@misc{9247100,
  abstract     = {{This thesis investigated the chemical cleaning of a polymeric ultrafiltration membrane after
black liquor filtration. The main objective was to evaluate how cleaning temperature, cleaning-
agent concentration, and cleaning time affected flux recovery after cleaning.
Black liquor filtration caused a gradual decline in permeate flux during the 25 h fouling
experiment, confirming that fouling developed on the membrane. After fouling, eight cleaning
experiments were performed using a full factorial Design of Experiments approach. The fouling
factor was not identical in all experiments, which means that the initial degree of fouling varied
between membrane samples and should be considered when interpreting the cleaning results.
The cleaning experiments showed that the highest flux recovery was obtained using Ultrasil
110 at 50 °C and 1 wt.%. The highest measured recovery in the experimental design was
achieved after 30 min of cleaning, while the model suggested 60 min as the most favourable
condition within the investigated range. Therefore, the validation experiment was performed at
50 °C, 1 wt.% Ultrasil 110, and 60 min. The validation experiment resulted in a flux recovery
of 76.43%, which was slightly higher than the best result obtained in the original experimental
design. The model should be treated as a screening tool rather than a strong predictive model
because of the limited dataset and the absence of statistically significant effects.
Membrane characterisation was performed using scanning electron microscopy with energy-
dispersive X-ray spectroscopy (SEM–EDS), atomic force microscopy (AFM), and Brunauer–
Emmett–Teller (BET) nitrogen adsorption–desorption analysis. SEM–EDS and AFM showed
that black liquor fouling caused local surface deposits and increased surface heterogeneity.
After cleaning, the surface appeared partly restored, although some deposits and irregularities
remained. BET analysis showed only small differences between the conditioned, fouled, and
cleaned samples, suggesting that major changes in the nitrogen-accessible pore structure were
not detected.
Overall, the results showed that cleaning temperature and cleaning-agent concentration were
the most important parameters within the tested range, while cleaning time had a weaker effect.
Chemical cleaning improved membrane performance after black liquor fouling, but additional
experiments with repetitions and more factor levels would be needed to confirm the trends and
improve reliability of the model.}},
  author       = {{Svyrhun, Kateryna}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Evaluation of cleaning conditions for polymeric ultrafiltration membranes after black liquor filtration}},
  year         = {{2026}},
}