Removal of perfluoroalkyl and polyfluoroalkyl substances in water and water/soil slurry using Fe0 -modified reactive activated carbon conjugated with persulfate.

Treatment of highly persistent perfluoroalkyl and polyfluoroalkyl substances (PFAS) has been a challenging but significant task. Herein, we propose adsorption-mediated chemical decomposition of PFAS implemented by using granular activated carbon (GAC) impregnated with zerovalent nanoiron (ZVI, Fe0 ), so-called reactive activated carbon (RAC). The effects of reaction temperature, injection of persulfate (PS), and presence of soil on removal of PFAS in water were evaluated. Results showed that RAC conjugated with PS at 60°C exhibited decomposition of PFAS, exclusively all three carboxylic PFAS tested, obviously producing various identifiable short-chain PFAS. Carboxylic PFAS were removed via physical adsorption combined with chemical decomposition while sulfonic PFAS were removed via solely adsorption mechanism. The presence of soil particles did not greatly affect the overall removal of PFAS. Carbon mass balance suggested that chemical oxidation by radical mechanisms mutually influences, in a complex manner, PFAS adsorption to GAC, ZVI and its iron derivatives, and soil particles. Nonetheless, all tested six PFAS were removed significantly. If successfully developed, the adsorption-mediated decomposition strategy may work for treatment of complex media containing PFAS and co-contaminants under different environmental settings. PRACTITIONERS POINTS: Treatment of persistent per- and polyfluoroalkyl substances (PFAS) was addressed. Activated carbon with zerovalent iron was examined in the presence of persulfate. The system significantly removed and decomposed PFAS in water and soil mixture.

LED-Based Ultraviolet Oxidation of Pharmaceuticals: Effects of Wavelength and Intensity, pH, and TiO2 Loading.

The presence of pharmaceuticals in water resources has alarmed water and health authorities. This study evaluated ultraviolet-based oxidation as a means to decompose sulfamethoxazole, ibuprofen, and triclosan. In particular, the study evaluated using light emitting diodes (LEDs), the so-called ultraviolet LEDs (UV-LEDs), as an alternative ultraviolet source to the problematic mercury lamps that are conventionally used in the decomposition of pharmaceuticals in water. The study explored various conditions of varying ultraviolet wavelength, irradiation intensity, reaction pH, and TiO2 loading. It compared the photolytic decomposition of the pharmaceuticals with their photocatalytic decomposition. The photolytic decomposition of the pharmaceuticals was solely determined by the relation between their ultraviolet absorption characteristics and the ultraviolet emission spectra of the LEDs. Reaction pH greatly affected both photolytic decomposition and photocatalytic decomposition. The presence of TiO2 in cases where significant photolysis was present inhibited the overall decomposition process. However, in all cases, photocatalysis showed better mineralization than photolysis.