Katarzyna Majewska-Nowak

Analysis of membrane fouling in the treatment of water solutions containing humic acids and mineral salts

The separation of humic substances from aqueous solution by ultrafiltration was investigated with flat Intersep Nadir membranes. Special consideration was given to the decrease of membrane permeability in the course of the ultrafiltration process. The decrease of membrane permeability was related to the increase of pH and calcium ion concentration in the solution. Transport properties were found to be strongly dependent on the hydrophilicity of the membranes. The membrane made of regenerated cellulose, the most hydrophilic of the membranes tested, displayed the highest permeability with respect to both water and humic substance containing solutions, and the lowest proneness to fouling by organic colloids. Analysis of the relationship between the properties of the solution and the course of the separation process revealed that the rise of pH from 4.6 to 7.0 reduced membrane fouling. The presence of mineral salts in the solution deteriorated the separation and transport properties of the membranes and intensified the fouling process.

Effect of flow conditions on ultrafiltration efficiency of dye solutions and textile effluents

Abstract An ultrafiltration system with a tubular membrane module was used in an experimental study on the efficiency of organic dye removal from aqueous solutions and actual textile effluents. The module consisted of a polysulfone membrane which had been cast on the surface of a porous poly(methyl methacrylate) bar. It has been found that at an optimum velocity of feed flow (0.76 m/s), the retention coefficient for organic dyes of molecular weight greater than 780 exceeds 97%. A 200-h ultrafiltration of the textile effluent yielded removal efficiencies of 75–85% and 50–60% for COD and TOC, respectively. Volume flux varied from 0.8 to 1.0 m 3 /m 2 d.

Separation of anionic surfactants on ultrafiltration membranes

Abstract The objective of this study was to investigate the influence of MWCO, pressure, SDS concentration, salt amount and temperature on surfactant removal and permeate flux. Intersep Nadir membranes made from polyethersulphone (PES) and polysulphone (PS) were used. With the addition of a mineral salt to the SDS solution, a dramatic decrease in retention of SDS was observed. There was no discernible effect on the retention coefficient of the membranes with the increase in the amount of the mineral salt added to the SDS solution. The volume flux was slightly dependent on the ionic concentration in the feed solution: high ion concentration caused a small decrease of the water flux. The effect of pressure on the separation efficiency for the PES and PS membranes was evaluated; it produced only a small reduction in the retention as the pressure was increased. With the increase of temperature of SDS solutions, a decrease in the retention of SDS was observed. The permeate flux increased with temperature due to the solution viscosity decrease.

Synthesis and properties of polysulfone membranes

Abstract The ultrafiltration process described involved polysulfone membranes prepared on a flat glass support and on a surface of poly(methyl methacrylate) bar. Comparable studies including the effect of casting parameters an hydraulic conditions existing in the system on membrane performance were reported. Separation characteristics of each membrane module were determined. The influence of the concentration of some dyes on transport and separation membrane properties was analyzed. Long-term studies were carried out for different types of textile wastewaters. It has been found that tubular membrane modules can be used efficiently for the treatment of dyehouse effluents by ultrafiltration provided that the conditions of fluid flow are turbulent in nature.

Salt effect on the dye separation by hydrophilic membranes

Abstract The preliminary studies were initiated to determine the influence of salt concentration and electrolyte type on the efficiency of dye ultrafiltration. On the variety of commercial UF membranes the Intersep Nadir membranes (PES, C, CA, PS and PA series) have been chosen. They are characterized by different MWCO and various surface hydrophilicity. Transport and separation properties of the membranes were tested with respect to three organic dyes of anionic nature (methyl orange, helion grey, direct meta black) and having various molecular weights (327, 617 and 781.2 daltons, respectively). The permeation measurements were carried out with distilled water, aqueous solutions of dyes, and aqueous solutions of dyes and salts (NaCl or CaCl2). Dye concentration in the aqueous solution was equal to 100 g/m3. Salt concentration amounted to 1, 10 and 25 kg/m3. An Amicon stirred cell was used in this experiments. The ultrafiltration process involved a pressure of 0.2 MPa. The results showed that increasing the salt concentration generally worsens the efficiency of dye ultrafiltration. This relationship becomes particularly pronounced for low-molecular-weight dyes and for CaCl2. The greatest decrement of transport properties was found to occur at the lowest salt concentration applied. The effect of salt on the rejection coefficient depended on the membrane type and dye particles applied.

