Influência de complexantes de ferro na degradação de compostos orgânicos por processo foto-Fenton/solar
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Data
2007-08-23
Autores
Silva, Milady Renata Apolinário da [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A contaminação da água por substâncias refratárias ao tratamento convencional afeta significativamente sua viabilidade de re-uso. Assim processos de tratamento, como o foto-Fenton, capazes de degradar esse tipo de substância são cada vez mais necessários. Neste trabalho avaliou-se a utilização de ácidos orgânicos como ligantes de ferro no processo foto-Fenton solar. Os ácidos cítrico, oxálico, succínico, o EDTA e os complexos ferrioxalato de potássio (FeOx) e citrato de amônio e ferro (III) (FecitNH3) foram utilizados como ligantes de ferro. A presença de ligantes (exceto EDTA) influenciou positivamente a degradação de 2,4- diclorofenol (DCF) em relação ao Fe(NO3)3 na concentração 0,25 mmol L-1 resultando em aproximadamente 90 % de conversão de DCF (12 minutos de irradiação). Também permitiu o uso da reação de Fenton em valores de pH próximos ao neutro com alta eficiência de degradação de DCF. O estudo da influência dos complexos de ferro na degradação de diferentes classes de compostos orgânicos mostrou que a degradação de 4-clorofenol (4CF) foi mais eficiente na presença de ferro livre, comportamento contrário foi observado para formaldeído e os herbicidas diuron e tebuthiuron (TBH). A degradação do corante verde de malaquita não se mostrou tão influenciada pelas diferentes espécies de ferro. TBH foi o composto cuja degradação foi mais fortemente influenciada pela presença de ligantes de ferro. A hipótese para explicar este resultado é que na ausência de ligantes orgânicos há a formação de um complexo entre TBH e Fe, conforme verificado por voltametria cíclica, dificultando a participação dos íons ferro na reação de Fenton. O ácido cítrico (Fecit) possibilitou a utilização do processo foto-Fenton em valores de pH próximos da neutralidade com alta eficiência, visto que 77% e 37% de TBH...
Contamination of water by non-biodegradable substances difficult significantly its reuse. Thus, treatment processes, as the photo-Fenton, capable to degrade this type of substances are necessary. In this work the use of organic acids as iron ligand in the solar photo-Fenton process was evaluated. The citric, oxalic and succinic acid, EDTA, potassium ferrioxalate and ammonium iron (III) citrate (FecitNH3) were used as iron ligand. The presence of ligands (except EDTA) influenced positively the degradation of 2,4-dichlorophenol (DCF) in comparison to 0.25 mmol L-1 Fe(NO3)3, resulting in approximately 90 % of DCF conversion (12 minutes irradiation). It also allowed the use of Fenton reaction at pH values near to the neutrality with high efficiency of DCF degradation. The study of iron complexes influence in the degradation of different classes of organic compounds showed that the degradation of 4-chlorophenol (4CF) is more efficient in the presence of free iron, opposite behavior was observed for formaldehyde and the herbicides diuron and tebuthiuron (TBH). The degradation of malachite green dye was not very influenced by the iron species showing only a slight improvement when iron complexes were used. TBH was the compound which degradation was most strongly influenced by the presence of iron ligands. The hypothesis to explain this behavior is that in the absence of organic acids, the formation of complexes between the TBH and Fe occurs, as verified by cyclic voltametry, difficults the participation of iron in the Fenton reaction. Citric acid (Fecit) made possible the use of the photo-Fenton process at circumneutral pH values with high efficiency, since 77% and 37% of TBH and TOC, respectively, had been removed at pH 6 (7.5 J cm-2). The use of FecitNH3 in the degradation of TBH also resulted in high efficiency mainly at pH 7.5. The reduction of the toxicity...(Complete abstract click electronic access below)
Contamination of water by non-biodegradable substances difficult significantly its reuse. Thus, treatment processes, as the photo-Fenton, capable to degrade this type of substances are necessary. In this work the use of organic acids as iron ligand in the solar photo-Fenton process was evaluated. The citric, oxalic and succinic acid, EDTA, potassium ferrioxalate and ammonium iron (III) citrate (FecitNH3) were used as iron ligand. The presence of ligands (except EDTA) influenced positively the degradation of 2,4-dichlorophenol (DCF) in comparison to 0.25 mmol L-1 Fe(NO3)3, resulting in approximately 90 % of DCF conversion (12 minutes irradiation). It also allowed the use of Fenton reaction at pH values near to the neutrality with high efficiency of DCF degradation. The study of iron complexes influence in the degradation of different classes of organic compounds showed that the degradation of 4-chlorophenol (4CF) is more efficient in the presence of free iron, opposite behavior was observed for formaldehyde and the herbicides diuron and tebuthiuron (TBH). The degradation of malachite green dye was not very influenced by the iron species showing only a slight improvement when iron complexes were used. TBH was the compound which degradation was most strongly influenced by the presence of iron ligands. The hypothesis to explain this behavior is that in the absence of organic acids, the formation of complexes between the TBH and Fe occurs, as verified by cyclic voltametry, difficults the participation of iron in the Fenton reaction. Citric acid (Fecit) made possible the use of the photo-Fenton process at circumneutral pH values with high efficiency, since 77% and 37% of TBH and TOC, respectively, had been removed at pH 6 (7.5 J cm-2). The use of FecitNH3 in the degradation of TBH also resulted in high efficiency mainly at pH 7.5. The reduction of the toxicity...(Complete abstract click electronic access below)
Descrição
Palavras-chave
Química ambiental, Tratamento de efluentes, Foto-fenton
Como citar
SILVA, Milady Renata Apolinário da. Influência de complexantes de ferro na degradação de compostos orgânicos por processo foto-Fenton/solar. 2007. 191 f. Tese (doutorado) - Universidade Estadual Paulista, Instituto de Química, 2007.