A membrane fractionation study of an oxidized industrial kraft liquor was performed with 50, 5 and 1 kDa molecular weight cut-off membranes to study the productivity of each membrane and the respective apparent rejection coefficients (R_i) to total solids (TS), ashes and low molecular weight phenolates (TP). Cleaning efficiency of each membrane was evaluated and the contribution of fouling for flux decline was analyzed by applying the resistances-in-series approach.

During membrane fractionation sequence, TS content in the permeate stream gradually decreased from 86.5 g L⁻¹ to 75.3 g L⁻¹ (50 kDa), 64 g L⁻¹ (5 kDa) and 58.6 g L⁻¹ (1 kDa). The R_i values observed for TS were 25.3%, 29.1% and 15.1% for 50, 5 and 1 kDa membrane processing, respectively. TP were not retained by the 50 kDa membrane while, for the 5 and 1 kDa membranes, R_i of 11.5% and 9.0% were observed, respectively. The initial TP concentration (2.4 g L⁻¹) was maintained in the first membrane stage, while for the other stages decreased slightly for 2.22 g L⁻¹ (5 kDa) and 2.15 g L⁻¹ (1 kDa). Nevertheless, in terms of composition (%w/w_TS), an enrichment in TP was observed in all three stages from 2.8% (feed) to 3.2% (50 kDa), 3.5% (5 kDa) and 3.7% (1 kDa).

The initial water fluxes were recovered within 2–3 cycles of chemical cleaning and fouling evaluation indicated that reversible fouling was very relevant component for the 50 and 1 kDa membrane processing while irreversible fouling component was more pronounced for the 5 kDa membrane processing.

用截留分子量分别为50、5和1 kDa的工业硫酸盐牛皮纸液进行膜分级研究，以研究每种膜的生产率以及各自对总固体（TS），灰分的表观截留系数（R _i）和低分子量酚盐（TP）。评估了每个膜的清洁效率，并通过应用串联电阻方法分析了结垢对通量下降的贡献。

在膜分级过程中，渗透物流中的TS含量逐渐从86.5 g L ^-1降至75.3 g L ^-1（50 kDa），64 g L ^-1（5 kDa）和58.6 g L ^-1（1 kDa）。对于50、5和1kDa的膜处理，TS的R _i值分别为25.3％，29.1％和15.1％。TP不被50 kDa的膜保留，而对于5 kDa和1 kDa的膜，R _i分别为11.5％和9.0％。在第一个膜阶段中保持初始TP浓度（2.4 g L ^-1），而在其他阶段中，2.22 g L ^-1（5 kDa）和2.15 g L ^-1略有降低（1 kDa）。然而，就组成（％w / w _TS）而言，在从2.8％（进料）到3.2％（50 kDa），3.5％（5 kDa）和3.7％（1 kDa）的三个阶段中均观察到TP富集。 ）。

在化学清洗的2-3个循环内恢复了初始水通量，污垢评估表明，可逆污垢是与50 kDa和1 kDa膜工艺非常相关的成分，而不可逆污垢成分在5 kDa膜工艺中更为明显。