Colloidal extractives particles are potential foulants in pulp and paper mill applications. Characterization of them as foulants is a challenging task because of the complexity of these mill waters. In this study one regenerated cellulose (RC) membrane and two polyethersulphone (PES) membranes were used to study the fouling of extractives in ultraifltration (UF) of two chemithermomechanical (CTMP) pulp mill process waters. The process waters originated from a pulping process using softwood and a mixture of hardwood and softwood. Extractives were analyzed by extracting them from the membranes and further analyzing them with gas chromatography and by measuring Fourier Transform Infrared (FTIR) spectra for the pure, fouled, and extracted membrane samples. In this study retention of extractives was over 90% even though their molar masses are less than 1 kg/mol. Both dissolved and colloidal extractives fouled the membranes. The fouling behavior was different for the process waters used and it seems that the individual extractive groups had different fouling mechanisms. Mostly fatty and resin acids fouled the membranes, but sterols contributed to the fouling of RC membrane remarkably even though their amount in the process waters used was low.%胶体抽出物颗粒是制浆造纸厂生产过程中的潜在污染物。研究采用了一种再生纤维素（R C）膜和两种聚醚砜(P E S)膜考察两种化学热磨机械浆生产用水在超滤过程中抽出物的污染行为。实验用生产用水取自针叶木制浆流程及针叶木和阔叶木混合制浆流程。从膜上提取分析抽出物，并通过气相色谱法进一步分析，用傅立叶红外变换光谱（FTIR）法分析洁净的、被污染的及抽提过的膜样品。尽管研究中木材抽出物的摩尔质量小于1kg/mol，其在膜上的截留率仍超过90%。溶解和胶体抽出物均能污染滤膜。两种生产用水中抽出物的污染行为有所不同，似乎不同的抽出物基团的污染机理各有差异。大部分脂肪酸和树脂酸能污染滤膜，但甾醇显著污染再生纤维素膜，即使其在所用的生产用水中含量很低。
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