Membrane filtration nanofiltration

Membrane filtration (nanofiltration) Partial rejection of DOM Decolorization, softening... 

Membrane Filtration. Membrane filtration describes a number of weU-known processes including reverse osmosis, ultrafiltration, nanofiltration, microfiltration, and electro dialysis. The basic principle behind this technology is the use of a driving force (electricity or pressure) to filter... 

The individual membrane filtration processes are defined chiefly by pore size although there is some overlap. The smallest membrane pore size is used in reverse osmosis (0.0005—0.002 microns), followed by nanofiltration (0.001—0.01 microns), ultrafHtration (0.002—0.1 microns), and microfiltration (0.1—1.0 microns). Electro dialysis uses electric current to transport ionic species across a membrane. Micro- and ultrafHtration rely on pore size for material separation, reverse osmosis on pore size and diffusion, and electro dialysis on diffusion. Separation efficiency does not reach 100% for any of these membrane processes. For example, when used to desalinate—soften water for industrial processes, the concentrated salt stream (reject) from reverse osmosis can be 20% of the total flow. These concentrated, yet stiH dilute streams, may require additional treatment or special disposal methods. 

Recently, membrane filtration has become popular for treating industrial effluent. Membrane filtration includes microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse... 

The separation of homogeneous catalysts by means of membrane filtration has been pioneered by Wandrey and Kragl. Based on the enzyme-membrane-reactor (EMR),[3,4] that Wandrey developed and Degussa nowadays applies for the production of amino acids, they started to use polymer-bound ligands for homogeneous catalysis in a chemical membrane reactor (CMR).[5] For large enzymes, concentration polarization is less of an issue, as the dimension of an enzyme is well above the pore-size of a nanofiltration membrane. 

In the field of membrane filtration, a distinction is made based upon the size of the particles, which are retained by the membrane. That is micro-, ultra-, nanofiltration and reverse osmosis. Figure 4.8 shows a schematic picture of the classification of membrane processes. The areas of importance for application with homogeneous catalysts are ultra- and nanofiltration, depicted in gray. 

Membrane filtration (reverse osmosis, nanofiltration, ultrafiltration, microfiltration)... 

Since membrane filtration methods such as ultra filtration or nanofiltration can discriminate according to the size of a given molecule, they can easily be used to retain biocatalysts (which are macromolecules). For chemical catalysts additional procedures have to be applied mostly. Immobilization on a solid support is used... 

This sensory property was used to probe the suitability of metalloden-drimers for nanofiltration membrane techniques in homogeneous systems. During continuous-flow membrane filtration, any leaching of a metalloden-... 

However, it can be assumed for most electrochemical applications of ionic liquids, especially for electroplating, that suitable regeneration procedures can be found. This is first, because transfer of several regeneration options that have been established for aqueous solutions should be possible, allowing regeneration and reuse of ionic liquid based electrolytes. Secondly, for purification of fiesh ionic liquids on the laboratory scale a number of methods, such as distillation, recrystallization, extraction, membrane filtration, batch adsorption and semi-continuous adsorption in a chromatography column, have already been tested. The recovery of ionic liquids from rinse or washing water, e.g. by nanofiltration, can also be an important issue. 

Concentration Units. Typical concentrators for rinsing solutions are membrane filtration units, which split the feed into diluate and concentrate streams, meaning purification and recovery, respectively [106], Both nanofiltration and reverse osmosis might be applied, depending on the physico-chemical properties of the solutes. 

Another already mentioned application of membrane filtration is for the recovery of ionic liquids from wastewaters. Here the challenge is to find appropriate membranes, since rejection values that have been reported to date [136] are too low for industrial application. However, for similar ionic liquids we found a membrane that shows rejection rates above 99% throughout at considerably high permeate flow rates above 50 L m 2 h 1 in cross flow filtration. Such numbers make washing in combination with nanofiltration an interesting option. 

Eriksson, P., Nanofiltration extends the range of membrane filtration. Environ. Prog., 7, 58, 1988. 

