Adsorptive Removal Of Perfluorinated Compounds From Industrial Wastewater And Preparation Of Highly Selective Fluorinated Adsorbents

Perfluorinated compounds(PFCs),a type of typical organic pollutants,have drawn great attention recently due to their wide distribution in aquatic environments and potential toxic to animals and human beings.The contamination of PFCs in water is mainly due to the discharge of industrial wastewater.However,the removal efficiency of PFCs by traditional water treatment approaches is limited.By contrast,adsorption is suggested as a promising technology to remove PFCs from wastewater.The objectives of this study were therefore to(1)develop adsorbents with high sorption capacity for the effective removal of PFCs from actual wastewater,(2)prepare highly selective adsorbents for PFCs removal from water based on the fluorophility of C-F chains and investigate the mechanisms of selective sorption.The main results and conclusions are listed below.The washing wastewater of perfluorooctane sulfonyl fluoride contains high concentrations of perfluorinated carboxylates(PFCAs).For the first time,the optimal bamboo-derived activated carbon(BAC)and anion-exchange resin IRA67 were used and found to be able to effectively remove PFCAs from this wastewater.Both spent BAC and IRA67 were successfully regenerated by ethanol solution or Na Cl/methanol mixture,and IRA67 showed the stable removal of PFCAs in five adsorption cycles.Wastewater from chrome plating industry contains high concentrations of PFOS and F-53 B.A granular reactivated carbon(R-CAC)with enlarged pores in the range of 2-5 nm was prepared from commercial coconut-based activated carbon through one-step KOH activation.Over 90% removal of PFOS and F-53 B was achieved at the R-CAC dose of above 200 mg/L.The spent R-CAC was effectively regenerated by hydrothermal-activated persulfate oxidation.A novel fluorinated alkyl chain modified montmorillonite(F-MT)was synthesized via exchange of cationic fluorinated surfactant to selectively adsorb PFOS and PFOA from water.The F-MT possessed excellent selectivity for PFOS and PFOA in the presence of other hydrocarbon organic pollutants.The results of competitive sorption and density functional theory calculations verified that PFOS and PFOA were adsorbed on the C-F chain of F-MT,while hydrocarbon organic pollutants sorption occurred on the hydrocarbon part of F-MT.A novel magnetic fluorinated adsorbent with selective and fast adsorption of PFOS was synthesized via a simple ball milling of Fe3O4 and vermiculite loaded with cationic fluorinated surfactant.Fe3O4-loaded F-VT has very fast adsorption for PFOS with initial adsorption rates of 3759.4 mg/g/h.The loaded Fe3O4 nanoparticles increased the dispersibility of fluorinated vermiculite(F-VT)in water and offered the magnetic separability.It also demonstrates highly selective adsorption for PFOS in the presence of other organic compounds,due to the fluorophilicity of C-F chains intercalated in the adsorbent interlayers.This novel adsorbent exhibited much higher removal of PFOS from fire-fighting foam wastewater than powdered activated carbon and resin.The used Fe3O4-loaded F-VT was successfully regenerated by methanol and reused five times without obvious loss of PFOS removal and magnetic performance.