The influence of organic carbon concentration on atrazine removal by UF membranes

Abstract The primary objective of the study described in the present paper was to investigate the problem of how the concentration of organic matter (expressed as dissolved organic carbon, DOC) contributes to the efficiency of separating atrazine form aqueous solutions by ultrafiltration. Another objective was to examine how the type of organic matter (humic substances HS, tannic acid TA) may affect the efficiency of atrazine separation. A series of experiments was carried out with model solutions containing atrazine (1000 mg/m 3 ), humic substances (10, 20, 50 g/m 3 ) or tannic acid (5, 10, 15, 20 g/m 3 ) at a neutral pH. The ultrafiltration process involved a DS-GE polysulfone/polyamide membrane (Osmonics) and a transmembrane pressure of 0.1 and 0.3 MPa. The highest atrazine rejection coefficient (80%) was achieved at the organic matter concentration, DOC = 8.1 g C/m 3 .

Effects of natural organic matter on atrazine rejection by pressure driven membrane processes

Abstract The objective of the study described in the present paper was to investigate transport and separation properties of ultrafiltration membranes for atrazine solutions in the presence of natural complexing agents (humic and tannic acids). Two ultrafiltration membranes made of various polymer materials were used in the tests. Atrazine concentrations in tested solutions amounted to 1000 mg/m 3 . The influence of pH of atrazine solutions as well as the dose of humic and tannic acids on the process efficiency was investigated. The highest efficiency of separation (80%) was achieved for DS-GE membrane at the concentration of humic substances equal to 20 g/m 3 .

Decolorization of dye solutions by continuous ultrafiltration

Abstract A method of decolorizing and concentrating aqueous of organic dyes in an ultrafiltration process is described. The process involved poly- sulfone membranes prepared from 15% (wt.%)polysulfone solution in dimethylformamide and formed on a glass support. The experiments were carried out under static and dynamic conditions for five organic dyes of a molecular weight ranging from 327 to 1048.2. The pressure applied was 1.5 MPa. Membranes exhibiting the best properties are capable of retaining 90 to 100% of organic dyes of a molecular wieght above 700 during their work under dynamic conditions. The measured volume fluxes through these membranes ranged from 0.08 to 0.18 m3 /m2 day.

Capillary membranes for separation of dye particles

Abstract The study aimed at investigating the suitability of capillary modules to the decolorization of both synthetic and actual dye solutions by ultrafiltration. The process involved capillary membranes made of polysulfone and modified polysulfone. Membrane modules (UFTA PS10; UFTA PS30, and UFTA PSA50) of various molecular cut-off were applied. Comparable studies including the effect of hydraulic conditions existing in the system on membrane performance were reported. Transport and separation properties of the membranes in the presence of model dye solutions were investigated at three pressure values (0.05; 0.1, and 0.15 MPa), the linear velocity in the modules being varied for each of them (0.5; 1.0, and 1.5 m/s). Three organic dyes (Direct Black Meta, Helion Grey and Methyl Orange) were used in the experiments. The study on actual textile effluents (exhausted dye and rinsing baths) were carried out for 50 h at a pressure of 0.1 MPa and a linear velocity of 1.0 m/s. The results showed that increasing the linear velocity generally improves the permeability and selectivity of the membranes. This relationship becomes particularly pronounced at increasing molecular weight and for the UFTA PS10 module. It has been found that at an optimum velocity of feed flow (1.0 m/s) the retention coefficient for organic dyes of molecular weight higher than 780 exceeds 92–99% for all tested modules. In the presence of actual textile effluents the removal efficiency of TOC and colour amounted to 42–65% and 70–98%, respectively, and the permeability remained on a constant level (0.5–0.65 m3/m2/d for the UFTA PS10 module).

The effect of gas bubble flow on ultrafiltration efficiency

We assessed the potentiality of reducing concentration polarization and enhancing ultrafiltration of macromolecules via gas sparging (gas bubbles supplied to the UF system with the feed solution). Consideration was given to the problem of how the quantity of the gas sparged and the duration of the process affect the transport and separation properties of hollow-fibre UF modules. Ultrafiltration tests were carried out with model solutions containing macroparticles either organic (dye) or mineral (kaolin). Gas sparging was found to increase the permeability of the module by approximately 25%, but there was a slight deterioration of selectivity. The rate of gas flow seems to be of negligible importance.