Caracterization and oxidation of organic compounds in wastewater from wet processing of coffee berries. / CaracterizaÃÃo e oxidaÃÃo de compostos orgÃnicos nas Ãguas residuÃrias da despolpa Ãmida dos frutos do cafeeiro.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

The wet processing of coffee berry is one of the most pollutant activities in brazilian agriculture. The main disadvantage of this method is the large volume of water used, wich returns to the environment with low quality. The goal of this work was to study the organic composition of the wastewater, as well as to prepare and test catalysts in order to oxidize the compounds present in the wastewater. Wastewater from three experimental sites was collected: two samples from an EPAMIG farm (Machado, MG) and one from Cepecafà farm (Lavras-MG). In each site collecting was done at four sampling points (Point 1 â pulp exit; Point 2 â beans wash; Point 3 â green berrys exit; Point 4 â wastewater exit). Experiments were carried out in two steps: (i) identification of organic compounds in wastewater and (ii) oxidation of organic compounds by using advanced oxidation process. The amount of organic and inorganic materials found in wastewater was high. The biochemichal oxygen demand found in the wastewater was greater than 4,500 mg L-1, while the chemical oxygen demand (COD) was greater than 6,000 mg L-1, for all analyses. Compounds like caffeine, sugars, phenolics, N, K, P, Ca, Mg, Fe, Mn and S were found in the wastewater. In the second step, catalysts based on iron oxide (Fe) and iron/niobium oxide (Fe/Nb), were prepared and tested as oxidizing agents of model molecules: caffeine, chlorogenic acid, and catechin. The prepared materials were characterized by x-ray diffraction (XRD), infrared spectroscopy (IR), MÃssbauer spectroscopy and scanning electron microscopy (SEM). XRD, IR, and MÃssbauer spectroscopy showed the presence of iron oxide: goethite and maghemite. SEM analyses suggest the presence of iron oxide distributed throughout the niobium surface. Oxidizing tests were carried out by using the heterogeneous Fenton system, photo-Fenton and UV/H2O2. For caffeine, just photo-Fenton and UV/H2O2 were efficient in oxidation. By monitoring oxidation through mass spectrometry, it could be observed that caffeine was successfully oxidized, but the organic material was not completely removed. The chlorogenic acid degraded in all processes, though not even organic material was removed in the COD analysis. For the catechin, only processes which utilized Fe/Nb as a catalyst and UV/H2O2 we efficient in the oxidation.

ASSUNTO(S)

cafà compostos fenÃlicos. caracterization Ãgua residuÃria caffeine phenolc compounds caracterizaÃÃo agronomia cafeÃna wastewater despolpa coffee

ACESSO AO ARTIGO

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