Efficient decomposition of perchlorate to chloride ions in subcritical water by use of steel slag.

Decomposition of perchlorate (ClO4-) in subcritical water in the presence of steel slag, a by-product of the steel industry, was investigated. Reactivity of ClO4- was low in pure subcritical water state up to 300 °C, whereas adding steel slag efficiently accelerated the decomposition of ClO4- to Cl-, with no leaching of heavy metals such as chromium and other environmentally undesirable elements (boron and fluorine). When the reaction was performed in subcritical water at a relatively low temperature (250 °C) for 6 h, virtually all ClO4- ions were removed from the reaction solution. The concentration of Cl- after the reaction was well accounted for by the sum of the amount of Cl- ascribed to the decomposition of ClO4- and the amount of Cl- leached from the slag. This method was successfully applied to decompose ClO4- in water samples collected from a man-made reflection pond following a fireworks display, even though these samples contained much higher concentrations of Cl- and SO42- than ClO4-.

High-performance liquid chromatography with conductimetric detection of perfluorocarboxylic acids and perfluorosulfonates.

A rapid and simple method for separating and determining various environmentally harmful perfluorocarboxylic acids and perfluorosulfonates was successfully developed using high- performance liquid chromatography with conductimetric detection, for product and waste management of these compounds at manufacturing and processing sites. Compounds having C(3)-C(8) perfluoroalkyl groups were separated using a Tosoh TSKgel Super-ODS column and a mobile phase consisting of a mixture of methanol and aqueous NaH(2)PO(4) at several mixing ratios. The best detection limits for the compounds ranged from 0.12 to 0.66 mg l(-1) (ppm), and linear calibration graphs were obtained up to 87-109 mg l(-1). The combination of this method with concentration of the sample by solid-phase extraction with cartridges based on styrene-divinylbenzene-copolymer enabled the determination of approximately 50 microg l(-1) (ppb) for compounds with C(4)-C(8) perfluoroalkyl groups. This method was successfully used to monitor the artificial decomposition of the perfluorocarboxylic acid n-C(4)F(9)COOH induced by a photocatalyst.

First radical homopolymerisation of 2-trifluoromethacrylic acid in water and study of the degradation of the resulting homopolymers.

The radical homopolymerisation of 2-trifluoromethacrylic acid (MAF) initiated by Na2S2O8 in water, under the influence of pH, led to original water soluble surfactants, the decomposition of which was investigated. The value of the square of the propagation rate constant to the termination rate constant, kp(2)/kte, of MAF was 4 × 10(-3) l mol(-1) s(-1) at 80 °C.