Effects of Surface Functional Groups and Porous Structures on Adsorption and Recovery of Perfluorinated Compounds by Inorganic Porous Silicas

Abstract

The effects of porous structures and surface functional groups (silanol, 3-aminopropyltriethoxy, 3-mercaptopropyltrimethoxy, n-octyldichloroethoxy, and titanium substitution) on perfluorinated compounds (PFCs) adsorption and recovery were evaluated. The adsorption of PFCs on all adsorbents followed the pseudo-second-order model, and the adsorption rate was controlled by the pore diffusion, except for microporous zeolites and powder activated carbon (PAC). 3-aminopropyltriethoxy-grafted surface produced the highest PFCs adsorption capacities. Perfluorooctane sulfonic acid (PFOS) recovery from silica-based adsorbents (by ethanol extraction) efficiencies were higher than those of PAC and approached 100%. Hydrophobic organic functional groups can protect mesoporous structure from hydrolysis reactions in adsorption and solvent recovery processes.

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Keywords:

• adsorption
• perfluorinated compound
• porous structure
• recovery
• surface functional group

ACKNOWLEDGEMENTS

The authors are grateful for financial support from the 90th Anniversary of Chulalongkorn University Fund (Ratchadaphiseksomphot Endowment Fund), and the Thailand Research Fund, Thailand under grant no. MRG5380172. This work was carried out as part of the research cluster “Fate and Removal of Emerging Micropollutants in Environment” granted by the Center of Excellence for Environmental and Hazardous Waste Management (EHWM) and Special Task Force for Activating Research (STAR), both of Chulalongkorn University. The authors are also grateful for support from the Research, Development and Engineering (RD&E) fund through The National Nanotechnology Center (NANOTEC), The National Science and Technology Development Agency (NSTDA), Thailand (Project No. P-11-00985) of Chulalongkorn University. This research was also supported by the Higher Education Research Promotion and National Research University Project of Thailand, Office of the Higher Education Commission (FW1017A). Technical support from Department of Environmental Engineering, Faculty of Engineering, Chulalongkorn University, is also gratefully acknowledged.

Notes

^a Calculated by SPARC, http://ibmlc2.chem.uga.edu/sparc.

^b Reference (31, 32).

^c Reference (33).

^a Reference (18).

^b Reference (16).

^c Reference (19).

^a Initial PFOS and PFOA concentrations were 300 mg L⁻¹.

^b Initial PFOS and PFOA concentrations were 100 mg L⁻¹.

^a The mass to solution mixture ratio was 100 mg/50 mL.

^a q _e = adsorption capacity at equilibrium concentration of 100 mg L⁻¹( mg g⁻¹) (calculated by the best suitable isotherm).

^b  t_equi.  = time at equilibrium (h) (at initial concentration range 50 to 185 mg L⁻¹).