Characterization of effluents from chlorine dioxide substitution bleaching and oxygen-reinforced extraction

Abstract

The effects of chlorine dioxide substitution for elemental chlorine in the chlorination stage, aimed at the minimization of chlorinated organics and subsequent oxygen reinforcement in the proceeding extraction stage on the characteristics of bleaching effluents have been examined. The characteristics of the effluents were assessed in terms of molecular weight distribution by gel filtration, so that alternatives for the treatment of these effluents can be proposed. The analysis of chlorination and extraction stage effluents with different chlorine dioxide substitution levels and varying available chlorine charges by using a Sephadex G-50 column have indicated that indeed a marked change in the molecular weight distribution of chlorinated organic compounds have occurred. The molecular size of chlorinated organic compounds in the chlorination stage has increased with the chlorine dioxide substitution, while that in the extraction stage has decreased when compared with the molecular size of these compounds in original bleaching effluents with only elemental chlorine used in the chlorination stage and followed by extraction stage. Molecular size of the chlorinated organic compounds in the chlorination stage effluents was not seriously affected by the chlorine dioxide substitution level; while it was increased greatly by the increased total chlorine dosage. In the extraction stage effluents, chlorine dioxide substitution level has not appeared to be an important parameter influencing the molecular size distribution.

Processo anaeróbio conjugado com processos oxidativos avançados (POA) no tratamento dos efluentes do processo industrial de branqueamento da polpa celulósica

“…Entretanto, há outros compostos organoclorados que são formados no processo de branqueamento da polpa celulósica, inclusive com o uso do dióxido de cloro. Segundo Yetis et al (1997), o dióxido de cloro também produz compostos organoclorados, mas apenas um quinto da quantidade produzida pela aplicação de cloro elementar.…”

“…A emissão desses compostos organoclorados é usualmente medida em termos de halogênios orgânicos adsorvíveis (Adsorbable Organic Halogen -AOX), que é uma medida genérica de uma grande série de compostos orgânicos que possuem ligações com um ou mais átomos de halogênio (YETIS et al, 1997). No caso dos efluentes dos processos de branqueamento, que utilizam cloro e/ou compostos clorados, as ligações dos compostos orgânicos sempre ocorrem com o átomo de cloro, o que faz da medida de AOX, uma análise direta da quantidade de compostos organoclorados.…”