Separation of an Anionic Surfactant by Nanofiltration (original) (raw)
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Removal of anionic surfactants by nanofiltration
This work addresses the assessment of nanofi ltration (NF) in terms of membrane characteristics, operating transmembrane pressure and feed composition for the maximal removal of anionic surfactants in wastewater from a detergent industry. Model solutions of linear alkylbenzene sulphonates (LAS) and sodium lauryl ether sulphates (SLES) covering a wide range of SLES/LAS ratios are used as surrogates of the wastewaters with 0.43 g l −1 of methylene blue active substances (MSAS). The NF experiments are carried out in a unit equipped with NF-90, NF-200 and NF-270 membranes (FilmTec Corp., USA). The applied pressure varied from 15 to 25 bar. The rejection coeffi cients to total organic carbon (TOC) are practically independent of pressure and are higher than 95% for all model solutions and higher than 92% for the wastewater. The SLES solutions have the highest permeation fl uxes of 20-33, 121-207 and 242-371 kg h −1 m −2 for NF90, NF200 and NF270 membranes, respectively. The permeation fl uxes for the other model solutions have intermediate values between the ones of the SLES solution and the ones of the wastewater. These present permeations fl uxes as low as 10-11 kg h −1 m −2 for the NF 200 and the NF 270 membranes.
Desalination, 2003
Surfactants are present in almost all aqueous solutions-either as additives for different purposes, or because they occur naturally. Because of the common occurrence of surfactants in process water it is important to know how they behave in membrane processes. Ultrafiltration membranes allow almost complete passage of surfactant monomers, but reject micelles almost completely. Concentration polarisation during ultraflltration of surfactant solutions is therefore mainly influenced by the presence ofmicelles. Operating parameters, e.g. the tmnsmembrane pressure and the concentration of surfactant, as well as the pure water flux of the membrane, have a marked influence on the performance of hydrophilic membranes, as shown in this investigation. A distinct difference between the interaction of a non-ionic surfactant with hydrophilic and hydrophobic membranes was observed. The hydrophobic membrane showed a flux reduction already at concentrations below the critical micelle concentration (CMC), whereas no flux reduction was observed for a hydrophilic membrane with the same nominal molecular weight cutoff , below the CMC.
Chapter 5 Nanofiltration Mediated by Surfactant Micelles : Micellar-Enhanced Ultrafiltration
2019
Surfactant micelle-assisted removal of ions and organic solutes from aqueous media by micellar enhanced ultrafiltration (MEUF), which is a membrane separation technique, is discussed in detail. Following general information about micellar structure, counterion binding, substrate solubilization, and medium effect functions of micelles which enable separation of cationic or anionic ions and organic molecules from aqueous media by MEUF are explained in a comprehensive manner. Some of the recent studies on removing pollutants from wastewater effluents of industrial plants by MEUF, and their results have been summarized to inform about the factors affecting the removal efficiency of this technique. Methods for recovery of surfactant and contaminants from retentate or permeate solutions are also given. Selective separation of metal ions of the same charge from multicomponent solutions is another topic of this chapter. In this context, the last part of the chapter provides an overview on e...
Nanofiltration Mediated by Surfactant Micelles: Micellar- Enhanced Ultrafiltration
Nanofiltration, 2018
Surfactant micelle-assisted removal of ions and organic solutes from aqueous media by micellar enhanced ultrafiltration (MEUF), which is a membrane separation technique, is discussed in detail. Following general information about micellar structure, counterion binding, substrate solubilization, and medium effect functions of micelles which enable separation of cationic or anionic ions and organic molecules from aqueous media by MEUF are explained in a comprehensive manner. Some of the recent studies on removing pollutants from wastewater effluents of industrial plants by MEUF, and their results have been summarized to inform about the factors affecting the removal efficiency of this technique. Methods for recovery of surfactant and contaminants from retentate or permeate solutions are also given. Selective separation of metal ions of the same charge from multicomponent solutions is another topic of this chapter. In this context, the last part of the chapter provides an overview on every aspects of ligand modified MEUF (LM-MEUF) process. This report comprises a comprehensive review of MEUF and LM-MEUF studies in the literature.
Industrial & Engineering Chemistry Research, 2005
Nonionic surfactants are widely used in industry, and large amounts of wastewater containing nonionic surfactants are produced each year. Nanofiltration (NF) is a possible option to purify these waters, reducing the overall water consumption and enhancing biological purification. However, the flux behavior of NF during purification of wastewaters containing nonionic surfactants is not well understood. NF tests were performed with both synthetic solutions and real wastewaters containing nonionic surfactants from carpet rinsing. When a membrane with a relatively high molecular weight cutoff (MWCO) was chosen, flux decreased to a level lower than that with most ultrafiltration membranes. When a low MWCO was chosen, flux either increased above pure water flux when a relatively hydrophobic membrane was chosen or decreased when a relatively hydrophilic membrane was chosen. NF thus seems feasible to reduce water usage in industrial processes involving nonionic surfactants when a proper membrane is selected. It appeared that flux is controlled by three mechanisms: first, the narrowing of membrane pores through adsorption of monomers when the MWCO is comparable or larger than the monomer size, causing flux decline; second, an improved wettability of the membrane surface through adsorption of monomers on hydrophobic groups, causing flux to increase above pure water flux; third, a decreased wettability through adsorption of monomers on hydrophilic groups, causing flux decline. The nonionic surfactant concentration, MWCO, and membrane's hydrophilicity determine which mechanism is dominant.
