Much has been written about theory and practice in the law, and the tension between practitioners and theorists. Judges do not cite theoretical articles often; they rarely "apply" theories to particular cases. These arguments are not revisited. Instead the Essay explores the working and interaction of theory and practice, practitioners and theorists. The Essay starts with a story about solving a legal issue using our intellectual tools - theory, practice, and their progenies: experience and "gut." Next the Essay elaborates on the nature of theory, practice, experience and "gut." The third part of the Essay discusses theories that are helpful to practitioners and those that are less helpful. The Essay concludes that practitioners theorize, and theorists practice. They use these intellectual tools differently because the goals and orientations of theorists and practitioners, and the constraints under which they act, differ. Theory, practice, experience and "gut" help us think, remember, decide and create. They complement each other like the two sides of the same coin: distinct but inseparable.

Of Theory and Practice

Activation of peroxymonosulfate by base: Implications for the degradation of organic pollutants.

An overview on the advanced oxidation processes applied for the treatment of water pollutants defined in the recently launched Directive 2013/39/EU.

Synthesis, properties and applications of ZnO nanomaterials with oxygen vacancies: A review

Preparation of ultrafine magnetic biochar and activated carbon for pharmaceutical adsorption and subsequent degradation by ball milling.

Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) have received high concerns due to their extreme persistence, and very few technologies have been reported for their complete destruction. For sound PFCs wastes disposal, mechanochemical method was employed using a planetary ball mill. Potassium hydroxide (KOH) was identified as the best comilling reagent and nearly complete destruction of both PFOS and PFOA was realized. The measured water-soluble fluoride accounted for most of the organic fluorine. The final products of PFOS after treatment were shown to be KF and K2SO4 by XRD analysis. The mass ratio between PFOS and KOH significantly affected the fluoride recovery but not for PFOS destruction and the sulfate recovery. The gradual formation of sulfate and fluoride reveals that the degradation of PFOS is initiated with the dissociation of the sulfonate group. FTIR spectra further showed the disappearance of the -CF3 and -CF2- groups with the generation of sulfate. The cleavage of C-F bonds in PFOS and the formation of fluoride ion were also identified by XPS spectra. On the basis of these results, possible reaction pathways were proposed. The approach was also successfully applied for the destruction of PFOS and PFOA homologues with different chain lengths.

Destruction of Perfluorooctane Sulfonate (PFOS) and Perfluorooctanoic Acid (PFOA) by Ball Milling

A rapid (1.5 h) one-step ball milling (BM) method was developed not only to modify commercial MnO2 via top-down approaches (BM0), but also to bottom-up synthesize MnOx by cogrinding of KMnO4 and MnC4H6O4 (BM1) or KMnO4 and MnSO4 (BM2). Catalysts activity on gaseous POPs removal was tested using hexachlorobenzene (HCBz) as surrogate. Catalytic performance decreases in the order of BM2 ≈ BM1 (T90% = 180–200 °C) > BM0 (260 °C) > CMO ≈ cryptomelane MnO2 (>300 °C). Both adsorption and destruction contribute to HCBz removal at 180 °C while destruction prevails at 200–300 °C. Mechanism studies show that destruction activity is lineally correlated with the amount of surface reactive oxygen species (Oads); stability is determined by the removal of surface chloride, which is associated with the mobility of bulk lattice oxygen (Olat); adsorption capacities are linearly correlated with surface area and pore structure. With the aid of extensive characterizations the excellent performance of BM prepared samples can be ...

Ball milling synthesized MnOx as highly active catalyst for gaseous POPs removal: significance of mechanochemically induced oxygen vacancies.

Mechanochemical destruction of halogenated organic pollutants: a critical review

Perfluorooctane sulfonate (PFOS), a widely used mist suppressant in hard chrome electroplating industry, has been listed in the Stockholm Convention for global ban. 6:2 Fluorotelomer sulfonate (6:2 FTS) acid and salts have been adopted as alternative products in the market, but no data about their abiotic degradation has been reported. In the present study, the degradability of 6:2 FTS potassium salt (6:2 FTS-K) was evaluated under various advanced oxidation processes, including ultraviolet (UV) irradiation, UV with hydrogen peroxide (H2O2), alkaline ozonation (O3, pH = 11), peroxone (O3/H2O2), and Fenton reagent oxidation (Fe(2+)/H2O2). UV/H2O2 was found to be the most effective approach, where the degradation of 6:2 FTS-K followed the pseudo-first-order kinetics. The intermediates were mainly shorter chain perfluoroalkyl carboxylic acid (C7 to C2), while sulfate (SO4 (2-)) and fluoride (F(-)) were found to be the final products. The high yields of SO4 (2-) and F(-) indicate that 6:2 FTS-K can be nearly completely desulfonated and defluorinated under UV/H2O2 condition. The degradation should firstly begin with the substitution of hydrogen atom by hydroxyl radicals, followed by desulfonation, carboxylation, and sequential "flake off" of CF2 unit. Compared with PFOS which is inert in most advanced oxidation processes, 6:2 FTS-K is more degradable as the alternative.

Kunlun Zhang

Papers

Destruction of Perfluorooctane Sulfonate (PFOS) and Perfluorooctanoic Acid (PFOA) by Ball Milling

Ball milling synthesized MnOx as highly active catalyst for gaseous POPs removal: significance of mechanochemically induced oxygen vacancies.

Mechanochemical destruction of halogenated organic pollutants: a critical review

Stability of 6:2 fluorotelomer sulfonate in advanced oxidation processes: degradation kinetics and pathway

Mechanochemical degradation of tetrabromobisphenol A: performance, products and pathway.