Transformative Catalysis Purifies Municipal Wastewater of Micropollutants

Abstract

We describe the use of TAML/peroxide to reduce micropollutants (MPs) in Tucson, AZ, secondary municipal wastewater. The laboratory studies establish simple-to-apply MP abatements rivaling ozone in technical performance. The approach rests on the latest-generation TAML catalyst, 2, currently the highest-technical performance H 2 O 2 activator across both chemistry and biology. Thirty-eight MPs were examined with five 2/H 2 O 2 treatments (50 nM 2 with 22.4 ppm H 2 O 2 , 100 nM 2 with 11.2 ppm H 2 O 2 , 100 nM 2 with 22.4 ppm H 2 O 2 , 200 nM 2 with 11.2 ppm H 2 O 2 , and 200 nM 2 with 22.4 ppm H 2 O 2 ) and four ozone treatments (2, 4, 6, and 8 ppm). Satisfactory analytical data were returned for 25 MPs that were monitored kinetically (LC-MS/MS) from 6 min to 6 h. For all 2/H 2 O 2 conditions, decreases in MP concentration had either ceased at 30 min or showed marginal improvements at 1 h remaining constant to 6 h. The highestperformance 2/H 2 O 2 system (200 nM 2 with 22.4 ppm H 2 O 2 ) outperformed 2 ppm ozone virtually across the board, delivering micropollutant percent reductions (MPPRs) of 26−98% corresponding to performance advantage ratios over 2 ppm ozone of ∼0.9− 8. These data indicate that 2 (1 kg at 70 nM) and H 2 O 2 (53.55 kg at 11.2 ppm) would treat the daily wastewater output of 150,000 Europeans [150 L day −1 (population equivalent) −1 , 22,500 tons total] in a manner comparable to that of a common ozone administration of 3 ppm, establishing a new approach worthy of further optimization for municipal wastewater MP treatment.

Curbing chlorine disinfection byproduct formation with a biomimetic FeTAML oxidation catalyst

“…These [Fe(TAML)] − species are oxidised by hydrogen peroxide to form extremely reactive iron(V)-oxo species (see Scheme 2) which, in turn, are capable of oxidising the strong C-H and C-C bonds in organic micropollutants. [10][11][12] Selectivity might also be engineered into the high-valent metal catalysts, such as the [Fe(O) (TAML)] − system described here, to enable more targeted removal of micropollutants in the presence of far greater Scheme 1 Top: Reactions of phenol, with chlorine disinfectant (ClOH/ClO − ). Below: One of the many pathways that generate chloroform from the reactions of phenol with chlorine disinfectant (ClOH), showing the consumption of at least four equivalents of chlorine for each molecule of chloroform produced.…”

“…[17][18][19] We have recently demonstrated that hydrophobic disinfection byproducts can be quantified in real time using a scaled down experimental laboratory reactor interfaced directly to a membrane inlet mass spectrometer, with detection limits for CHCl 3 and CHBrCl 2 trihalomethanes at 2 ppb (16 and 12 nM, respectively), 20 well below the guidelines for safe drinking water set by the WHO (300 and 60 ppb for CHCl 3 and CHBrCl 2 , respectively). 2 Previous quantification studies at realistic concentrations of micropollutants have largely relied on far less sensitive 1 H NMR or UV-vis absorbance spectroscopies, 10,15 or more sensitive chromatographic techniques (e.g., UHPLC), [10][11][12] which lose time resolution during sample preparation and analyte residence time (tens of minutes to hours). In this work, we follow the formation of disinfection byproducts on hypochlorite treatment of Danish tap water, laced with phenol (16 μM, 1.5 ppm) as a model micropollutant, and demonstrate that even very small concentrations of an [Fe(TAML)] − catalyst (tens of nM, ppb) result in rapid removal of phenol without halophenol or trihalomethane accumulation.…”

“…These [Fe(TAML)] − species are oxidised by hydrogen peroxide to form extremely reactive iron( v )-oxo species (see Scheme 2) which, in turn, are capable of oxidising the strong C–H and C–C bonds in organic micropollutants. 10–12 Selectivity might also be engineered into the high-valent metal catalysts, such as the [Fe(O)(TAML)] − system described here, to enable more targeted removal of micropollutants in the presence of far greater concentrations of harmless natural organic matter, which otherwise could consume and unnecessarily waste oxidising species. 13,14…”

“…2 Previous quantification studies at realistic concentrations of micropollutants have largely relied on far less sensitive 1 H NMR or UV-vis absorbance spectroscopies, 10,15 or more sensitive chromatographic techniques ( e.g. , UHPLC), 10–12 which lose time resolution during sample preparation and analyte residence time (tens of minutes to hours). In this work, we follow the formation of disinfection byproducts on hypochlorite treatment of Danish tap water, laced with phenol (16 μM, 1.5 ppm) as a model micropollutant, and demonstrate that even very small concentrations of an [Fe(TAML)] − catalyst (tens of nM, ppb) result in rapid removal of phenol without halophenol or trihalomethane accumulation.…”

Degradation of Model Compounds by 1O2-Generating Photosensitizer–Doped Membranes

“…There is considerable interest in sustainable new technologies that avoid disinfection byproducts. − Two conventional alternatives, ozonation and UV radiation, have their own limitations. − While little to no harm to humans and aquatic life is caused by UV-radiation-based processes, they are less cost-effective than chlorination . Alternatively, bacteria and viruses are more effectively destroyed by ozone.…”