Transport of lignin-type compounds in the receiving waters of pulp mills

Abstract

A method was developed to monitor qualitatively the transport of lignin-like high-molecular-mass materials (HMMs), such as lignins and humic substances. This method was used to monitor HMMs discharged by two mills producing kraft and mechanical pulps, respectively. Several water and sediment samples were collected up and downstream of these mills. The method included the separation of HMMs from water samples by ultrafiltration followed by the alkaline CuO oxidation of the separated HMMs. Freeze-dried sediment samples were oxidised as such. The degradation products formed were analysed by RP-HPLC and the ratios of 4-hydroxyacetophenone to vanillin or all 4-hydroxyphenyl compounds to guaiacyl-type compounds were used to study the transport of HMMs from different sources. The results were compared to those obtained using pyrolysis-GC/MS. Attempts were also made to analyse the oxidation products using GC/MS instead of HPLC, but the use of HPLC has some advantages over GC/MS and is therefore preferred. Principal component analysis was used to select the compounds suitable for monitoring the transport of HMMs. Several chlorinated and non-chlorinated compounds were synthesized as model compounds for the identification of CuO oxidation products of HMMs. The structures of the model compounds were verified by mass spectrometry and their chromatographic behaviour discussed.