11.2.1 SDS hydrolysis
All 400 ppm SDS samples were prepared by weighting SDS powder and diluting with milliQ-water (0.42 g SDS / L).
Hydrolysis by heating
50 ml of 400 ppm SDS solution was measured into 100 ml bottles and sealed with pres-sure balancing caps. The bottles were heated in an ovens at temperatures 60°C and 90°C for 4, 8 and 24 hours (3 samples/temperature). After heating samples were kept at room temperature and analysed within 24 h. Samples were diluted (10x) with milliQ-water for the HPLC-RP analysis.
Hydrolysis by pH change
50 ml of 400 ppm SDS solution was measured into 100 ml bottles, and pH (initial pH
~7) was adjusted with sulphuric acid. pH adjustments were pH 6, pH 5, pH 4, pH 3 and pH 2 (5 samples). Samples were kept at room temperature and analysed 24 h after prep-aration. Samples were diluted (10x) with milliQ-water for the HPLC-RP analysis.
Hydrolysis by combination of heat and pH
50 ml of 400 ppm SDS solution was measured into 100 ml bottles, and pH (initial pH
~7) was adjusted with sulphuric acid. pH adjustments were pH 4 and pH 3. The bottles were sealed with pressure balancing caps and heated in an oven at temperature 60°C for 4, 8 and 24 hours (3 samples/pH). After heating samples were kept at room temperature and analysed within 24 h. Samples were diluted (10x) with milliQ-water for the HPLC-RP analysis.
Time monitoring
SDS sample (400 ppm, 100 ml) was monitored for one week (7 days) using two differ-ent determination methods: Solvdiffer-ent extraction spectrophotometry and RP-ECD. Meas-urement days were day zero (fresh sample), one day old, two days old, five days old, and seven days old sample. Before measurements samples were diluted (10x) with mil-liQ-water for the HPLC-RP analysis and (500x) for the spectrophotometric analysis.
11.2.2 SDS and additives
Salt additives (10 x dilutions)
All SDS samples (40 ppm) were prepared from SDS stock solution (1000ppm, 1.05 g/L). Kraft and CTMP white waters were diluted (5x) with milliQ-water. Salt (NaCl, CaCl2 and FeSO4) additions were 0, 500 and 5000 ppm (salt stocks 10000 ppm). Sam-ples were prepared in measuring bottles (50 ml). The final volume was achieved by di-luting with milliQ-water. Sample preparation examples are shown in Table 18.
Table 18. SDS (40ppm) sample with NaCl salt additions (500 and 5000 ppm) and kraft white water. The final volume was achieved by diluting with milliQ-water.
Sample SDS dosage (stock
1000 ppm)
Salt dosage (stock 10000 ppm)
Kraft dosage
Final volume SDS (40 ppm) + NaCl
(500 ppm) 2 ml 2.5 ml 5 ml 50 ml
SDS (40 ppm) + NaCl
(5000 ppm) 2 ml 25 ml 5 ml 50 ml
Salt additives (500 x dilutions)
All SDS samples (0.8 ppm) were prepared from SDS stock solution (1000ppm, 1.05 g/L). Kraft and CTMP white waters (WW) were diluted (500x) with milliQ-water. Salt (NaCl, CaCl2 and FeSO4) additions were 0, 10, 100 and 1000 ppm (salt stocks 10000 ppm). Samples were prepared in measuring bottles (50 ml). The final volume was achieved by diluting with milliQ-water. Sample preparation examples are shown in Ta-ble 19.
Table 19. SDS (0.8 ppm) sample with NaCl salt additions (10, 100 and 1000 ppm) and kraft white water. The final volume was achieved by diluting with milliQ-water.
Sample SDS dosage (stock
All SDS samples (0.8 ppm) were prepared from SDS stock solution (1000ppm, 1.05 g/L). Kraft white waters (WW) were diluted (500x) with milliQ-water. Retention aid (c-Pam and microparticle) additions were 200, 400 and 800 g/t (aid stocks 500 ppm). Also, two component system with both retention aids were analysed. Additions were 200, 400 and 800 g/t per retention aid. Retention aid dosages were based on the knowledge that paper product of 80 g/m2 grammage can contain from 200 to 800 g/t of retention aid.
Samples were prepared in measuring bottles (50 ml). The final volume was achieved by diluting with milliQ-water. Sample preparation examples are shown in Table 20.
Table 20. Sample preparation examples. SDS (0.8 ppm) sample with c-Pam additions (200, 400 and 800 g/ts) and kraft white water. The final volume was achieved by dilut-ing with milliQ-water.
