Ultrafiltration seawater desalination

Polymeric materials are the most extensively applied for membrane preparation in science and industry [144-150], Polymers for the preparation of membranes are applied, fundamentally, for gas separation [146], reverse osmosis seawater desalination [147,148], microfiltration, ultrafiltration, and nanofiltration [149,150],... 

Xua J, Chang C-Y, and Gaoa C. Performance of a ceramic ultrafiltration membrane system in pre-treatment to seawater desalination. Sep. Purif. Technol. 2010 75 65-173. 

The removal of water from aqueous salt solutions by reverse osmosis, as in seawater desalination with cellulose acetate membranes or nylon hollow fibers, is believed to occur primarily by a diffusive transport mechanism for both water and solutes. On the other hand, in the use of membranes for the removal of water fiom aqueous solutions containing higher molecular weight solutes, such as the ultrafiltration of protein solutions, the solvent is believed transported by a viscous flow mechanism within the pores of the membrane and solute molecules are convected with the solvem in the huger pores." "... 

Integrated membrane process for seawater desalination. MF = microfiltration UF = ultrafiltration NF = nanofiltration MC = membrane contactor RO = reverse osmosis MD = membrane distillation. 

TABLE 7.4 Process Design Conditions for Seawater Desalination with Media Filtration and Ultrafiltration Pretreatment... 

Figure 7.10 Cost breakdown for seawater desalination with ultrafiltration pietieatment (a) Total life-cycle cost ( indicates a capital cost) and (b) energy cost (total 3.46 kWh/m ).

Ultrafiltration for seawater desalination is currently slightly more expensive than conventional media filtration. However, if the benefits of a better/safer pretreatment are taken into account (increased RO flux, operation of RO at higher recovery, and longer RO membrane life), UF has the potential to reduce the cost of seawater desalination below current levels. 

The advent of the Loeb-Sourirajan asyimnetric membrane some twenty years ago gave birth to an industry now exceeding 200 million dollars in annual sales. Reverse osmosis (RO) and ultrafiltration (UP) were previously only laboratory curiosities. Today, there are many large membrane plants (up to 16 million gallons per day) in service for applications as diverse as desalinating seawater concentrating serum proteins, or the recovery of paint and other by-products from waste streams. 

Lorain, O., B. Hersant, F. Persin, A. Grasmick, N. Brunard, and J. M. Espenan. 2007. Ultrafiltration membrane pre-treatment benefits for reverse osmosis process in seawater desalting. Quantification in terms of capital investment cost and operating cost reduction. Desalination 203 277-285. 

The most common uses of RO are for desalination of seawater and brackish water for potable and industrial applications. However, as demand for fresh water grows, RO is being pressed into service for wastewater and reuse applications. These will require extensive pretreatment, sometimes involving other membrane technologies such as micro- or ultrafiltration, to minimize fouling of the RO membranes (see Chapter 16). 

Membrane materials for reverse osmosis and ultrafiltration applications range from polysulfone and polyethersulfone, to cellulose acetate and cellulose diacetate [12,18-23]. Commercially available polyamide composite membranes for desalination of seawater, for example, are available from a variety of companies in the United States, Europe, and Japan [24]. The specific choice of membrane material to use depends on the process (e.g., type of liquid to be treated and operating conditions) and economic factors (e.g., cost of replacement membranes and cost of cleaning chemicals). The exact chemical composition and physical morphology of the membranes may vary from manufacturer to manufaemrer. Since the liquids to be treated and... 

Possible alternatives to cross-linked polymer supports are soluble and colloidal polymers. They would require large scale ultrafiltration for industrial use. Although ultrafiltration is not yet economical for desalination of seawater, it might be for a separation of a more expensive product. One example is the catalytic partial hydrogenation of soybean oil (361 with soluble polymer-bound transition metal complexes. Solid inorganic supports such as silica gel and alumina are usually not subject to these physical attrition and filtration problems. 

The evolution and expansion of the nse of ultrafiltration (UF) on an industrial scale became possible after the development of asymmetric polymeric membranes, especially of cellulose acetate and aromatic polysulfones (PSs). These membranes were initially developed for desalination of seawater by reverse osmosis and then were used in various applications from other polymeric materials. Until the development of asymmetric membranes, considered as second generation. 

G. Di Profio, X. Ji, E. Curcio, E. Drioli, Submerged hoUow fiber ultrafiltration as seawater pretreatment in the logic of integrated membrane desalination systems. Desalination 2011,269,128-135. 

Knops F, van Hoof S, Futselaar H, Broens L, (2007), Economic evaluation of a new ultrafiltration membrane for pretreatment of seawater reverse osmosis . Desalination, 203(1-3), 300-306. 

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