Filtration membrane filtration is a common process that is widely used in many industries. The examples of membrane filtration include microfiltration, ultrafiltration, nanofiltration, reverse osmosis, and the newly developed technology such as hydrophobic membrane. 

The influence of metal oxide derived membrane material with regard to permeability and solute rejection was first reported by Vernon Ballou et al. [42,43] in the early 70s concerning mesoporous glass membranes. Filtration of sodium chloride and urea was studied with porous glass membranes in close-end capillary form, to determine the effect of pressure, temperature and concentration variations on lifetime rejection and flux characteristics. In this work experiments were considered as hyperfiltration (reverse osmosis) due to the high pressure applied to the membranes, 40 to 120 atm. In fact, results reproduced in Table 12.3 show that these membranes do not behave as h)qjerfiltra-tion membranes but as membranes with intermediate performances between ultra- and nanofiltration in which surface charge effect of metal oxide material plays an important role in solute rejection. 

S. Sarrade, C. Bardot, M. Carles, R. Soria, S. Cominotti and R. Gillot, Elaboration of new multilayer membrane for nanofiltration. Proceedings of the 6th World Filtration Congress, 18-21 May 1993, Nagoya, Japan. 

RO membranes have a very small molecular weight cut-off (MWCO) and are expected to retain a large fraction of LMW compounds, such as amino acids or sugars, and are therefore useful for extracting a representative mixture of NOM from surface waters. For nanofiltration smdies it is important to retain the LMW fraction, as these molecules could be major contributors of pore pluming in membrane filtration. Pure HS solution cannot be obtained from such a mixture with a the salt content of the sample depending on its origin. 

In this chapter, membrane filtration in water treatment is reviewed. The aim is to assess the current status and reveal gaps in knowledge firom the wealth of literature. The background on models and principles is summarised for the relevant processes microfiltration (MF), ultrafiltration fUFJ, and nanofiltration (NF). Reverse osmosis is brifily considered to put NF, which is often described as a process "in between" UF and RO, in perspective. 

The speciation results presented here contribute to improved understanding of the electrolyte solution. This is essential in understanding the pH dependence of rejection in membrane filtration, specifically nanofiltration,... 

The crude Mal-/S-CD product contains maltose, /S-CD, Mal-/8-CD and a little branched-tetrose. Thus, membrane filtration technology, i.e. nanofiltration (NF), and chromatographic method can be utilized to isolate Mal-/8-CD from crude Mal-/S-CD. 

Van Gestel T, Kruidhof H, Blank DHA, and Bouwmeester HIM. Zr02 and Ti02 membranes for nanofiltration and per-vaporation. Part 1. Preparation and characterization of a corrosion-resistant Zr02 nano filtration membrane with a MWCO < 300. J. Membr. Set 2006 284 128-136. 

Likewise, nanofiltration can be integrated into waste water treatment. Combined reverse osmosis/nanofiltration processes can offer higher water recovery than either process alone [122]. Moreover, nanofiltration can be combined with other membrane filtration processes [123], electrodialysis [124], or other waste water treatment processes such as ozonation [125]. 

Treatment processes for wastewater reuse and water treatment usually have adopted process such as biological treatment, coagulation, sand filtration, membrane filtration and activated carbon adsorption [168]. Recently, membrane filtration in water treatment has been used worldwide for reduction of particle concentration and natural organic material in water. Among the membrane processes, nanofiltration (NF) is the most recent technology, having many applications, especially for drinking water and wastewater treatment [169]. 

Table 7.24 shows where nanofiltration fits in the spectrum of specialized membrane filtration processes. The process has application regardless of the type of chlor-alkali cell in use, and it also can remove sulfate from chlorate plant liquors. The membranes used in the filters are sensitive to free chlorine. In a membrane-cell plant, therefore, the filter usually will treat a sidestream of fully dechlorinated brine. After standard filtration and. 

Reverse osmosis units are used for molecular separations such as the removal of salt from seawater. Nanofiltration is another variant of membrane filtration whose separation characteristics fall between reverse osmosis and ultrafiltration. Their description is beyond the scope of this text. 

---