Ultrafiltration water treatment materials

Filtration (water treatment) Refers to the physical separation of particles, colloids, or other contaminants from water by passing the liquid through permeable or semipermeable materials (compare with microfiltration, nanofiltration, reverse osmosis, and ultrafiltration). 

Water-soluble materials can readily be removed. If the resulting wastewater containing the dissolved substances is discarded to the outside, environmental pollution issues may result, so that clarification treatment may be required. Water color may indicate the presence of organic material. It may be necessary to isolate and eliminate the water-soluble materials in wastewater by means other than boiling, which may not sufficiently remove dissolved contaminants (inorgaiuc, organic). Procedures employed include (a) Ultrafiltration membranes are made of polymers with... 

Microfiltration and ultrafiltration (MF/UF) membranes are flexible water treatment tools that can be used in a number of process configurations to meet advanced effluent treatment objectives. MF/UF membranes, when used by themselves, are limited to the removal of particulate and colloidal contaminants however, they can be combined with biological or chemical treatment to remove dissolved contaminants. Furthermore, they represent the ideal pretreatment to reverse osmosis by addressing their main weakness, fouling by particulate materials. 

Membrane-retained components are collectively called concentrate or retentate. Materials permeating the membrane are called filtrate, ultrafiltrate, or permeate. It is the objective of ultrafiltration to recover or concentrate particular species in the retentate (eg, latex concentration, pigment recovery, protein recovery from cheese and casein wheys, and concentration of proteins for biopharmaceuticals) or to produce a purified permeate (eg, sewage treatment, production of sterile water or antibiotics, etc). Diafiltration is a specific ultrafiltration process in which the retentate is further purified or the permeable sohds are extracted further by the addition of water or, in the case of proteins, buffer to the retentate. 

Pretreatment For most membrane applications, particularly for RO and NF, pretreatment of the feed is essential. If pretreatment is inadequate, success will be transient. For most applications, pretreatment is location specific. Well water is easier to treat than surface water and that is particularly true for sea wells. A reducing (anaerobic) environment is preferred. If heavy metals are present in the feed even in small amounts, they may catalyze membrane degradation. If surface sources are treated, chlorination followed by thorough dechlorination is required for high-performance membranes [Riley in Baker et al., op. cit., p. 5-29]. It is normal to adjust pH and add antisealants to prevent deposition of carbonates and siillates on the membrane. Iron can be a major problem, and equipment selection to avoid iron contamination is required. Freshly precipitated iron oxide fouls membranes and reqiiires an expensive cleaning procedure to remove. Humic acid is another foulant, and if it is present, conventional flocculation and filtration are normally used to remove it. The same treatment is appropriate for other colloidal materials. Ultrafiltration or microfiltration are excellent pretreatments, but in general they are... 

The individual membrane filtration processes are defined chiefly by pore size although there is some ovedap. The smallest membrane pore size is used in reverse osmosis (0.0005—0.002 microns), followed by nanofiltration (0.001—0.01 microns), ultrafiltration (0.002—0.1 microns), and micro filtration (0.1—1.0 microns). Klectrodialysis uses dectric current to transport ionic species across a membrane. Micro- and ultrafiltration rely on pore size for material separation, reverse osmosis on pore size and diffusion, and dectrodialysis 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 stiU dilute streams, may require additional treatment or special disposal methods. 

The use of ultrafiltration (UF) membranes for the separation of dissolved molecules of different size and nature has seen an increased interest in recent years. Depending on their pore size, membranes can be used in a variety of fields, such as removal of particulates from air, filtration of colloidal suspensions, treatment of product streams in the food and beverage industry, recovery of useful material from coating or dyeing baths in the automobile and textile industries and treatment of industrial waste waters (J, 2 ). UF membranes also serve as supports for ultrathin reverse osmosis (composite) membranes. 

Nanohybrid materials have been furthermore used for ultra-/nanofiltration applications. Nanofiltration is a pressure-driven membrane separation process and can be used for the production of drinking water as well as for the treatment of process and waste waters. Some apphcations are desalination of brackish water, water softening, removal of micropollutants, and retention of dyes. Ultrafiltration membranes based on polysulfones filled with zirconia nanoparticles are usually prepared via a phase-inversion technique and have been used since 1990 [328]. Various studies were done in order to assess the effect of the addition of Zr02 to polysulfone-based ultrafiltration membranes [329] and the influence of filler loading on the compaction and filtration properties of membranes. The results indicate that the elastic strain of the nanohybrid membranes decreases and the time-dependent strain... 

Latner (1948) described in a preliminary communication the application of the diazo reaction after the treatment of ultrafiltrates of blood or plasma with strong alkali. Touster (1951) made use of the reaction of ergothioneine with bromine water to form inorganic sulfate, which was determined colorimetrically. Quantitative recoveries were not obtained. Ohara et al. (1952) determined the amount of sulfate produced from blood and tissues by oxidation with alkaline peroxide. Jocelyn (1958) has determined free and bound ergothioneine in blood and proteins by a method based on the estimation of trimethylamine released by heating the material with strong alkali. The validity of results obtained with these methods cannot be assessed at this time since the absence of interfering substances has not, in the reviewer s opinion, been adequately demonstrated. 

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