1 Foulant characterisation in membrane filtration in pulp and paper applications M. Kallioinen 1,a*# , S.-P. Reinikainen 2,b , J. Nuortila-Jokinen 1,c 1 Laboratory of Membrane Technology and Technical Polymer Chemistry, Department of Chemical Technology, Lappeenranta University of Technology, PL 20, Lappeenranta, FIN-53810, Finland a Tel. +358 (5) 621 2186; Fax +358 (5) 621 2199; email: mari.kallioinen@lut.fi c Tel +358 (5) 621 2173; Fax +358 (5) 621 2199; email: jnj@lut.fi 2 Laboratory of Inorganic and Analytical Chemistry, Department of Chemical Technology, Lappeenranta University of Technology, PL 20, Lappeenranta, FIN-53810, Finland b Tel. +358 (5) 621 2112; Fax +358 (5) 621 2199; email: satu-pia.reinikainen@lut.fi Abstract Today, membrane filtration is becoming more common in water purification applications in the pulp and paper industry. However, a drag for wider use of membranes in these applications is membrane fouling. This study is a part of a larger study, the aim of which is to develop a practical direct analysis method for detailed foulant and fouling mechanism identification in the pulp and paper mill applications. In this study fouling of PES 50H membrane was characterised using chemical analysis of feed, permeate and concentrate and analysing both virgin and fouled membrane samples with SEM-EDS and ATR-FTIR. The groundwood mill (GWM) circulation water was used as a feed in these experiments. It was found that fouling layer contained at least resin and fatty acids and cellulosic species. Using principal component analysis (PCA) the peak indicating the adsorption of cellulosic species on the membrane was found to be the most crucial difference between the virgin and the fouled membrane samples. The presence of inorganic mineral compounds caused the pore blocking - type of fouling, however, the dominant fouling type was adsorptive fouling. Moreover, partial least squares (PLS) regression showed that adsorption both on the membrane and into the pores occurred during the filtration experiments. 1. Introduction There has been an increased interest in membrane filtration in water purification applications of pulp and paper industry over the last 15-20 years. A reason for this is that membrane processes offer a high level of purification coupled with a low footprint and relatively low energy consumption and are, due to this, very suitable for internal purification of process waters in closed water circuits. However, membrane fouling is still a limiting factor for utilisation of membrane filtration in a greater scale in the pulp and paper mill applications. Fouling is a very complex physico-chemical phenomenon and the factors effecting on it are various. It is found that the membrane material and the surface characteristics of the membrane have a significant effect on fouling [1, 2, 3] and that the chemical surrounding has also a strong influence on the membrane performance [3], but the deeper knowledge on the emergence and the character of the fouling layer in the pulp and paper mill applications is still lacking. Therefore, the goal of the present study was to obtain more information on the fouling layer by characterising the fouling layer originating from the ultrafiltration of the groundwood mill (GWM) circulation water. ______ *Corresponding author # Presenting author