Sulfonated derivatives of naphthalene in water samples of an Italian river

Naphthalenesulfonates were found in water samples of the Italian river Bormida. Samples were collected at increasing distances from the point of emission of pollutants, and their analyses showed that these compounds can persist in river water and that they can propagate for considerable distances.     

Electrochemical or UV-photochemical oxidation of industrial wastes containing polar aromatic sulphonates

BACKGROUND AND INTENTION: Aromatic sulphonates other than surfactants and their hydroxy and amino-derivatives are important intermediates for the production of azo dyes. Their production on a large scale can be detrimental for the environment, if the by-products of their synthesis are not disposed of appropriately. An industrial waste, the organic components of which were mainly amino and hydroxy-substituted aromatic sulphonates, seriously endangers the environment close to an dismissed Italian industrial site. Inorganic sulphates and chlorides contained in the waste seriously hinder its disposal by incineration, since they corrode furnace walls. In this work, preliminary exploration of aqueous-phase electrochemically and photochemically induced oxidation techniques have been performed as possible alternatives to incineration. METHODS: Electrochemically-induced oxidation was experimented on individual aromatic sulphonates and on an industrial waste by electrolysing them between smooth platinum electrodes at low temperature (5 degrees C) and high current densities (0.4 A/cm2) with aqueous 0.5 M NaHSO4 electrolyte. Photochemically-induced oxidation was performed by irradiating individual aromatic sulphonates or industrial waste with a 500 W mercury lamp in the presence of sodium peroxydisulphate. RESULTS AND DISCUSSION: After 200 min electrodegradation, 90% of the original compounds disappeared, while 50% Total Organic Carbon (TOC) of an industrial waste was removed from solution after 10 hours. After 180 min UV-photodegradation, 90% of two test aromatic sulphonates disappeared, while 65% of TOC of industrial waste was removed after 5 hours. CONCLUSIONS: Two methods, electrochemical and UV-persulphate oxidation of an industrial waste, were used in order to propose a disposal procedure alternative to incineration. Electrodegradation with smooth Pt anode in 0.5 M NaHSO4 at 5 degrees C halved TOC concentration within 10 hours, while persulphate-assisted UV-photochemical oxidation with a 500 W high pressure Hg lamp abated two-thirds of TOC concentration after 5 hours. Energetic consumption of electrodegradation was 0.33 kWh/g TOC, while that of photooxidation was larger than 2 kWh/g TOC. Although both techniques can be considered efficient from a purely chemical point of view, since both are capable of wet-oxidising the aromatic sulphonates and the industrial waste, electrodegradation seems more promising than a photochemical degradation if economical considerations are also taken into account. Considering also that neither cell design nor catalyst were optimised in this preliminary study, the energy yield of electrodegradation seems likely to be largely improved.     

Oxidative and energetic efficiency of different electrochemical oxidation processes for chloroanilines abatement in aqueous medium

The oxidative efficiency and energy consumption, in the degradation of chloroanilines by anodic oxidation, indirect oxidation with electrogenerated hydrogen peroxide and electro-Fenton have been compared, using a laboratory system driven by a LabVIEW virtual controller. Solutions were oxidized in an undivided cell, where H(2)O(2) was generated electrochemically by reduction of atmospheric oxygen bubbled at a carbon cloth cathode. The electro-Fenton process showed the best degradation power, in terms of efficiency of removal and energy consumption. This process was applied to the purification of a solution obtained by washing a polluted soil. Under laboratory conditions, electro-Fenton removed 75% COD of this wastewater with a specific energy consumption of 0.3kWh per gram of COD, corresponding to 41.8kWhm(-3).