Polymer-enhanced ultrafiltration

Rajesh, S., Maheswari, P., Senthilkumar, S., Jayalakshmi, A., and Mohan, D. 2011. Pi-eparation and characterisation of poly(amide-unide) incorporated cellulose acetate membranes for polymer enhanced ultrafiltration of metal ions. Chemical... 

Llorens, J., Pujola, M., and Sabate, J. 2004. Separation of cadmium from aqueous streams by polymer enhanced ultrafiltration A two-phase model for complexation binding. J. Membr. Sci. 239 173-181. 

Cellulose acetate membranes with superior properties could be prepared by phase inversion technique using high performance thermoplastic PAI as the modification agent [82,83]. An improvement of surface porosity due to the addition of PAI and a decrease in mean pore size was found. The membranes were checked for the separation of metal ions from aqueous solutions by polymer enhanced ultrafiltration. 

Muslehiddinojlu J, Uludag Y, Ozbelege HO, Yilmaz Z. Determination of heavy metal concentration in feed and permeate streams of polymer enhanced ultrafiltration process. Talanta 1998 46 1557-1565. 

Based on the above mentioned arrangement, several techniques were applied for the removal of heavy metals. One of these techniques is called polymer enhanced ultrafiltration process (Cahizares et al, 2005 Geckeler et al, 1986 Juang and Shiau, 2000 Verbych et al, 2005). The used polymer could be biomaterials or other types of polymers, which can complex (chelate) with heavy metals. The polymer enhanced UF process is composed of three steps (i) com-plexing of metals with water-soluble polymer, (ii) metal-complex retention by membrane and... 

Kuncoro, E. P., Roussy, J., and Guibal, E. 2005. Mercury recovery by polymer-enhanced ultrafiltration Comparison of chitosan and Poly(ethylenimine) used as macroligand. Sep. Sci. Technol. 40 659-684. 

The addition of water-soluble polymers followed by ultrafiltration, named as polyelectrol)de-enhanced ultrafiltration (PEUF), can be efficiently exploited to remove ionic species from aqueous solutions. This process is based on the use of a polyelectrol)de having an opposite charge to that of the target ions and the formation of macromolecular complexes between pollutant ions and polymer due to electrostatic attractions. These complexes are too large to pass through a UF membrane so they are retained in the retentate streams. Examples of separation of both cationic and anionic metal ions by PEUF have been extensively reported (Christian et al., 1995 Tabatabai et al, 1995a Tangvijitsri et al, 2002). 

A solution containing the metal ion to be extracted and a water-soluble polymer is delivered into an ultrafiltration unit (Figure 29.5). The feed stream, upstream of the UF system, is adequately stirred to enhance recovery of the radioactive ions. The metallic macromolecular complex is retained while low-molecular-weight solutes pass through the membrane. The efficiency of the process is mainly characterized by the passage of each species through the membrane. The transfer coefficient of a given solute, i, is defined by... 

In the meantime, other types of dendrimers are reported to enhance the permeation properties of PAMAM. Pentaerythrityl tetraethylenediamine (PETEDA) dendrimer was synthesized from pentaerythrityl tetrabromide and ethylenediamine. The composite membranes for selectively permeating CO2 were prepared by using PETEDA-PVA blend polymer as the active layer and polyethersulfone (PES) ultrafiltration membrane as the support layer. For pure gases, the membrane eontaining 78.6 wt% PETEDA and 21.4 wt% PVA in the blend has a CO2 permeance of 81 GPU and CO2/CH4 selectivity of 52. 

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