Degradation products of lignocellulosics in pulp mill effluents – comparison and evaluation of different gas chromatographic techniques for a comprehensive analysis

Abstract

Pulp mill effl uents contain potentially valuable compounds and will gain even greater importance than today in future biorefi nery scenarios as possible resources. Analysis of effl uents of process streams is not straightforward because of the vast variety of substances embedded in the complex inorganic matrix of high concentration. In the present comparative investigation, different combinations of gas chromatography (GC) and derivatisation techniques were tested and critically evaluated aiming at a comprehensive description of all major compound classes (low-molecular weight and long-chain carboxylic acids, lignin fragments, carbohydrates and aldehydes). As derivatisation techniques, trimethylsilylation, (trimethyl silyl)methylation and methylation were applied. In addition, the effl uents were analysed by pyrolysis-GC/mass spectrometry (MS), either directly or with simultaneous methylation. The study provides comprehensive information on the composition of effl uents, the suitability of the various combinations of derivatisation and GC/MS techniques. The discrimination effects of the different approaches are compared. The comprehensive analytical approach led to a coherent balance in terms of the contribution of the major portion of organic compounds to the total organic carbon (TOC) content in pulp mill effl uents.

Removal of hard COD from acidic eucalyptus kraft pulp bleach plant effluent streams using oxidoreductases

“…44 In addition, five aromatic compounds were previously identified, whereof benzoic acid, syringaldehyde, vanillic acid, and syringic acid were found to be persistent and therefore labeled as hard COD in this study. 8,43,44 In contrast to the study by Holmbom, which revealed a myriad of chlorinated and polychlorinated compounds, we found only a single chlorinated compound. 43 This discrepancy can be explained by the difference in the bleaching method: Chlorine dioxide (ECF) used in this study creates less chlorinated products than elemental chlorine-based bleaching processes present in the study by Holmbom. In line with this observation, the study by Moodley et al, which used wastewaters from an ECF process, did not identify any chlorinated compounds.…”

“…Among the 64 compounds identified in the D 0 filtrate, 24 organic acids have been previously described to be present in an effluent originating from a hardwood TCF bleaching process using GC-MS methods. 8 Moreover, two of the organic acids defined as hard COD, palmitic acid and stearic acid, have been described in other studies using wastewater from an elemental chlorine bleach plant with birch, pine, and spruce as substrate 43 and from an elemental chlorine-free (ECF) bleach plant. 44 In addition, five aromatic compounds were previously identified, whereof benzoic acid, syringaldehyde, vanillic acid, and syringic acid were found to be persistent and therefore labeled as hard COD in this study.…”

“…5 Their characterization was attempted by scientists utilizing an array of methods. [6][7][8] The chemical oxygen demand (COD) is a measure of the amount of organic matter in the wastewater, obtained by monitoring the degree of chemical oxidation, usually by measuring levels of potassium dichromate (K 2 Cr 2 O 7 ) or potassium permanganate (KMnO 4 ). 9 Recalcitrant compounds, also referred to as hard COD, are those that cannot be dealt with by wastewater treatment processes due to low efficiencies.…”

“…The pollutants are a complex mixture of low and high molecular weight organic compounds 5 . Their characterization was attempted by scientists utilizing an array of methods 6–8 …”