Analysis of nanofiltration parameters of removal of an anionic detergent
Desalination, 2008
The demand for clean water is currently increasing because of the decreasing sources of drinking water the stringent environmental legislation and the rigorous quality demands. Nanofiltration may be a solution for the effective separation of anionic detergents from used water or wastewater. In this work the removal of an anionic surfactant cleaning agent by nanofiltration was investigated. The nanofiltration of aqueous solutions of the anionic surfactant was examined at detergent concentrations of 0.5, 1.0 and 5.0 g L −1 at 20, 30 and 40°C and at 20, 30 and 40 bar. Statistical evaluation of the data revealed that the retention was principally affected by the temperature. The highest retention was observed at 20°C. Increase of both pressure and temperature increased the flux, but the impact of pressure was higher than that of temperature. The highest flux was measured at 40°C. There was no appreciable difference between 30 and 40 bar. The fouling index, calculated by fitting a power function to the measured data, was mainly affected by the temperature: it decreased with increasing temperature. The ideal parameters for the best retention and a reasonable flux were found to be 20°C and 30 bar and for the minimal fouling were 30°C and 30 bar.
Interaction between surfactants of different classes and nanofiltration membranes
Scientia Plena
The presence of surfactants in aquatic environments may alter the water quality parameters. Nanofiltration is a promising technique that can separate surfactants from water with high rejections. Nevertheless, negative charges on nanofiltration membranes could facilitate the occurrence of electrostatic interactions between the charged surfactants and the surface of these membranes, increasing the membrane-fouling tendency. In this work, the interaction of surfactants commonly found in residential laundry wastewater with membranes used in nanofiltration was investigated. For this purpose, the surface, and transport properties of four commercial membranes were analyzed. The zeta potential of the NF90 membrane in the presence of individual and mixture of surfactants was performed to evaluate the effect of adsorption of these surfactants on the performance of the membrane. Additionally, a central composite rotatable design (CCDR) and response surface model were applied to investigate the...
Journal of Membrane Science, 2011
The effects of feed concentration and transmembrane pressure (TMP) on membrane fouling in the treatment of cleaning-in-place (CIP) wastewater originated from the production of liquid dishwashing detergent with a nanofiltration (NF) membrane were investigated. The resistance-in-series model was used to evaluate the flux decline caused by a gel layer, a concentration polarisation layer, and internal pore blocking in the NF membrane for CIP solutions of varying concentration termed CIP 5, CIP 10 and CIP 20. With an increase in feed concentration and TMP, it was observed that resistance of the gel layer (R g) played a more important role in the flux decline than that of the concentration polarisation layer or internal pore fouling (R cp + in). Considering the membrane resistance (R m) values, the CIP solutions containing high concentrations of anionic and nonionic surfactants and low dye and salt concentrations did not cause serious fouling of the NF membrane. Characterisation of the membrane surface by atomic force microscopy (AFM) and contact angle measurements also showed that the deposition of surfactant aggregates on the NF membrane surface likely played an important role in the gel layer fouling. The NF membrane showed a rejection efficiency of over 98% for anionic surfactants, nonionic surfactant and dye in all CIP solutions. Salt rejection was not achieved in the CIP 5 solution because of the Donnan effect, whereas salt rejections were around 11-34% and 28-54% in the CIP 10 and CIP 20 solutions, respectively. The resistance-in-series model was successfully tested to evaluate the flux decline for the CIP solutions containing anionic and nonionic surfactants, dye and salt at various TMPs.
Lead, chromium, and chlorobenzene (CB) were removed simultaneously by micellar enhanced ultrafiltration with a mixture of anionic and nonionic surfactants. The process parameters, including the molar ratio of the nonionic surfactant to the ionic surfactant (a), surfactant to metal ion (S/M) molar ratio, applied pressure, and inlet flow rate, were investigated. As a was varied from 0 to 1.5, the rejection of the metal ions increased. The optimum a value was 0.5. The permeate flux decreased by 28% with increasing a from 0 to 1.5. The S/M ratio was optimized at 10 in the presence of CB. The addition of CB increased the rejection of surfactants and decreased the metal-ion rejection. The effect of the applied pressure and inlet flow were studied and found to be optimum at 1 bar and 150 mL/min, respectively. The optimized parameters were applied to the steady-state process. The multiple-solute model was applied to the steady-state data. The relative error for solute rejection was varied from 5 to 9%, and the relative error for flux was 5%. V
Ultrafiltration of Surfactant and Aromatic/Surfactant Solutions Using Ceramic Membranes
Industrial & Engineering Chemistry Research, 1996
Rejection and permeate flux taken together establish the efficiency of an ultrafiltration separation. The controllable factors that may influence the efficiency are systematically studied. These factors include transmembrane pressure, recirculation rate, membrane pore size, and solute and surfactant structure and concentration. Experiments carried out using both cationic and nonionic surfactants show that rejection decreases and permeate flux increases with membranes of increasing pore sizes. However, for the large pore size membrane (200 Å), it is also observed that rejection increases and permeate flux decreases as the filtration proceeds. These unexpected results suggest that micelles penetrate and accumulate into the larger pores, thereby reducing the effective membrane pore size. Depending on the molecular structure and concentration of the surfactant, rejection as high as 99.9% is achieved with a ceramic membrane having 65 Å pores. Permeate fluxes between 30 and 70% of pure water are observed. The addition of a solute tends to improve surfactant rejection and to decrease the permeate flux. Solute rejection increases with surfactant concentration and hydrophobicity. Solubilization isotherms determined here by ultrafiltration are shown to be in agreement with isotherms obtained with head space gas chromatography.