capacity for Cr(III)-EDTA after three repeated cycles. The results reflect the effective removal of Cr(III)-EDTA by Fe3O4@C-ZrO2 in high-salinity water, providing a new method for removing heavy metals in complex water.
W ater flux and hydrophobic durability play important roles in membrane distillation(MD) applications. Compared with the method of adsorbing nanoparticles by electrostatic adsorption, the surface roughness constructed by chemical bonding is more conducive to the performance of membrane. This paper reports a facile approach to fabricating superhydrophobic fluoroalkyl silane/polydimethylsiloxane@FeOOH@stabilized polyacrylonitrile(FAS/PDMS@FeOOH@SPAN) nanofibrous membrane(NFM) with outstanding hierarchical structures, aiming to achieve efficient and stable performance in MD. Electrospun polyacrylonitrile(PAN) membrane after peroxidation was chosen as the base membrane, followed by in-situ synthesis of iron oxyhydroxide and liquid-phase silanization. We tested the characteristics of FAS/PDMS@FeOOH@SPAN NFM in each preparation stage and its performance in direct contact membrane distillation(DCMD). The chemical bond between iron oxyhydroxide and the membrane is stronger, making the rough structure steady and dense. The FAS/PDMS@FeOOH@SPAN NFM exhibited a water contact angle of 155.4° and excellent hydrophobicity towards different pollutants. Besides, it showed satisfied properties with a water flux of 24.7 L·m −2 ·h −1 , a high salts rejection of ca. 100% and an extended-term stability in DCMD using hypersaline water(10%, mass ratio). It is believed that this novel study proposes a universal and efficient method to fabricate a superhydrophobic surface and has great potential for high-salinity wastewater treatment in MD.
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