BENEFICIAL-EFFECTS OF HETEROGENEOUS PHOTOCATALYSIS ON THE BIODEGRADATION OF ANTHRAQUINONE SULFONATE OBSERVED IN WATER-TREATMENT

The experimental results of the photocatalytic degradation of Anthraqu inone 2-Sulfonic Acid Sodium Salt (ASS) using TiO2P-25 Degussa suspens ions irradiated in Pyrex flasks are reported. The photocatalyst drasti cally accelerated the degradation in comparison with direct photolysis of the substrate at lambda>290 nm. The influence of various parameter s on the degradation process, e.g., substrate concentration, TiO2 cont ent, pH solution, anions present and catalyst pretreatment, was invest igated. The complete oxidation of the substrate to CO2 in aerated disp ersions of TiO2 needed irradiation for about 50 h. After approximately 20 h, ca. 75-80% of the organic carbon was degraded to CO2 when dearo matization was achieved. Degradation of the substrate was small when t he photolysis was carried out in the absence of TiO2 and negligible in the absence of light. This study also tested the biodegrability of th e substrate using micro-organisms (water treatment waste water plant s ludge bacteria). These latter results indicate that photocatalysis has potential, either as a primary treatment technique or a pre-treatment step to enhance biodegradation. The solar radiation as employed throu gh this work (AM 1), was adequate to produce the near u.v. needed in t he photocatalytic processes. The products obtained from the photochemi cal runs were characterized by: spectroscopical measurements; total or ganic carbon determination (TOC); chemical oxygen demand (COD); diffus e reflectance spectroscopy (DRS); nuclear magnetic resonance (NMR); an d high pressure liquid chromatography (HPLC).