Removal of p-aminobenzenesulfanilamide from water solutions by catalytic photo-oxidation over Fe-pillared clay.

The catalytic photo-oxidation of p-aminobenzenesulfanilnamide (ABS) with hydrogen peroxide in the presence of Fe-pillared clay as heterogeneous catalyst has been investigated under UV-irradiation (λmax = 254 nm). Fe-pillared clay was synthesized by intercalating the iron polyhydroxycomplexes into the interlayer space of a natural layered aluminosilicate - montmorillonite and a subsequent heat treatment at 500 °C. The catalyst was characterized by chemical analysis, low temperature nitrogen adsorption and XRD. The kinetics of photocatalytic oxidative degradation of ABS in aqueous solutions under various experimental conditions was studied. The dependence of the photo-oxidation rate on such experimental factors as pH, hydrogen peroxide concentration and catalyst content was established. The conversion of ABS was 100% and the mineralization efficiency was 52.3% at optimal conditions. The intermediate products of ABS photo-oxidation identified by HPLC were a sulfanilic acid, benzenesulfonamide, benzenesulfonic acid, hydroquinone, pyrocatechol, benzoquinone and aliphatic acids. Fe-pillared clay remained highly active in three consecutive catalytic cycles without regeneration. The results of the study suggested that the heterogeneous photo-system «Fe-pillared clay/H2O2/UV¼ was effective in the oxidative degradation of aminobenzenesulfanilnamide. This system may be of interest for use in organic wastewater treatment processes.

Fenton degradation of sulfanilamide in the presence of Al,Fe-pillared clay: Catalytic behavior and identification of the intermediates.

Liquid phase catalytic degradation of sulfanilamide with H2O2 was carried out in the presence of Fe,Al/M-pillared clay (Fe,Al/M-MM, M=Na(+), Ca(2+) and Ba(2+)) as heterogeneous Fenton type catalyst. Fe,Al/M-MMs were prepared by swelling of layered aluminosilicate (90-95 wt.% montmorillonite) from a bed located in Mukhortala (Buryatia, Russia) in Na(+), Ca(2+) and Ba(2+) forms by means of the exchange of these cations with bulky Fe,Al-polyoxocations prepared at Al/Fe=10/1 and OH/(Al+Fe)=2.0, and then calcinated at 500°C. XRD method and chemical analysis demonstrated that the rate of crystalline swelling was dependent on the interlayer cations and decreased in the order: Fe,Al-/Na-MM>Fe,Al/Ca-MM>Fe,Al/Ba-MM. It was found that the catalytic properties of Fe,Al/M-MMs depended on the type of exchangeable cations. The effect of the H2O2/sulfanilamide molar ratio, the catalyst content, the reaction temperature and the reaction pH on the removal rate of sulfanilamide has been studied in the presence of Fe,Al/Na-MM. The catalyst can be applied for degradation of sulfanilamide with H2O2 for at least three successive cycles without loss of activity. HPLC analyses pointed out that the main degradation intermediate products were sulfanilic acid, benzenesulfonic acid, p-benzoquinone and aliphatic carboxylic acids.