Identification of some sludge components using methods of gas chromatography-mass spectrometry (GC/MS) and X-ray diffraction (XRD)

This study aimed to extract, identify and compare the compounds in activated sludge treated with furfural and acetic acid. Gas chromatography-mass spectrometry (MS/GC), FTIR spectroscopy and X-ray diffraction (XRD) techniques were used to identify the components of activated sludge.

For this purpose, test samples of activated sludge from Mazandaran Wood and Paper Factory were randomly selected and treated with furfural and acetic acid. According to TAPPI standard tests, the extractive materials were then separated/isolated from activated sludge flour by acetone solvent and the residual of the extractive materials were transferred to a glass vial and BSTFA reagent was added to it. After preparation, the samples were injected into GC-MS. The retention-time diagram, quartz coefficient calculation and Adams table were used to identify the compounds.

The results of gas chromatogram of the extractive materials of the test samples showed that in activated sludge, activated sludge treated in furfural and activated sludge treated with acetic acid, there are 59, 138, and 48 identifiable compounds, respectively. Comparison of chromatograms also showed that two bis (2-ethylhexyl) phthalate and 2-methyl-naphthalene compounds were commonly present in 3 test samples. Squelin is one of the pure and mineral hydrocarbon oils of the identified in activated sludge treated with acetic acid at the rate of 2.26%. According to chromatograms, alkanes have formed a remarkable percentage of all non-polar compounds in activated sludge and treated samples. The most abundant of these compounds are light to relatively heavy alkanes, which can be mentioned to compunds of Dodecane, 3-decane in activated sludge, nano-decane, hexadecane and octa-decane in activated sludge treated with acetic acid and on-decane and hexadecane in the treated samples with furfural. Comparison of chromatograms also indicated that 2-compounds of 2-ethyl acridine and hexadecane were in the activated sludge treated with furfural and acetic acid so that it was not observed in the primary activated sludge. The results of X-ray diffraction (XRD) analysis also showed that the activated sludge of the paper factory resulting from CMP and NSSC processes is composed of calcite (2ϴ=39) and colloidal materials. FT-IR spectrum showed that acetic acid treatment has strengthened and activated the functional groups present on the activated sludge surface, especially in the range of 1500-1600 cm-1 wave number. In addition, the tensile vibrations are mostly related to the C-C bond and the skeletal vibrations of the aromatic units. Also, the wave number 3200 to 3400 cm-1 is related to the active hydroxyl groups.

The most important saturated and unsaturated fatty acids in activated sludge can be introduced tetradcanoic acid, 7-bromohebtyl isobutyl phthalic acid, palmitoleic acid, linoladic acid and 2,1-benzene d-carboxylic acid, which during activated sludge treatment with furfural and acetic acid have been removed. Depending on the type of treatment, these compounds can have negative or positive effects on activated sludge applications.