The membrane-supported extraction of HSS from alkanolamine solvents was performed using a self-made liquid-liquid membrane contactor system. To build a contactor system PVDF or PSF hollow fibers were placed inside a glass tube and its ends were sealed with epoxy resin. Table 1 contains the geometrical properties of the membrane contactor.
Model alkanolamine solvents and extractant were prepared gravimetrically. A 30 wt.% MEA solution containing about 2360 mg/L HSS [21 (link)] and a solution of OH-Aliquat® 336 in n-octanol were supplied to the contactor in counter-current mode using peristaltic pumps. The extractant was fed from the lumen side of the fiber and the MEA solvent was fed from the shell side of the membrane. The liquid flow was carried out in laminar mode (Re = 140) with a linear flow rate of phases varied within 0.5–0.8 cm/s. To smooth out potential local concentration fluctuations that could affect the sampling process, magnetic anchors were placed in the vessels with used liquids and placed on the magnetic stirrers (C-MAG HS 7, IKA, Staufen, Germany). The 30 wt.% MEA solution containing about 2360 mg/L HSS and a solution of OH-Aliquat® 336 in n-octanol in the vessels were stirred at a speed of 200 rpm. This mode was set according to preliminary experiments to establish the optimal process parameters. With an increase or decrease in the difference in the linear flow rate of the phases, dispersion of the MEA solution and the extractant solution was observed. The scheme for the process of membrane-supported HSS extraction from alkanolamine solvents using a liquid-liquid membrane contactor is shown inFigure 1 .
The efficiency of the membrane-supported extraction process was indicated by HSS concentration change in the MEA solution, which was monitored every hour using an ion chromatography method. In this case, a sample of 1–2 mL of the MEA solution was used. The concentration of HSS in MEA solutions was determined as formic or oxalic acid anion concentration using the ionic chromatograph (“Akvilon Stayer-Ì”, chromatographic column Shodex ICSI-50 4E, eluent—3.2 mmole NaHCO3 and 0.1 mmole Na2CO3) equipped with the electromembrane suppressor EMCES 21, and conductometric detector CD-510 (JSC “Akvilon”, Podolsk, Russia). The error in determining the HSS ion concentration was not greater than 3%. For a more detailed comparison of the efficiency of the membrane-supported extraction process under different conditions, the concentration of the HSS ions in the MEA solution was calculated as Ct/C0, where Ct is the concentration of HSS ions at a given time, and C0 is the initial concentration of HSS ions.
Model alkanolamine solvents and extractant were prepared gravimetrically. A 30 wt.% MEA solution containing about 2360 mg/L HSS [21 (link)] and a solution of OH-Aliquat® 336 in n-octanol were supplied to the contactor in counter-current mode using peristaltic pumps. The extractant was fed from the lumen side of the fiber and the MEA solvent was fed from the shell side of the membrane. The liquid flow was carried out in laminar mode (Re = 140) with a linear flow rate of phases varied within 0.5–0.8 cm/s. To smooth out potential local concentration fluctuations that could affect the sampling process, magnetic anchors were placed in the vessels with used liquids and placed on the magnetic stirrers (C-MAG HS 7, IKA, Staufen, Germany). The 30 wt.% MEA solution containing about 2360 mg/L HSS and a solution of OH-Aliquat® 336 in n-octanol in the vessels were stirred at a speed of 200 rpm. This mode was set according to preliminary experiments to establish the optimal process parameters. With an increase or decrease in the difference in the linear flow rate of the phases, dispersion of the MEA solution and the extractant solution was observed. The scheme for the process of membrane-supported HSS extraction from alkanolamine solvents using a liquid-liquid membrane contactor is shown in
The efficiency of the membrane-supported extraction process was indicated by HSS concentration change in the MEA solution, which was monitored every hour using an ion chromatography method. In this case, a sample of 1–2 mL of the MEA solution was used. The concentration of HSS in MEA solutions was determined as formic or oxalic acid anion concentration using the ionic chromatograph (“Akvilon Stayer-Ì”, chromatographic column Shodex ICSI-50 4E, eluent—3.2 mmole NaHCO3 and 0.1 mmole Na2CO3) equipped with the electromembrane suppressor EMCES 21, and conductometric detector CD-510 (JSC “Akvilon”, Podolsk, Russia). The error in determining the HSS ion concentration was not greater than 3%. For a more detailed comparison of the efficiency of the membrane-supported extraction process under different conditions, the concentration of the HSS ions in the MEA solution was calculated as Ct/C0, where Ct is the concentration of HSS ions at a given time, and C0 is the initial concentration of HSS ions.
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