title: In-situ regeneration of saturated granular activated carbon by an iron oxide nanocatalyst.
abstract: Granular activated carbon (GAC) can remove trace organic pollutants and natural organic matter (NOM) from industrial and municipal waters. This paper evaluates an iron nanocatalyst approach, based on Fenton-like oxidation reactions, to regenerate spent GAC within a packed bed configuration after saturation by organic compounds. Specifically, we focus on regenerating GAC packed beds equilibrated with varying influent concentrations of phenol, a model organic compound. Iron nanocatalysts were synthesized using ferric chloride, a chemical already used as a coagulant at municipal WTPs, and reacted with hydrogen peroxide (H(2)O(2)) for the purpose of in-situ regeneration. Up to 95% of phenol adsorption capacity was regenerated for GAC equilibrated with 1000 mg/L of phenol. Using this technique, at least four adsorption-regeneration cycles can be performed sequentially for the same batch of GAC with fresh iron nanocatalysts while achieving a regeneration efficiency of 90 ± 5% between each loading. Moreover, the iron nanocatalyst can be recovered and reused multiple times. Lower initial adsorbate concentrations (10-500 mg/L) resulted in a slightly lower saturated adsorbent-phase concentration of phenol and lower regeneration efficiencies (72 ± 5%). Additionally, this catalytic in-situ regeneration was applied to GAC saturated by NOM. A slightly lower regeneration efficiency (60%) was observed for the Suwannee River NOM adsorption capacity of GAC. The next step is validation in a pilot-scale test that applies this regeneration technique to a GAC adsorber employed in NOM removal.
authors.affiliation: School of Sustainable Engineering and Built Environment, Ira A. Fulton Schools of Engineering, Arizona State University, 501 E. Tyler Mall, ECG 252, Tempe, AZ 85287-5306, USA. cchiu8@asu.edu
authors.forename: Chao-An
authors.initials: CA
authors.lastname: Chiu
authors.forename: Kiril
authors.initials: K
authors.lastname: Hristovski
authors.forename: Scott
authors.initials: S
authors.lastname: Huling
authors.forename: Paul
authors.initials: P
authors.lastname: Westerhoff
mesh_terms: D000327:Adsorption; D002244:Carbon / Q000737:chemistry*; D002384:Catalysis; D005290:Ferric Compounds / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry; D049329:Nanostructures; D010084:Oxidation-Reduction; D010636:Phenols / Q000737:chemistry; D059027:Recycling; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
chemical_list: D005290:Ferric Compounds; D010636:Phenols; D014874:Water Pollutants, Chemical; C000499:ferric oxide; D002244:Carbon; D006861:Hydrogen Peroxide