SDS samples (40 ppm) were prepared by diluting SDS stock solution (1000 ppm) with milliQ-water and filtrated through GHP (13mm, 0.45 µm) or nylon (17 mm, 0.45 µm) syringe filters.
Vacuum filtration using GH membrane
SDS samples (0.8 ppm) were prepared by diluting SDS stock solution (1000 ppm) with milliQ-water. Retention aid (c-Pam) wad added (dosages 200 g/t and 800 g/t) into the SDS samples and filtrated through GH-membrane (47 mm, 0.45 µm) using vacuum filtration. Prepared samples are listed in Table 21.
Table 21. SDS samples for vacuum filtration tests.
Pure SDS reference
Effect of NaCl on the SDS determination by RP-ECD method was also examined. Dif-ferent dilutions of SDS (10-100 ppm) with and without NaCl addition (500 ppm) were analysed. Samples were analysed crude, meaning without syringe filtration. Prepared samples are presented in Table 22.
Table 22. SDS samples (10-100 ppm) of crude sample NaCl tests. Addition of NaCl 500 ppm.
Crude SDSsamples Crude SDS samples with NaCl addition 10 ppm 10 ppm + 500 ppm NaCl
SDS samples (40 ppm) for the SPE purification tests were prepared from SDS stock solution (1000ppm, 1.05 g/L). Salt (NaCl, CaCl2 and FeSO4) additions were 0, 500 and 5000 ppm (salt stocks 10000 ppm). Kraft white water was diluted (5x) with milliQ-water. Samples were prepared in measuring bottles (50 ml). The final volume was achieved by diluting with milliQ-water. Sample preparation examples are shown in Ta-ble 24.
Table 23. SDS (40ppm) sample with NaCl salt additions (500 and 5000 ppm) and kraft white water. The final volume was achieved by diluting with milliQ-water.
Sample SDS dosage (stock
SPE cartridges contained nonpolar C18 stationary phase that retains effectively hydro-phobic organic compounds but polar molecules, such as salts, are passed through unre-tained. The solid phase extraction procedure includes four main steps. First the SPE cartridge was preconditioned (or activated) by wetting with methanol (3 ml) and then washed with milliQ-water (3 ml). An approximately 20 bar pressure was used in the vacuum chamber to eluate the solvents through the SPE column. Elution was performed slowly, and it was carefully controlled that the stationary phase remained wet.
In the second step, the SDS samples (10 ml) were slowly passed through the SPE car-tridges and then washed with milliQ-water (3ml) (step three). Loaded sample solution and washing water can be collected by placing a rack with centrifuge tubes inside the vacuum chamber. After washing the taps of the SPE cartridges were let open left open and the stationary phase was dried under air suction for 30 min. In the final step, a rack with centrifuge tubes was placed inside the vacuum chamber for sample collection. The samples were eluted slowly form the SPE cartridge with pure acetonitrile (3 ml) into the centrifuge tubes. All the SPE-procedure steps are presented in Figure 30.
Figure 30. SPE-procedure steps
11.2.5 Another surfactant: Miranol Ultra
Miranol Ultra samples (1, 2.4 and 4 g/L) were prepared from 10 % stock solution and diluted with white water (kraft, CTMP) made from the pulp by filtrating through the former fabric. The salt (NaCl and CaCl2) addition was 100 ppm (salt stocks 10000 ppm). Samples were prepared in measuring bottles (50 ml). The determination was done with HPLC-RP combined with UV-detector at wavelength 205 nm. Sample preparation examples are shown in Table 25.
Table 24. Miranol Ultra (1, 2.4 and 4 g/L) samples with NaCl addition (100 ppm) dilut-ed with kraft white water. The final volume was 50 ml.
Sample Miranol Ultra
All 400 ppm SDS samples for aeration tests were prepared by measuring 10 % SDS stock solution (90 %, Sigma) in the water sample (10 L).The water sample (10 L) was poured into the aeration devise and oxygen concentration, temperature, conductivity and pH were measured. Oxygen concentration and temperature were monitored through the experiment. 10 % SDS solution was pipetted to the sample and stirred carefully. Aera-tion was switched on and adjusted by a rotameter. AeraAera-tion time was 90 min and after the aeration, the foam dying was recorded for 15 min. Table 25 shows procedure details of performed aeration experiments and in Table 26 is the shooting sequence of the aera-tion tests.
Table 25. SDS concentrations of 10 L water samples (tap water/white water/wastewater) and 10 % SDS stock dosages. Two set of experiments were performed: Aeration exper-iments 1 were done with tap water and white water samples using air flow rate 8.0