Um novo processo para o tratamento de efluente Kraft : biologico e fotoquimico

AUTOR(ES)
DATA DE PUBLICAÇÃO

1992

RESUMO

The release of spent liquors from conventional bleaching of chemical pulps into receiving water represents the most important environmental problem of the pulp and paper industry. These effIuents have an intense color (brown or black) due to dissolved lignin-based compounds derived from the Kraft process. So, a treatment to reduce their intense color and toxicity is required. Some of the employed treatments are: precipitation, ultrafiltration, aerobic and/or anaerobic lagoons among others. These methods are very expensive, then it is necessary to search for some low-expensive that have the same efficiency. This work consists in effluents treatment, or more particularly the treatment of the first stage of alkaline extraction (E1) in the paper industry. Three differents methods have beem used to the bleaching effluent: (i) Chrysonilia sitophila fungus treatments, which shows a ligninolytic activity; (ii) treatment with the enzymes produced by the Chrysonilia sitophila fungus (Iigninases) an peroxidase immobilized in silica and in sepharose, and (iii) photochemical treatment where UV and visible radiations were used in the presence of ZnO ano TiO2 as semiconductors. Mycelial pellets adsorbed 25% - 30% of liquor chromophores of which 60% - 65% were oxidized and a bleaching of 98% was obtained (under treatment conditions). Culture broth containing lignin - degrading enzymes efficiently removes in 6 h the color by oxidation in the presence of H2O2. Lignin peroxidase type llI, lyophilized fungal culture and horseradish peroxidase immobilized on CNBr - Sepharose-4 B decolorized in 48 hs a 38,4%, 29,5% and 53,5%, respectively. Ligninase II and lII immobilized in silica produced also on effluent decoloration. ln a photochemical treatment, under continued illumination, the solution becomes colorless and the molecular weight distribution in 2 h indicated almost total mineralization. These three treatments gave good results on effluent bleaching, indicating such an extent interesting alternative for the treatments of this kind of effluent.

ASSUNTO(S)

quimica organica papel - produtos quimicos

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