Recebido em 6/3/03; aceito em 28/4/03 EDTA: THE CHELATING AGENT UNDER ENVIRONMENTAL SCRUTINY. The chelating agent EDTA (ethylenediaminetetraacetic acid) is a compound of massive use world wide with household and industrial applications, being one of the anthropogenic compounds with highest concentrations in inland European waters. In this review, the applications of EDTA and its behavior once it has been released into the environment are described. At a laboratory scale, degradation of EDTA has been achieved; however, in natural environments studies detect poor biodegradability. It is concluded that EDTA behaves as a persistent substance in the environment and that its contribution to heavy metals bioavailability and remobilization processes in the environment is a major concern.

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A set of 7 different lignin preparations was generated from a range of organosolv (acidic, alkaline, ammonia-treated and dioxane-based), ionic liquid, autohydrolysis and Kraft pretreatments of lignocelluloses. Each lignin was characterised by 2D HSQC NMR spectroscopy, showing significant variability in the -O-4 content of the different lignin samples. Each lignin was then valorised using three biocatalytic methods (microbial biotransformation with Rhodococcus jostii RHA045, treatment with Pseudomonas fluorescens Dyp1B or Sphingobacterium sp. T2 manganese superoxide dismutase) and two chemocatalytic methods (catalytic hydrogenation using Pt/alumina catalyst, DDQ benzylic oxidation/Zn reduction). Highest product yields for DDQ/Zn valorisation were observed from poplar ammonia percolation-organosolv lignin, which had the highest -O-4 content of the investigated lignins and also gave the highest yield of syringaldehyde (243 mg/L)

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COMPOUNDS. The mechanism and applications of the Fenton reaction assisted by iron-reducing phenolic compounds (IRPC) is reviewed. The presence of IRPC leads to the formation of a larger number of free radicals. The relationship between the redox potential and the IRPC structure is discussed. The effect of humic substances in the degradation of xenobiotics is also included, since these substances are able to reduce metallic ions. The natural occurrence of Fe 3+ /H 2 O 2 /IRPC in wood biodegradation processes, as well as their application is also discussed. The review concludes with the advantages of the Fe 3+ /H 2 O 2 /IRPC systems and some considerations for further process optimization and their applications at industrial levels.Keywords: Fenton reaction; xenobiotics; iron-reducing phenolic compounds. OS PROCESSOS OXIDATIVOS AVANÇADOS (POA)Xenobióticos são substâncias estranhas aos organismos vivos presentes em águas, solos e na atmosfera, produzidas pela ação do homem e de difícil biodegradabilidade. Para tratamento de águas residuárias contendo compostos não biodegradáveis, os métodos de coagulação química (floculação), adsorção com carvão ativo e separação por membranas demonstram grande eficiência, no entanto, os poluentes retidos (concentrados) necessitam ser posteriormente tratados. Os processos oxidativos avançados (POA) têm recebido grande interesse no tratamento e pré-tratamento de compostos não biodegradáveis em águas, atmosferas e solos contaminados, pois convertem a matéria orgânica em CO 2 e H 2 O ou no caso de pré-tratamentos, tornando-os biodegradáveis. Os POA são definidos como processos que geram radicais hidroxila (

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